[Rob Thompson] Manufacturing Processes for Design
Short Description
Manufacturing Processes for Design...
Description
Manufacturing Processes for
Design Professionals
¦;*>
Hob Thompson
Manufacturing Processes for
Design Professionals
Contents On the previous spread: The Eye chair, designed by
How to use this book 8
Introduction 10
Jackie Choi for Boss Design (see pages 342-343).
The importance of materials and manufacturing knowledge for successful design practice
Any copy of this book issued by the publisher as a paperback is sold subject to the condition that it shall not by way of trade or otherwise be lent, resold,
hired out or otherwise circulated without the publisher's prior consent in any form of binding or cover other than that in which it is published and
Part One
Forming Technology
without a similar condition including these words being imposed on a subsequent purchaser.
Plastics and Rubber First published in the United Kingdom in 2007 by Thames & Hudson Ltd,i8iA High Holborn, London wcivyox
Blow Molding
Tube and Section Bending
22
Extrusion Blow Molding (EBM)
Thermoforming
© 2007 Rob Thompson
Reprinted 2010
All Rights Reserved. No part of this publication may
Forging
Plug-assisted Forming
Drop Forging
Twin Sheet Thermoforming
Roll Forging
Vacuum Casting
36 40
Compression Molding
Ul*
Compression Molding Rubber
any means, electronic or mechanical, including
Compression Molding Plastic
Injection Molding
Sand Casting Die Casting
50
Metal Injection Molding
Moldflow analysis
Electroforming
permission in writing from the publisher.
Gas-assisted Injection Molding
Centrifugal Casting
Multishot Injection Molding
Press Braking
Reaction Injection Molding
the British Library
Dip Molding
Designed by Christopher Perkins Printed and bound in China
72
Dishing
Open Bending
120 124
Glassblowing
Wet Lay-up
130 136 140 144 148
Rapid Prototyping 232
Backpressure Forming Diaphragm Forming
Stereolithography (SLA)
160
Mandrel Forming
Clay Throwing Ceramic Slip Casting
88 92
Press Molding Ceramics Jiggering Ram Pressing
Selective Laser Sintering (SLS) Direct Metal Laser Sintering (DMLS)
Bending
78 82
Secondary Pressing
Bubble Forming
3D Rotary Laminating (3Drl
152
Machine Press and Blow
Lampworking
Planishing
Cavity Forming
Filament Winding 222 3D Thermal Laminating 228
Layered Manufacturing
Hole Boring
Deep Drawing
Resin Transfer Molding
DMC and SMC Molding 218
Machine Blow and Blow
Wheel Forming
Superforming
Pre-preg Lay-up
Studio Glassblowing
Blowing
Metal Stamping
Composites Composite Laminating 206
Glass and Ceramics
Jig Chasing
Metal Spinning
Circle Bending
3D Laminating I3DL)
64 68
Metal Panel Beating
Steam Bending 198
Paper Pulp Molding 202
In-Mold Decoration
A catalogue record for this book is available from
ISBN 978-0-500-51375-0
m
Low Pressure Die Casting
storage and retrieval system, without prior
British Library Cataloguing-in-Publication Data
Veneer Lamination
110
High Pressure Die Casting
Investment Casting
Kerfing Solid Wood Lamination
Hydraulic Swaging
Pressure Forming
be reproduced or transmitted in any form or by
photocopy, recording or any other information
30
Roll Forming
Rotation Molding
104
Rotary Swaging
Vacuum Forming
Wood CNC Machining 182 Wood Laminating 190
Ring Rolling
Swaging
Injection Blow Molding lIBM) Injection Stretch Blow Molding (ISBM)
www.thamesandhudson.com
98
Mandrel Bending
168 172 176
/•
Part Two
Part Four
Cutting Technology
Finishing Technology
Chemical Photochemical Machining
Mechanical
Additive Processes
Subtractive Processes
Printing
2UU Punching and Blanking 260
Spray Painting 350
Grinding, Sanding and Polishing 376
Screen Printing 400
Die Cutting 266
Powder Coating 356
Thermal
Wheel Cutting
Pad Printing 404
Laser Cutting
248 Water Jet Cutting 272
Electrostatic Spraying
Belt Sanding
Hydro Transfer Printing 408
Electrical Discharge Machining
254 Glass Scoring 276
Fluidized Bed Powder Coating
Honing
Foil Blocking and Embossing 412
Die Sink EDM
Anodizing 360
Wire EDM
Electroplating 364
Electropolishing 384
Galvanizing 368
Abrasive Blasting 388
Vacuum Metalizing 372
Lapping
Photo Etching 392 CNC Engraving 396
Part Three
Part Five
Joining Technology
Materials
Thermal Arc Welding
Soldering and Brazing 312
Introduction to Materials 418
Wood and natural fibres
282 Conduction Method
Manual Metal Arc Welding (MMA)
Torch Method
Plastics
introduction to Wood 464
Metal Inert Gas Welding IMIG)
Furnace Method
Introduction to Plastics 424
Softwoods 470
Staking 316
Thermoplastic 430
Hardwoods 472
Plasma Welding
Hot Air Staking
Thermoset 440
Natural fibres 480
Submerged Arc Welding (SAW)
Ultrasonic Staking
Bioplastic 446
Tungsten Inert Gas Welding (TIG)
Power Beam Welding Laser Beam Welding [LBW]
Mechanical
Electron Beam Welding (EBW)
Friction Welding
294 Joinery 324
Rotary Friction Welding (RFW)
Weaving 332
Linear Friction Welding (LFW)
Upholstery 338
Orbital Friction Welding (OFW)
Timber Frame Structures 344
Friction Stir Welding (FSWl
Vibration Welding Ultrasonic Welding Resistance Welding Projection Welding
Ceramics and Glass
288 Hot Plate Welding 320
Metals
Introduction to Ceramics and Glass 482
Introduction to Metals 448
Ceramics
Ferrous
Glass
454
488
490
Non-Ferrous 457
Directory Glossary and Abbreviations 496
298 302 308
Featured Companies 502 Organizations and Other Sources 512
of Information Further Reading 516
Spot Welding
Illustration Credits 519
Seam Welding
Acknowledgments 522 Index
524
Manufacturing Processes for Design Professionals
How to use this book Manufacturing Processes for Design Professionals explores established, emerging and cutting-edge production techniques that have, or will have, an important impact on the design industry. There is a danger today of designers becoming detached from manufacturing as a result of CAD, globalization and design education. This book aims to restore the balance with
Forming Functions
a hands-on and inspiring approach to design and production. It is a comprehensive, accessible and practical resource that focuses on providing relevant information to aid fast and efficient
Bend
Continuous
Sheet
Internal
decision-making in design projects. Cutting Functions
STRUCTURE
the process through 3 key elements.
HOWTO USE THE CASE STUDIES
This book is organized into 2 main
The text gives an analysis of the typical
The Processes section features real-life
sections: Processes and Materials.These
applications, competing or related
case studies from factories around
can be used separately or in combination.
processes, quality and cost, design
the world.The processes are explained
Each section contains design guidance
opportunities and considerations, and
with photographs and analytical and
supplied by manufacturers to ease
environmental impacts of a process.
descriptive text. All types of production
the transition between design and
There is also a full technical description
are included, from one-off to batch and
production and provides information
of the process and how the machinery
mass. For cross-comparison the case
that will inspire decision-making,
involved works, with diagrams, and a case
studies can be set against each other on
encourage experimentation and support
study showing products or components
many levels, including functions, cost,
pollination of ideas between industry
design ideas.
being made by a leading manufacturer
typical applications, suitability, quality,
and design.This ensures that designers
using the featured process.
competing processes and speed.This
fully utilize the potential of their
information is accessible, logical and at
industrial toolbox to create forward-
External
Internal
Channel
Surface
Joining Functions
Overlap
HOWTO USE PROCESSES
On the opening spread of each
The Processes section is organized into
process you will find a data panel, which
4 parts, each focusing on a specific
provides a bullet-pointed summary of
type of technology, and each process is
factors such as the typical applications,
HOWTO USE MATERIALS
explained with photographs, diagrams
quality and cost, as well as function
Each manufacturing process can be used
and analytical and descriptive text.The 4
diagrams (see opposite) which, when highlighted, indicate the particular
to shape,fabricate andfinish anumber
are: Forming Technology (blue), Cutting Technology (red), Joining Technology (orange) and Finishing Technology
functions and design outcomes of each
of the material profiles is to support
process. These function diagrams quickly
the processes, expand opportunities
enable the reader to compare a wide
for designers and provide relevant
(yellow). Each featured manufacturing
range of similar processes to see which is
information for potential applications.
process is fully illustrated and provides
the most effective in producing a given
The layout of the Processes and Materials
a comprehensive understanding of
item or component.
sections is designed to encourage cross-
parts (colour coded for ease of reference)
the forefront of each process.
Finishing Functions
thinking and engaging products for the future.
of different materials.The main objective
Preparation Colour Appearai
Protection Information
HOW TO USE THE FUNCTION ICONS
materials are more suitable for certain
These Icons represent the function that
functions than others. These Icons guide
each process performs. The functions are
designers In the early stage of product
different for forming, cutting, joining and
development by highlighting the relevant
finishing processes. Likewise, different
processes and materials for their project.
vlanufactui ing Processes for Design Professionals
Introduction Manufacturing technology is both fascinating and inspiring. The products around us are the result of the delicate touch of craftsmen, highly mechanized production, or both. The Processes section gives first-hand insight into a range of manufacturing techniques including mass producing everyday products, batch producing furniture and prototyping with some of the most advanced
Manufacturing is continually in a state of transition.The level of technology is different in various industries, so whilst some manufacturers are leading the way, such as in the production of
carbon fibre composites (page 214) and rapid prototyped plastics and metals (page 232), others are maintaining
highly skilled traditional crafts. The
technologies we have at our disposal. The visual case studies,
combination of craft and industrial
combined with in-depth technical analysis, show what happens now
techniques in processes such as panel
and how designers and research institutes are continually pushing
beating metal (page72),jiggering and jolleying ceramics (page 176) and steam
the boundaries of what will be possible in the future.
bending wood (page 198) produces
Bellini Chair
Panasonic P901iS smartphone
Designer/client: Mario Bellini/Heller Inc. Date: 1998 Material: Polypropylene and glass fibre
Designer: Panasonic. Japan
Manufacture: Injection molded
Date: 2005 Manufacture: Injection molded plastic covers using Yoshida Technoworks in-mold decoration technology
articles that unite the user and maker with a sense of pride and ownership.
The examples in this book demonstratethe inner worldngs
50) is now one of the most important
(page 50). It is also possible to integrate
of a 1 arg e ran g e of m anufacturin g
processes for designers, and probably
fabric, metal foils and leather (see image,
processes. In some cases the tasks are
the most widely used. It is utilized to
above right) into plastic moldings. Gas
carried out by hand to demonstrate the
sh ape th erm opl asti cs an d th erm os etti n g
assist injection molding produces hollow,
techniques more clearly.The continued
plastics, waxes for investment casting
rigid and lightweight plastic parts (see
importance of an operator is evident in
(page 130) and even metals (page 136). It is continually developing and in
image, above left).The introduction of
many processes. Even mass-production techniques, such as die cutting and
recent years has been revolutionized by
the amount of pressure required in the
assembling packaging (page 266),rely
in-mold decoration (page 50) and gas
molding cycle. Surface finish is improved
on an operator to set up and fine tune
assist technologies (page 50). In-mold
because the gas applies internal pressure
the production line. But, where possible,
decoration is the application of graphics
while the moldis closed.
manual labour is being replaced by
during the molding process, eliminating
computer-guided robotic systems.The
finishing operations such as printing.
within injection molding is multishot.
aim is to reduce imperfections caused
With this technology it is possible to
This is the process of injecting more
by human error and minimize labour
apply graphics on 1 side, both sides or
than 1 plastic into the same die cavity to
costs. Even so, many metal, glass, wood
onto multishot injection molded parts
produce parts made up of materials with
and ceramic processes are based on manufacturing principles that have changed very little over the years.
DEVELOPMENTS IN FORMING Plastic products have come a long way since they were first formed by
compression molding (page 44) in the 1920s. Injection molding (page
gas reduces material consumption and
Another area of important progress
^3
o a c: o ;H o z
widely used to describe the matt texture produced by EDM. Nowadays, mobile phones and similar products are more often produced with in-mold decoration, which requires a gloss finish. Whereas mass production is limited
by high tooling costs and thus high volume production of identical parts, each product directly manufactured
from CAD data is limited only by the imagination and capabilities of the designer. Rapid prototyping (page 232) is one of these processes: it is not yet suitable for mass production, but it is capable of producing similar volume parts whose shape is different each time without significant cost implications.
Combined with the possibility of making shapes not possible with any other process, these techniques are giving rise to a new design language. For example, one-off and 1 ow volume products have emerged in recent years that are designed by the customers and merely
facilitated by the designer. Also, the US military are using rapid prototyping to Entropia
different colours,hardnesses,textures or
make spare parts for their equipment, as
Designer/client: Lionel Dean, FutureFactories/
transparency. Over-molding is a similar
opposed to waiting for delivery.
Kundalini Date: 2006 Material: Polyamide (PA) nylon Manufacture: Selective laser sintering (SLS1
process; the difference is that over-
Recently metal powders have been
molding is not carried out in the same
added to the list of materials that can be
tool. Using this technique, materials other than plastic can be integrated into
shaped by rapid prototyping. At present, rapid prototyping metal is best suited
injection molding.
to the production of parts no larger
Developments in plastic molding
than about 0.01 m3 (0.35 ft3). Even so, the
are also affected by improvements in
opportunities of this process are vast,
metalworking technologies.The surface
because larger parts can be made by
finish on mobile phones and other
investment casting (page 130) a rapid
small consumer electronic equipment
prototyped wax or plastic pattern.
became almost standardized due to the development of electrical discharge
Thermoforming (page 30) is a process generally associated with plastic
machining (EDM) for plastic mold
packaging. However,Superform
making.This process makes it possible to
Aluminium in the USA and UK have
machine concave profiles (molds) to the same high degree of precision as relief profiles. High voltage sparks between
a copper electrode (tool) and metal workpiece vaporize surface material. The rate of spark erosion determines the surface finish and so it is used to simultaneously cut and finish metal parts. Hence the term 'sparked' finish was
Roses on the Vine Designer/client: Studio Job/Swarovski Crystal Palace Project Date: 2005 Material: Aluminium base with red and peridot coloured Swarovski® crystal Manufacture: Base laser cut and gold anodized
Laser Vent polo shirt
Outrageous painted guitar
Designer: Vexed Generation
Date: Spring/Summer 2004 Material: Quick dry polyester microfibre
Paint by: Cambridgeshire Coatings Ltd/US US Chemicals and Plastics Date: 2003
Manufacture: Laser cutting and stitching
Material: Illusion Outrageous paint Manufacture: Spray painting
Biomega MN01 bike
Camouflage printed rifle stock
Designer: Marc Newson
Designer:
Date: 2000
Material:
Material: Aluminium alloy frame
Manufacture:
Hydrographies Plastic stock Hydro transfer printing
Manufacture: Superforming and welding
Notes:
The transfer films can be decorated with artwork, photographs or patterns.
developed a range of processes, known as
materials. Indeed, laser cutting is used
cut edge is sealed by the heat of the
superforming (page 92), that are capable
a great deal by architects for model
laser, eliminating conventional hems
of shaping aluminium alloys (page 457)
making within short timeframes.
and magnesium alloys (page 458) using
Roses on the Vine by Studio Job (see
and reducing material usage. Another
benefit of specifying laser cutting was
a similar technique. At around 4500C
image, page 13), is an example of how
that vents could be integrated into areas
(8400F) certain grades of these metals
laser cutting can be used to produce
that needed better ventilation or greater
become superplastic and so can be
intricate, complex and otherwise
freedom of movement.
stretched to many times their length
impractical shapes with very high
without breaking. Since the development
precision.This cutting process is not
DEVELOPMENTS IN JOINING
of commercially viable metals and
limited to rigid materials. In 2004 Vexed
Powerbeam technologies (page 288),
processes in the mid 1970s, superforming
Generation launched Laser Vent. The
which include laser beam and electron
has had a major impact in the
aim of the designers was to create ultra
beam, are making an impact in joining
automotive, aerospace and rail
lightweight clothing for cyclists, but with
as well as cutting applications. Electron
industries. Recently, designers such as
the aesthetic of low-key leisurewear and
beam welding is capable of producing
Marc Newson have begun to explore the
so suitable for the office.They achieved
coalesced joints in steels up to 150 mm
possibilities of using this technology to
this by laser cutting synthetic fibre. The
(5.9 in) thick and aluminium up to
produce consumer products such as bicycles (see image,opposite).
DEVELOPMENTS IN CUTTING Like rapid prototyping, laser cutting (page 248) works directly from CAD data. This means that data can be translated very readily from a designer's computer onto th e surface of a wi de ran g e of
I
450 mm (17,7 in) thick. Laser welding is not usually applied to thick materials,
interiors, mobile phones, packaging and
cannot always be produced with lower
camouflaging gun stocks (see image,
volumes ones. For example, blow
but a recent development known as
page 15 above right).
molding plastic (page 22) and machine glassblowing (page 152) are limited
weld clear plastics and textiles (page 288).This technique has the potential to
SELECTING A PROCESS
to continuous production due to the
Process and material selection is integral
nature of the process. Therefore, there
transform applications that are currently
to the design of a product. Economically,
is very little room for experimentation.
limited to coloured materials.
it is about striking a balance between the
In contrast, the qualities of injection
Joinery (page 324) and timber frame construction (page 344) have changed
investment costs (research, development
molding can be reproduced with
and tooling) and running costs (labour
very little over the years. Developments
vacuum casting (page 40) and reaction injection molding (page 64), for instance.
have mostly been concentrated in
and materials). The role of the designer is to ensure that the available technology
This means that low volumes can be
materials such as new types of
will deliver the expected level of quality.
produced with much lower initial
Clearweld® makes it possible to laser
engineering timbers (page 465) and
High investment costs are usually
costs and therefore a higher level of
biocomposites. However, in 2005 TWI
only justifiable for high volume products,
experimentation is usually possible.
assessed the possibility of joining wood with techniques similar to friction
whereas low volume products are limited
Process selection will affect the
by high labour and material costs.
quality of the finish part and therefore
welding metals (page 294) and plastics (page 298). Beech and oak were successfully joined by linear friction
Therefore, the tipping point comes when
the perceived value. This is especially
expected volumes outweigh the initial
important when 2 processes can produce
costs.This can happen before a product
the same geometry of part. For example,
welding (see image, page 295). Friction welding revolutionizedmetalwork by eliminating the need for mechanical
has reached the market, or after years of
sand casting (page 120) and investment
manufacturing at relatively low volumes.
casting (page 130) can both be used to
The cost of materials tends to have a
manufacture 3D bulk shapes in steel.
fasteners, and in the future the same
greater impact in high volume processes.
However, due to the lower levels of
could happen in woodwork.
This is because labour costs are generally
turbulence, investment casting will
reduced through automation.Therefore,
produce parts with less porosity. It is
DEVELOPMENTS IN FINISHING
fluctuations in material value caused by
forthis reason that aerospace and
There have been many developments in
rising fuel prices and increased demand
automotive parts are investment cast.
finishing, but spray painting remains one
affect the cost of mass produced items.
of the most widely used processes, from
Occasionally the cost of production is
33
o o
c o H o
DESIGN SOFTWARE
irrelevant, such as composite laminating
Predicting and testing the quality of
years arange of sprayed finishes have
carbon fibre racing cars (page 214). Until
the finished part has become more
evolved including high gloss, soft touch,
recently, this has been too expensive
reliable with developments in computer
thermochromatic, pearlescent and
for application in commodity products,
simulation software, such as finite
to maximize the efficiency of the
iridescent. The cost of paint varies
but due to recent developments in
element analysis (FEA).There are
operation (see images, above); previously,
FEA is used to predict accurately how the
dramatically depending on the type and can be very high for specialist paints such
the production techniques it is now
many different programmes, which
tools were engineered and then tested
part will perform in application (pages
becoming more common in sports
are becoming more widely used in the
and adjusted accordingly. FEA software
124-9,214 and 226-7).This does not
as the Outrageous range (see image,
equipment and automotive parts.This is
process of design for manufacture
is not used in all forming applications,
de-skill the process of engineering;
pageij above left). A film of aluminium is incorporated into spray painted finishes
(pages 50-63,64-7 and 130-5), and
but it does have many advantages.
it is another tool that can help to
it is no longer limited to high volume
Most importantly, it reduces tooling
minimize material consumption and
by vacuum metalizing (page 372) to give
also partly due to the obvious benefits of improved strength to weight. The design features that can be
production. The forming of many
costs, because parts can be molded
double-check calculations made by
the appearance of chrome, silver or
achieved with high volume processes
products is simulated using FEA software
'right first time'.
designers and engineers.
one-off to mass production. Over the
an 0di zin g, or for functi on al purposes, such as heat reflection.
Hydro transfer printing (page 408) has recently transformed spray painting.
With this process it is possible to wrap printed graphics around 3D shapes.This
means anything that can be digitally printed can be applied to almost any surface. Applications include car
As well as mold flow simulation,
FEA simulation of an aluminium forging Software: Professional Engineer (Pro E) and
Forge3 SimuLatlon by: Bruce Burden, W.H. Tildesley Ltd
Material: Aluminium alloy Manufacture: Forging
Case Study
^ Binding this book I ~ This bool< demonstrates the techniques used
cut to size on a guillotine. Therefore, the
to manufacture many of the products that
extent of books bound in this way is divisible
surround us in our day-to-day lives. Like most
by the number of pages in a section, which
commercial books, it is manufactured using
is typically 4,8 or 16. Perfect binding is not
a process similar to traditional bookbinding.
limited by the same factors and so can be
And whether hardcover or paperback, it is
any number of pages.
made of folded sections stitched together
Linen tape is adhesive bonded onto
in a process known as section-sewn binding
the sewn edges of the sections and
(image i). An alternative method is perfect
the sewn assembly is cut to size in a
binding, which is the process of adhesive
guillotine (image 3). This produces a neat
bonding Individual pages into a scored paper
edge (image 4). Hard covers are made up
cover. It is less durable and so is limited to
of heavy-duty grey board 2.5 mm (0.1 in.)
thinner books, but the advantage is that the
thick concealed in paper, cloth or leather.
pages can be opened out flatter than section-
By contrast, paperback covers are heavy-
sewn bindings.
duty paper, which is typically around
This sequence of images demonstrates section-sewn case binding on a smaller book
0.25 mm (0.01 in.) thick. Any printed
decoration, such as hot foiling (pages 412-
than this, but the principles are the same.
5) is applied prior to assembly. The cover
In this case, the sections are made up of i5
Is adhesive bonded to the first and last
pages (image 2), which consist of a large
page, the assembly is clamped in a press
signature (printed sheet) folded 4 times and
and the adhesive cures (image 5).
Featured Company
R S Bookbinders www.rsbookbinders.co.uk
Forming Technology
Extrusion Blow Molding Process Polymer granules Conventional extrusion screw and barrel assembly
fj11
Forming Technology
{=^
Blow Molding
Part sealed
1 Extrusion die
Blow pin removed
. Extrused parison Split mold
ft
Molds open
Flash removed with profiled cutter
w
This group of processes is typically used to mass produce hollow packaging containers. They are a very rapid production method
O
for large volumes of thin walled parts.
Finished part
A
u 1 Moderate tooling costs 1 Low unit costs
Quality • High quality, uniform thin walled parts • High quality surface finish that can be gloss, textured or matt
Typical Applications
Suitability
• Chemical packaging • Consumer packaging • Medical packaging
• Suitable only for high volume production runs
Related Processes
Speed
• Injection molding • Rotation molding • Thermoforming
Stage 2: Blowing
Stage 3: Demolding
Stage A: Trimming
In stage 1 of the EBM process, a conventional
once the parison has reached a sufficient
parison to take the shape of the mold. The
extrusion assembly feeds plastlcized
length the 2 sides of the mold close around
hot polymer solidifies as It makes contact
polymer into the die. The polymer is forced
It. A seal Is formed along the bottom edge.
with the cold tool. In stage 3, when the part
over the mandrel and emerges as a circular
The parison Is cut at the top by a knife and
Is sufficiently cool the mold opens and the
tube, known as an extrused parison. The
moved sideways to the second station, where
part Is ejected. In stage U, the container Is
extrusion process Is continuous. In stage 2,
air Is blown In through a blow pin, forcing the
deflashed using a trimmer.
RELATED PROCESSES
that a wider range of anti-tamper and
pints). EBM can create the largest variety
among other materials.Typical materials
Thermoforming (page 30),rotation molding (page 36) and injection molding (page 50) can all be used to form the
other caps can be introduced.
of containers ranging between 3 ml
for the ISBM process include PE and PET
a wide choice of materials can be used in
molding is a complex process with which
COSTS
care applications.
same geometry parts. Even so, blow
this process, and complex and intricate
to work. Expert advice from engineers
Tooling costs are moderate. EBM is the
shapes manufactured.
and toolmakers is required to guide the
least expensive, the tooling for I BM is
TYPICAL APPLICATIONS
molding is the process of choice for large volumes of hollowthin walled packaging.
design process through to completion.
typically twice as much and ISBM is the most expensive.
• Very rapid cycle time (typically 1-2 minutes)
INTRODUCTION
very accurate neck finishes and the
Blow molding is carried out In 3 different
stretch cycle gives superior mechanical
ways: extrusion blow molding (EBM), injection blow molding (IBM) and injection stretch blow molding (ISBM).
properties. ISBM is particularly suitable for beverage, agrochemical and personal
Each of the processes has its particular
design opportunities and is suitable for
Stage 1: Extruded parison
TECHNICAL DESCRIPTION
The main advantages of EBM are that
ISBM can be used to produce clear
and 220 litres (0.005-387 pints). Blow
containers with very high clarity.
There are many considerations that need
chemical,veterinary and consumer
QUALITY
Stretching the pre-form during blowing
to be taken into account when designing
applications because it has low tooling
industries to produce intravenous
The surface finish is very high for all
greatly increases the mechanical
for blow molding, including the user
may contain ic or more cavities and eject
and running costs. It is a versatile process
containers, medicine bottles and vials,
of these processes.The IBM and ISBM
and con sum er packaging.
technologies have the additional
strength of the container by aligning the polymer chains longitudinally.These
(ergonomics), product (light sensitivity of contents andviscosity), filling (neck,
a batch of parts every 1-2 minutes.
that can be used to produce a wide
advantage of precise control over neck
containers also have good gas and
details, wall thickness and weight.
solvent barrier properties and so can
contents and filling line), packaging (shelf height) and presentation (labelling
be expensive, however, so machines are
be used to package aggressive foods,
using sleeves or print, for example).
often dedicated to a single product.
different industries. EBM is favourable for many
variety of shapes in an extensive choice of materials. Containers can be molded
with integral handles and multiple layered walls. IBM is a precise process that
EBM is used mainly in the medical,
IBM is utilized especially for consumer packaging and medical packaging (medicine bottles, tablet and diagnostic bottles and vials). ISBM is predominant in the personal
DESIGN OPPORTUNITIES
Cycle time is very rapid. A single mold
Labour costs are low, as production is automated. Set-up and changeover can
concentrates and chemicals.
All of the blow molding processes can be
COMPATIBLE MATERIALS
ENVIRONMENTAL IMPACTS
All thermoplastics can be shaped using
All thermoplastic scrap can be directly
is suitable for more demanding
care, agrochemicals, general chemicals,
used to produce thin walled and strong
DESIGN CONSIDERATIONS
applications such as medical containers
food and beverages and pharmaceutical
containers.The neck does not have to
A major difference between these blow
blow molding, but certain materials are
recycled. Process scrap is recycled in-
molding techniques is the capacity that
more suited to each of the technologies.
house. Post-consumer waste can also be
and cosmetic packaging. It is used to
industries to produce carbonated and
be vertical or tubular. Features such as
produce containers with very accurate
soft drink bottles, cooking oil containers,
handles, screw necks and surface texture
each can accommodate. IBM is generally
Typical materials used in the EBM process
recycled and turned into new products.
neck finishes as well as wide mouths.
agrochemical containers, health and oral
can be integrated into all 3 processes.
limited to the production of containers
include polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET) and polyvinyl chloride (PVC), while the IBM process is suitable for PP and HDPE
Recycled PET is used in the production of
ISBM is typically used to produce high
hygiene products, bathroom and toiletry
The principal reason to select I BM
between 3 ml and 1 litre (0.005-1.760
quality glass clear PET containers such as
products, and a number of other food
is that there is more control over wall
pints) and ISBM can produce containers
water bottles. The injection cycle ensures
application containers.
thickness and neck details.This means
between 50 ml and 5 litres (0.088-8.799
certain items of clothing, for example.
Blow molding plastics is more energy efficient than glassblowing.
"ase Study
Extrusion blow molding a cleaning agent container The PE polymer granules are stored in a
(116 psi) forcing the parison to take the shape
communal hopper and coloured individually
of the mold (image 4). The molds separate
(image io). The finished product is packaged
for each machine (image i). In this case a
to reveal the blown part with the blow rods
and shipped.
small percentage of blue granules are added
still inserted (image 5). The rods retract and
just prior to extrusion. The extrusion process
the part is deflashed with a profiled trimmer
is continuous and produces an even wall
(image 6).
thickness parison (image 2). The 2 halves of
4
Each batch is conveyed from the blow
the mold close around the parison to form a
molding machine to labelling and capping via
seal and the parison is cut to length (image
pressure testing (image 7). The EBM bottles
3). A blow rod is then inserted into the neck,
pass through the filling line (image 8). The
and air is blown into the mold at 8 bar
caps are screwed on automatically (image 9)
and the labels adhesive bonded to the bottle
Injection Blow Molding Process
Blowing mold
Polymer granules
ection blow molding a roll-on deodorant bottle Conventional injection screw and barrel assembly Pre-form mold Stage 2: Blowing
The polished core rods are prepared so the
when it makes contact with the relatively
pre-forms can be injection molded onto
cooler walls of the mold (image 3). The parts
them (image i). Each core rod is inserted
are stripped from the core rods (image 4),
into a split mold and hot molten white PP is
counted by a laser sensor (image 5) and
molded around it. The necl< is fully formed
pressure tested (image 6). The parts (image
(image 2). The parts are rotated through
7) are then fed into a filling and capping
120° and are inserted into the blowing
system similar to the EBM process.
mold. Air is blown in through the core rod Stripper
Stage 1: injection molding the pre-form
and the plastic is forced to take the shape of the mold cavity. The polymer solidifies
Stage 3: Stripping
TECHNICAL DESCRIPTION The IBM process is based on a rotary table
blowing station. In stage 2, air is blown into
that transfers the parts onto each stage
the pre-form forcing the parison to take the
in the process. In stage 1, a pre-form is
shape of the mold. In stage 3. after sufficient
injection molded over a core rod with
cooling, the part is rotated through 120° and
finished neck details. The pre-form and
stripped from the core rod complete. No
Staged: Final product
core rod are transferred through 120° to the trimming or deflashing is needed.
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Featured Manufacturer Polimoon www.poiimoon.com
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Case Study
Injection stretch blow molding a chemical container The pre-form is injection molded over a
and blown to form the container (Image 3),
core rod, which is removed prior to blowing.
The blown product is ejected and does not
The injection molded part is thin walled,
require any trimming. It is demolded (image
as demonstrated by the operator (Image i).
4), pressure tested (image 5) and a handle
There is not usually operator contact with
is fitted around the neck of the injection
the parts during production. The pre-form
molded container, using an annular snap
is transferred to the blow molds (image 2),
fit (image 6).The container is then sent for
The molds close around the pre-form and it
capping (image 7).
is simultaneously stretched longitudinally
TECHNICAL DESCRIPTION In stage 1, the ISBM process uses the same technique as IBM, In that the pre¬ form is injection molded over a core rod. In stage 2, however, in ISBM the core rod is removed and replaced by a stretch rod. The pre-form is inserted
into the blow mold, which is clamped shut. In stage 3, air is blown in through the stretch rod, which simultaneously
Injection Stretch Blow Molding Process
orientates the pre-form longitudinally. In stage 4, the mold opens and the parts are stripped from the stretch rod. „ . Air blown Core rod
Stretch Air blown in—fj Molds separate
rod
Blown part
Injection molded pre-form Pre-form stretched longitudinally Stage 1: Injection Stage 2: Pre-form molded pre-form stretched and blown
Stage 3: Blowing cycle
8
Blown part ejected Featured Manufacturer Polimoon
Staged: Demolded and stripped
www.polimoon.com 7
Forming Technology
Thermoforming In this group of processes, thermoplastic sheet materials are formed with the use of heat and pressure. Low pressures are inexpensive and versatile, whereas higher pressures can produce surface finishes and details similar to injection molding.
Costs
Typical Applications
Suitability
• Low to moderate tooling costs • Low to moderate unit costs, roughly 3 times material cost
• Baths and shower trays • Packaging • Transportation and aerospace interiors
• Roll fed; batch to mass production • Sheet fed: one-off to batch production
Quality • Depends on material, pressure and technique
Related Processes • Composite laminating • Injection molding • Rotation and blow molding
Speed • Roll fed cycle time: 10 seconds to 1 minute • Sheet fed cycle time: 1-8 minutes
INTRODUCTION
while they are still hot. This complicated
There are 2 distinct categories of
process is more expensive than
finishes similarto injection molding.
thermoforming: sheet fed androli fed.
conventional thermoforming.
The tooling is more expensive, but for
Pressure forming can produce surface
Above left Textured light diffuser manufactured by
Above
vacuum forming.
sheet thermoforming.
Foam filledTerracover®
ice pallet made by twin
some applications it will be less than
Sheet fed thermoforming is for heavy duty applications, such as pallets, baths,
TYPICAL APPLICATIONS
shower trays and luggage.The sheet
Thermoforming is used extensively to
single-sided tool is used, as opposed to
material is typically cut to size and
produce everything from disposable
matched tooling which is required for
loaded by hand. Roll fed processes, on the
food packaging to heavy-duty returnable
injection molding.
other hand, are supplied by a roll of sheet
transit packaging. Some typical examples
for injection molding.This is because a
Twin sheet thermoforming is used to
Pressure forming produces a fine surface finish with excellent
material from areel. It is sometimes
include clear plastic point-of-sale
produce 3D hollow geometries. Similar
referred to as the 'in-line' process because
packaging,clamshell packaging, cosmetic
parts can be produced by blow molding
it thermoforms, trims and stacks in a
trays, drinking cups and briefcases.
(page 22) and rotation molding (page 36), yet the benefit of thermoforming is that
Thermoforming is typically carried out
lighting diffusers; bath and shower trays;
it is ideal for large and flat panels. Also,
on a single mold. In vacuum forming the
forming, pressure forming, plug-assisted
garden pots; signage; vending machines;
the 2 sides are not limited to the same
mold can be made from metal, wood
forming and twin sheet thermoforming.
small andlargetanks;motorcycle
colour or even type of material.
continuous operation. Thermoforming includes vacuum
This process is also used to produce
reproduction of detail.
DESIGN OPPORTUNITIES
or resin. Wood and resin are ideal for
fairings; interiors for cars, aeroplanes and
Material developments mean that
least expensive of these sheet forming
trains;housing for consumer electronics;
twin sheet thermoformed products will
A resin tool will last between io and
processes. A sheet of hot plastic is blown
and protective head gear.
sometimes have suitable characteristics
500 cycles, depending on complexity of
Vacuum forming is the simplest and
into a bubble and then sucked onto the
Blister packaging (bubble wrap) is
prototyping andlow volume production.
for parts that were previously made by
shape. For more products, aluminium
composite laminating (page 206).
molds are cast or machined.
surface of the tool. It is a single-sided
made by thermoforming. It is produced
tool and so only one side of the plastic
continuously on a roller, which is the
will be affected by its surface. In pressure
vacuum former, and is laminated to
QUALITY
inserts can be used to form re-entrant
forming the hot softened sheet is forced
seal air into the individual blisters
Heating and forming a sheet of
angles.They are typically inserted
into the mold with pressure. Higher
and provide protective cushioning for
thermoplastic stretches it.Aproperly
and removed manually. Routing or
pressure means that more complex
packaged goods.
designed mold will pull it in a uniform
cutting into the part after molding
Vacuum forming tooling can be
manner. Otherwise, the properties of the
can sometimes produce the same
including surface textures. For relatively
very inexpensive and so is suitable for
material will remain largely unchanged.
effect. Otherwise, parts can be molded
low volumes this process is capable of
prototypin g an d 10w volum e product! on.
Thus a combination of the mold finish,
separately and welded together.
and intricate details can be molded,
molding pressure and material will
producing parts similarto injection
molding (page 50). The above 2 processes are suited
Similarto othermolding operations
RELATED PROCESSES Low pressure thermoforming techniques
determine surface finish.
The side of thermoformed plastic
Many thermoplastic materials are suitable.Therefore, there are numerous decorative and functional opportunities
to forming shallow sheet geometries.
are versatile and inexpensive.This
sheet that comes into contact with
associated with each of them. Also,
For deep profiles the process is plug
is because the plastic is formed as
the tool will have an inferior finish
materials have been developed
assisted.The role of the plug is to push
a softened sheet, as opposed to a
to pressure formed parts. However,
forthermoforming.These include
the softened material into the recess,
mass of molten material.This sets
the reverse side will be smooth and
preprinted sheets (such as carbon
stretching it evenly.
thermoforming apart from many
unmarked.Therefore, parts are
fibre-effect), which are a coextrusion of
other plastic forming processes.
generally designed so that the
acrylonitrile butadiene styrene (ABS) and
the qualities of these processes with
However, the use of sheet increases
side that came into contact with the
poly methyl methacrylate (PMMA) with
the production of hollow parts. In
the material cost slightly.To minimize
tool is concealed in application.Tools
aprintedfilm sandwiched in between.
essence, 2 sheets are thermoformed
this some factories extrude their own
can be outward (male) or inward
These materials are usually affected by a
simultaneously and bonded together
materials.
(female) curving.
minimum order in the region of 3 tonnes.
Twin sheet thermoforming combines
o ~n o
TECHNICAL DESCRIPTION
Thermoforming Processes
Plug-assisted forming
Vacuum forming is a straightforward Heated and softened sheet
process and provides the foundation for the other thermoforming techniques. A sheet of
Sheet conforms to mold profile
Clamp ring Mold pushes up into sheet
material is heated to its softening point. This is different for each material. For example,
Female mold
the softening point of polystyrene (PS) is 127-182°C (261-360°F| and PP is U3-165°C
Air channels
(289-329°F). Certain materials, such as
1—
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It!
1——
Plug-assisted preheated sheet Forming the vacuum
HIPS, have a larger operating window (that
Twin sheet thermoforming
is, the temperature range in which they are
Air sucked out from both sides
formable), which makes them much easier
Upper mold
to thermoform.
fiH]
1 \
/
The softened plastic sheet is blown into a bubble, which stretches it in a uniform manner. The airflow is then reversed and
the tool is pushed up into the sheet. The Lower mold
material is drawn onto the surface of the
mold by vacuum at about 0.96 bar (14 psi).
Preheated sheet
Forming the vacuum Preheated sheets
To assist the flow of air, channels are drilled into the tool. They are located in recesses
Plug-assisted forming is used to bring
This forms an enclosed and thin walled
and across the surface of the mold to extract
the benefits of male mold forming to female
product. Both sides of the product are
the air as efficiently as possible.
parts because blowing a softened sheet into
functional, unlike the single sheet processes.
Pressure forming is the reverse of
a bubble stretches it evenly while draping
The machines are rotary. The clamps
vacuum forming; the sheet is formed onto
the sheet into a female mold produces more
transfer the sheet into the heating chamber,
the surface of the mold under approximately
localized stretching. The plug stretches
where it is raised to softening temperature;
6.9 bar (100 psi) of air pressure. This
the sheet prior to forming and so ensures
it Is then thermoformed and clamped; and
means that a greater level of detail can be
that there is adequate wall thickness for
finally rotated to the unloading station. The
achieved. Surface details on the mold will
deep profiles. Otherwise the material
2 sheets are thermoformed individually, one
be reproduced with much more accuracy
will tear. When the air Is drawn out, the
above the other. Once fully formed they are
than vacuum forming. Surface finish can be
sheet conforms to the mold profile and the
clamped together. Residual heat from the
more accurately controlled and is therefore
hydraulic plug retracts.
functional. However, like vacuum forming only one side of the sheet will be functional.
In twin sheet thermoforming, 2 sheets are thermoformed and clamped together.
Textures are sometimes necessary
Twin sheet thermoforming
COMPATIBLE MATERIALS
on the surface of the mold to assist the
Although almost all thermoplastic
flow of air and avoid air pockets forming.
materials can be thermoformed, the
These are known as 'open textures'.
most common are ABS, polyethylene
Sheet fed thermoforming is used to
terephthalate (PET) (including PETG, which is PET modified with glycol),
Top Above
is supplied by a reel and so is limited to
polypropylene (PP), polycarbonate (PC), high impact polystyrene (HIPS) andhigh
moldmaking material, thermoforming shaped by CNC machining, produced in a single
thermoforming enables the bond to form
o.i mm to 2.5 mm (0.004-0.1 in.).The size
density polyethylene (H DPE).The glycol in
with prolonged contact. The bond has similar
of part is typically restricted to 1.5 x 3.5 m
PETG reduces brittleness and premature
Textured design feature
strength to the parent material.
(5 x 11.5 ft), although some machines are
ageing. PETG is clear (almost like PC)
vacuum formed on mold
capable of dealing with sheets of 2.5 X4m (8 x13 ft).
and is therefore often the material of
made of microporous
process sheet materials ranging from i mm to 12 mm (0.04-0.47 in.). Roll fed
Draft angles are essential when Multilayered materials are
Forming the vacuum and clamping
walled parts. It is not usually practical
th erm oformi n g over protrusi on s, or m al e
choice for lighting diffusers and medical
Microporous aluminium Carpet covered
operation.
Middle
aluminium.
packaging, for example. of parts per minute. Roll fed machines
coextruded to provide benefits: for
produces 3D hollow parts.This has
forthe depth to exceed the diameter.
molds. This is because the heated plastic
COSTS
example, providing a barrier to moisture
added benefits including lightness
Materials can be stretched more evenly
sheet is expanded; as it cools it will shrink
Tooling costs are typically low to
are generally loaded by hand. This
or bacteria; different colours; and
and rigidity, insulation and 2 separate
over the surface of a deep profile using
by up to 2%. Different materials have
moderate, depending on the size,
increases labour costs.
sandwiching recycled material between
m ateri al s (upper an d 1 ower). Sin gl e sheet thermoforming is typically limited
plug-assisted forming.
films of virgin (aesthetic) material to reduce energy.
to only a single side of functionality.
mold will leave slight pimples.These
Textured sheets can be thermoformed
(see image, page 31, above left).Typically sheets are textured on one side and
Air channels on the surface of the
are automated, while sheet fed machines
different levels of shrinkage: for example,
complexity and quantity of parts. The
ABS will shrink 0,6% and H DPE 2%. A draft
most expensive tools are machined
ENVIRONMENTAL IMPACTS
angle of 2° is usually recommended.
aluminium.Tooling for pressure forming
This process Is only used to form
Twin sheet, on the other hand, provides
can be eliminated on aesthetic surfaces
is 30-50% more expensive than vacuum
thermoplastic materials, so the majority
functional surfaces on both sides.
with the use of microporous aluminium
thermoformed, and this will be more
forming, but is still considerably cheaper
of scrap can be recycled. Kaysersberg
molds (see image, top).This material
prominent in deeper and undulating
Pi asti cs, wh o provi ded th e extrudl n g the sheet material case study (page 34),
Foam can be molded into twin sheet,
The material stretches as it Is
so the smooth side is formed against
or be injected post-forming for added
has a much shorter molding lifespan
profiles.Therefore, care must be taken
than tooling for injection molding. The speed of thermoforming depends
the m old. There is a range of standard
rigidity and strength (see image, page
because the pores clog up eventually.
to avoid sharp corners and points where
on the selected process and material
produce only 1.4% scrap material; the rest
textures, which are cast or extruded by
31, above, right).
However, they are very useful for design
three corners meet.These will cause
thickness. Sheet fed processes typically
is recycled.
details (see image, middle), which would
excessive thinning and thus weak points.
the material manufacturer. Examples
produce 1-8 parts per minute. Roll
include frosted, haircell, lens, embossed
DESIGN CONSIDERATIONS
otherwise require hundreds of air
fed machines are generally faster and
and relief.
Thermoforming is ideal for shallow thin
channels (holes).
multiple cavity tools can make hundreds
ixtruding the sheet material aysersberg Plastics extrude sheet material
in operation the sheet is pulled through
to length. The finished sheets are stacked in
ar thermoforming. They can very accurately
the rollers. However, when the process
preparation for thermoforming.
Dntrol the quality of the material and mal :=> [=> i=> Flow and heating of polymer granules Costs Solidified part ejected
• Very high tooling costs but depends on complexity and number of cavities • Very low unit costs
Injection molding process
; Quality | • Very high surface finish I • Highly repeatable process
Speed
DESIGN OPPORTUNITIES
• injection cycle time is generally between 30 and 60 seconds
So much is practically possible with injection molding that restrictions generally come down to economics. The process is least expensive when using
INTRODUCTION
housingofcon sum erelectronics,plastic
of grades, colours and hardnesses. It can
a simple split mold. Most expensive
injection molding is a widely used and
cookware handles and buttons.
be solid or foamed. Reaction injection
are very complex shapes, which are
well-developed process that is excellent
for rapid production of identical parts
RELATED PROCESSES
Ejection cycle
TECHNICAL DESCRIPTION Polymer granules are dried to exactly
are made up of water cooling channels
the right water content and fed into the
[for temperature control), an injection
hopper. Any pigments are added at this
point (gate), runner systems (connecting
stage at between 0.5% and 5% dilution.
parts) and electronic measuring
The material is fed into the barrel,
equipment which continuously monitors
where it is simultaneously heated, mixed
temperature. Good heat dispersal
molding is used for a diverse range of
achievable in a range of sizes, from large
products, including foam moldings for
and moved towards the mold by the
within the tool is essential to ensure the
car bumpers to the tiniest widgets.
rotating action of the Archimedean screw.
steady flow of melted polymer through
The relative suitability of related
upholstering furniture and car seats, and
Retractable cores controlled by cams or
processes depends on factors such as
low volume production of car bumpers
The melted polymer is held In the barrel
the die cavity. To this end, some cores
hydraulics can make undercuts from
products. Accurately engineered tools
momentarily as the pressure builds up
part size and configuration, materials
and dashboards.
are machined from copper, which has
the sides, top or bottom of the tool
ready for injection into the mold cavity.
and high injection pressures are essential
being used,functional and aesthetic
with tight tolerances. It is used to create a huge diversity of our day-to-day plastic
for achieving excellent surface finish and reproduction of detail. Consequently, this
requirements, and budget.
Although injection molding is
simultaneously and will not affect the
QUALITY
cost significantly, depending on the
the melted plastic is injected into the die
The high pressures used during injection
complexity of the action.
cavity. Cycle time is determined by the
process is suitable only for high volume
very often the most desirable process
molding ensure good surface finish,
production runs.
due to its repeatability and speed,
There are many different variations
The least expensive injection molding tooling consists of 2 halves, known as the
size of the part and how long the polymer
male tool and female tool. But engineers
fine reproduction of detail and, most
are often integrated into the molding
takes to resolidify, and is usually between
and toolmakers are constantly pushing
cycle, so eliminating finishing processes
30 and 60 seconds.
the boundaries of the process with more
thermoforming (page 30) is a suitable
importantly, excellent repeatability.
alternative for certain sheet geometries,
of the most popular include gas-assisted
and extrusion Is more cost-effective
The downside of the high pressure is that the resolidified polymer has a
injection molding (page 58), multishot injection molding (page 60) and in-mold decoration (page 62).
for the production of continuous
tendency to shrink and warp. These
pearlescent,thermochromatic and
profiles.
defects can be designed out using rib
photochromatic effects, as well as vibrant
by injection molding can be prototyped
much better conductive qualities than aluminium or steel.
In-mold and insert film decoration
on injection molding technology. Some
Parts that will ultimately be made
The correct pressure is achieved and
details and careful flow analysis. Surface defects can include sink
such as printing. There is also a range of pigments available to produce metallic,
fluorescent and regular colour ranges. Inserts and snap-fits can be molded into
Clamping pressure Is maintained
multiple gates and multishot injection
shrinkage once the part is ejected.
of contrasting materials.
To eject the part, the tools move apart, the cores retract and force is applied
by the ejector pins to separate the part from the surface of the tool. The part is
TYPICAL APPLICATIONS
and produced in low volumes by vacuum
marks, weld lines and streaks of
Injection-molded parts can be found
pigment.Sink marks occur on the
in every market sector, in particular in
casting (page 40) and reaction injection molding (page 64). Both of these
surface opposite a rib detail, and
combine up to 6 materials in one
autom oti ve, i n dustri al an d h ous eh ol d
processes are used to form polyurethane
weld lines appear where the material
product.The combination possibilities
products.They include shopping baskets,
resin (PUR).This is a thermosetting
machined from either aluminium or tool
is forced to flow around obstacles, such
include density,rigidity, colour, texture
stationery, garden furniture,keypads, the
steel. The tools are very complex parts
plastic that Is available in a wide range
as holes and recesses.
and varying levels of transparency.
of the injection molding process. They
the product to assist assembly.
Multishot injection molding can
complex tooling, retractable cores,
after injection to minimize warpage and
dispensed onto a conveyor belt or holding container, sometimes by a robotic arm. Tools and cores are generally
DESIGN CONSIDERATIONS
Case Study
Designing for Injection molding is a
Manufacturing and assembling a Pedalite
complex and demanding task that involves designers, polymer specialists, engineers, toolmakers and molders. Full
This bicycle pedal light is powered by an
ensuring a 'right first time' product. The
collaboration by these experts will help
energy storage capacitor and microgenerator
technically challenging combined overmold
anatomy of the injection-molded parts as
realize the many benefits of this process.
rather than any form of chemical battery.
assembly, for instance, was approved at the
well as the internal mechanisms and parts,
It was designed by Product Partners, in
first-off tool trials.
Injection molding operates at high
The cutaway drawing (below) shows the
injection-molded casings very often have to
temperaturesandinjectsplasticized
conjunction with the ciient (Pedalite Limited),
material into the die cavity at high
toolmaker/molder (ENL Limited), gearbox
feasible Davall Gears were recruited to
case, specific spindle bearings have been used
pressure.This means that problems
manufacturer (Davall Gears) and polymer
provide expertise in gear ratios, gear
to satisfy legislations and the gear system is
distributor (Distrupol Limited).
detail design, materials specification and
designed for optimum energy generation.
can occur as a result of shrinkage and
A dose working partnership with ENL
stress build-up. Shrinkage can result in warpage, distortion, cracking and sink marks. Stress can build up in areas with
die cavity and so the material must be
fed into the thickest wall section and finish in the areas with the thinnest wall sections. For best results wall thickness should be uniform, or at least within io%. Uneven wall sections will
gloss areas are more expensive to
as mold preparation anddemolding,
produce different rates of cooling, which
produce than matt or textured ones.
increase the costs significantly.
cause the part to warp. The factors
that determine optimal wall thickness
COMPATIBLE MATERIALS
ENVIRONMENTAL IMPACTS
include cost,functional requirements
Almost all thermoplastic materials can
Thermoplastic scrap can be directly
and molding consideration.
be injection molded. It is also possible to
recycled in this process. Some
mold certain thermosetting plastics and
applications, such as medical andfood
metal powders in a polymer matrix.
packaging, require a high level of virgin material, whereas garden furniture may
of the part, while decreasing wall thickness; and secondly, they aid the
COSTS
require only 50% virgin material for
flow of material during molding. Ribs
Tooling costs are very high and depend
adequate structural integrity,hygiene
should not exceed 5 times the height of
on the number of cavities and cores and
and colouring capability.
the wall thickness. Therefore, it is often
the complexity of design. Injection molding can produce small parts very rapidly, especially because
Injection molded plastic is commonly associated with mass produced short term products, such as disposables.
All protruding features are treated as
multicavity tools can be used to increase
However, it is possible to design products
ribs and must be 'tied-in' (connected) to
production rates dramatically. Cycle time
so that they can be disassembled
the walls of the part to reduce air traps
is between 30 and 60 seconds, even for
easily, which is advantageous for both
and possible stress concentration points.
multiple cavity tools. Larger parts have
maintenance and recycling. If different
Holes and recesses are often integrated
longer cycle times, especially because the
types of materials are used, then snap
in part design in order to avoid costly
polymer will take longer to resolidify and so will need to be held in the tool while
fits and other mechanical fasteners
it cools.
and dispose of the parts with minimal
Injection molded parts are often finished with afine texture, which disguises surface imperfections. Large
about materials selection andmoldflow
lines and so forth.
path of least resistance as it enters the
secondary operations.
Polymer distributor Distrupol was consulted
problems of sinkage, flow marks, weid
The injected plastic will follow the
as opposed to fewer deep ribs.
MOLDFLOW ANALYSIS
and self-lubrication properties.
components in CAD to reduce potential
ejection from the tool.
recommended to use lots of shallow ribs,
chosen for its exceptional wear characteristics
successfully translated through the design,
design led to the modification of the
0.5° to avoid stressing the part during
design: firstly, they increase the strength
manufacture. Polyamide (PA) nylon was
analysis. Feedback on the developing
too small. Draft angles should be at least
Ribs serve a dual function in part
accommodate a fixed-space package. In this
ensured Product Partners'ideas were
development and toolmaking process,
sharp corners and draft angles that are
To ensure the gearbox concept was
Labour costs are relatively low. However,manual operations, such
make it more convenient to disassemble environmental impact.
MOLDING THE PEDALITE
ASSEMBLING THE PEDALITE
The raw material 1s a glass-filled nylon
There are many parts that make up the
that is white in its raw state, if a colour
Pedalite (see image, page 54). All of the
is required, then pigment is added. In
plastic parts are injection molded.The
this case a small quantity of Clariant
bearing locator is a friction fit, which
masterbatch yellow was used (Image i).
requires more precise tolerance than
The end result is a surprisingly vivid
can be achieved with injection molding.
yellow colouring.
Therefore, it is drilled post-forming
In normal operations, the injection
(image 6) and the bearing locator and
molding process takes place behind a
bearing inserted. The overmolded end
screen within the machine (image 2),
cap is fixed to the pedal housing with
but for the purposes of this case study
screw fixings (image 7). The reflectors
the dies are shown in close-up with the
snap fit into place (image 8), ensuring
screen open.
that all the components are held together
The polymer is melted and mixed
securely.The snap fits can be released so
before injection into the die cavity. Once
that the Pedalite can be dismantled for
the die cavity has been filled, packed
maintenance and recycling (image 9).
and clamped, and the polymer has
The finished product is installed by
resolidified, the male and female halves
conventional means onto a bicycle
of the mold move apart. The product
(image 10).
is held in the moving tool by the upper
Cycle pedal design is subject to
and lower retractable cores and the 2
considerable safety and technical
side-action cores (image 3), The injection
restrictions. Pedalite eliminates the
point is indicated by the sprue, which has
expense and inconvenience of battery
remained intact, to be removed either
replacement, as well as the negative
by hand or robotically. The 4 cores are
environmental Impact of battery disposal.
retracted in sequence, to reveal the true
The 24/7 light output of Pedalite does
complexity of this molding (image 4).
not replace existing cycle safety lighting,
Finally, the part is ejected from the mold
but supplements it and also provides a
by a series of ejector pins (image 5).
unique light 'signature' (lights moving up and down) that helps motorists judge their distance from the cyclist.
Featured Manufacturer
ENL www.enl.co.uk IO
ase Study
Moldflow analysis Prior to manufacturing, Moldflow software is
The examples below illustrate analysis of flow,
used to analyse and maximize the efficiency
warp, fibre orientation, cooling and stress,
the automotive hubcap for PolyOne (image 3)
This analysis too] is used to predict
it was possible to reduce stress and make sure
shrinkage and warping, which are the
all types of plastic injection molding and
MPI/FLOW
there were no air traps in critical areas.The
result of stresses built up during the
metal die casting. It brings together part
MPI/Flow simulates the filling and packing
colour scale indicates bulk stress.
molding process. The Information is
design, material selection, mold design and
phases in the molding process, helping to
The colour scale on the automotive
processing conditions to determine the
predict the behaviour of the material as it
Interior product manufactured by Resinex
processing parameters to minimize
manufacturability of the part. This reduces
flows through the die cavity. This is used to
and Gaertner & Lang (image 4) indicates
potential problems.
the costs and time delays associated with
optimize the location of the gate, balance
fill time in seconds. Appearance is very
otherwise unforeseen manufacturing
runner systems and predict potential
Important, so the flow analysis software
problems. It also maximizes the efficiency
problems. Different versions are used
was used to eliminate weld lines and colour
switchboard cabin (image 5). The analysis
of production and can reduce material
to simulate different plastic and metal
variation in critical areas. This was achieved
found that by reducing wall thickness
consumption with significant savings.
molding techniques.
by changing the location of the gate and
warp could be reduced by go%.
of a design. The software is suitable for
A 3D model of the required part is
The MPI/Flow is here demonstrated on
By changing the location of the gate on
MPI/WARP
used to specify material selection and
Any more than 5 mm (0.2 in.) warp
was unacceptable on this Efen electronic
On the CAD model for a Jokon
temperature of the runner system.
generated in a suitable computer aided
3 products. Two stages of an Abtec part are
automotive lamp assembly (image 6), it
design (CAD) or computer aided engineering
simulated (images 1 and 2) to demonstrate
was essential that the part did not warp
(CAE) software package.
confidence of fill, which is colour coded, MPI/
so that it would maintain a water-tight
Moldflow is a predictive analysis tool
Flow was used to simulate various
seal in application. Warpage was reduced
used to simulate the 3D model in production
gate positions and runner system
by 50% by optimizing wall thickness
to analyse filling, packing and cooling.
configurations.
(images 7 and 8).
Confidence Of Fill
MPI/COOL
Confidence Of Fill
MPI/Cool 1s used to analyse the design
Low 1
Low
of mold cooling circuits. Uniform cooling is important to make sure that the part does not warp and to minimize cycle times.
A filter housing manufactured by Hozelock shows the configuration of the mold cooling circuits (images 9 High
to 11). Changing the layout of the circuit reduced cycle time by 2 seconds and so saved more than 4% of the production cost; reducing the wall thickness reduced cycle time by 7.3 seconds and shot weight
[sec]
by 19,6%, saving 24% of the production costs. Combining the 2 produced 26.1% overall savings.
Featured Manufacturer
Moldflow www. m 0 Id flow, com
TECHNICAL DESCRIPTION
Gas-Assisted Injection Molding Process
Gas-assisted injection molding Partially filled die cavity
techniques were first used in mass production in 1985. Since then the
technology has steadily improved and
The Air Chair was designed by Jasper
is now into the third generation of development. Initially it was developed to overcome the problem of sink marks
Gas injection molding the Magis Air Chair
Modified injection molding equipment
caused by shrinking. A smalt amount of
gas was blown in during the injection polymer cooled before the tool opened.
Stage 1: Conventional injection molding
With very precise computer control,
it is now possible to gas fill long and Air pocket
complex moldings. Each cycle will be slightly different because the computer
breaching it. Finally, the gas is injected to
skin is aesthetic and therefore should not
produce a hollow section and make it rigid
(image i).The gas injection molding sequence
be filled. However, unfilled PP is not strong
but lightweight.
takes approximately 3 minutes (images 2-5).
enough to make the entire structure.
The sample cut from the leg of the Air
cycle to apply internal pressure as the
Two materials are used because the outer
Morrison and production began in 2000
The 2 layers of material in this sample are
The gas injection molding technique produces a plastic chair with a very good
Table shows 2 technologies (image 6). The
produced in a similar way to gas injection.
surface finish. It weighs only 4.5 kg (9.92 lb)
first is gas injection, which creates the hollow
The outer skin is injected first. The glass
and is capable of withstanding heavy use.
profile.The second technology is the thin skin
filled PP is injected behind it in a technique
around the outside of the material: there is a
known as 'packing out'. The second material
clear division between the outer unfilled PP
acts like a bubble of air and pushes the first
and the glass filled structural internal PP.
material further into the die cavity without
makes adjustments for slight changes in material properties and flow.
The process uses modified injection Injection continues
molding equipment, in stage 1, plastic
is injected into the mold cavity but does not completely fill it. In stage 2, gas is
Gas injected
injected, which forms a bubble In the molten plastic and forces It Into the
Stage 2: Gas injected
extremities of the mold. The plastic and gas injection cycles overlap. This
Finished part
produces a more even wall thickness
because as more plastic is injected the air pressure pushes It through the mold like a viscous bubble. The gas bubble maintains equal pressure even over long and narrow profiles. Wall thickness can be 3 mm (0.118 in.) or more. In stage 3, as the plastic cools and solidifies, the gas pressure is
Stage 3: Finished product
maintained. This minimizes shrinkage.
Less pressure is applied to the plastic because the gas assists its flow around the die cavity.
Featured Company Magis www.magisdesign.com
Multishot Injection Molding Process
Multishot injection molding a handheld gas detector Polymer B granules
This product is molded by Hymid for Crowcon.
molded over it. The TPE provides integral
are inserted into the mold by hand prior to
It is a handheld gas detection unit (image
features with hermetic seals, such as flexible
each injection cycle.
i). Multishot injection molding has very
buttons and a seal between the 2 halves.
important benefits that are essential for Platen rotates 180°
Rotating platen
Static platen
Part A rotated into die cavity ready for njection of polymer B
Moving and rotating platen
The mold half with the moldings rotates
The finished moldings are stacked (image 7) ready for assembly. The integral and
the effectiveness of this device, which is
through 180° (images 3 and 4), In doing so, it
flexible button detail is shown in the final
potentially lifesaving.The part is made up of
brings the solidified PC into alignment with
product (image 8).
a water clear polycarbonate (PC) body and
the second injection cavity. Then the finished
thermoplastic electrometric (TPE) covering.
molding is ejected (image 5) ready for the
The features of these materials are combined
next injection cycle to commence.
by multishot injection molding. This is a tricky combination because the
The knurled metal inserts (image 6) are incorporated in the PC by overmolding,These
materials operate at different temperatures.
Therefore, the runner system for the PC is heated with oil, whereas the TPE runner is cooled with water. Molten polymer A injected into lower die cavity
Of the 2 die cavities (image 2), the
Molten polymer B injection molded over solidified polymer A
Empty die cavity Stage 3: Rotation
Stage 2: Ejection
Stage 1: Injection
closest has just been injected with water clear PC, This gives the product rigidity, toughness and impact resistance. The
farthest die cavity is the PC with aTPE
TECHNICAL DESCRIPTION Injection molding 2 or more plastics together
In stage 1, polymers A and B are injected
In stage 2, the molds separate and the
is known as multishot or overmolding. The
at the same time Into different die cavities:
sprue is removed from molded polymer A.
difference is that multishot is carried out
polymer A is injected into the lower die
Meanwhile the finished molding is ejected
in the same tool. Overmolding is a term
cavity; meanwhile, polymer B is Injected
from the upper die cavity. The rotating
used to describe injection molding over
over a previously molded polymer A in the
platen spins to align molded polymer A with
any preformed material, including another
upper cavity. The molten polymers form a
the upper die cavity. In stage 3, the mold
thermoplastic, or metal insert, for example.
strong bond because they are fused together
closes again and the sequence of operations
under pressure.
is repeated.
The process of multishot Injection molding uses conventional Injection molding machines. It is possible to multishot up to 6 different materials simultaneously,
each one into a different die cavity in the same tool.
The tool is made up of 2 halves: one Is mounted onto a static platen, the other onto a rotating platen. Like conventional injection, this process can have complex cores, Inserts and other features.
Featured Manufacturer
Hymid Multi-Shot www.hymid.co,uk
TECHNICAL DESCRIPTION
In-Mold Decoration Process
Case Study
The in-mold decoration process is used Printed PC film loaded
to apply print to plastic products during
In-mold decoration Luceplan Lightdisc
injection molding, thus eliminating secondary operations such as printing and spraying. However, the cycle time of
injection molding is increased slightly. The process is used in the production of nearly every modern mobile phone, camera and other small injection molded product.
In stage 1, a printed PC film is loaded
Stage 1: Film inserted
side of the mold is textured to provide the
fixed in place (image 8). Then the 2 halves of
of the Luceplan Lightdisc (image i). It was
diffusing effect in the light (image 4). The
the Lightdisc are screwed together (image 9).
designed by Alberto Meda and Paolo Rizzatto
mold is clamped shut under 600 tonnes
The fixings are covered with a snap fit
in 2002. By incorporating in-mold decoration,
(66i US tons) of hydraulic pressure and the
enclosure (image 10), which means the whole
the diffuser acts as shade, too. Graphics and
injection molding takes place (image 5).The
product can be taken apart for maintenance
instructions are included on the in-mold film
part is demoldedby hand (image 6), but this
and recycling.
and this eliminates all secondary printing.
can also be carried out using a robot.
The process is similar to conventional
into the die cavity prior to injection molding. The print side is placed
This case study demonstrates the production
Plastic injected behind film
inwards, so that when it is injection
This finished molding is inspected prior
injection molding, except that a printed film
to assembly (image 7). Screw bosses are
is placed into the die cavity.
incorporated into the injection molding,
The film is prepared and placed into the
molded the print will be protected
so the assembly procedure is relatively
mold by hand (images 2 and 3).The opposite
behind a thin film of PC.
straightforward. The electrics are inserted and
In stage 2, when the hot plastic is injected in the die cavity, it bonds with
Conventional injection molding equipment
the PC film. (This is similar to multishot injection molding.) In stage 3, the film becomes integral with the injection molded plastic and has a seamless finish, with a printed surface.
Stage 2: Conventional Injection molding
If the surface of the mold is not flat or slightly curved then the film is
Finished part with printed surface
thermoformed to fit exactly. When the
hot plastic is injected it is forced against the mold face at pressures between 30
and 17,000 N/cm2 (20-11,720 psi). The pressure is determined by the type of material and surface finish. Another technique, known as insert
film molding, differs because the film is supplied as a continuous sheet. It is
Stage 3: Finished product
sucked into the die cavity by a strong vacuum (similar to the thermoforming process), the mold closes and the injection process follows.
8
Featured Company Luceplan www.Luceplan.com
9
IO
Cold Cure Foam Molding Process Part A: liquid isocyanate Part B: liquid polyol
Upper mold
Forming Technology
Reaction Injection Molding
Lower mold Upper mold raised
Runners Retractable core Steel framework
Bung inserted
Reaction injection molding (RIM) includes cold cure foam Core retracted
molding. Both processes are used to shape thermosetting foam by injecting thermosetting polyurethane resin (PUR) into a mold, where it reacts to form a foamed or solid part. Stage 1; Mold filled
• Low to moderate tooling costs, depending on the size and complexity of molding
Typical Applications
Suitability
• Automotive • Furniture • Sporting goods and toys
• One-off to high volume production
Stage 2: Polyurethane formed
Stage 3: Demolded and trimmed
TECHNICAL DESCRIPTION In stage 1, the molds are cleaned and a release agent is applied. Inserts and frames are then put into place and the
Quality • High quality moldings with good reproduction of detail
Related Processes
Speed
mold Is clamped shut. The 2 ingredients
• CNC machining • Injection molding • Vacuum casting
• Rapid cycle time (5-15 minutes), depending on complexity of molding
that react to form PUR are stored In separate containers. The polyol and
Isocyanate are fed Into the mixing head, where they are combined at high
INTRODUCTION
RIM is chosen a great deal in the
properties of the part are similar to
pressure. The predetermined quantities
injection molding.
of liquid chemicals are dispensed into the
These are low pressure, cold cure
automotive industry for products such as
processes. Cold cure foam molding
bumpers,under-bonnet applications and
is generally attributed to molding PL) R foam for upholstery and sports
car interiors. It is utilized in the medical
QUALITY
they begin to go through a chemical
and aerospace industries for niche
The quality of the surface finish is
exothermic reaction to create PUR.
equipment, whereas RIM covers molding
products and low volume production
determined by the surface of the mold.
mold at a low pressure. As they are mixed
During stage 2 the polymer begins to expand to fill the mold. The only pressure
The tooling can be produced in glass reinforced plastic (GRP), etched or alloyed
on the mold is from the expanding liquid,
RELATED PROCESSES
steel. Even though this is a low pressure
so molds have to be designed and filled to
Bulk foam geometries are also formed
process, the liquid PUR reproduces fine
volume production, this process is
by CNC machining (page 186) orfoam
surface textures and details very well.
commonly used to prototype parts
fabrication.This technique is often
that will be injection molded (page 50) because the tooling is much less
utilized to cover wooden structures in
DESIGN OPPORTUNITIES
upholstery (page 342). Foam molding is
This is an extremely versatile process
expensive than for injection molding,
becoming more widely used, for example,
as the mechanical properties of the
while repeatability and accuracy are high.
in the production of furniture and car
cured PUR can be designed to suit the
seats-new formulations of PURfoam
application.The flexibility of foam can
of the part. The upper and lower sections
TYPICAL APPLICATIONS
producing fewer isocyanates, so they are
range from semi-rigid to very rigid, and
of the mold are separated and the cores
Popular uses include domestic and
therefore less toxic.
the density can be adjusted from 40 kg/
are removed. The mold Is then cleaned
m3 to 400 kg/m3 (2.5-25 lb/ft3).The outer
and prepared for the next cycle.
all types of PUR including foam. In both
runs, too.
processes, the density and structure of PUR are chosen to suit the application.
As well as low, medium and high
commercial furniture such as chairs,
Vacuum casting (page 40) is used to form similar geometries in PUR,
skin andinnerfoam can have contrasting
and cushions.These processes are also
but is typically applied to smaller and
properties to form parts with a rigid skin
suitable for cushioning functions in
more complex shapes. Vacuum casting
andlightweight foam core, for example.
and RIM are chosen to prototype
safety and tactility in toys.
and manufacture low volumes.The
Above
Above
A predetermined measure of polyol and isocyanate is dispensed into a plastic bag to demonstrate the
The 2 liquids react and expand to form lightweight and flexible
expands the runners allow trapped air to
car, train and aeroplane seats, armrests
footwear, such as in the soles, and for
ensure even spread of the polymer while
it is still in its liquid state. As the polymer
RIM is similarto injection molding: parts can be textured and the surface
escape. A bung is Inserted in the gate to maintain internal pressure in the mold.
In stage 3, the product is demolded after 5-15 minutes. Shot and cycle times vary according to the size and complexity
reaction process.
foam.The reaction isi-way,so once the material has been
formed it cannot be modified except by CNC machining.
Case Study
Cold cure foam molding the Eye chair The Eye chair has a parallel Internal core,
the mold through the gate at the top
complex internal steel structure and plastic
(image 3). After 12 minutes the chemical
back plate for upholstery, so has a challenging
reaction is complete and the part can be
geometry for foam molding.
demolded.The 2 halves of the mold are
The first step in the molding cycle is
separated to reveal the foam product
the mold preparation. A release agent is
(image 4). The chair is removed from the
sprayed onto the internal surfaces of the
internal core and checked for any defects
mold (image ij.The steelwork is then loaded
(image 5). Excess flash is then removed
into the mold over the internal core and the
with a rotating trimmer (image 6). This
whole assembly is closed and clamped shut
foam seat is part of the Eye chair (image
(image 2). A predetermined quantity of polyol
7), which is upholstered (page 342) by Boss
and isocyanate are mixed and injected into
Design.
molding) or RRIM (reinforced reaction
be softer and are upholstered or covered.
injection molding). Finally,fibre mats
Closed-cell foams are self-skinning and
and other textiles can be molded in,
used in applications such as armrests.
XI
m > o
o O O r~ a
for improved resistance to tearing and stretching.
COSTS
The molds can be made in various
Tooling costs arelowtomoderate.They
materials, depending on the quantities
are considerably less than when tooling
and required surface finish. GRP is often
for injection molding due to reduced
used to produce molds for prototyping; it
pressure andtemperature.GRPtooling is
is relatively inexpensive and reduces lead
cheaper than aluminium and steel.
times. For production runs above 1,000,
Cycle time is quite rapid (5-15 minutes). Atypical mold will produce
units, aluminium or steel tools are used.
50 components per day.
DESIGN CONSIDERATIONS The size of part that can be molded ranges from minute to very large (up to
significantly. Prototyping and low volume
3 m/10 ft long).The polymer is very liquid
production require more labour Input.
printed with in~mold decoration.
in its non-catalysed state, so will easily
Preformed materials are used to decorate
fl ow aroun d 1 arg e an d complex m ol ds.
the surface of the part, and colour is
A predetermined quantity of PU R is
framework, the foam must be at least
mixed and Injected in each cycle to
10-15 mm (04-0.59 in.) larger, to ensure
ensure minimal waste. Flash has to
plastic molding processes. For example,
the structure is not visible on the surface
be trimmed from the molded part.
both thick and thin wall sections from
of the foam.
RIM has many advantages over other
5 mm (0.2 in.) upwards can be molded
The Eye chair is molded in cold cure MD1
This CAD visual shows the supporting metal framework, which is
are included in the molding for upholstery.
ENVIRONMENTAL IMPACTS
When foam molding over steel
specified by Pantone reference.
Above
Labour costs are low to moderate and automated processes reduce labour costs
Reconstituted foam blocks are often
Incorporated into the molded part to
into the same part. Also, inserts such as
COMPATIBLE MATERIALS
plywood laminates, plastic moldings,
PUR is the most suitable material
threaded bushes and metal structures
because it is available in a range of
during the reaction are harmful and
can be molded into the part (see
densities, colours and hardnesses. It can
known to cause asthma.The polyol/MDI
reduce virgin material consumption. The Isocyanates that are off gassed
formulation of around
overmolded with foam.
image, left). Fibre reinforcement can be
55lC
hardens in about 24 hours.
geometries to thermoforming and 1
temperature and slow dipping speed;
|1^0°F|, so as the tool cools and the wall
RELATED PROCESSES
Case Study
Dip molding a flexible bellow The pre-heated aluminium tools are dipped
ensuring that the viscous liquid does not fold
Compressed air is blown in, which frees the
in dilute silicone solution (image i).Ttie
over on itself and trap air (image 3). After 45
plastic part from the metal and allows it to be
silicone promotes the flow of liquid over the
seconds the tank is lowered to reveal the dip
removed (image 7).
surface of the tool and then acts as a release
molded parts (image 4), which are quickly
The inside of the final part is matt
agent once it has solidified. The water steams
inverted (image 5) and placed in an oven to
(replicating the tool) and the outside is
from the surface of the tool to leave a very
fully cure.
smooth and glossy (image 8).
thin film of concentrated silicone. The tools are mounted above the tank
They are removed from the oven and
lowered into a bath of cold water (image 6).
of room temperature liquid plastisol PVC
The water lowers the temperature of the tool
(image 2). They are submerged steadily.
enough for the operatorto handle the parts.
on the other hand, air bubbles can form if
There are many vivid colours available
the dipping speed is too fast. Prototyping Is essential to calculate the optimum dip
matt or foam-like finishes. PVC is also
speed and tool temperature.
available in clear, metallic, fluorescent
and parts can be produced with gloss,
and translucent grades.
DESIGN OPPORTUNITIES A major advantage is that tooling for
DESIGN CONSIDERATIONS
this process is very low cost. There is no
This process is only suitable for molding
pressure applied to the tool and wear
over a single tool, therefore the accuracy
is minimal with flexible materials,
of the outside details is difficult to
PVC Is the most suitable material for the
so the same tooling can be used for
maintain.The PVC will smooth over
prototyping and actual production. Multiple tools can be mounted together
features such as sharp corners.This will
dip process and so makes up the majority of dip molded and coated products. The environmental credibility of PVC
ENVIRONMENTAL IMPACTS
produce variable wall thicknesses, which
for simultaneous dipping to reduce cycle
can be a problem with protruding details
has been under Investigation In recent
time considerably.Typically, the tooling
because sufficient material may not
years due to dioxins, harmful organic
is machined or cast aluminium, and It 1s
build over them.
a male tool, which Is simpler to machine
Tool design is affected by the nature of the liquid material. Plastisol PVC is
compounds that are given off during both the production andthe incineration
than a cavity.
Wall thickness Is determined by 2
viscous and gels on contact with hot
the liquid polymer. It is also advised that radii are used to help the flow of plastic.
There are many additives, which are used to Improve the material's
in dip molding because the reaction
resistance, UV stability and temperature
process is i-way. It can be ground up and
avoid air bubbles in molten metal. This
resistance, and to reduce its toxicity
used In other applications.
means that sand casting is suitable for
for food-approved grades. The level of
metal. Therefore, flat surfaces, un dercuts
the dip time (dwell). Within reason, high
and holes become air traps if they are not
This is similar to sand casting (page 120), which requires draft angles and fillets to
temperatures and long dips produce thick wall sections. Wall thickness is
designed carefully. Air traps will stop the material coming Into contact with the
generally between 1 mm and 5 mm
hot metal tool, resulting in depressions and even holes where the material has
the production of the tooling because if it can be sand cast effectively then
plastlcizer affects the hardness of PVC.
(0.04-0.2 In.).
not gelled sufficiently. In contrast, air
chances are it will dip mold just as well.
to 100; whereby 30 is very soft and 100 is
include dual colour and different
traps might be deliberately designed into a tool to produce holes that would
COMPATIBLE MATERIALS
shore hardness. As well as the obvious
otherwise need to be punched as a
PVC is the most common material used
COSTS
aesthetic advantages, twin dip can
secondary operation.
for dip molding and coating. Other
Tooling costs are minimal. Cycle time is
To avoid air traps, a draft angle of
materials, in eluding nylon, silicone, latex
rapid and multiple tools reduce cycle
electrical insulation that wears to
between 5° and 15° is recommended on
and urethane, are also used, but only for
time dramatically.
highlight material thinning.
faces that are parallel to the surface of
specialist applications.
It is possible to dip twice to build
provide functional benefits, such as
Gelled material cannot be reused
flame retardant qualities, chemical
factors: the temperature of the tool and
up 2 layers of material.The advantages
of the material.
It Is available from shore hardness A 30 semi-rigid.
Labour costs are moderate.
Featured Manufacturer Cove Industries www.cove-industries.co.uk
Forming Technology
Panel Beating Smooth curves and undulating shapes in sheet metal can be produced with this sheet forming process. Combined with metal
INTRODUCTION Panel beating is controlled stretching
Manual panel beating is a highly skilled process. Coventry Prototype Panels
and compressing of sheet metal. Many
operate a 5-year apprenticeship, which
welding technologies, panel beating by a skilled operator is
techniques are used, including press
is required to learn all of the necessary
braking (page 148), dishing, crimping, wheel forming (English wheeling) and
skills. Wheeling and jig chasing are
capable of producing almost any shape.
jig chasing (hammerforming).These
both smooth and sharp multi-directional
processes in conjunction with arc
curves, embosses, beads andflanges.
1 Low to moderate tooling costs 1 Moderate to high unit costs
Quality High quality handmade
Typical Applications
Suitability
welding (page 288) produce almost any
• Aerospace • Automotive • Furniture
• One-off to low volume production
profile in sheet metal. Panel beating is
Related Processes Deep drawing Stamping Superforming
Speed • Long cycle time, dependent on the size and complexity of part
combined to form sheet materials into
TYPICAL APPLICATIONS
used in the automotive, aerospace and
Panel beating is used in prototyping,
furniture industries for prototyping, pre-
production and repair work for the
production and low volume production
automotive,furniture and aerospace
runs. It is used to produce the entire
industries. Examples of cars that are
chassis and bodywork of cars.
manufactured in this way include Spyker, Rolls Royce, Bentley, Austin Martin and
Above Dishing into a sand bag is now largely confined to prototyping.
CD
Right This Austin Healey 3000 was given a completely new body by Coventry Prototype Panels.
Jaguar. Designers Ron Arad and Ross Lovegrove harness the opportunities of these techniques to produce seamless
Surfaces are planished and polished (page 388) and a skilled operator can
A range of sheet materials can be formed, including stainless steel,
achieve a superior A-class'finish.These
aluminium and magnesium. Even
techniques are used to finish stainless
though magnesium is more expensive
RELATED PROCESSES
steel brightwork for Bentley production
than aluminium, it has superior strength
Stamping (page 82), deep drawing (page 88) and superforming (page 92) are
cars because the requirements of the
to weight and is approximately one-third
surface finish are so high.
lighter.
difference is that panel beating is labour
DESIGN OPPORTUNITIES
production, panel beating is used in
intensive and thus has higher unit costs.
The most important benefit for designers
combination with superforming.These
metal furniture, interiors and sculpture.
For low to medium volume
used to produce similar geometries. The
Stamping and deep drawing require
is that almost any shape can be produced
processes complement each other
matched tooling, which means very
in metal by panel beating. Large and
because superforming produces sheet
high investment costs but dramatically
small radius curves are produced with
profiles with a high surface finish in a
reduced unit costs and improved cycle
similar ease by a skilled operator. Sheets
single operation. Panel beating is used to
time.Therefore, panel beating is usually
can be embossed, beaded or flanged to
produce details such as fins, air intakes
reserved for production volumes of under
improve their rigidity without increasing
and beading that have re-entrant angles
1 o parts per year. Any m ore th an thi s an d
their weight.
and are not suitable for superforming in
it becomes more economical to invest in matched tooling or superforming.
Parts are not limited to the size of the
a single operation.
sheet metal because multiple forms can be seamlessly welded together. In fact,
DESIGN CONSIDERATIONS
QUALITY
most shapes are produced from multiple
A significant consideration is cost. A
Shaped metal profiles use the ductility
panels because they would be too
great deal of skill is required to produce
and strength of metals to produce
impractical to make from a single piece
accurate profiles with a high surface
lightweight and high strength parts.
of material.
finish.This means high labour costs.
Panel Beating Process
Epoxy or steel jig
Dishing into a sandbag
Jig chasing
It also means that there are very few
COSTS
facilities that can carry out such work.
Tooling costs are low to moderate
the level of skill required is very high.
Soft tooling (epoxy) is only suitable for production of up to 10 parts. After this
depending on the size and complexity.
Therefore, labour costs are high, but,
For one-offs and low volumes they
combined with low tooling, costs are
hard tooling in steel is required because
are 5-axis CNC machined (page 186)
considerably cheaper than start-up costs
the soft tooling will continuously have to be replaced. Material thickness is limited
from blocks of epoxy and can be used
for the related processes.
to 0.8 mm to 6 mm (0.024-0.236 in.)
tools are machined from steel, which is
for aluminium and 0.8 mm to 3 mm
considerably more expensive but still a
Panel beating is an efficient use of
(0.024- o.n8 in.) for steel.
great deal less expensive than tooling for
materials and energy.There is no scrap
stamping or superforming.
produced in the forming operations,
COMPATIBLE MATERIALS
Wheel
for up to 10 parts. For higher volumes
Cycle time is long but depends on
Planishing
can be shaped in this way. Aluminium,
is possible to construct the chassis and
bodywork of a car from 3D CAD drawings
operations.
most commonly used sheet materials.
in approximately 6 weeks.
Panel beating the Spyker C8 Spyder ofthe Spyker C8 Spyder in aluminium (image 1), In 1914 Spyker cars merged with the Dutch Aircraft Factory to combine
TECHNICAL DESCRIPTION
their skills in automotives, aircraft and Planishing is a finishing operation and
Panel beating is made up of different
epoxy, or 'hard' and made of steel. Epoxy
operations, such as dishing, jig chasing and
tools will typically only produce up to 10
is essentially smoothing over the surface
been producing lightweight and high
wheel forming. Planishing is used to produce
parts or so before the edge details are
with repeated and overlapping hammer
performance cars.They are manufactured
a smooth finish on panel beaten sheet metal.
too worn. Large circumference curves are
blows. Aflat-faced planishing hammer
in low volumes and so can be modified
typically formed by another method prior
or slap hammer are used to hammer the
to bespoke customer requirements. It is
for certain applications. They are useful
to jig chasing. For example, a sheet may be
surface gently against a dolly or dome. The
even possible for customers to watch cars
in the forming of deep profiles such as
wheel formed to the general shape of the
process stretches the metal slightly but is
being built by the skilled operators via a
motorcycle mudguards. Dishing is rapid,
tool and then jig chased to form accurate
not considered a forming operation. After
dedicated webcam in the factory.
but it is the least accurate and controllable
sheet metal shapes. An engineer's hammer
a succession of taps with the hammer, the
of the panel beating techniques. A wooden,
is used to beat a plastic or metal chaser
operator abrades the surface with a metal
handcrafted aluminium. Sheet
leather or plastic mallet (generally shaped
against the surface of the metal. Plastic
file to highlight remaining undulations. This
aluminium is cut to size (Image 2).
like a teardrop) is used to beat the metal
chasers are used for soft profiles and dish
process is repeated until the desired surface
A crimping machine is used to compress
into shape. With each blow the sand or metal
shapes, while metal chasers are used for
finish is required. After this the metal work
(gather) the metal together in a selected
shot displaces and conforms to the shape
tight bends, sharp angles and flat surfaces.
is sanded and polished.
area for increased curvature on the wheel
Bags of sand or metal shot are still used
of the profile of the hammer, which allows
Wheel forming is also known as English
the metal to be formed. It requires a great
Wheeling. It was developed and mastered by
deal of skill to stretch and compress the
panel beaters in early automotive production
metal accurately Into the bag. Hammering
in England. The metal workpiece is passed
into a shaped dolly or over a stake is more
back and forth between a wheel and an anvil.
accurate but less versatile.
The wheel is flat faced and the anvil has a
Jig chasing (also known as hammerformingl is the process of stretching
profile (crown). The role of the anvil is to stretch the sheet progressively with each
and compressing Igatheringl sheet metal
overlapping pass. Low-crown anvils produce
to conform to the shape of a CNC machined
a large radius curve and high-crown anvils
tool. The tool is either 'soft' and made of
produce a tighter bend.
although there may be scrap produced
magnesium and all types of steel are the
the size and complexity of the part. It
This case study illustrates the production Wheel forming
ENVIRONMENTAL IMPACTS
in the preparation (ofthe blank,for instance) and subsequent finishing
Most ferrous and non-ferrous metals
Case Study Preformed metal workpiece
This is a labour intensive process and
aerodynamics. Since then they have
The chassis and bodywork are
former (image 3). It works like 2 pairs of pliers, gripping and forcing the sheet together in tandem.
r other side of the metal by the operator
The wheel former is made up of a flat-
(image 12). It takes a great deal of skill and
faced wheel and a low- or high-crowned
anvil (image 4). The sheet is passed bacl< and
patience to achieve the desired finish.
forth between the rolls in overlapping strokes
The finished panels are polished to a very
(image 5). Each pass stretches the metal
smooth finish and spray painted. In the
slightly and so forms a 2-directional bow in
meantime, the brightwork is polished on
the sheet.
conventional polishing wheels (image 13).
When the correct curvature is
Assembly of the car engine, suspension
approximately achieved in the sheet, it is
and interior (images 14 and 15) is carried out
transferred onto the jig chaser. It is clamped
by Karmann in Germany.
onto the surface of the epoxy tool and gradually stretched and compressed to conform to the shape (image 6).The sheet is worked gently with a variety of chasers until it matches the shape of the epoxy tool precisely. Polyamide (PA) nylon chasers are used to stretch selected areas of the
sheet into embossed details (image 7). Aluminium chasers are used to form flat
>
areas (image 8).
The sheet is removed from the tool CD
m >
and holes are cut and filed (image 9). After this it is mounted onto the tool once again and reworked with an aluminium
chaser (image 10). The panels are shaped individually and then brought together on a jig. They are TIG welded (page 290) to form strong and seamless joints (image 11). Each weld is carefully levelled by grinding, planishing, filing and polishing. A slap hammer is used to planish the curved metal onto a dolly, which is held on the
7
Featured Manufacturer Coventry Prototype Panels 6
8
www.covproto.com
TECHNICAL DESCRIPTION
Spinning Process
In stage 1 of the spinning process, a
circular metal blank is loaded onto the tool (mandrel). In stage 2, the metal blank and mandrel are spun on the lathe and a rolling wheel forces the metal sheet onto
Forming Technology
Metal Spinning
the surface of the mandrel. This stage of
the process is similar to throwing clay on a potter's wheel. The metal is gradually
Spinning is the process of forming rotationally symmetrical sheet metal profiles. It is carried out on a single-sided tool, as progressive tooling or - in a process known as spinning on-air'
- without tooling at all.
shaped and thinned as it is pressed onto
INTRODUCTION
the mandrel. In this case the finished part
Although metal spinning is an industrial
cannot be removed from the mandrel until it
process, it has retained elements of
is trimmed. In stage 3, the mandrel is split
craft. The combination of these qualities
so that a re-entrant angle can be shaped
makes this a very satisfying process with
in the neck of the part. The top and bottom
which to work.
are trimmed and the part is demolded. The
Metal spinning can be utilized to form sheet profiles including cylinders,
whole process takes less than a minute.
Costs
Typical Applications
Suitability
cones and hemispheres. It is frequently
• Low tooling costs • Moderate unit costs
• Automotive and aerospace • Jewelry • Lighting and furniture
• One-offs and low to medium volume production
combined with punching, fabrication
Quality 1 • Variable: surface finish is largely dependent on the skill of the operator and the speed of the process
Related Processes
Speed
• Deep drawing • Metal stamping
• Moderate to rapid cycle time, depending on part size and complexity, and the type and thickness of material
DESIGN OPPORTUNITIES
or pressing to provide a wider range
Metal spinning is an adaptable process.
of design opportunities such as
Tooling for manually operated low
flanged edges, asymmetric profiles and
production runs is relatively inexpensive. This means that designers can realize
perforated shapes.
their ideas with this process early on and make structural and aesthetic adjustments to the 3D form. Ribs, undulations and surface texture can
be integrated into a single spinning operation. Steps or ribs can reduce wall thickness and so produce thinner and more cost-effective parts. Textures can be integrated onto only
1 side of the part because a low profile texture on the mold will not be visible on the opposite surface. Metal spinning
TYPICAL APPLICATIONS
of shapes and technical features. Simple
can also form meshes and perforated
This process is utilized in the furniture,
profiles can be extruded or fabricated
sheet materials.
lighting, kitchenware, automotive,
and time scales, quantities andbudget
aerospace and jewelry Industries. Some
determine the appropriate choice.
The tool (mandrel) can be male or female depending on the part geometry. In both cases only 1 tool is required, unlike
typical products made in this way include anglepoise lampshades, lamp
QUALITY
matched tooling used in deep drawing
stands, flanged caps and covers, clock
A very high finish is achievable by skilled
and stamping.Therefore, changes are
operators with manual and automated
relatively inexpensive and the tooling
processes.The quality of the inside
costs are considerably reduced.
facades, bowls and dishes.
RELATED PROCESSES Metal stamping (page 82) and deep drawing (page 88) are capable of
surface finish is determined by the mold and the outside surface finish is shaped
DESIGN CONSIDERATIONS
by the tool. Manual and automated
Metal spinning is limited to rotationally
producing similar profiles in sheet metal.
techniques are often combined for
symmetrical parts. The ideal shape for
Metal spinning is often combined with
optimum quality. There is no tooling for
this process is a hemisphere, where the
pressing and metal fabrication to achieve
spinning on-air and the inside surface
diameter is greater than or equal to
more complex geometries, a wider range
finish is therefore not affected.
twice the depth. Parts that have a greater
Case Study
Spinning the Grito lampshade A combination of automated and manual
determined by the design of the part. In
techniques is used to shape the Grito
this case manual metal spinning is required
lampshade. The metal blank is cut and
to achieve a re-entrant angle on the neck
loaded onto the mandrel (image i) and the
of the lampshade. This is made possible by
CNC metal rolling wheel guides the blank
splitting the mandrel inside the part so that
over the surface of the mandrel in stages
each piece can be removed independently.
(image 2). With each pass the metal sheet
The shape is worked by the craftsman,
is manipulated and controlled in much
who gradually improves the surface finish
the same way as clay throwing (page 172).
with a polished profiled metal tool (image
The metal can be drawn out and thinned,
7). Once spinning is complete, the surface
or simply pressed onto the surface of the
finish is improved further by polishing with
spinning mandrel. It takes only 30 seconds
an abrasive pad (image 8). The top and
to complete the first stage of the spinning
bottom are trimmed and the 2 parts of the
process (image 3).
mandrel removed. Post-spinning operations
The parts are made in batches, which
include punching in 2 stages (image 9) and
are stacked up in preparation for the next
painting. The parts are masked (image 10)
stage of spinning (image 4). The pre-spun
and then sprayed (image 11). The finished
parts are now loaded onto a manually
part (image 12) is slipped over the cord and
operated spinning lathe and worked by
bulb and is supported by the undercut in
hand (image 5). This requires a profiled
the neck.
tool (image 6), the shape of the too! being
depth than diameter are achievable but
runs. Materials include wood, plastic,
will greatly increase costs. Parallel sides
aluminium and steel. For large
and re-entrant angles are also possible.
production runs the metal tooling costs
However, this can entail multiple
are considerably cheaper than for metal
interlocking tools and will increase cost.
stamping and deep drawing because
Work hardening in steels Is another
metal spinning uses a single-sided tool.
consideration for a designer,This factor
Spinning on-air needs no tooling, but the
can prove advantageous: for example,
labour costs tend to be higher.
work hardening can increase the durability of a part. However, parts that
Cycle time is determined by the size and complexity of the part and the
need to be worked on after spinning have
choice of material. Forming aluminium
to be stress-relieved by heat treatment
is far quicker than steel because of its
processes, which is a disadvantage.
ductility and malleability. Steel may also
Small to very large parts can be metal spun up to 2.5 m (8 ft) in diameter and tolerances down to 1.5 mm (0.059 in.).
require heat treatment, which further increases cycle time. Labour costs can be moderate to high for manual operations, especially if a
COMPATIBLE MATERIALS
very high quality, A-class aesthetic finish
sheet is cut into a circle. However, waste
Mild steel, stainless steel, brass, copper,
is required. Automation reduces labour
metal is readily recycled. In operation, a
aluminium and titanium can all be
costs considerably.
small amount of metal is trimmed from the part, in order to finish the edges.
formed by metal spinning,
ENVIRONMENTAL IMPACTS
Energy requirements for this process
COSTS
The metal blank is often supplied as a
are quite low, especially if it is manually
Tooling costs can be very low, especially
square sheet, so there is waste produced
operated. The energy used is equivalent
for prototyping and low production
at the beginning of each cycle when the
to turning a lathe.
Featured Company Mathmos www,ma[hmos.co.uk
Metal Stamping Process
This cold metal pressing technique is used to form shallow sheet
sheet materials. Round, square and
polygonal shapes can be made with
and bend profiles in sheet metal. It is rapid and precise, and is
similar ease.
used to produce a wide range of everyday products from car
Ribs can be integrated into parts to reduce the required wall thickness.This
bodies to metal trays.
has a knock on effect in reducing weight and cost.
Shapes with compound curves and
TECHNICAL DESCRIPTION
Costs
Typical Applications
Suitability
complex undulating profiles can be
Metal stamping is carried out on a
• High tooling costs • Low to moderate unit costs
• Automotive • Consumer products • Furniture
• High volume production
formed between matched tools.The
punch press. The power is transferred
up to eject the part, which Is removed.
only other practical way of forming
to the punch by either hydraulic rams or
Sometimes the part is formed in a
these profiles is by panel beating, which is labour intensive and a highly skilled
mechanical means such as a flypress.
continuous strip, out of which it then
Hydraulic rams are generally preferred
has to be punched. This is common in
process. Soft tooling can be used to
because they supply even pressure
progressive die forming.
progress from panel beating to metal
throughout the stamping cycle. Even so,
Quality • High quality and precise bends as a result of matched tooling
Related Processes • Deep drawing • Metal spinning • Press braking
Speed • Rapid cycle time (under 1 second to 1 minute)
stamping.This is where 1 side of the tooling is made of semi-rigid rubber,
INTRODUCTION
TYPICAL APPLICATIONS
have to be drawn out and their wall
Metal stamping is used to describe forming shallow metal profiles between
Stamping is widely used. Most mass
thickness reduced.This has to be carried
matched steel tools.Tooling costs are
high and so this process is only suitable for high volume production.
production metalwork in the automotive industry is stamped or pressed. Examples include bodywork, door linings and trim. Metal camera bodies, mobile phones,
which applies enough pressure to form the metal blank over the punch.
out gradually and more slowly to avoid overstretching and tearing the material.
DESIGN CONSIDERATIONS
Superforming (page 92) can produce large and deep parts in a single
Stamping is carried out on a vertical to be formed with a secondary pressing
axis.Therefore, re-entrant angles have
flypresses still have their place in the metalworklng industry.
The punch and die (matched toolingl
After forming, the stripper rises
In progressive die forming the stamped metal workpiece would now be transferred to the next workstation. This is either carried out manually,
are dedicated and generally carry out
or by a transfer yoke. Most systems
a single operation such as forming or
are automated for very high-speed
punching. In operation, the metal blank
production. The next operation may be
is loaded onto the stripper. The punch
further pressing, punching, beading or
then clamps and forms the part in a
another secondary operation.
single stroke.
television housing, appliances and MP3
operation. However, it is limited to
precise shapes without significantly
players are formed by stamping. Kitchen
aluminium, magnesium and titanium
operation. Secondary operations include
reducing the material's thickness. It is
and office equipment, tools and cutlery
because they are the only materials with
further press forming, cutting, deburring
known as deep drawing (page 88) when the relationship between depth and
are made in this way. Not only are the
suitable superplastic properties.
and edge rolling.
0.4 mm and 2 mm (0.02-0.08 in.). It is
a single-sided steel tool and is only
external features stamped, but also much of the internal metalwork and
QUALITY
possible to stamp thicker sheet, up to 6 mm (0.236 in.), but this will affect the
capable of low volume production.
diameter mean that controlled drawing
The first stamping operation can only reduce the diameter of the blank by up to
is required, which slightly reduces the
structure is shaped in the same way.
Shaped metal profiles combine the
30%. Subsequent operations can reduce
shape that can be formed.
to ovenoo parts per minute. Changeover
ductility and strength of metals in parts
the diameter by 20%. This indicates the
with improved rigidity and lightness.
number or operations (workstations)
COMPATIBLE MATERIALS
required in the production of apart.
Most sheet metals can be formed in this
because this process is mechanized
way including carbon steel, stainless
It is a rapid process used to form
material's thickness during forming. Mass produced parts that require
RELATED PROCESSES
Cycle time is rapid and ranges from 1 and setup can be time consuming. Labour costs are generally low
multiple forming and cutting operations
Low volume parts are manufactured by
are produced with progressive dies,
panel beating (page 72) metal spinning
simply deburred after forming. Polishing
a process made up of a series of dies
(page 78) or press braking (page 148).
(page 388) is used to improved surface
this process are often determined by
steel, aluminium, magnesium, titanium,
and often fully automated. Finishing products by polishing will increase
working very rapidly and in tandem.
These can produce similar geometries
finish. Parts can also be powder coated
the capabilities of the machine; bed
copper, brass and zinc.
labour costs considerably.
While a part is being formed the
to metal stamping, but they are labour
size determines the size of blank and
second operation is being carried out
intensive and require skilled operators.
(page 356), spray painted (page 350) or electroplated (page 364).
stroke determines the length of draw
COSTS
ENVIRONMENTAL IMPACTS
simultaneously on the part that was
Even though stamping and deep
achievable. Speed is determined by stroke
Tooling costs are high because tools have
All scrap can be recycled. Metal stamping
to be machined precisely from high-
produces long lasting and durable items.
tooling is less expensive, but still requires
If appearance is not critical, parts are
As in deep drawing, the limits of
formed previously and so on. Parts may
drawing are similar, there are distinct
DESIGN OPPORTUNITIES
require 5 operations or more, which is
differences between them. Parts with a
These are rapid and precise methods
height andthe complexity of the part. The thickness of stainless steel that
reflected in the number of workstations.
depth greater than half their diameter
forforming shallow metal profiles from
can be stamped is generally between
strength tool steel. Semi-rigid rubber
Case Study
Blank preparation There are 2 main processes used to cut
s
out the blanks for metal pressing.The first is punching.The tooling is expensive and so it is limited to parts that are produced in high volumes and are relatively simple shapes (images 1 and 2). This example is the Cactus! bowl, made by stamping and punching. It was designed by Marta Sansoni and production began in 2002,
The alternative is to laser cut the parts. This can produce very complex blanks and thus reduce secondary operations
(images 3 and 4). The Mediterraneo bowl illustrated here was designed by Emma Silvestris in 2005.
Featured Manufacturer
Alessi www.alessi.com
Case Study
Metal stamping Stamping is used across many industries and
onto a spinning clamp, a rolling cutter is
for a wide range of applications. Alessi is an
introduced from the side and the excess is
example of a manufacturer who uses metal
trimmed (image 8). The formed parts are
pressing (stamping and deep drawing) to
stacked up in preparation for secondary
produce parts of the highest standard. The example that is used to demonstrate
operations (image 9). In this case, a small
bead of wire is rolled into the perimeter
the stamping process is a serving plate,
of the tray to give it rigidity. This helps to
which is formed in stainless steel sheet. It
reduce the gauge of metal used.
was designed by Jasper Morrison in 2000 (image 1). The metal blanks are laser cut in batches.
They are coated with a thin film of oil just prior to stamping (image 2). This is essential to ensure that the metal will slide between the die and punch during operation. The blank is loaded onto the tool and stamped (images 3-6). It is a rapid process and each part takes only a few seconds to complete. The part is removed from
Featured Manufacturer
the stripper (image 7). It is transferred
Alessi www.alessi.com
T
TECHNICAL DESCRIPTION
Secondary Pressing Processes
Case Study
Secondary pressing covers a range of processes, including further stamping,
Secondary pressing operations
bending, rolling, beading or embossing. Side action tools are used to create re-entrant angles that are not possible in a single operation.
page 263. If this product was manufactured
the edge ofthe plate; without a roll it would
secondary pressing and deburring operations.
in very large volumes, these processes would
feel very thin and would damage easily.
The first example is a product from the
Exchanging the punch for a roller die and spinning the part makes it possible to apply
These images demonstrate some typical
Kalisto family, designed by Clare Brass in 1992
Metal platform
(image 1). First of all the metal is deep drawn.
Side action
a bead, rolled edge or other detail that runs continuously around the product.
Stripper
Stage 2: Press
Stage 3; Strip
progressive die forming.
The stamped plate is placed onto a
Then it is placed onto separate tooling that
spinning clamp (image 5). There is a sequence
applies sideways pressure (image 2). The parts
of 3 operations, which include cutting (see
are spun against the side ofthe tool, forming
image 8, page 85), deburring (image 6) and
the side profile (image 3).
then edge rolling (image 7).
The second example is the Tralcio Muto Stage 1: Load
be combined into adjacent workstations as
The rolled edge increases the stiffness of
tray (image 4), which was designed for Alessi
the part and means thinner gauge steel can
by Marta Sansoni in 2000. It is punched on
be used (image 8). It also improves the feel of
¦¦
geometries. Simple cup-like geometries
i Hollow
Forming Technology
Deep Drawing
(which is restricted by stroke height and complexity of part).
can be produced in a single operation,
Surface finish is generally very good, but
while very deep parts and complex
depends on the quality of the punch and
geometries are made using progressive
die. Wrinkling and surface issues usually
dies or the reverse drawing technique.
occur around the edge, which is trimmed
Deep drawing relies on a combination of
Reverse drawing presses the sheet
post-forming.
a metal's malleability and resistance to
that forces a sheet metal blank into a closely matched die to produce sheet geometries. Very deep parts can be formed using progressive dies.
Typical Applications
Suitability
• Automotive and aerospace • Food and beverage packaging • Furniture and lighting
• Medium to high volume production
inverting the shape after the first draw.
DESIGN OPPORTUNITIES
Operating in this way accelerates
Various sheet geometries can be
cycle time and reduces the number
produced with the deep drawing,
Cold metal pressing is known as 'deep
of progressive tools required.
including cylindrical, box-shaped and
TECHNICAL DESCRIPTION
irregular profiles, which can be formed
The deep drawing process is carried
drawi n g' wh en th e depth of th e draw i s greater then the diameter (sometimes
TYPICAL APPLICATIONS
when the depth is only 0.5 times greater
The most common products
than the diameter).This process can
manufactured by deep drawing include
progressive dies or perpendicular action
be used to produce seamless sheet
beverage cans and kitchen sinks.
in the drawing press. However, this will
geometries without the need for any
However, these techniques are also
greatly increase the tooling costs.
further forming or joining operations.
used to produce a variety of items in
There is a limit to how much sheet
with straight, tapered or curved sides.
the automotive, aerospace, packaging,
DESIGN CONSIDERATIONS
furniture andlighting industries.
Depending on the type of material
Speed
• Good surface finish
• Metal spinning • Metal stamping • Superforming
• Rapid cycle time (a few seconds to several minutes), depending on the number of operations
out in different ways - the method
of process being determined by the
Undercuts can be achieved with
andthe type of material and sheet Related Processes
steels, zinc, copper and aluminium alloys.
INTRODUCTION
metal can be deformed in 1 operation,
Quality
COMPATIBLE MATERIALS
thinning.The most suitable materials are
material twice in a single operation,
In this cold metal forming process, the part is made by a punch
1 High to very high tooling cost 1 Moderate unit cost
QUALITY
complexity of the shape, depth of draw, material and thickness. In stage 1, a
sheet metal blank is loaded into the hydraulic press and clamped into the blank holder. In stage 2, as the blank holder progresses downwards the material flows over the sides of the
and thickness, parts ranging from less
lower die to form a symmetrical cup
thickness determine the level of
RELATED PROCESSES
than 5 mm to 500 mm (0.2-19.69 in.)
shape. In stage 3, the punch forces the
deformation. A variety of techniques
Shallow profiles are formed by metal
in diameter can be formed by deep
material through the lower die in the
are therefore used to produce different
stamping (page 82). Metal spinning (page 78), sheet ring rolling (see tube
drawing.The length of draw can be
opposite direction. The metal flows
up to 5 times the diameter of the part.
over the edge of the lower die to take
and section bending, page 98) and
Longer profiles require thicker materials
the shape of the punch. In stage U, the
superforming (page 92) can be used
because material thickness is reduced in
part is ejected.
to make similar geometries in sheet
long draws.
metal. Deep drawing and metal spinning
produce seamless parts that typically do
The tonnage of the press is
The limits of deep drawing are often
determined by the capabilities of the machine such as bed size (controls the
need to be welded post-forming.
determined by the tooling. Anything up to 1,000 tonnes may be applied to shape a long or large profile.
size of blank), stroke (determines the length of draw achievable) and speed
Deep Drawing Process Punch
Metal blank
Profile of first draw
Blank holder
Lower die
4 Stage 1: Load
Stage 2: Draw
Stage 3: Reverse draw
Stage 4: Finished part
r
Case Study
Deep drawing the Cribbio Blanks are cut to suit each deep drawing
metal to flow over the lower die (image 4).
(image 7). At this point the metal blank has
application. In this case, the Cribbio is circular,
The punch simultaneously forces the material
been forced through 2 progressive deep
so a circular blank is cut from a sheet of 0.8
inside the lower die (turning it inside out).
drawing cycles, which both applied reverse
mm (0.031 in.) carbon steel (image 1). The final
The first stage of this part's forming is
draw. Even though the Cribbio is a complex
part has a reduced wall thickness of 0.7 mm
complete and it is removed (image 5).
part to deep draw, production remains as
(0.028 in.) as a result of thinning during
The drawn part is loaded onto the second
high as 50 parts per hour. The top edge is then
drawing. A fine layer of oil is then applied
of the progressive dies (image 6). A punch
trimmed to remove any wrinkles and tearing
to both sides of the blank, forlubrication
forces the material into the lower die, turning
that may have occurred to the perimeter
(image 2).
it inside out once again.This process of
of the metal blank during clamping and
reverse deep drawing means that fewer
drawing (image 8) and so produce a clean
(image 3) on a 500 tonne press, which
tools are required to achieve the same length
edge detail. The parts are transferred onto a
progresses downwards, forcing the sheet
of draw. The drawn part is then removed
punch that perforates the surface (image 9).
The blank is loaded into the blank holder
Side actions are extremely expensive
to incorporate into the deep drawing cycle, so are often carried out postforming. After perforation a ring of
pressed metal is crimped over the top edge to create a safe and ergonomic
trim (images 10 and 11).The steel Cribbio is finished with a hardwearing epoxy
i
coating (image 12). 5
4
Metals with high resistance to thinning
to precise tolerances. Progressive
ENVIRONMENTAL IMPACTS
are less likely to tear, wrinkle or fracture
tooling, required to produce complex
Scrap is produced when the sheet
during processing, so thinner sheet
or especially deep parts, increases costs
material is cut to size and the finished
material can be used to start with,
considerably for this process.
part trimmed. Fortunately, all scrap
Cycle time is quite rapid but depends
COSTS
on the number of stages in the pressing
Tooling costs are very expensive because
cycle, while labour costs are moderate
the punch and die have to be engineered
due to th e 1 evel of autom ati on.
material can be recycled into new sheet Featured Manufacturer
metals or other metal products. Rexite www.rexite.il
Lett Tests show that a piece of superplastic aluminium alloy will stretch several times its length without breaking.
superplastic alloys such as 2014,2024, 2219 and 6061, making the process ideal for producing structural components.
Finite element analysis (FEA) flow simulation software helps to reduce the
Forming Technology
time needed to get from CAD design to
Superforming
superformed product.
TYPICAL APPLICATIONS This recently developed hot forming process is used to produce sheet metal parts following similar principles to thermoforming: a metal blank is heated to softening point and formed onto a single-sided tool using air pressure.
INTRODUCTION
The use of these processes to create
Superform alummium developed the
complex sheet geometries from a single
technique of superforming aluminium
piece of material has been rapidly
alloys and more recently magnesium
growing in many applications, including
alloys. The process was developed to
aerospace, automotive, buildings, trains,
reduce the weight of metal components
electronics,furniture and sculpture.
aerospace designers are beginning to
Superforming of 5083 is performed using the cavity or bubble forming technique.
RELATED PROCESSES
see the benefits that the superforming
A heat treatable alloy processed to
Metal stamping (page 82) and deep drawing (page 88) are used to make
of such alloys brings to the design and
give excellent superplasticforming
manufacture process. For example, they
properties-with component strains in
similar sheet metal geometries, while
eliminate costly fabrication work by
excess of 200%-is 2004, which allows
thermoforming (page 30) and composite laminating (page 206) produce similar
forming large parts from a single sheet,
complex detail to be achieved.Typical
thereby enhancing structural integrity
uses include electronic enclosures,
onto a single surface male or female
geometries in thermoplastics and glass
while reducing costs and improving
aerospace components and smaller
tool using air pressure. There are 4 main
reinforced plastic (GRP) composites.
repeatability.
complex form components. Unprotected
by minimizing fabrication operations and required wall thickness. Typical Applications
Suitability
• Aerospace • Automotive • Furniture
• Low to medium volume production
Quality
Related Processes
Speed
• Very good surface finish
• Deep drawing • Metal stamping • Thermoforming
• Rapid cycle time (5-20 minutes! • Trimming and assembly operations increase overall processing time
Low to moderate tooling costs Moderate to high unit costs
.
Superforming is a hot metal forming process that uses similar principles
to thermoforming plastics (page 30). A sheet of aluminium is heated to 450-5000C (840-9320F) and then forced
types of superforming: cavity, bubble,
successfully shaping such materials, and
Another advantage of the
2004has similar corrosion resistance
backpressure and diaphragm. Each of
QUALITY
superforming process is the range of
these techniques has been developed to
The surface finish on the tool and the
aluminium alloys that can be formed,
alloys. In most service situations it
fulfil specific application requirements.
accuracy of any post-forming operations
providing solutions to virtually any
is necessary to have some form of
affect the quality of a superformed part. Like thermoforming, the side of the sheet
engineering problem.
complex parts such as automotive body
panels and is excellent for shaping 5083
that does not come into contact with the
magnesium and manganese. It is used
enhance the corrosion resistance of these
aluminium alloy.
mold will have the highest quality finish.
for applications requiring a weldable moderate strength alloy having good
give enhanced corrosion resistance.
Cavity forming is good for large and
Bubble forming is suitable for deep
Typically, the aluminium alloys exhibit
The alloy 5083 contains aluminium,
to other copper containing aluminium
surface protection. Cladding with pure aluminium is commonly used to
alloys with Clad 2004 being designed to The alloy 7475 contains aluminium,
complex components, especially where
good corrosion resistance, mechanical
corrosion resistance. As such it is an
wall thickness needs to remain relatively
strength and surface finish.The alloys
excellent all-round alloy and ideal
constant.This process can be used
that are suitable for superforming have
for many applications. Superformed
suitable for applications requiring the
to manufacture geometries that are
differing characteristics, which make
high strength of 7075 and increased
impossible to achieve using any other
them useful for a variety of applications.
components using 5083 alloy sheet are supplied in the 0 temper and offer many advantages over parts fabricated
DESIGN OPPORTUNITIES
from 1200 or 3000 series and other
is approximately the same as that of 7075 combined with toughness similar
developed to produce structural aircraft
Like other aluminium parts, superformed
5000 series alloys. Simple or complex 3D
to 2024-T3 at room temperature. Its
components in 7475 alloys. Although
components can undergo a range of
sheet geometries can be manufactured
high strength to weight ratio allows
similarto cavityforming,the process
post-forming operations to achieve the
as a single piece forming with high
its extensive use within the aerospace
differs by using air pressure from both sides of the sheet. It is gradually pulled
final desired part or assembly.
quality surface finish, making 5083
industry for structural components.
forming process. The backpressure forming process was
The diaphragm forming process can
zinc, magnesium and copper. It is
fracture toughness.The sheet's strength
particularly suitable for automotive, rail,
Resistance to stress corrosion cracking
onto the surface of the tool using slight
be used to form parts that are generally
architectural and marine applications.
and exfoliation are similar to that of
pressure differential.This maintains the
classified as 'non-superplastic'.This
This alloy allows a good compromise
7075.The T76 type temper provides for
integrity of the sheet and means that
allows alloys used for aircraft structures,
between formability and corrosion
improved exfoliation resistance over
'difficult' alloys can be formed.
such as 2014,2024,2219 and 6o5i,to be
resistance, combined with moderate
T6 type temper, with some decrease in
superformed. In many cases diaphragm
strength.Typical applications of 5083
strength. Stress corrosion cracking in
forming is the only practical way of
include transportation and construction.
7475 T76 is not anticipated if the total
Diaphragm forming is used to shape complex sheet geometries in non-
TECHNICAL DESCRIPTION
Superforming Process
In all U superforming processes a sheet of
Cavity forming
metal is loaded into the machine, clamped in place and heated to between 450°C and
500°C (840-932oF). The temperature is determined by the type and thickness of sheet material. Stage 1; Preheated sheet loaded stage 2; Pressure applied
In cavity forming, the hot metal sheet is forced onto the inside surface of the tool by air pressure at 1-30 bar (U.5-435 psi|. The
Bubble forming
LUl
hot metal is superplastic and so forms easily over complex and intricate shapes. This process is generally used to manufacture
EH]
large shallow parts.
Bubble forming is similar to Stage 2: Vacuum applied
thermoforming. In stage 1, the hot metal
sheet is blown into a bubble and the tool rises into the mold chamber. In stage 2, the Stage 1; Preheated sheet loaded and blown
pressure is then reversed and the bubble of
Backpressure forming
the tool. This process is ideal for deep and
metal is forced onto the outside surface of
complex parts. The wall thickness is uniform because the bubble process stretches the material evenly prior to forming.
D 1} Stage 1: Preheated sheet loaded Stage 2: Pressure applied
Backpressure forming is very similar
to cavity forming. The difference is that in backpressure forming air pressure is also
applied to the reverse side of the hot metal sheet as it is being superformed. In this way
Diaphragm forming
the forming process is more controlled and
allowing unrestrained movement of the
the metal bubble. Only a virtual image of
can be retracted (image 4). The part is now
reduces the stress on the hot metal sheet.
component sheet.
this stage of the process is shown in image
formed and ready for trimming and any
2 because the metal sheet is not usually
other post-forming operations.
Diaphragm forming was developed to
1} ft D Stage 1: Preheated sheet loaded Stage 2: Pressure applied
superform so-called 'non-superplastic'
THE BUBBLE FORMING SEQUENCE
translucent. As the tool rises up the hot
alloys. It can achieve this because the
The bubble forming sequence shows how
metal is forced onto its surface by air
metallic sheet diaphragm supports the
aluminium is superformed. The hot metal
pressure (image 3). The tool continues to
hot metal sheet and aids the flow of
sheet is blown Into a bubble in the molding
rise and the metal is forced onto it until the
material into complex 3D profiles, by
chamber (image 1). The tool rises up into
forming process is complete and the tool
sustained tensile stress is less than 25%
produce parts up to 950 x 650 x 300 mm
Primary structure applications for the
In the formed condition the alloy has
COSTS
of the minimum specified yield strength.
(37 x 26 x 12 in.) and 6 mm (0.236 in.) thick.
aerospace industry require high strength
suitable mechanical properties for
Although tooling costs can be quite low
Backpressure forming has a maximum
alloys accompanied with good service
internal fittings such as kicking panels andlight fittings.
compared to matched die tooling, they do depend on the size and complexity
DESIGN CONSIDERATIONS
plan area of roughly 4,500 mm2 (6.97
properties such as fatigue toughness
The maximum size of part that
in.2), and diaphragm forming can be used
and stress corrosion resistance.These
can be formed is different for each
to produce parts up to 2,800 x 1,600 x
requirements are adequately met
COMPATIBLE MATERIALS
superforming technique. In each case, 1
600 mm (110 x 63x24 in.).
with the alloy 7475, which has been
Superplastic metals that can be shaped
of the limiting dimensions can often be
Different alloys have different
of the part. Cycle time is rapid, typically
successfully used to form air intake
in this manner include aluminium,
exceeded depending on part geometry
mechanical and physical properties, and
lip skins and access door assemblies,
magnesium and titanium alloys.The
and alloy selection.
this must be taken into consideration
for example. For less demanding
most commonly formed aluminium
Cavity forming can be used to produce
5-20 minutes.
Labour costs are moderate. Each part is trimmed and cleaned post-forming.
ENVIRONMENTAL IMPACTS
during the design process. It may well
applications the heat-treated version
sheet materials include 5083,2004
Scrap and offcuts are recycled to produce
parts up to 3,000 x2,000 x600 mm (n8
be possible to form a complex shape in
of 2004 has found many applications
and 7475.
new sheets of aluminium and other
x 79 x 24in.) and 10 mm (0.4in.) thick,
i alloy, but that alloy may not have the
for secondary structures such as
while bubble forming can be used to
properties requiredfor in-service use.
aerodynamicfairings and stiffeners.
aluminium products.
Case Study
Superforming the Siemens Desiro train facade The aluminium sheet is loaded into the superforming mold (image i).The clamps are brought down onto the perimeter of the sheet (image 2) and the temperature increased to 4500C (8400F). The superforming cycle takes approximately 50 minutes, after which the part is unloaded (image 3).The demolded part is loaded onto a support structure and CNC trimmed and machined (image 4),The scale and complexity of the part can vary greatly before it is assembled (image 5). The train front is made in 2 halves so it has to be tungsten inert gas (TIG) welded to form the complete front unit. The 2
oi
c
halves are brought together in a specially
n m
designed jig (image 6) and welded (image
o
7). CAD renderings are available of the Siemens Desiro train facade, which the
panels are destined to become (image 8).
50 Tl
xi
Forming Technology
Tube and Section Bending Used mainly in the furniture, automotive and construction industries, this process is used to form continuous and fluid metal structures. Tight bends can be formed with a mandrel over a rotating die, or long and undulating curves between rollers.
Costs r] • No cost for standard tooling i • Moderate to high cost for specialized tooling • Low to moderate unit costs
INTRODUCTION
Steam bent (page 198) furniture was
Architects and designers have long
the precursor to tubular steel and uses
utilized the functional and aesthetic
similar bending techniques.Tubular
properties of bent metal, especially
steel was developed in Germany for the
tubular steel. Bending methods are
automotive and aerospace industries,
generally inexpensive and make use
andThonet saw its potential. In the 1920s
of the ductility and strength of metal.
they began developing tubular steel
Bending minimizes cutting andjoining
furniture with members of the Bauhaus,
Typical Applications
Suitability
in certain applications, which reduces
including Mart Stam, Marcel Breuer and
profiles with multiple bends on a suitably Above, left
• Construction • Furniture • Transport and automotive
• One-off to high volume production
waste and cost.
Mies van der Rohe. Many of the designs
shaped punch. An example of this is
from this time are still in production.
chairs are commonly
hexagonal lampposts that are tapered
Above Ring rolling can shape tube, extruded profile
produced by mandrel
and metal sheets. The
along their length.
bending.
arc can be adjusted along its length to give
There are 2 main types of tube and section bending, which are mandrel
Quality • High
CD m >
Related Processes • Arc welding • Press braking • Swaging
Speed • Rapid cycle time • Machine setup time can be long
in
bending and ring rolling (see images,
TYPICAL APPLICATIONS
opposite, above).
Metalwork is either bent as a continuous
profiles to roll forging (page 114). The
Mandrel bending is specifically designed for making small radii in metal
length, or fabricated using cast or
difference is that roll forged components
sections. Many products are formed by
is inserted into the metal tube to prevent
mandrel bending, including domestic
it from collapsing during bending. Ring
and office furniture, security fencing
rolling is used to form continuous and
and automotive applications (such as ,
generally larger bends in both tube and
exhaust pipes).
commonly known as section bending.
Ring rolling can produce similar
non-circular bends.
pre-bent 'elbows' to join straight
tube. It is named after the mandrel that
section (extruded profile or bar). It is also
The legs of tables and
Mandrel Bending Process
Ring rolling can be used to bend a range of profiles (tube, extrusions and bar) into large-radius bends. Many products are formed using this technique such as structural beams (for
bridges and buildings), architectural trims (on curved facades) and street
Mandrel Stage 1: Load
Stage 2: 90° bend
furniture. In fact, most bent metalwork in construction will be processed using ring rolling. Rolling sheet materials is known as plate rolling.
It is even possible to produce 3D section bends such as the tracks on a rollercoaster, which can be achieved with careful manipulation on aring roller.
RELATED PROCESSES
TECHNICAL DESCRIPTION The metal blank Itubel Is loaded over
inside of the bend, especially for very thin
the mandrel and clamped onto the die.
walled sections.
Non-mandrel forming Is only possible for certain parts with thicker walls.
The blank Is drawn onto the rotating die as It spins, and the mandrel stops the walls collapsing at the point of bending. The pressure clamp travels with the tube
Tubular metalwork consists of mainly
to maintain an accurate and wrinkle free
bending,press braking (page 148) and arc welding (page 282). Press braking is capable of producing taperedhollow
bend. An additional clamp Is sometimes required to prevent wrinkling on the
The size of the rotating die determines the radius of the bend. The distance travelled determines the angle of bend.
m o
z D
Case Study
Mandrel bending the S4.3 chair Mart Stam designed the S43 chair (image 1),
to forming, because it is much more easily
and back are laminated, CNC machined and
which was introduced by Thonet in 1931. In
done at this stage. The blank is loaded by
lacquered in preparation (images 12 and 13).
1926 it began as a chair made from straight
hand over the mandrel and into the pressure
The final parts are brought together and
sections of gas pipe connected with cast
clamps (image 4).
assembled with rivets (image 14), The careful
'eibows'.The design was later refined and
The CNC machine aligns the tube and
design, refinement and production of this
produced by Thonet from a single, continuous
the bending sequence begins.The first bend
chair make the process look easy. The final
bent steel tube. It has since been made using
is made at the start point (image 5). From
product is simple, lightweight and uses the
the same technique; the only difference is
there, the blank is extended and twisted to
minimum material (image 15).
that new technology is making the process
the second bend point and so on (images 6,
faster and more accurate. The majority
7 and 8). The operation is precisely controlled
of mandrel bending is still performed on
and there is no scrap; the bending process
semi-automated machines because set ud
uses the entire length of tube. When the
time is quicker and tooling is less expensive.
process is complete the bent structure is
However, it is much more cost effective in the
removed by hand and each piece is checked
long run to produce large volumes on fully
for accuracy (image 9) and then hung up
automated machines.
(image 10).
The steel tube, or blank (image 2), is carefully cleaned and polished (image 3) prior
Featured Manufacturer
Thonet www.thonet.de
The bent metal forms are metal plated prior to assembly (image 11). The wooden seat
TECHNICAL DESCRIPTION
Ring Rolling Process
Metal section
Ring rolling is much simpler than mandrel bending in operation. The tube, profile, or sheet is passed between 3 rollers. One of the rollers,
in this case the bottom right, is moved Inwards to make the bend tighter.
The radius of the bend is decreased gradually over several cycles to avoid
cracking or wrinkling the metal. The blank is rolled back and forth until the curve meets the required shape.
Case Study
Ring rolling In this process metal tube is cut to length (image 1) and fed into the rollers. The rollers are adjusted to gradually bend the pipe into the desired radius (image 2), As the rollers move closer together the radius of the bend will be decreased. These are parts of a larger structure,
which do not require a tight radius (image 3), In this case the process is being
Dynamic rotating roller
used to bend tubular steel; a range of profiles and flat sections can be bent, but
Rotating cores (spindles)
require rollers with fitting profiles.
The aesthetic quality of manual
tooling can be very expensive, especially
or sheet,The thickest solid section that
operations, such as mandrel bends, is
for large section bending). It is possible
can be ring rolled is 80 mm (3.15 in.),
largely dependent on the skill of the
to form either a specific section or the
whereas roll forging can produce solid
operator and their experience with the
complete length; metal rings can be
parts of up to 150 tonnes (165 US tons).
particular machine set up.The dies are
formed along their entire length and
Roll forging is sometimes referred to as
often not exact, so an operator must
welded (see image, left).The radius does
'ring rolling', which can be confusing.
know how to compensate for optimum
not have to be constant; this process
bend angles. Automated and CNC
can be used to produce arcs that do not
operations are more precise.
fit into a circle.This technique is used
to the length apiece of material once it
COSTS
predominantly in the construction
has been bent.
Standard tooling is used to produce
are solid and ring rolled parts are hollow
QUALITY Applying a bend to a sheet of material increases its strength; these processes
DESIGN OPPORTUNITIES
combine the ductility and strength of
Mandrel bending is more versatile than
metals to produce parts with improved rigidity and lightness.
ring rolling for certain applications;
industry for structural beams.
In mandrel bending, the maximum
are bending lengths or forming rings.
size of tube is typically 80 mm (3,15 in.), but depends on the tooling available.
a variety of bend radii can be applied
Lengths of tube up to i m (3.3 ft) in
Wall thickness ranges from 0.5 mm to
to a single length of metal across any
diameter can be bent. Alternatively,
2 mm (0.002-0.079 in.).
axis. However, it is limited to relatively
metal sheet 4.5 m (14.8 ft) wide can be
The 2 main functions of ring rolling
Minimum bend radius is typically
a wide range of bent geometries.
Specialized tooling will increase the unit price considerably,but will depend on the size and complexity of the bend. Cycle time 1s rapid In most operations. Labour costs are high for manual
small diameter tube and can only form
rolled to form a tube, or cone, in materials
around 50 mm (2 in.). However,bends
operations, because a high level of skill
bends up to 200 mm (7.87 in.) radius. It
have to fit into the equipment; in other
and experience is required to produce
is suitable for one-offs, batch and mass
up to 80 mm thick (plate rolling), Lengths of metal, including profile, tube
words, several bends in close proximity
accurate bends,
production.
and sheet, can be rolled into rings, the
may not be feasible.
The advantage of ring rolling is that it is capable of producing a range of bends
maximum radius of which is determined by the capabilities of the manufacturer,
in almost any metal profile (although it must be remembered that specialized
Left Continuous circular metal profiles, such as these heating elements,
are produced by ring rolling and then arc welding the seam.
Mandrel bending is capable of
ENVIRONMENTAL IMPACTS
producing tight bends because the
Bending, as opposed to cutting and
internal mandrel prevents wrinkling
weld1ng,1s generally less wasteful and a
DESIGN CONSIDERATIONS
and failure. Ring rolling does not use a
more efficient use of energy. There is no
All of the bending processes stretch
mandrel and so is generally limited to
scrap produced in the bending operation,
material on the outside of the bend and
bend radii above 200 mm (7.87 in.).
although there maybe scrap produced in the preparation (of a blank for instance)
COMPATIBLE MATERIALS
and subsequent finishing operations.
compress material on the inside of the bend. However, metal is more willing to stretch than compress. Therefore, a bent
Almost all metals can be formed in this
piece of metal will be slightly longer,
way including steel, aluminium, copper
especially the outside dimension. This
and titanium. Ductile metals will bend
means that the length of a piece of
more easily.
material on a drawing rarely corresponds
Featured Manufacturer
Pipecraft www,pipecraft,co.uk
Rotary Swaging Process
Hammer block
Forming Technology
Swaging
Channel
There are 2 swaging techniques, hammering and pressing. These processes are used to reduce or expand metal pipe into tapers, joints or sealed ends.
INTRODUCTION
Pressing is a hydraulic operation and
Swaging is the manipulation of metal
is often referred to as'endforming'.The
tube, rod or wire, in a die. It is typically
pressing action is applied from multiple
used to reduce cross section by
angles simultaneously and can be used
drawing out the material, but pressing
to expand or reduce the diameter of pipe,
Die opening control key Open
techniques are also capable of expanding
the diameter of pipe by stretching. Hammering techniques are a rotary
TYPICAL APPLICATIONS Applications for swaging are diverse.
TECHNICAL DESCRIPTION
Cost
Typical Applications
Suitability
operation, known as rotary swaging and
It is used to form large parts such as
In rotary swaging, the metal is
and the hammer block rolls fall between
• Low to moderate tooling costs • Low to moderate unit costs
• Probes and spikes • Rigging • Telescopic poles
• One-off to high volume production
tube tapering.The ideal angle of taper
cylindrical lampposts, connectors
manipulated by a hammering action. This
the annular rolls, determines the size
is no more than 300,but it is possible to
andjoints for load bearing cables,
is generated by hammer blocks, which
of the tube that can be swaged. The
swage up to 450 where necessary. Smaller
and piping for gas and water. It is also
move in and out on the hammer block roll
dies are machined from tool steel (see
widely employed for small and precise
as the spindle head rotates rapidly.
image, belowl.
Quality • High precision
Related Processes • Arc welding • Tube and section bending
Speed • Rapid cycle time, but depends on complexity of operation
angles are simpler, quicker and more cost effective to produce. Rotary swaging is
products such as ammunition casing,
capable of producing sealed ends in pipe.
electrodes for welding torches and
The die opening, which is at its full extent when the spindle head rotates
thermometer probes. Swaging is used a great deal to form Right
joints.There are 2 main types of joint,
Fresh dies are machined
friction fit andformed. Friction fit joints
from tool steel for each
can be taken apart any number of
application, because
times, whereas formed joints tend to be
it is uncommon for 2
swaged products to
permanent. Friction fit examples include
be alike.
tent poles, walking frames, crutches and other telescopic parts. Formed joint examples include swaging a metal
lug or terminal onto cable for rigging
expensive and specialized. Applications
(sometimes known as atalurit splice),
include automotive chassis and high end
electrical cables and throttle cables.
bicycle frames.
Tubes can also be swaged together to form apermanent joint.
QUALITY Swaging compresses or expands metal
RELATED PROCESSES
during operation. Steel work hardens
Swaging is the most rapid and widely used method for tapering and end
in these conditions, which improves its
forming.Tapered metal profiles can
mechanical properties.
Components are typically produced to
DESIGN OPPORTUNITIES
also be produced by ring rolling plate
tolerances of o.i mm (o.oo4in.).They can
It is possible to rotary swage tapers along
(see tube and section bending, page
be made even more accurate, but this
the entire length of pipe. For example,
98) and arc welding (page 282) the
will increase cycle time considerably.
if the maximum length of swage on a
seam. Hydroforming is a recently
Ultimately, the quality is dependent
particular machine is 350 mm (13.78 in.),
developed process that is capable of
on the skill of the operator. The surface
forming complex hollow parts from
finish is generally very good and can be
stages. End forming, on the other hand,
tube. However, it is currently much more
improved with polishing (page 376).
is generally limited to short lengths of
then longer tapers are made in 2 or more
Case Study
Rotary swaging steel pipe Rotary swaging is capable of forming not only open-ended tapers but also sealed
ends in a length of pipe. This is especially useful for hollow probes and spikes. In the first images, 25 mm (0.98 in.) diameter tube (image 1) is being formed into a 30° taper to a sealed end.The pipe
is forced into the swaging die as it rotates at high speed (image 2). After 20 seconds or so, the pipe is retracted fully formed (image 3). The last 10 mm (0.4 in.) is likely to be solid metal. Small diameter tube is rotary swaged using the same technique (images 4 to 6). In this case the finished part does nothave a solid sealed end (image 6).The CO
diameter of the hole at the end can be
o
[n made precise by swaging the pipe over metal wire.
deformation due to the pressure that
rotary swaging and end forming can
COMPATIBLE MATERIALS
ENVIRONMENTAL IMPACTS
is required.
accommodate diameters over 150 mm,
Almost all metals can be formed in this
Th ere i s very 1 ittl e waste m ade by
(5.91 In.) such aslampposts.They can
way including steel, aluminium, copper,
swaging. It is not a reductive process like
MIG welding (page 282), are formed in a
also form very fine wire, as small as 1 mm
brass and titanium. Ductile metals will
machining. In fact, the hammering or
rotary swage die over an Internal die.This
(0.04 In.) diameter.
swage more easily. Tube, rod and wire are
pressing action can strengthen the metal
all suitable for swaging.
blank, contributing towards a longer
Precision parts, such as nozzles for
ensures maximum precision on both the inside and outside measurements.
Material thickness is also determined
by the capabilities of the swager.The gauge of material affects the ability of
lasting product.
COSTS
Rotary swaging is generally a
DESIGN CONSIDERATIONS
the pipe to be formed. There is no rule of
Metal is more willing to stretch than
thumb as to whether thicker of thinner
depends on the length and complexity
can cause 'white finger', especially In
to compress, so swaging tends to draw
gauges are more suitable because both
of the swage.
larger parts.
out metal into longer lengths.Therefore
thread tapping and hole making should
can be formed equally well.The benefit of thicker wall sections is that there is
be carried out as secondary operations.
more material to manipulate, but It will
operations because a high level of skill
take more hammering or pressing. Each
and experience 1s required to produce
design must be judged on Its merits.
accurate parts.
The machinery determines the
feasible diameter of metal blank. Both
Tooling is generally Inexpensive, but
manually operated process.The vibration
Cycle time is rapid. Labour costs are high for manual Featured Manufacturer
Elmill Swaging www.elmill.co.uk
r Hydraulic Swaging Process Reducing
Expanding
Open
Open
TECHNICAL DESCRIPTION In hydraulic swaging the pressure is applied
guide block is wedge shaped and forces the
to either the inside or the outside of the
die to either contract or expand. The die
pipe diameter. It is typically applied from at
determines the shape and angle of swage,
least 5 die segments simultaneously, which
which can be parallel or tapered.
surround the pipe wall. Turning the pipe
For parallel end forming, such as joint
during forming ensures even deformation
forming, standard tools are available for
of the wall section.
each pipe diameter. Tapered swaging
The hydraulic action is applied along the axis of the pipe being formed. The
Case Study
Hydraulic swaging Swaging dies are used to either expand the diameter of a pipe (images i, 2 and 3) or reduce it (images 4,5 and 6). The part is continuously rotated during operation to produce a uniform finish. Hydraulic swaging can be applied to a variety of profiles, including square and triangular sections, as well as round.
requires specially designed tooling.
Cold Roll Forming Process Roll formers driven
Upper roll former in highly polished hardened sleel
Upper roll former
Forming Technology
Roll Forming
Metal strip from coil
Leg
Finished profile
EJ
Sheet and strip metal can be formed into ribbed panels, channels, angles or polygons with progressive rollers. Such roll
Blind corners
forming is a continuous process capable of producing A,500 m (15,000 ft) of rolled steel per hour.
Workpiece I Lower roll former
Re-entrant angle (blind corner) formed by sequence of roll formers
Stage 1: Progressive roller A
Typical Applications
Suitability
• Automotive and transportation • Construction • Enclosures for white goods
• Batch production of minimum 1.500 m (5,000 ft)
Lower roll former
Stage 2: Progressive roller B
jj High specialized tooling costs Low to moderate unit costs
Quality • Good pitch accuracy (0.125-0.25 mm/ 0.005-0.01 in.)
Related Processes
• Very rapid, but depends on the complexity of bends and length of parts • Long changeover limes
process is suitable only for production
seam welded because they are formed to
runs greater than 1,500 m (5,000 ft).
As the name suggests, cold roll
maintain the enclosed shape.
The most significant consideration is
forming is carried out at room
Complex shapes with undercut
Speed
• Forging and extrusion • Metal stamping • Press braking
and box sections made in this way are
j:
TECHNICAL DESCRIPTION
that bends can onlybemadein the line
temperature. Sheet or strip metal
features (blind corners that cannot be
of production. They will have a radius
is generally fed into the roll forming
directly pressed by rollers), tight bends andhemmedjoints can be formed with
that is equivalent to, or greater than,
multiple roll formers in sequence.
process from a coil, and it Is bent
into the desired shape by a series of
_material thickness. The depth of cross-section will affect
progressive roll formers. However, it
INTRODUCTION
RELATED PROCESSES
combines the ductility and strength of
the costs of tooling. Parts are generally
is also possible to form precut sheets.
This metal sheet forming process is
Extrusion, press braking (page 148)
metal to produce parts with improved
process parts of any length can be made
designed so that their depth is less than
The bends are formed gradually over
used to produce 2D continuous profiles
and roll forging (see forging, page 114)
the opening to the roll former, in order to
several metres (yards); each set of
with a constant wall thickness. It will,
are all used to produce similar
rigidity and lightness. Cold working steel significantly
Because roll forming is a continuous
for example, bend metal strip (up to 0.5
continuous profiles to roll forming.
improves the grain alignment and thus
but they are generally limited to 20 m (66 ft) for ease of handling.The profile is cut to length as it is rolled and it is
m/1.6 ft wide) into continuous lengths
Short parts, cut to length during roll
the strength of the material.
possible to produce lengths as short as
of angle, channel, tube and polygon
forming, can also be made by metal
shapes. Roll formers (tools) are mounted
stamping (page 82). Roll forming is limited to profiles
The roll formers do not affect the
0.02 m (7.87 in.) at full speed.
surface finish of the metal being shaped,
ensure accurate and high quality bends in the workpiece.
The width of strip or sheet that can be processed is limited by the capabilities of the manufacturer. It is not uncommon
and angles are accurate to within +10
DESIGN CONSIDERATIONS
to be restricted to less than 0.5 m (1.6 ft)
with a constant wall thickness, whereas
andbetween 0.125 Tnm 0.25 mm
Tooling and changeover (set-up) is
wide. Multiple rolls alongside one
into ribbed, corrugated and crimped
extrusion and roll forging can be used
(0.005-0.01 in.).
expensive in roll forming and so this
another can form sheet materials over
patterns up to 1.4 m (4.6 ft) wide.
to produce profiles with varying wall
alongside one another so in a continuous process they can form sheet materials
DESIGN OPPORTUNITIES
that operates at speeds up to 1.25 m (4.1
produced by bending a single sheet of
Roll forming is used to make standard
ft) per second. Holes, ridges and other
material, such as an I-beam.
auxiliary patterning are carried out
Like roll forming, press braking can
The diagram illustrates 2 roll formers in a series of 8 or more. The roll formers are expensive because they are engineered to match
precisely. They are typically machined from hardened steel and polished to a very high finish. Water-cooling and lubricants reduce tool wear and help to
thickness and parts that cannot be
Rolling is a continuous operation
rollers is shaped to form the bend slightly more than the previous one.
Left
Highly polished roll
maintain high speed production. The roll formers, which are fixed
and custom-made products. Many items
forming tools such
in place, apply an even pressure on
are readily available, which eliminates
as these are used
the surface of the metal. Therefore,
to manufacture
produce continuous profiles. However,
tooling costs and minimum production
each bend is another operation in
volumes. However, new and original
TYPICAL APPLICATIONS
press braking, whereas roll forming is
Examples of cold rolled products include
continuous and therefore a much more
profiles can be designed and analysed using finite element analysis (FEA)
simultaneously to reduce cycle time.
roof and wall panels, lorry sidings, chassis
rapid production process.
software.Tooling is an investment that is offset by the volume of production.
for trains and cars, aerospace structural parts, shop fittings, structural beams
QUALITY
for construction and brackets and
Applying a bend to a sheet of material
range of profiles, from ribbed panels to
enclosures for white goods.
increases its strength; roll forming
channels and box sections. Hollow tube
This process can be used to produce a
continuous metal
profiles at speeds up to 4,500 m (15,000 ft) per hour.
symmetrical designs are simple to produce and less likely to have camber or curve.
Operations including punching and notching are integrated into the production cycle. Holes that are not
critical are precut into the flat metal to reduce roll forming cycle times.
o
o ?0
y Case Study
Roll forming an angle This simple roll forming process is used to
part (image 3). The finished parts are then
produce an angle within strip steel. A coil of
cut to length and stacked (image 4).
metal strip is loaded onto the tool (image i) and is then pulled through a series of 8
Varying levels of complexity, including hem, re-entrant and asymmetric profiles
progressive roll formers (image 2), in order
(image 5), can be achieved on thin-walled
to make this single bend. The formers are
parts formed by roll forming.
powered by electric motors, which drive each roll at exactly the same speed. Tension
is maintained by pressure on top of the coil. The finished part emerges from a die at the end of the production cycle, which ensures the dimensional consistency of the
this width but are more specialized and expensive to tool up for.
Sheet thickness for roll forming is typically limited to 0.5-5 (0.02-0.2
COSTS Specialized tooling will increase the unit price considerably, but will depend on the size and complexity of the bend. Tooling
in.). Bends should be at least 3 times
costs are generally equal to progressive
material thickness from the edge of the
tooling for metal stamping.
strip, otherwise it may not be possible to
Cycle time depends on the complexity of profil e, thi ckn es s of m etal an d 1 en gth
form the bend.
of cut-off. Simple profiles can be formed
COMPATIBLE MATERIALS
at up to 4,500 m (15,000 ft) perhour.
Almost all metals can be formed in this way. However, it Is most commonly
ENVIRONMENTAL IMPACTS
used for metals that are not feasible to
Bending is an efficient use of materials
extrude such as stainless steel, carbon
and energy. No scrap is produced in roll
steel and galvanized steel.
forming, although it may occur during
Featured Manufacturer
Blagg & Johnson www.blaggs.co.uk
machining or finishing operations.
Drop Forging Process Closed die forging Ram
Open die forging
Forming Technology
Forging
Upper die Hardened 1 steel
The forming of metal by heating and hammering or pressing was traditionally performed by blacksmiths on anvils. Nowadays, forgings are made by hammering, pressing or rolling hot metal
INTRODUCTION
.—. y-" '-7
metal
1
Metal has been forged into high-
billet 1
strength tools and implements for many centuries. Examples include horseshoes,
tool
,
\
/
Metal
Lower die is drawn out under
Flash
Anv"l
swords and axe heads, which were
with sophisticated dies and extreme pressure.
formed by blacksmiths hammering hot
Loading
Initial press
Loading
Completed forging
metal on anvils.There are now many
Typical Applications 1 Moderate to high tooling costs 1 Moderate unit costs
• Automotive and aerospace • Hand tools and metal implements • Heavy duty machinery
different types of forging, which are used
TYPICAL APPLICATIONS
Suitability
to produce an array of products from
The high-strength nature of forged metal
TECHNICAL DESCRIPTION
• All types of production
crankshafts to ice axes.The different
parts makes them ideal for demanding
The drop forging process is carried out
must be heated to over 1250°C (2282°F)
techniques can be dividedinto drop
applications and critical components
using either a closed or open die. An
and so stresses and wears the surface
forging, press forging and roll forging.
that require excellent resistance to
open die Is typically used for drawing
of the tool much more rapidly than
fatigue. Forged components are found
out (elongating a part and reducing its
aluminium, which is forged at only 500°C
an open or closed die operation.The
in lifting equipment, aerospace, military
cross-section), upsetting (shortening a
(932°F). During operation, lubricant that
processes forms hot metal billets
applications, cars and heavy machinery.
part and increasing its cross-section) and
acts as coolant is applied to the surface of
Many gears, plumbing parts, hand
conditioning (preparing a part for closed
the tool to cool it down and reduce wear.
Quality
Related Processes
Speed
• Excellent grain structure
• Casting • Machining • Tube bending (ring rolling]
• Rapid cycle time [typically less than a minute) depending on size, shape and metal
Drop forging is carried out as either
through repeated hammering.The main difference between the closed and open
die techniques is that open die forging is generally carried out with flat dies, where as closed die forging shapes metal
tools and implements are forged. Car
die forging). Open die forging is also used
axles and crankshafts are open die
to shape hexagonal and square section
forged. The heads of nails and bolts are cold forged.
by forcing it into a die cavity. Closed die
In drop forging, the ram brings the upper die into contact with the workpiece
bars. The tool face is generally square
under great pressure, from 50 kg/m2
or v-shaped for simple forming. The
to 10,000 kg/m2 (362-72,330 lb/ft2).
workpiece is repositioned between each
The force is generated by gravity fed
drop of the hammer by the operator. This
weights or by powered means (hydraulic
requires a great deal of operator skill
or compression) forcing the ram down.
and experience and is not suitable for
Press forging is powered by hydraulic
forging (also referred to as impression
RELATED PROCESSES
die forging) is used to produce complex
Forging is suitable for one-offs and low
and intricate bulk shapes. Open die
volume production as well as mass
forging, on the other hand, is typically
production runs. At low volumes it is an
used to 'draw out' a billet of metal into shafts and bars and can produce parts up
alternative to CNC machining (page 182), and at high volumes it competes with die
for high volume production. The tools are
hot or cold. Cold metal forging is typically
to 3 m (10ft) long.
or Investment casting (pages 124 and 130).
fabricated in tool steels (chromium-based
used for small parts, no larger than
Ring rolling as covered in tube bending
or tungsten-based) or low alloy steels.
10 kg (22 lb). The advantage of cold
(page 98) produces similar geometries to roll forging, but they require welding,
The life expectancy of a tool is largely
forging is that it can be used to produce
dependent on the shape of the part, but is
near net shape parts that do not require
whereas roll forged rings are seamless.
also affected by the ductility of the forging
secondary operations.
Press forging is essentially the same as drop forging, except that parts are formed by continuous hydraulic pressure, as opposed to hammering. Press forging
by the material, part size and geometry. Roll forging forms continuous metal
rams, which force the metal into the
in sections.
die cavity in a squeezing action. This
Closed die forging can be automated
technique can be used to process metals
material. For example, stainless steel
is used to shape hot and cold metals; the temperature of the metal is determined
automation. Long profiles can be forged
QUALITY By its very nature,forging improves grain
structure in the finished part. Metal
can be machined post-forging with no
tolerances increases costs. Forging is
parts through a series of metal rollers.
billets go through plastic deformation as
loss of quality because there are no voids
often combined with machining for
This process is used to forge straight
they are forged and as a result the metal
or porosity in the finished article.
Improved accuracy.
profiles andrings (washers), which can be up to 8.5 m (28 ft) In diameter and 3 m
produces exceptional strength to weight
(0.04 in.) in small parts up to 5 mm
DESIGN OPPORTUNITIES
and reduces stress concentrations that
(0.2 in.) in large parts,but vary according
Forging is suitable for low volume
tend to occur in corners and fillets. Parts
to requirements because reducing
production and one-offs.This is
grains align in the direction of flow. This
The tolerances range from 1 mm
Rollers draw out and reduce cross-section of metal
Roll Forging Process Billet cross-section
Profiled rollers shape metal bars
Finished profile cross-section
Drop forging a piston end cap
®or metal
'0 ® Stage 1: Reducing cross-section
In this case study a piston end cap is being
Stage 2: Profiling
is removed from the furnace with a pair of
closed dies. The metal billet is preformed and
tongs (image 2).
the scale is broken off 1n open die forging in preparation for closed die forging.
TECHNICAL DESCRIPTION Roll forging carried out as a continuous process. Metal bar or plate is fed into the
rollers, which draw out and profile the hot metal in stages. Each stage reduces the cross-section gradually, easing
the metal into the desired profile. This
forgings.They are joined together by upset forging a stopper on the shaft of the eyelet. Upset forging increases the cross-section and reduces the length of the shaft, a process similarto shaping the
such as aluminium and brass. Radii, however, are very important because
(19.7 ft) lengths (image 1), which are cut
of the part is changed but the volume
they encourage the flow of metal and
into billets. The size of billet is determined
stays the same. The metal spraying out
reduce tool wear.The minimum radius
by the weight and geometry of the part.
with impact is mill scale, which is formed
increases with depth of protrusion.
The billets are loaded into a furnace, which
as the steel surface oxidizes. This has to
heats them up to i25o'C (2282^). Each billet
be removed because otherwise it will
takes approximately 30 minutes to heat up
contaminate the final part.
COMPATIBLE MATERIALS
process is generally used to shape metal
Most ferrous metals, including carbon,
into simple continuous profiles.
no restriction on step changes in wall
alloy and stainless steels, can be forged.
thickness with this process.
Non-ferrous metals including titanium,
this way. First, a hole is punched in the
Forging can be used to make a
roll forged into the desired profile. This
geometries. Drop forgings can weigh
COSTS
is also known as ring rolling.
as little as 0.25 kg (0.55 lb) or as much as
Tooling costs are moderate to high,
5o kg (132 lb). Roll forging can produce
depending on the size and geometry of
seamless rings weighing more than
the part. Closed die forging tools typically last between 50 and 5000 cycles.Tool
life expectancies are affected by the
properties that cannot be manufactured
DESIGN CONSIDERATIONS
complexity of forging geometry, the
Designing for forging must take into
design of the forging cavities, sharpness
machined, but will have to compensate
account many factors that also affect
of radii, the material to be forged, the
for reduced strength resulting from
design for casting, including partition
temperature required to forge that
random grain alignment.
line, draft angles, ribs, radii and fillets.
material and the quality of the surface
Parts are formed by hammering, or
finish of the tool. Incorporating multiple
However, it is possible to form undercuts
pressing, which can produce surprisingly
cavities into a tool and pre-forming the
and joints with secondary forging
deep protrusions, up to 6 times the
metal billet increase the cycle time.
operations. An example of this is the
thickness of material. Draft angles can be
swivel link (see image,below).These are
minimized and even eliminated by clever
complete in less than a minute. However,
produced by first making 2 separate drop
design, especially in ductile materials
mass production forging can produce
Left To unite the 2 parts of the swivel link, the heated shaft of the eyelet is driven through the hole into a die that shapes the stopper.
1 vaA
aa
in any other way. Small volumes can be
Undercuts are not possible in forging.
.
o
huge range of component sizes and
because it produces parts with superior
11
copper and aluminium are also suitable.
middle of a forged disk, which is then
100 tonnes (110 US tons).
(image 3) and formed by repeated blows from the hammer (image 4). The shape
5 mm to 250 mm (0.2- 9.84 in.).There is
Seamless rings can also be formed in
The metal is aligned in the open die
The mild steel is delivered in 6 m
head of a bolt.
Typically, wall thickness should be
sufficiently for forging. The 'cherry red' billet
drop forged in a combination of open and
Cycle time is rapid. A typical forging is
parts in less than 15 seconds. Labour costs are moderate to high
duetothelevel of skill andexperience required.This is a relatively dangerous process, so health and safety depend on
the abilities of the workforce.
ENVIRONMENTAL IMPACTS A great deal of energy is required to heat metal billets to working temperature and hammer or press them into shape. No material is wasted because all scrap and off cuts can be recycled.
cd
I
The part is now ready for the dosed die forging process (image 5). The floor shakes with the impact of the hammer (image 6), With each cycle the hot metal is forced further into the upper and lower die cavities. Once the flash has
formed, it cools more rapidly than the rest of the metal because it is thinner and less ductile. Therefore, the remaining
hot metal is maintained within the die cavity and is forced into the extremities of it with each repeated blow from the hammer (images 7 and 8). It is a gradual, but rapid process. In
this case the metal does not need to be reheated at any point and so the entire forging operation is complete within 30 seconds. Due to the depth of this forging it must be carried out while the metal is 'cherry red'. The extremities are the first to cool off, and can be seen as
duller patches (image 9). These lumps of metal are too heavy for a single operator to manhandle with tongs, so they have to work In pairs to move the metal between workstations
(image 10). it requires a great deal of skill and experience to work in this environment. The flash is sheared off In a punch (image 11) and the part, which Is still very hot, is dispensed (image 12).
t '
Featured Manufacturer W. H. Tildesley www.whtildesley.com
designed parts with sufficient draft
TYPICAL APPLICATIONS
which causes porosity. When the parts
angles will result in higher quality parts.
Sand casting is used a great deal in the
are removed from the sand molds the
automotive industry to make engine
surface finish is distinctive, so all cast
to shape metals. Glass can also be cast in
block and cylinder heads, for example.
parts are blasted with an abrasive.
this way, but because of its high viscosity it will not flow through a mold.
Other applications include furniture,
lighting and architectural fittings.
Varying grits are used to produce the highest quality finish. Parts can then be polished to achieve very high surface
of the sand casting and investment
RELATED PROCESSES
finish. Because sand casting relies on
Sand casting is most commonly used
Forming Technology
Sand Casting
Evaporative pattern casting is a hybrid
Molten metal is here cast in expendable sand molds, which are broken apart to remove the solidified part. For one-off and low volume production this is relatively inexpensive and suitable for casting a range of ferrous metals and non-ferrous alloys.
Costs 1 Low tooling costs 1 Moderate unit costs
Quality • Poor surface finish and high level of porosity.
Typical Applications • Architectural fittings • Automotive • Furniture and lighting
Related Processes • Centrifugal casting • Die casting • Forging
Suitability • One-off to medium volume production
Speed • Moderate cycle time (30 minutes typically), but depends on secondary operations
casting (page 130) processes, and it can
Die casting (page 124), centrifugal casting
gravity to draw the molten material into
INTRODUCTION
beinexpensive. Instead of a permanent
(page 144) and forging (page 114) are all
the mold cavity, there will always be an
Sand casting is a manual process used
pattern, evaporative pattern casting
alternatives to sand casting metals. Sand
element of porosityin the cast part,
to shape molten ferrous metals and
uses an expendable foam pattern (often
casting is often combined with forging
non-ferrous alloys. It relies on gravity to
polystyrene), which is embedded in the
or CNC machining and arc welding (page
DESIGN OPPORTUNITIES
draw the molten material into the die
sand mold. The foam pattern istypically
282) to create more complex parts. Die
There is plenty of scope for designers
cavity and so produces rough parts that have to be finished by abrasive blasting,
formed by CNC machining (page 182) or injection molding (page 50).The molten
casting produces parts more accurately
using this process. For low volume
and rapidly and so is generally reserved
production it is generally less expensive
machining or polishing.
metal burns out the foam pattern as it
for high volume production.
than die casting and investment casting.
The sand casting process uses regular
is poured in. Parts made in this way have
Draft angles are required on the sand
sand, which is bonded together with
inferior surface finish, but this technique
QUALITY
mold to ensure removal of the pattern.
clay (green sand casting) or synthetic materials (dry sand casting) to make the
is very useful for prototyping, one-off and
The quality of surface finish and
The cores also require draft angles so that
manufacturing very low volumes.
mechanical properties depend largely
they can be removed from their molds.
molds. Synthetic sand molds are quicker
on the quality of the foundry. For
However, multiple cores can be used
to make and produce a higher quality
example, nitrogen is pumped through
and they do not have to correspond to
surface finish. However, the quality of the
molten aluminium to remove hydrogen,
external draft angles because the mold
casting is largely dependent on the skill of the operator in the foundry. There are many variables in the
TECHNICAL DESCRIPTION
casting process that the designer can
The sand casting process is made up of
do nothing about, although properly
2 main stages: moldmaking and casting.
Sand Casting Process Molten metal poured into runner
In stage 1, the mold is made in 2 halves, known as the cope and drag. A metal casting box is placed over the wooden pattern and sand is poured in and compacted down.
For dry sand casting the sand has a vinyl ester polymer coating, which is room temperature cured. The polymer coating on
each sand particle helps to achieve a better finish on the cast part because it creates a
film of polymer around the pattern, which forms the surface finish in the cast metal.
Stage 1: Moldmaking
Stage 2: Sand casting
For green sand casting, the sand Is mixed
with clay and water until it is sufficiently wet
In stage 2, the 2 halves of the mold are
the metal at the top of the mold molten for
to be rammed into the mold and over the
clamped together with the cores in place.
longer. This means that as the metal inside
pattern. The clay mix is left to dry so that
The metal is heated up to several hundred
the mold solidifies and shrinks as it cools
there is no water left in the mix. Water must
degrees above its melting temperature. This
it can draw on surplus molten metal in the
be removed because otherwise it will boil
is to ensure that during casting it remains
runner and risers. Porosity on the surface
and expand during casting, thereby causing
sufficiently molten to flow around the mold.
of the part is therefore minimized.
pockets of air in the mold.
A predetermined quantity of molten metal
Meanwhile, sand cores are made in
is poured into the runner, so it fills the
separate split molds and then placed In
mold and risers. Once the mold is full an
the drag. The runner and risers, which
exothermic metal oxide powder is poured
are covered with an insulating sleeve, will
into the runner and risers, which burns
already have been built into the pattern.
at a very high temperature and so keeps
is broken to remove the solidified metal
Case Study
parts.This means that complex internal shapes can be formed, which may not be
Sand casting a lamp housing
practical for the die casting processes. Sand casting can be used to produce
The casting temperature of aluminium is
in this case) is poured into the runner and
much larger castings than other casting
between 7300C and 78o0C (1346-1436^), yet
risers (image 10). The powder burns at a
methods (up to several tonnes).The
in preparation the aluminium is heated up
very high temperature, which keeps the
molds for castings can weigh a lot more
to more than 900°C (i652°F) in a kiln (image
aluminium molten in the top ofthe mold
than the casting itself. It is therefore not
i).The mold is prepared by placing a metal
for longer. This is important to minimize
practical or economical to produce very
casting box over the pattern (image 2). Sand
porosity in the top surface of the cast part.
large castings any other way.
coated in afiim of vinyl ester is poured
After 15 minutes the casting boxes are
over the pattern (image 3).The box is filled
separated along the partition line and
DESIGN CONSIDERATIONS
incrementally and rammed down after each
the part is revealed - covered in a layer of
Many design considerations must be
fill (image 4). The quality of the fill and so
charred sand (image 11).The sand is broken
taken into account for sand casting parts.
the quality ofthe final casting are largely
away from around the metal casting
dependent on the skill ofthe operator
(image 12). The surface finish is relatively
These include draft angles (range from 1° to 5°, although 2° is usually adequate), 1 ribs, recesses, mold flow and partition
(image 5). The vinyl ester cures at room
good and so little finishing is required. The
temperatures and solidifies rapidly.
parts are cut free from the runner system
In the meantime, the cores are prepared
lines. The part must be designed to take
COSTS
into account all aspects ofthe casting
Tooling costs arelowforone-offandlow
process,from patternmaking to finishing.
volume production, the main cost being
These elements affect the design and so
for patternmaking, which is inexpensive
rammed to compact it (image 6).The mold
all parties should be consulted early on in
compared to die casting tooling. Low
can be opened almost immediately. The core
the design process for optimum results.
cost patterns can be machined in wood
can then be removed (image 7), but it is still
or aluminium. Foam patterns for the 4
very delicate at this stage and so must be
2.5mm up to 130mm (1-5.12 in.). Changes
evaporative pattern method are the least
handled carefully.
in wall thickness are best avoided,
expensive of all.
The wall thickness that can be cast is
although small changes can be overcome
Cycle time is moderate but depends
in a separate mold. They are made with the
metal is poured into the runner (image 9),
minutes, but secondary and finishing
material ofchoice at the design stageto
the majority of this process is manually 5
ensure accurate castings in the selected
operated and the quality of casting is affected by the skill ofthe operator.
material. Steel will shrink nearly twice as
cn
brought together and clamped. Hot molten where it spreads through the mold and
Labour costs can be high, especially as
>
Once the cores have been placed into
Casting usually takes less than 30
Therefore it is essential to know the
CO
the drag (image 8), the mold is ready to be
in cross-section is required, then parts
operations increase cycle time.
>
carefully packed into the mold cavity and
on the size and complexity ofthe part.
Metals cool at different rates.
(/).
same sand coated in vinyl ester.The sand is
with tapers and fillets. If a large change are often cast separately and assembled.
(image 13) and are now ready for abrasive blasting and finishing (image 14).
up the risers. When the mold is full an exothermic metal oxide (aluminium oxide
much as aluminium and iron, whereas brass will shrink about 50% more than
ENVIRONMENTAL IMPACTS
aluminium. Shrinkage increases with
Alarge percentage of each casting
cross-section and part size.
solidifies in the runner and risers. This material can be directly recycled in most
COMPATIBLE MATERIALS
cases.The mold sand can be reused by
This process can be used to cast ferrous
mixing it with virgin material. In green
metals and non-ferrous alloys.The most
sand casting up to 95% ofthe mold
commonly sand cast materials include
material can be recycled after each use.
iron, steel, copper alloys (brass, bronze)
Energy requirements for sand casting
and aluminium alloys. Magnesium
are quite high because the metal has
is becoming increasingly popular,
to be raised to several hundred degrees
especially in aerospace applications
above its melting temperature.
because of its lightness.
Featured Manufacturer Luton Engineering Pattern Company www.chilterncastingcompany.co.uk
Die casting is a precise method of forming parts from metal. This high speed process uses pressure to force molten metal into reusable steel molds, to create intricate and complex 3-dimensional geometries.
Typical Applications
Suitability
• Automotive • Furniture • Kitchenware
• High volume production
Quality
Related Processes
Speed
• Very high surface finish • Variable mechanical properties
• Forging • Investment casting • Sand casting
• Rapid cycle time that depends on size and complexity of part
High tooling costs Low unit costs
INTRODUCTION
Gravity die casting is also known as
There are various techniques in die
permanent mold casting; steel molds
casting, including high pressure die
are the only feature that differentiate
RELATED PROCESSES Forging (page 114), sand casting and investment casting (page 130) are
casting, low pressure die casting and
it from sand casting (page 120).The
alternative processes. However, die
gravity die casting. High pressure die casting is a versatile
molds can be manually operated or
casting is the process of choice forlarge
automated for larger volume production.
volume production of metal parts due to
process and the most rapid way of
Reduced pressure means that tooling
its versatility, speed, quality, minimum
forming non-ferrous metal parts. Molten
and equipment costs are lower, so
wall section, high strength to weight and
metal is forced at high pressure into
gravity die casting is often used for short
repeatability.
the die cavity to form the part.The high
productions runs, which would not be
pressures mean that small parts, thin
economic for other die casting methods.
wall sections,intricate details andfine surface finishes can be achieved.The tooling and equipment is very expensive, and so this process is suitable only for high volume production. In low pressure die casting molten
Die casting is often compared to
injection molding (page 50).The main differences are related to the material
TYPICAL APPLICATIONS High pressure die casting is used to produce the majority of die cast metal parts such as for the automotive
qualities. Compared to plastics, metals are more resistant to extreme temperatures, they are durable and have superior electrical properties.
industry, white goods, consumer
Therefore, die castings are more suitable
material is forced into the die cavity
el ectroni cs, packagin g, furn iture,
for applications that demand these
by low pressure gas.There is very little
lighting, jewelry and toys.
properties such as engine parts.
turbulence as the material flows in
Low pressure methods are widely
and so the parts have good mechanical
utilized in the automotive industry
properties. This process is most suitable
to make wheels and engine parts,
QUALITY Die cast parts have superior surface finish, which improves with pressure.
High speed injection methods cause turbulence in the flow of metal, which can lead to porosity in the casting. Voids and porosity are an inevitable part of
Right Strength analysis of Chair One shows the resilience of the structure. This software
is used to double check that the engineering of the product is correct before manufacturing the tools for casting.
S, Miees SHEG, ( fraction = ( Ave. Crit. : 75%) - +1.65e+008
H +1. 50e+008
. 38e+008 .25e+008 +1.13e+008
a +8.00e+008 .75e+007 .50e+007 .25e+007 .006+007 .75e+007 .50e+007 .256+007 .006+000
metal casting that can be limited when engineering the product at the design stage. Mold flow simulation is used to
optimize the filling of the cavity of the mould and eradicate any potential voids and porosity. Strength analysis is carried out prior to manufacture to test the
for rotationally symmetrical parts in low
for example.They are also used to
melt temperature alloys. A good example
make products for the home such as
mechanical properties of the part (see
would be an aluminium alloy wheel.
kitchenware and tableware.
image, right).
a
k"
Low Pressure Die Casting Process
High Pressure Die Casting Process
Water cooling channels
Partition line Water cooling channel
Cold chamber method
Part ejected mold platten
Hydraulic rams provide clamping force
Moving mold platten
Die cavity Ejector pins
Runner system Part ejected
Die cavity Hydraulic rams provide clamping force
Molten metal
Runner system
Shot piston Remaining molten metal
Gas pressure i
Stage 1: Metal injection
Stage 2: Part ejected Stage 1: Metal injection
COMPATIBLE MATERIALS
TECHNICAL DESCRIPTION
Stage 2: Part ejected
TECHNICAL DESCRIPTION
High pressure die casting is carried out as
In the hot chamber method the shot cylinder
have to be trimmed before the part is ready
Choice of material is an essential part
In low pressure die casting the mold and
half of the mold is raised and the part
a hot or cold chamber process. The only
is fed through the furnace. The hot liquid
for joining and finishing operations. High
of the design process in die casting
furnace are connected by a feed tube. The
ejected. The nature of this process means
difference is that in the hot chamber method
metal is forced into the die cavity by the
pressure die cast parts require very little
because each material has particular
mold is mounted on top of the furnace
that it Is most suitable for parts that are
the molten metal is pumped directly from
shot piston at high pressure. The pressure
machining or finishing, because a very high
properties to be exploited. Die casting
with a horizontal split line. In stage 1, the
symmetrical around a vertical axis.
the furnace into the die cavity. The machine
is maintained until the part has solidified.
surface finish can be achieved in the mold.
is only suitable for non-ferrous metals.
molten material is forced up the feed tube
sizes range from 500 tonnes (551 US tons) to
Water cooling channels help to keep the
The melting point of ferrous metals is
and into the die cavity by gas pressure on
more than 3,000 tonnes (3,307 US tons). The
mold temperature lower than the casting
too high, so liquid forming is carried out
the surface of the metal in the furnace.
required clamp force is determined by the
material and so accelerate cooling within the
by investment or sand casting, and solid
Gas pressure is maintained until the part
size and complexity of the part being made.
die cavity.
state forming by forging.
Metal ingots and scrap are melted
in stage 2, when the parts are sufficiently
together in a furnace that runs 24 hours a
cool, which can take anything from a few
day. In stage 1 of the cold chamber method,
seconds to several minutes depending on
a crucible collects a measure of molten
size, the mold halves open and the part
metal and deposits it into the shot cylinder.
is ejected. The flash and runner systems
Non-ferrous metals including aluminium, magnesium, zinc, copper,
lead and tin are all suitable for die casting.A1 uminium andmagnesium
has solidified. In stage 2, when the gas pressure
is released, the molten metal still remaining In the feed tube runs back down into the crucible. The casting is left for a short time to solidify before the top
are becoming popularfor consumer
electronics due to their high strength to weight properties.They are dimensionally stable, even at high
DESIGN OPPORTUNITIES
form thinner wall sections than other
toolmaking to finishing, so all parties
temperatures, resistant to corrosion
There are many advantages to using
casting processes. Parts are produced to
should be consulted early on in the
and can be protected and coloured by
die casting if the quantities justify it.
high tolerances and often require little or
design process for optimum results.
anodizing (page 360).
Intricate or bulky fabrications can be
no machining andfinishing.
Labour costs are low for automated die casting methods.
ENVIRONMENTAL IMPACTS
Casting is most suitable for small parts because the steel tooling becomes
COSTS
All the waste metal generated in casting
cast into the product.
very large and expensive for parts above
Tooling costs are high because tools
can be directly recycled.There is no loss of
g kg (20 lb). Side action and cores can
have to be made in steel to be able
strength and so the waste metal can be
material are seen as waste, whereas
DESIGN CONSIDERATIONS
increase the cost of the tool considerably.
to withstandthe temperature of the
mixed with ingots of the same material,
holes in die castings are savings because
This process has technical considerations
However,there maybe an associated
molten alloys. For gravity die casting,
melted down and recast immediately.
they are produced directly in the mold
similar to injection molding.These are
benefit if the same feature reduces
sand cores can be used for complex
This process uses a great deal of
and so reduce material consumption.
rib design, draft angles (1,5° is usually
wall thickness, by increasing strength,
shapes and slight re-entrant angles.
energy to melt the alloys and maintain
These processes can be used to
sufficient), recesses, external features,
for example.
redesigned to become more economic with improved strength and reduced
External threads and inserts can be
weight. For example, holes in sheet
Especially if a multiple cavity mold
produce complex shapes with internal
mold flow and partition lines.The part
is used, cycle time is rapid-from a few
cores and ribs. High pressure methods
must be designed to take into account
seconds to several minutes, depending
will reproduce very fine details and can
all aspects of the casting process, from
on the size of the casting.
them at high temperatures for casting.
r
Case Study
High pressure die casting Chair One This chair was designed by Konstantin
After 2 minutes the molds separate to
[T* I i 1
Grcic for Magis in 2001 and took 3 years
reveal the solidified part, which is collected
mlkztl
to develop from brief to production. It
by a robotic arm (image 4). Once the part
was designed specifically for die casting
has been extracted the mold is steam
in aluminium, which is a very common
cleaned and lubricated for the next cycle
material in high pressure die casting and
(image 5). Meanwhile, the part is dipped in
so is used in large quantities by foundries
water to cool it down and ensure that it is
(image i).The raw material (which may
completely solidified (image 6).
come from recycled stock) is melted in the
The flash and runner systems are
holding furnace and mixed with scrap
removed (image 7) and the scrap material
from the casting process. A crucible for
is fed straight back into the holding furnace
transferring the molten aluminium into
so that it can be recast. Although the
the shot cylinder lowers into the holding
stacked chair seats already have a very high
furnace and collects a measured charge of
surface finish (image 8), this is improved by
the metal (image 2). It is poured into the
polishing (page 376). Inserts are used in the
shot cylinder (image 3) and forced into the
tools so that different leg assemblies can be
die cavity by a shot piston. This machine has
fitted (image 9).
a clamping force of 1,300 tonnes (1,433 US tons), which is necessary for casting the 4 kg (8.82 lb) chair seat.
Featured Company
Magis www.magisde5ign.com
mfgil 5, t'S Is* \ ''
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if • ¦ ' n
P'Ste lisS'fP J*-"::
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Liquid metals are formed into complex and intricate shapes in this process, which uses non-permanent ceramic molds. It is also known as lost wax casting.
Typical Applications
Suitability
» Low to moderate cost wax injection tooling » Non-permanent molds 1 Moderate to high unit costs
• Aerospace » Construction • Consumer electronics and appliances
• Low to high volume production
Quality
Related Processes
Speed
• Die casting • Metal injection molding • Sand casting
» Long cycle time (24 hours)
1 Very high 1 Complex shapes with high Integrity
INTRODUCTION
TYPICAL APPLICATIONS
This is a versatile metal casting process. It
Applications are widespread and include
within 125 microns (0.0049 i11-) for every
There are many stages to the investment
by hand. The wax is injected at low pressure,
In stages 5 and 6, the wax patterns
is more expensive than die casting (page
products for the aerospace, automotive,
25 mm (0.98 in.) of cast metal.
casting process, which are divided into
and so there is little flash, or other problems
and runner system are melted out in a
124), but the opportunities outweigh the
construction, furniture, sculpture and
pattern making, ceramic mold making
that are associated with high-pressure
steam autoclave and the ceramic shell is
DESIGN OPPORTUNITIES
and casting.
injection techniques.
subsequently fired at 1095°C (2003°F1. It
price difference for many applications. Due to its many advantages,
jewelry industries. Parts include gears,
Dimensions are typically accurate to
housings, electronic chassis, covers and
Investment casting does not have the
investment casting is used to produce a
fascias, engine parts, turbine blades
same shape limitations as other casting
wide range of products from only afew
and wheels (see image, above), medical
techniques.This is because neither the
grams to more than 35 kg (77.16 lb) and
impl ants, brackets, 1 evers an d h an dl es.
less than 5 mm (0.2 in.) long up to over 0.5 m3 (17.66 ft3). Investment casting is made up of
pattern nor metal part has to be ejected at any point.The pattern and mold are
RELATED PROCESSES
both non-permanent: the wax is melted
Some parts made by investment casting
from the ceramic shell, which in turn
TECHNICAL DESCRIPTION
The wax parts are molded with the gate
is removed from the kiln at between SOCTC
formed, which in this case is wax injection.
and runner system attached. In stage 2, the
and 1095°C (932-2003°F)depending on the
The tooling is typically aluminium. Unlike
whole assembly is mounted onto a central
metal being cast.
conventional injection molding, these tools
feed system. Everything is wax and so can be
can have many parts, which are assembled
melted and joined together. Each assembly
In stage 1, the expendable pattern is
Itree) may hold tens or even hundreds
In stage 7, whilst the shell mold is still very hot, molten metal is poured in. In most cases gravity is used to fill the mold.
of products, depending on the size of the
It is also possible to pull the molten metal
parts, which increases production rates.
through using a vacuum, or force it into the
3 elements: expendable pattern, non-
are also suitable for die casting, sand
is broken from the cast part. In other
are used.These are Injection molded
permanent ceramic mold and metal
casting (page 120) or metal injection
words, it is possible to cast shapes with
separately and then over-molded with
dipped in ceramic slurry and then coated
casting.The patterns are typically
molding (page 136). When volumes
undercuts and varying wall thickness
conventional wax. When the casting is
with fine grains of refractory material.
cooled, in stage 8 it is broken out of the
injection molded (page 50) wax, but
exceed 5,000, production may shift to
that are not feasible with other liquid
complete it is submerged in water and
The primary coating is made up of very
shell mold using impact and vibration. For
other materials are also used, including
die casting if the design is suitable.
forming processes.This eliminates costly
the soluble wax melts away.
fine particles, which ensures a good
delicate parts, the shell is removed using
Injection molded wax is still the most
surface finish on the inside of the shell
chemical dissolution or high-pressure water.
commonly used pattern material. Other
mold. The number of coats depends on the size of part and the metal being cast.
rapid prototyped (page 232) models. Both small and large volumes can be
fabrication operations.
QUALITY
Complex internal shapes are feasible
accommodated, from prototypes to mass
Investment casting produces high
in the injection molding of the wax
materials and techniques include rapid
production of 40,000 or more parts per
integrity metal parts with superior
pattern.The molds are sometimes very
month. It is also possible to produce very
metallurgical properties.The surface
complex, consisting of many parts, to
prototyped wax (thermojet) and plastic models (quickcast), acrylic and machined
complex, intricate parts with thin and thick wall sections that cannot be cast in any other way.
finish is generally very good and is determined by the quality of the expendable pattern.
reduce assembly operations later on. For precise and critical internal geometries, soluble wax or ceramic pre-formed cores
or molded expanded polystyrene (EPS), known as lost foam casting. In fact, any material that can be burnt out and has a
In stages 3 and 4, the assembly is
mold under pressure.
Once the casting has solidified and
The individual parts have to be removed from the runner system and cleaned up.
This wet dipping and dry stuccoing
Machining is needed to clean up the surfaces
process, known as investing, is repeated
that were in contact with the runner system.
7 to 15 times with progressively coarser
The parts are then finished with abrasive
refractory materials. Between each
blasting (page 3881, or left 'as cast', because
cycle the shell is left to dry for 3 hours.
the surface finish is generally very good.
The simulation shows
potential problem areas in the original part.
Investment casting a window support
Left
CAD
The part is modified in
The assembly, known as a 'tree', is dipped
All parts are designed and developed on
by hand into a water-based zircon ceramic
ceramic. This is carried out automatically
shows that no problem
CAD. Flow simulation software is used to
solution (image 3). The primary coating
by a robot (images 6 and 7). The secondary
reduce problem areas such as porosity. The
is always carried out by hand because it
coatings are applied every 3 hours.
image sequence demonstrates this process.
is the most critical and essential for good
areas remain.
The original part (see image, far left) was
surface finish. The wax tree is transferred
gradually modified (see image, left). Areas of
into a coating chamber, which applies fine
potential porosity are highlighted in yellow.
refractory powder (image 4) and hung up to dry (image 5).
INVESTMENT CASTING This is the production of a 'spider' used in
the construction industry for supporting panes of glass. They are manufactured
in stainless steel and often finished by electropolishing (page 384). The expendable pattern is injection molded wax (image i) in a tool very similar to that used in conventional
injection molding. The process is fully automated, but molds with complex internal cores are manually operated.
The mold tool is 3% larger than the final metal casting, to allow for the wax sufficiently low coefficient of expansion
Cast parts are dimensionally accurate
for complex molds with removable
is suitable for the pattern, although some
and minimize machining operations.
core segments. A simple split mold is
materials will take longer than others to
However, internal threads and long blind
relatively low cost and has along life
burn out. Wax has proved to be the most
holes can only be formed on parts as a
expectancy, as the wax has alow melting
effective material for large volumes and
secondary operations.
temperature and in not very abrasive.
high surface finish.
As with other liquid forming processes, cast parts are typically ribbed
DESIGN CONSIDERATIONS
and reinforced to eliminate warping and
Wall sections do not have to have a
distortion when cooling.
Cycle time is long and generally 24 hours or more.
Investment casting is a complex process that requires skilled operators. Therefore,labour costs can be quite high.
uniform thickness; sometimes thicker sections are actually required to aid
COMPATIBLE MATERIALS
the flow of metal into the mold cavity.
Almost all ferrous and non-ferrous
ENVIRONMENTAL IMPACTS Very little metal is wasted in operation
It is possible to feed metal to the cavity
metal alloys can be investment cast.This
through multiple gates, ensuring good
process is suitable for casting metals that
and any scrap and offcuts can be directly
distribution around even complex parts.
cannot be machined and fabricated in
recycled 1n the furnaces.The melted wax
any other way such as superalloys.
is reused in the runner systems.
The wall thickness depends on the
alloy. The typical wall thickness for
coatings of a more substantial mullite
CAD. A new simulation
The most commonly cast materials
The ceramic shells cannot be recycled,
aluminium and zinc is between 2 mm
are carbon and low alloy steels, stainless
but their material is totally inert and
and 3 mm (0.079-0.118 in.), although it
steels, aluminium, titanium, zinc, copper
non-toxic.The smoke and particles
is possible to cast wall sections as thin
alloys and precious metals. Nickel, cobalt
produced by casting are captured by
as 1.5 mm (0.059 'n-)- Steel and copper
and magnetic alloys are also cast.
ceramic filtration.
alloys require thicker wall sections, typically greater than 3 mm (0.118 in.),
COSTS
but for small areas a thickness of 2 mm
There are tooling costs for the wax
(0.079 in.) is possible.
injection process.These can be moderate
to shrink 1% and the metal to shrink 2%. The wax patterns, which are molded
with a gate attached, are assembled onto a runner system (image 2). The joint interface is melted with a hot knife and held together to form a bond.
At this stage the ceramic shell is very fine and has to be reinforced with secondary
After at least 7 coats the ceramic shells
heat as the molten metal is poured in. This
are sufficiently robust. Metals with higher
encourages the metal to flow through even
melting point and large parts require
the most complex shapes.
more coats. The wax is removed In a steam
The mold is left to cool for approximately
autoclave and recycled. The hollow ceramic
3 hours (image ii).The ceramic shell is broken
shell is placed in a kiln at 109 50C (20 030F) to
from the solidified metal with a pneumatic
harden it fully and remove any residual wax.
hammer (image 12).
It is an exact replica of the wax pattern.
The ceramic mold is red hot when it is removed from the kiln 3 hours later (image 8). In the meantime, the molten stainless steel is
prepared in a crucible, which is used to pour the metal into the mold (image 9).The metal is poured by hand into the mold (image 10). The ceramic molds retain a great deal of
The individual parts are removed from the runner system, ground off and polished up to produce the finished article (image 13).
to accommodate the plasticized powder
Metal Injection Molding Process
composite material. Powder parts
Moving core
In stage 1, the injection cycle is much the same as for other injection molding
Water cooling channels
Heater bands
processes, although the molded parts are
roughly 20% larger in every dimension
Hydraulic clamping arm
prior to heating and sintering. This is to allow for the shrinkage, which will take place as the binder is removed.
o
This process combines powder metallurgy with injection molding
In stage 2, the 'green' parts are heated
1
technology. It is suitable for the production of small parts in
In a special debind oven, to vaporize and remove the thermoplastic and wax binder. The molded parts are now in pure metal,
steel, stainless steel, magnetic alloys, bronze, nickel alloys
Die cavity filled under pressure
with all binder material removed. Mold tool
Support plate
and cobalt alloys. Stage 1: Injection molding
Stage 2: Heating and sintering
The final stage Is to sinter the parts in a vacuum furnace. This typically starts
with a nitrogen/hydrogen mixture, (depending on material type) changing to
High tooling costs Moderate to low unit costs
Typical Applications
Suitability
• Aerospace • Automotive • Consumer electronics
• High volume production • Low to medium volume production for certain applications
Quality
Related Processes
• Very high quality surface finish • High level of density
• Die casting • Forging • Investment casting
Speed
TECHNICAL DESCRIPTION
a vacuum as the sintering temperature
after sintering.This is normally readily
Fine metal powder, typically no larger
Increases. The 'green' part will shrink
removed after molding, but may be
than 25 microns (0.00098 in.) in diameter,
roughly 15-20% during sintering, to
problematic in surface textures and
is compounded with a thermoplastic
accommodate the loss of material during
threads. Incorporating flat areas in
and wax binder. The spherical metal
debinding. The resulting metal part has
particles make up roughly 80% of the
very little porosity.
threads and locating the partition line in
• Rapid cycle time similar to injection molding (30-60 seconds typically) • Debinding and sintering (2-3 days)
non-critical areas reduce such problems. After sintering, MIM parts are almost 100% dense and have isotropic
mixture. The manufacturers themselves
Certain parts, especially those with
often make up this feedstock and so the
overhanging features, are supported
exact ingredients are likely to be a well-
in specially designed ceramic support
guarded secret.
plates so that they do not sag at high
INTRODUCTION
TYPICAL APPLICATIONS
produce the intricate features and
characteristics. In other words, there
Metal injection molding (MIM) is a
MIM is capable of producing a wide
accuracy of MIM.
is very little porosity.This ensures the
powder process and a similar technique,
range of geometries and so is utilized
MIM reduces, or eliminates, the
structural integrity and ductility of the
known as powder injection molding
in many industries. The accuracy and
needfor secondary operations such as
metal part (see artwork, above, stage 2).
(PIM), is used to shape ceramic materials
speed of the process mate it ideal for
machining. It is capable of producing
and metal composites.
manufacturing components for the
parts with a complexity and intricacy that may not be feasible in any other
DESIGN OPPORTUNITIES
Left These bent samples
Design opportunities and consideration
demonstrate the
processes. Secondary operations can also
for MIM are more closely related to
structural integrity and ductility of
work out much more expensive for large
injection molding than to conventional
MIM material.
volumes of production.
metalwork. For example, MIM can
MIM combines the processing
advantages of injection molding with
aerospace, automotive and consumer electronics industries.
the physical characteristics of metals. It is thereby possible to form complex shapes,
RELATED PROCESSES
with intricate surface details and precise
Investment casting (page 130), die
dimensions. Parts are ductile, resilient
QUALITY
subsequent secondary operations of
and strong, and can be processed in the
casting (page 124),forging (page 114) and CNC machining (page 182) can be
Like injection molding, the high
conventional metalworking because
same way as other metal parts, including
used to produce similar geometries. In
pressures used in this process ensure
it can produce complex and intricate
welding, machining, bending, polishing
fact, investment casting and MIM are
good surface finish, fine reproduction of
geometries in a single operation.Tools
an d el ectropl ati n g.
often interchangeable, depending on
detail and, most importantly, excellent
can have moving cores and unscrewing
tolerances and intricacy of features.
repeatability. However, MIM has the
threads for example, making the
small components generally up to 100 g
While die casting can produce similar
same potential defects, including sink
inclusion of internal threads, undercuts andblindholes possible.
This process is suitable for forming
For MIM, the injection molding machines are modified slightly in order
temperature. Parts with flat bases usually do not require additional support.
reduce the number of components and
(3-53 oz). As with conventional injection
features and tolerances to MIM, it can be
marks, weld lines andflash. Unlike many
molding (page 50), MIM is predominantly
used only for non-ferrous materials, not
plastics, metal parts can be ground and
used for high volume production,
for steels and high melting point metals.
polished to improve surface finish.
although low to medium volumes can be
Forging is generally chosen for larger
viable where MIM offers technical, design
components, typically those weighing
Careful design will eliminate the
Complex tooling, because it comprises m ovin g parts, m ay in crease tool
costs significantly, but if it eliminates
needfor secondary operations.This is
secondary operations on the MIM parts
or production advantages over other
more than 100 g (3.53 oz), in ferrous and
especially important for flash at joint
the extra costs can be offset, particularly
manufacturing processes.
non-ferrous metals, but forging cannot
lines, which becomes a metal burr
where large volumes are required.
Left This range of parts has been produced by the MiM process.
Case Study a-EsoH
Metal injection molding a cog from a window lock mechanism The compounded metal powder and
ejector systems for intricate shapes (image 3).
causes the metal particles to fuse together.
thermoplastic and wax binder are formed
On release from the injection molding
The finished parts have a bright lustre
into pellets for Injection molding (image
equipment, the parts are a dull greyish colour
(image 6). They are solid metal, with very little
i).The metal powder is very fine and the
- which Is referred to as 'green' state - and
porosity. MIM parts have good mechanical
particles spherical to give a final dense
they are surprisingly heavy, due to their high
properties and are stronger and less brittle
sintered structure.
level of metal content. They are replaced onto
than conventionally sintered components.
The injection molding equipment Is
support trays, which are stacked up In the
similar to that used for plastic injection
debind oven (Images 4 and 5). This stage is
(image 2).The mixed materials are not
often manually operated, but Is suitable for
as fluid as thermoplastics. The tooling is
automation If the volumes justify it.
generally machined from tool steel and can have moving cores, inserts and complex
The binder is completely removed in the rn
debind oven, then high temperature sintering
o —j o o
r*
E3
Without any additional costs
A significant consideration and
problems. Like injection molding, the
COMPATIBLE MATERIALS
wall thickness should remain constant.
The most common metallic materials for
pi asti c in j ecti on, th e part 1 s m ol ded in
sintered it cannot be recycled so easily,
MIM are ferrous metals including low
30-60 seconds. Unlike injection molding,
but rejects are rare at that stage as parts
the parts need to have the binder
are accurate andrepeatable.
The plastic binder is vaporized during the debinding operation and collected in
textures and other surface details can be
limitation on the process is the size of
incorporated into the molding process,
part.The general size rangeisfrom o.i g
eliminating these as finishing operations.
to 100 g (0.0035-3.53 oz).or UP to 15° t11"11
and keep material consumption to a
alloy steels, tool steels, stainless steels,
To maintain a uniform wall thickness
Injection cycle time is rapid: like
recycled. Once the material has been
(5.91 in.) in length. Such size restrictions
minimum, it is necessary to core out bulk
magnetic alloys and bronze. Aluminium
removed and then be sintered, which is
relate to the sintering operation, which
parts with recesses, blind holes and even
and zinc are not suitable, and parts in
usually done over a further 2-3 days, as
produce these with a depth to diameter
removes the plastic matrix and causes
through holes.
these materials can usually be made as
the debinding time is 15-20 hours, plus
waste traps, without any environmental
ratio of up toiotoi.
the part to shrink considerably. Large
die castings.
several hours for sintering. Labour costs
problem.
Holes and recesses can be molded
into the metal part and it is feasible to
Internal corners are a source of stress
parts and thick wall sections are more
concentration and so should have a
DESIGN CONSIDERATIONS
likely to distort during the heating and
minimum radius of 0.4mm (0.016 in.).
COSTS
is often fully automated. However, MIM
Like conventional injection molding,
sintering process.
Outside corners can be sharp or curved,
Tooling costs are similarto plastic
requires sintering, which does Increase manual operations and so costs.
when designing for MIM it is essential
are low for injection molding because it
depending on the requirements of the
injection moldtools.The MIM materials
to involve the manufacturer in the
1 mm and 5 mm (0.04-0.2 in.). It is
design. Draft angles are not normally
are typically high cost, due to the level of
development process to ensure that
possible to produce wall thicknesses
required, except for long draw faces,
processing andpretreatment necessary
ENVIRONMENTAL IMPACTS
the part is designed to optimize the full
of 0.3 mm to 10 mm (0.012-0.4 in.), but
which makes the designer's job easier.
to make them suitable for the Injection
Scrap material in the injection molding
Wall thickness is generally between
Featured Manufacturer
Metal Injection Mouldings www.metalinjection.co.uk
advantage of the MIM process.
such extreme measurements may cause
molding operation.
cycle, including feeders, can be directly
Electroforming Process
Forming Technology
Electroforming Electroforming is electroplating onto non-conductive surfaces. The object being electroformed can be used as a mold, or encapsulated. Electroforming is an extremely precise technique for reproducing sheet geometries.
Costs
Typical Applications
Suitability
• Low tooling costs generally • High unit costs, partly dependent on electroforming material
• Architecture and interiors • Biomedical • Jewelry, silversmithing and sculpture
• One-off to batch production
INTRODUCTION
The electroforming process is carried
Electroforming is the same as
out in solution and on a mandrel.
electroplating (page 364), but it is carried
Therefore, part geometry is not restricted
out on non-conductive or non-adherent
by conventional mechanical problems
metal surfaces (such as stainless steel).
such as the application of pressure.
It is made possible by covering the non-
This means that a perfectly flat surface
conductive material (mandrel) with
is made in exactly the same way as an
a layer of silver particles. This forms a
undulating and intricate engraving.
surface onto which metal is deposited.
Adding ribs, recesses and embossed
TECHNICAL DESCRIPTION
design features affects neither the cycle
The difference in operation between
onto a plastic support, which holds them
time northe cost of electroforming.
electroforming and electroplating is that
in shape during electroforming. Rigid
the forming process is generally carried
plastics can be molded or machined and
out more slowly, for improved accuracy.
used for mandrels for more precise parts.
The process builds up the metal layer in a gradual andprecise manner.The electroformed product will be an exact
Quality
Related Processes
Speed
• Very high: exact replica of the mold with relatively uniform wall thickness
• CNC machining • Investment casting • Laser cutting and engraving
• Very long cycle time (a few hours up to several weeks), depends on the materials and thickness of electroforming
replica of the mandrel. It is suitable for
TYPICAL APPLICATIONS
very small parts as well as large and
Due to its exceptional accuracy,
complex shapes.
electroforming is used in applications
mandrel is connected to a DC power
builds up on the surface of the workpiece,
that are dimensionally precise. For
supply. This causes suspended metal ions
the ionic content of the electrolytic
in the electrolytic solution to bond with it
solution is constantly replenished by
and build up a layer of pure metal.
dissolution of the metal anodes, which
example, it is popular for biomedical equipment, microsieves, filters, optical equipment and razor foils. It is used to make tools for composite
laminating (page 206), embossing and metal stamping (page 82). Electroformed nickel tooling largerthan 1 m3 (35 ft3)
The coating on the surface of the
The mandrel is generally designed to be removed and reused; it may also
be permanently encapsulated within
As the thickness of electroplating
are suspended in the electrolyte in a perforated conductive basket.
The process is indefinite, although
the electroforming, or dissolved away.
wall thickness is generally between
Encapsulation can take place on almost
5 microns (0.00019 in.) and 25 mm (1 in.).
any material, including wood, plastic
Process time, which can take anything
can work out less expensive than CNC
and ceramics. An example of a mandrel
from a few hours to 3 weeks, is computer-
machining (page 182) steel mold tools
material is silicone rubber, which is
controlled to ensure a high degree of
frojn solid.
durable and reusable. They are mounted
accuracy and repeatability.
Decorative applications include interior fittings, sculptures, lighting, jewelry and tableware. Metal film props,
QUALITY
such as masks and goblets, are also made
holograms. Similar sheet geometries
in this way because electroforming
can be made by investment casting
The metals used in electroforming
can reproduce very fine details and is
(page 130), with its lost wax process, and
-nickel, copper, silver and gold - are
suitable for small batch production runs.
electroforming is sometimes used to
generally quite soft, with the exception
Examples of mandrels include molded
produce the molds for the wax patterns
of nickel, and so have to be built up in
rubber and wooden carvings. Either can
that are used for investment casting.
sufficient thicknesses to produce self-
be used to produce electroformings or
Electroforming mandrels are made
supporting structures.The metal content can be controlled with extreme precision:
by rapid prototyping (page 232), laser cutting and engraving (page 248),
for example, silver electroformed parts
RELATED PROCESSES ^
manual engraving, CNC machining,
are 100% silver, which is more than
Electroforming is unmatched in its ability
vacuum casting (page 40) and injection
sterling silver parts.
to reproduce the surface of a mandrel to
molding (page 50).
metal encapsulations.
within sub microns. It is used to replicate
The surface finish is an exact replica of the surface of the mandrel in reverse.
Case Study
Metal encapsulated wood with gold
Electroforming copper This silicone mandrel is a molding taken from
electroforming tank (images 4 and 5), where
This follows the same basic electroforming
which coat the object In water-based silver
a hand engraving (image i). It is the negative
the electrolytic solution is supplied with fresh
process as In the case study opposite except
nitrate and a reducing agent. Combined,
of the product, so will make replicas of the
ions by pure copper anodes (image 6). The
that the mandrel Is covered entirely by
they react to leave a thin film of pure silver
original as electroformings.
copper is deposited on the surface of the
a uniform metal layer and so cannot be
(image 3).This Is the same process as the
mandrel to form a uniform wall thickness.
reused. The permanently encapsulated
mirroring of glass.
The mandrel is coated with pure silver powder (image 2), which provides a base
mandrel is often used as a pattern to
After 48 hours this part will be
The metal encapsulated mandrel
onto which the copper will deposit and grow.
fully formed (image 7) and have a wall
make reusable mandrels for subsequent
is then ready to be coated in gold by
The whole face needs to be charged with
thickness of 1 mm (0,04 in.). It is then
electroforming operations.
electroforming. After processing, the part is
a DC electrical current, so copper wires are
removed from the mandrel, which can be
The original wooden carving (image 1) is
connected away from the critical face of the
cleaned up and reused. The electroformed
sprayed so It has a silver conductive surface
part, on the flange of the mandrel (image 3).
part is cleaned, too, and trimmed prior to
(image 2). The spray gun has 2 nozzles.
The mandrel Is then submerged in the
subsequent processing (image 8).
selectively polished to highlight the carving details (image 4).
DESIGN CONSIDERATIONS This process has high operating costs,
which do not come down significantly with an increase in volume. The wall thickness of an electroformed part is uniform. Depending on the requirements of the application,
4
these are typically between 5 microns (0.00019 in-) arici 25171171
(i in.) thick. The maximum size for electroforming
is determined by the tank size. Typically
Featured Manufacturer
this is up to 2 m2 (21.5 ft2). However, there BJS Company
are tanks large enough to form metal
www.bjsco.com
parts up to 16 m2 (172 ft2). At this size dimensional tolerance is reduced to 500 microns (0.019 i1"1-)- Parts electroformed in very large tanks can take up to 3 weeks
such as wood or metal, while others are
depending on the finishing involved.
made specially for electroforming, which
Some parts require a high level of surface
can be more expensive.
finish, which tends to be a manual job.
COMPATIBLE MATERIALS
BJS Company
Therefore, quality of finish is determined by the original product.
Labour costs are moderate to high
needs of the application. Featured Manufacturer
www.bjsco.com
produced directly from a carved master,
to form a sufficient wall thickness for the
Cycle time depends on the thickness
Almost any material, such as
of electroforming. It is also determined
ENVIRONMENTAL IMPACTS
wood, ceramics and plastic, can be
by the rate of deposition, temperature
Electroforming is an additive rather than
electroformed or encapsulated with
an d el ectropl ated m etal.
Wall thickness on a part is built up at
reductive process. In other words, only the required amount of material is used
base material with the decorative and
m etal. Any m ateri al th at can n ot be
manufactured in a relatively inexpensive
hardwearing properties of another
used as a mandrel can be reproduced
approximately 25 microns (0.00098 in.)
material, such as copper or nickel, which
material on the surface.
in silicone, which is also suitable for the
per hour for silver and up to 250 microns
electroforming process.
(0.0098 in.) per hour for nickel.The rate
of deposition will influence the quality
are carefully controlled with extraction
of the electroforming: slower processes
and filtration to ensure minimal environmental impact.
Electroformed products can be
DESIGN OPPORTUNITIES
can be deposited at faster rates than
Because mandrels can be made from
other metals. Once the process has been
Electroforming can be used to reproduce work that would take too long
semi-flexible rubber, intricate shapes and
completed, the electroformed part can
by h an d or any oth er m ean s: for exam pi e,
COSTS
re-entrant angles can be produced with a
then be electroplated, to combine the
intricate engravings can be reproduced
Tooling costs depend on the complexity
tend to produce a more precise coating
single mandrel.
cost effectiveness and strength of the
many times with electroforming.
of the mandrel Some mandrels are
thickness than faster ones.
and so there is less waste. However, plenty of hazardous chemicals are used in the process.These
Centrifugal Casting Process Central feed core
Runner Central system feed core
Die cavity
Solidified wall thickness
Open mold
Half
Forming Technology
Centrifugal Casting Spinning axis
Centrifugal casting is inexpensive and suitable for casting
INTRODUCTION Centrifugal casting covers a range
metals, plastics, composites and glass. Because tooling costs are very low, this process is used to prototype as well as mass
of spinning processes used to shape
spinning at high speed, the material is forced to flow through the mold cavities.
produce millions of parts.
The mold material - silicone or metal
Costs 1 • Low tooling costs 1 • Low unit costs, but depends on chosen 1 material
Typical Applications
Suitability
• Bathroom fittings • Jewelry • Prototyping and model making
• One-off to high volume production
Quality
Related Processes
Speed
• Very good reproduction of fine detail and surface texture
• Die casting • Investment casting • Sand casting
• Rapid cycle time (0.5-5 minutes typically)
Horizontal casting with multicavity tool
materials in their liquid state. By
Horizontal casting with single cavity tool
Vertical casting with open tool
TECHNICAL DESCRIPTION The tooling for centrifugal casting is either
the silicone to form the die cavity, or It can
Runners can be integrated Into the tooling to
silicone or machined metal. The former
be machined.
encourage air flow out of the die cavity.
- differentiates the 2 main types of
material is used to produce small and
centrifugal casting. Small parts,from
asymmetric parts. Metals are utilized to cast
shown above use tooling made from silicone
afew grams up to 1.5 kg {3.3 lb), can be
high melting temperature materials and
or metal. Molten material is fed along the
centrifugal casting the mold rotates around
cast in silicone molds.This technique
larger parts. Large molds can only produce
central feed core, which Is In the upright
a single axis, whereas rotation molding
is cost effective for producing any
parts that are rotationally symmetrical
position. As the mold spins the metal Is
tools are spun around 2 axes or more. In
quantity of small parts from one-off to
because of the nature of the spinning
forced along the runner system and info
operation, a skin of molten material forms
mass production because the molds are
process. Silicone tooling Is extremely cost
the die cavities. Flash forms between
over the inside surface of the mold to form
relatively inexpensive and are quick to
effective. The pattern can be pushed into
the meeting point of the 2 mold halves.
sheet or hollow geometries.
The 2 horizontal casting techniques
Vertical casting methods are similar to
rotation molding. The difference Is that in
make. Materials that can be cast include white metal, pewter, zinc and plastic. This technique is generally chosen for
RELATED PROCESSES
QUALITY
point materials (steel, aluminium
products that are symmetrical around
Regardless of the material used, this is a
and glass) are cast in metal molds.
an axis of rotation and can be i m (39.4
casting process and many comparable
Spinning the mold at high speed forces thematerial to flow through small die
in.) or more in diameter.The shape and
processes are available for shaping a
cavities. Surface details, complex shapes
complexity of part is limited by the
spectrum of material s: for example,
and thin wall sections are reproduced
nature of the process itself.
metal casting includes sand (page 120),
very well. In small parts tolerances of 250
die (page 124) and investment (page 130)
microns (0.00984 in.) are realistic.
Larger products and higher melting
Composites and powders are also
The fact that centrifugal casting is a
formed in metal molds.This technique
techniques. Comparable shapes can be
is similar to rotation molding (page 36), except that the mold is spun around only
formed in plastic by injection molding
low pressure process has benefits and
(page 50), vacuum casting (page 40) and reaction injection molding (page
limitations for the material quality. For
64). Also, similar glassware can be
the die cavity-as in injection molding
TYPICAL APPLICATIONS
made by press molding (page 176) and
and pressure die casting - so the parts
Silicone molds are used to produce
glassblowing (page 152). The quality that differentiates
therefore tends to be used for parts that
parts for a range of industries.The largest
centrifugal casting from all these
do not have to withstand high loads.
areas of application are for jewelry,
processes is that it combines relatively
However, the benefit of low pressures is
bathroom fittings and architectural
low costs for small parts in materials
that there is less distortion as the part
models.These products are within the
with a melting point below 5000C
cools and shrinks.
size limitations of silicone tooling and
(9320F).The tooling costs for larger parts
Large metal parts that are formed
the low melting point metals are also
and higher melting point materials can
centrifugally have a harder outer surface
sufficiently strong for centrifugal casting.
be relatively small, too, because it is a low
because a higher concentration of
pressure process.
heavier molecules will be forced to the
i axis,instead of 2 axes ormore.
prototypes, models and mass production
Metal molds are used to cast metal pressure vessels,flywheels, pipes and glass tableware.
example, materials are not packed into
will be more porous.This process
periphery of the die cavity.
while in metal molds wall thicknesses can be much larger. Metals produced in silicone mold
centrifugal casting have a low melting point. Therefore, they will not be as
Case Study
Centrifugal casting a pewter scale model This cast pewter part is quite large (image
the flash metal can be collected. The mold is
strong and resilient as metals formed
very hot and so it is set to 1 side and allowed
1) and so each mold can produce only 1 part
spun at high speed. Molten pewter is poured
to cool. From molten to solid state it will
in other ways.To overcome this problem
at a time. The silicone mold is assembled
into the central feed core at more than 4500C
shrink approximately 6%. Centrifugal casting
wall thickness can be increased and ribs
with cores (image 2}. These make it possible
(84O0F) (image 5) and enters the mold, where
is a low pressure process, so the part is less
likely to distort as it cools.
added to the part.
to form re-entrant angles. The 2 halves of
it is pushed through the runner system by
the mold are brought together and located
centrifugal force. It begins to cool and solidify
COMPATIBLE MATERIALS
with pimples and matching recesses on the
very quickly. Once the mold is full of metal the
Silicone molds can be used to cast some
interface (image 3).
plastics including polyurethane. Metals include white metal, pewter and zinc. Metal molds are used to shape most
The mold is placed onto a spinning table
spinning is stopped and the pewter is allowed to rest for 3 minutes.
and clamped between 2 metal discs (image 4),
The mold halves are separated and the
It is sealed into a box during spinning so that
cast metal part is removed (image 6). It is still
other metals, powders (metal, plastic, ceramic and glass) and metal matrix composites.
COSTS Silicone tooling costs are very low,
especially for multiple cavity molds. Metal molds are more expensive, but still relatively inexpensive for their size.
The cycle time for low melting point metals and plastics ranges from 0.5 Top Really small parts, such as this 40:1 scale oil
which is part of a model Raleigh car, displays
to 5 minutes. Glass products can take many days to anneal, depending on the
very fine detailing.
thickness of material. Labour costs are
can for a model railway,
are feasible with
Right
centrifugal casting.
Above
This multi-cavity silicone split mold produces 35 metal parts
A un scale model of an
in a single cycle.
generally low.
ENVIRONMENTAL IMPACTS All scrap metal, thermoplastics and glass
alloy wheel in pewter.
can be directly recycled. Small parts require very little energy to produce,
DESIGN OPPORTUNITIES
Because centrifugal casting is a
while multicavity molds are cost effective
The main opportunities for designers are
low-pressure process, step changes in
and reduce material consumption.
associated with silicone mold centrifugal
wall thickness do not cause significant
casting.This technique can produce from
problems. Also, parts can be fed with
White metal and pewter are alloys of lead.The exception to this rule is British
i to 100 parts in a single cycle.
molten material from multiple points to
Standard pewter, which contains no lead.
Large parts are cast around the central core. Separate gates feed small parts, which are placed around the central coTe,
overcome small wall sections in between
Even though it is a naturally occurring
larger sections.
material, in large enough quantities
As with other metal casting
lead is a pollutant: for example, it causes problems with the nervous system
so many can be cast in a single mold (see
techniques, metal parts can be molded
image, right).
with inserts and removable cores. Parts
if ingested in sufficient quantities.
can also be polished, electroplated,
Therefore, lead should not be used in
painted and powder coated.
products designed for drinking or eating.
Using semi-rigid silicone means complex details and re-entTant angles
that are not suitable in hard tooling can be cast. Multiple cores can be Inserted by
DESIGN CONSIDERATIONS
hand for shapes that even silicone will
In silicone molds wall thickness ranges
CMA Moldform
not tolerate.
from 0.25 mm to 12 mm (0.01-0.472 in.),
www.cmamoldform.co.uk
Featured Manufacturer
Press Braking Process
Hydraulic ram
Forming Technology
Press Braking This simple and versatile technique is utilized to bend sheet
INTRODUCTION
Workpiece
[blank]
Press brakes are fundamental to low
metal profiles for prototypes and batch production. A range of geometries can be formed including bend, continuous and sheet,
to medium volume metalwork.When
t
¦>i4
combined with cutting and joining Die I
equipment, press brakes are capable of producing a range of products including
it is also referred to as brake forming.
Stage 1: Load
continuous, bend and sheet geometries.
Bottom bending
Stage 2: Air bending
Gooseneck bending
They tend to be manually operated and Costs • No cost for standard tooling • Low to moderate unit costs
Typical Applications
Suitability
• Consumer electronics and appliances • Packaging • Transport and automotive
• One-off to batch production
are used for one-off, low volume and batch production up to 5,000 units. Pressure is applied by a hydraulic ram, which forces the metal to bend along a single axis between a punch and die.
Quality • High quality and accurate bends to within ±0.1 mm (0.004 in.)
Related Processes • Extrusion • Metal stamping • Roll forming
Speed • Cycle time of up to 6 bends per minute • Machine set-up time can be long
There are many standard punches and dies, which are used to produce a range
TECHNICAL DESCRIPTION Press brakes are driven by hydraulic rams,
tonnage required to make the form. A typical
which apply vertical pressure. The tonnage
press brake of 100 tonnes (110.2 US tons)
the type of punch and die that are used;
required is determined by U factors: bend
will fold 3 m 110 ft) of 5 mm (0.2 in.) steel in a
there are many different types, including
length, thickness, tensile strength and bend
32 mm (1.26 in.) wide lower die. A narrower
air bending dies, V-dies for bottom bending,
radii. Increasing the width of the lower die
die will require more tonnage.
gooseneck dies, acute angle dies and
increases the bend radii and reduces the
loaded onto the die. In stage 2, pressure
of bends with different angles and
is applied by the hydraulic ram so the
circumferences (see image, opposite),but always in a straight line.
TYPICAL APPLICATIONS Press brakes are versatile machines,
capable of bending both thick and thin sections up to 16 m (52 ft) long. Examples include lorry sidings, architectural metalwork, interiors, kitchens, furniture
In stage 1, the prepared workpiece is
Metal stamping (page 82) can produce shapes with complex undulating profiles in a single operation. Design for this process is very different from that of press braking.
Metal folding is similar to press
punch forces the part to bend. Each bend
structural metalwork and repairs.
into a sheet metalworking production
RELATED PROCESSES
thin walled metal enclosures, packaging
bottom bending with matched dies (also
between bends. Alternatively, the same
for high precision metalwork because it
bend can be made on a batch of parts
needs more pressure to operate.Gooseneck
before the machine is repositioned for
dies are for bending re-entrant angles that
the next operation.
cannot be accessed by a conventional tool.
Right Many different shapes of bend can be formed
volumes less than 5,000 parts. Each bend is another operation andthe machine
include squares, rectangles, pentagons,
has to be set up to accommodate
each bend. While this is not a lengthy process with modern computer-guided machinery, every second counts in high volume production.Thus large volumes of manufacture often justify processes
with highertooling costs provided they reduce the number of operations and cycle time.
without investment in tooling, using standard
and electronics housing, for example. The sorts of geometries that can be made hexagons and tapered shapes.
punches like these.
QUALITY
Roll forming (page 110) shapes
Applying a bend to a sheet of material
metal sheet into continuous profiles
increases its strength, while bending
with a constant wall section and is
processes combine the ductility and
similar to extrusion. Roll forming has
strength of metals to produce parts with
the advantage of being able to process
improved rigidity and lightness.
almost any metal. Extrusion, on the other hand, is capable of producing hollow profiles with varying wall thicknesses.
Air bending is used for most general work such as precision metalwork, while
called V-die bending or coining) is reserved
line.They are used in the manufacture of
This process tends to be limited to
improved durability.
guided machines reposition themselves
bends in thin sheet materials. Metal
and lighting, prototypes and general
rotary dies. Tools can be laser hardened for
takes only a few seconds. Computer-
braking: they are both used to form tight folding machines are often integrated
The geometry of the bend determines
Machines are computer guided, which means they are precise to within at least o.oi mm (0.0004 in-) and can be preprogrammed for any given part.
Even so, the aesthetic quality of press
Case Study
braking is largely dependent on the skill of the operator and their experience with
Press braking an aluminium enclosure
that particular machine, Aluminium blanks are prepared for press
In air bending with standard tooling, the
conventional punch because of the length
DESIGN OPPORTUNITIES
braking by turret punching (page 260) and
metal blank is inserted against a computer-
Press brakes form continuous bends in
deburring, guillotining or laser cutting (page
guided stop (image 2), which ensures that the
sheet material up to 8 m (26 ft) long; 16 m (52 ft) is possible by literally bolting
248). In this case study, the 3 mm (0.118 in.)
part is located precisely prior to bending. The
a way that the punch can access the joint
aluminium blanks were cut out using a turret
downstroke of the punch is smooth to avoid
line as easily as possible and so that bends
machines together. Using an air bending
punch. As much of the preparatory work as
stressing the material unnecessarily and
do not run too dose to the edge (image 10).
die, it is possible to bend a range of
possible is carried out before the bending
takes only a couple of seconds (image 3). The
Bends that run off at an angle, for example,
angles very quickly by depressing the ram
process is done, because this is quicker and
process is repeated to form the second go0
may have to be formed in matched dies to
easier on a flat sheet.
bend (images 4 and 5).
maintain accuracy.
only as much as necessary. Acute-angle
The blanks are processed in batches
dies can form sheet material into acute bends down to 30°, Segmented dies can
produce bends up to specific lengths,
Gooseneck bending (images 6 and 7) is
of the overhang.
The formed joints are designed in a such
Finally the joints are TIG welded, ground
(image 1) so the factory can supply its
used when it would not be possible to form
and polished in preparations for spray
customers just-in-time (JIT).
the second bend (images 8 and 9) with a
painting (images 11 and 12).
which means multiple bends can be made simultaneously.
Press brakes have the capability of producing long, tapered and segmented
profiles, which are not possible with roll forming or extrusion.
DESIGN CONSIDERATIONS The main limitation of press braking is that it can do only straight line bends. The internal radius is roughly 1 times
is cold formed. Beyond this, the surface
tooling will increase the unit price,
material thickness for ductile material and 3 times material thickness for
of the material reaches the extent of its
depending on the size and complexity
ductility and will tear. Introducing heat
of the bend.
hard materials. Bend allowance (also
to the bend area means the process
Cycle time is up to 6 bends per minute
referred to as stretch allowance) is
can bend higher thicknesses and the
used to calculate the dimensions of a
limitation is then machine capability.
Set-up can take a long time but is greatly
piece of metal post-forming. Generally,
Maximum dimensions are generally
reduced by a skilled operator.
it is sufficient to add the length of arc through the middle of the material
limited by sheet size because lengths up to 16 m (52 ft) have been bent for street
operations because a high level of skill
thickness to calculate the dimensions
lighting, for example.
and experience are required to produce
on modern computer guided equipment.
Labour costs are high for manual
accurate parts.
of the flat net shape.
COMPATIBLE MATERIALS
The punch has to apply pressure along the entire length of the bend. Hollow
Almost all metals can be formed
parts are produced by fabricating sheet
using press braking, including steel,
Bending is an efficient use of materials
geometries post-bending.This is also a
aluminium, copper and titanium. Ductile
and energy.There is no scrap in the
consideration for enclosures with 2 close
metals will bend more easily and so
bending operation, although there may
90° angle bends that form an undercut
thicker sections can be formed.
be scrap produced in the preparation
Punches with overhanging features can
COSTS
subsequent finishing operations.
be used; they reach into undercuts and
Standard tooling is used to produce
apply pressure along the entire length of
a wide range of bent geometries: for
the bend.
example, an air bending die can produce
(of the metal blank, for example) and in
feature (re-entrant), for example.
The maximum thickness (subject
ENVIRONMENTAL IMPACTS
arange of angles down to very acute
to the capability of the machine) is
bends. However, this is less accurate than
approximately 50 mm (2 in.) if the metal
V-dies for bottom bending. Specialized
Featured Manufacturer Cove Industries www.cove-industries.co.uk
TECHNICAL DESCRIPTION
Studio Glassblowing Process
There are many stages to glassblowing by
Air blown in Blowing iron
hand, and everything that is needed for this process must be prepared in advance in order not to waste time and fuel because
Forming Technology
glassblowing is carried out at temperatures
Glassblowing
Cracked off
in excess of 600°C (1112°F). The glass used in studio glassblowing is typically soda lime or crystal glass. It is
Both decorative and functional, hollow and open-ended vessels can be created by glassblowing. The process involves blowing
INTRODUCTION Glassblowing has been used to create a
multitude of household and industrial
maintained at more than 1120°C (2(K8°F) in a crucible, which is accessible through a small hole in the side of the furnace. It is only cooled down when the crucible needs
a bubble of air inside a mass of molten glass, which is either
products for centuries. However, many
to be removed and replenished, which is
of the blown glass products that we
gathered on the end of a blowing iron or pressed into a mold.
approximately every 18 months. The surface
use today are manufactured in 2 ways.
of the glass can develop a skin over time;
Th e fi rst m eth od i s "kn 0wn as 'studio
this is periodically skimmed off.
glass' and is the production of one-off Costs • High tooling costs for mechanized production, low for studio glassblowing • Unit cost for mechanized production is low
Quality • High quality and high perceived value
Typical Applications • Food and beverage packaging • Pharmaceutical packaging • Tableware and cookware
Related Processes • Glass press molding • Plastic blow molding • Water jet cutting and scoring
Suitability • One-off to high volume production
Speed • Fast cycle time if mechanized • Slow to very slow cycle time for studio glassblowing
In stage 1, the nose of the blowing
Stage 1
Stage 2
Stage 3
Stage U
Stage 5
Stage 6
Stage 7 Finished container
glass at a working temperature because if
way. In stage 3, profiled formers or molds
the glass cools below 600°C (1112°F) and is
may be used to shape the glass accurately.
pieces, generally with artistic expression.
iron is preheated in a small kiln, raising
The second method is mechanized
its temperature to above 600oC (1112°F).
reheated it may suffer thermal shock, which
In stage 4, pucellas (sprung metal tongsj
production and can be divided into 2
Once it is glowing red hot a small piece of
will cause it to shatter.
are used to reduce the diameter of the glass
main categories: machine press and
coloured glass is attached to the blowing
press; and machine press and blow.
end. The coloured glass and nose of the
decorated in many ways. Coloured glass and
shaping of the glass and to achieve straight-
blowing iron are dipped into the crucible of
silver foils can be rolled onto the surface and
sided vessels, for example.
molten glass at between 30° and ^5°. Molten
then encapsulated into the part with another
glass is gathered onto the end of the blowing
layer of clear glass. Coloured threads of
onto a punting iron, or 'punty'. This is a
iron by making up to 4 full turns so that even
glass can be trailed over the surface of the
steel rod with a small glass gather, which
coverage is achieved. The blowing iron must
parison from a separate gather. These trails
is attached to the base of the workpiece
now be constantly turned for the duration
can be dragged over the surface of the glass
by an assistant guided by the glassmaker.
of the process to prevent the glass from
to create patterns, in a technique known as
In stage 5, the glass vessel is 'cracked off
slumping.
'feathering'.
the blowing Iron and in stages 6 and 7 it is
Mouth glassblowing has been practised for over 20 centuries. Before the development of blowing irons, hollow containers were made using friable cores that could be scraped out once the glass
had solidified. High volume mechanized production uses compressed air to blow molten glass into cooled molds, which greatly accelerates the rate of production.
The parison of hot glass is rolled on a
The molten glass can be marked and
Many tools are needed to shape the hot
vessel. Formers are utilized to control the
In stage 4, the workpiece is transferred
shaped from the open end. The finished part
'marvering' table, which has a polished
glass when it is being blown. Blocks of wood
Is placed in an annealing kiln. Annealing
metal surface. The process of 'marvering'
and paper are used to prepare the parison
is the process of cooling glass down over a
TYPICAL APPLICATIONS
begins the shaping of the glass. In stage
and shape the glass. The blocks of wood are
prolonged period. This is essential because
Glassblowing is suitable for a variety of
2, air is blown in and it is intermittently
kept submerged in water so that they do not
stress build-up occurs in glass of varying
vessels, containers and bottles, which
inserted into the 'gloryhole' to maintain its
catch fire when they are held directly against
thickness as it cools at different rates and
include tableware, cookware, food and
temperature above 600°C (1112°F). This is
the surface of the glass. Paper pads are
this can result in shattering. The annealing
pharmaceutical packaging, storage
a gas-fired chamber that is used to keep the
sprinkled with water and used in the same
process gradually relieves these stresses.
scoring (page 276) are used to profile
the raw material. Surface imperfections
exciting effects. A method called'graal'
sheet materials.
can be minimized by tempering, and
is used to create sophisticated patterns
jars and tumblers. Glassware is ideal
for applications that require chemical resistance and hygienic qualities.
RELATED PROCESSES Many items of packaging that were
QUALITY
previously made in glass are now
Glass is a material that has a high
producedbyblowmolding plastic (page
perceived value because it combines
22).This process is used to manufacture
decorative qualities with great inherent
careful mixing and heating of batch
and textures on the surface of glass
glass with cullet (recyclate) will ensure the highest quality of finished product.
by etching into a layer of colour on the surface of a blown and cooled parison, which is then reheated and coated in
DESIGN OPPORTUNITIES
another layer of glass to form the final
domestic, pharmaceutical, agricultural
strength. Certain glass materials can
Because the studio glass processes
product. It is possible to create a layer of
and industrial containers. Glass press
withstand intense heating and cooling,
are free from the limitations of mass
cracks in the surface of glass by dipping
molding (page 176) is used to produce
and sudden temperature changes.
production, there are many ways that
ahot parison into warm water and then
glassmakers can manipulate the shape
reheating it.The effect of the water is to
and surface of the glass to create
cover the surface with cracks. Air bubbles
open-mouthed and sheet geometries,
The structure is weakened only by
while water jet cutting (page 272) and
surface imperfections and impurities in
Case Study
Studio glassblowing into a mold The glass vessel being made here was
All the time the studio glassblower is rolling
designed by Peter Furlonger in 2005 and
the hot glass back and forth on the blowing
and 6oo°C (932-1112^) in a small kiln.The
is being blown by the studio team at The
iron. This ensures that the glass does not
blown glass parison is placed in the mold,
National Glass Centre.
slump and deform.
rotated and blown simultaneously forcing it
The blowing iron is preheated until it is
The hot glass parison is then laid into a
The mold is preheated to between 500°C
against the relatively cooler mold walls, which
glowing red, around 5oo0C (iii20F).Then a
dish of blue powdered glass (image 5). Layers
lump of coloured glass is attached to the end
of colour are built up in this way to create
glass cools down and loses its red glow. The
of the blowing iron (image 1). It is brought up
added'depth'in the abrasive blasted finish,
glassblower then uses a blowtorch to produce
to working temperature in a 'gloryhole' and
which is applied later (page 388).
a metallic effect on the outside of the vessel
'marvered' on a polished steel table (image 2).
The coloured glass is then dipped into a
The gloryhole is used to maintain the temperature of the glass at above 6oo0C
starts to harden the glass (image 9).The
(image 10).This effect will be used to enhance the effects of abrasive blasting.
crucible of molten glass in a furnace, which
(ni20F) and around 8oo0C (i4720F) (image 6),
is maintained at more than 1120C (20480F),
where it feels like sticky toffee, and can be
to size by'cracking-off'the top (image 11).
and an even coating of clear glass is gathered
easily shaped and worked (image 7).
The final blown vessel (image 12) is annealed
over the coloured glass (image 3). The hot
The glass parison is blown and heated
glass is shaped into a parison using cherry
and shaped until it is a suitable size with
wood formers that have been soaked in water
adequate wall thickness for molding
(image 4). This process is repeated several times
The parison is in its final shape. It Is cut
before it is finished with abrasive blasting.
(image 8). During blowing the temperature of the glass must be above 6oo0C (in20F) so
until there is plenty of glass on the end of the
that it can be manipulated: any colder and it
blowing iron for the next stage of the process.
will become too rigid.
can be encapsulated in the walls of
DESIGN CONSIDERATIONS
high tooling costs and set-up time mean
a glass vessel by pricking the molten parison with pins andthen sealing the small bubbles of air in with another
Studio glassblowing is limited in size onlyby the dimensions ofthe'gloryhole'
that this process is suitable only for runs
layer of glass. Coloured glass can be
This process is nearly always carried out
about stress concentrations in the final
trailed across the surface of the parison,
by 2 people and so can be expensive. A
product. Smoothing out the shape as
or coloured glass pieces can be rolled
typical blown part can be made in 20
much as possible will reduce stress,
onto the surface to create controlled and
minutes or so, while more complex and
although tight radii can be achieved
beautiful patterns. Mechanized methods are used only for mass production. Very precise detail
and what the glassmaker can handle.
Designers must be very considerate
sophisticated techniques will increase
where necessary. Problems may occur
the operation times dramatically. The
in screw cap features, for example.
experience of the maker, however, will
Designers generally work to draft angles of 5° but this is not a problem when working with round and elliptical
can be achieved such as screw threads
limit the effects that can be achieved and
and embossed logos.The tolerances are
the rate of production.
fine and repeatability is good.
of at least 10,000 parts.
Products for mass production
shapes. It is advised that parts are
glassblowing have to be designed to
kept symmetrical and that the neck is
accommodate the production line.The
centralized because the product has to fit
Case Study
Studio glassblowing with coloured effects mass of glass is wound around a punty, which
coils the glass and transfers the spiralling
of the glass is also maintained throughout
glass. This is a relatively simple piece designed
pattern from longitudinal to helix (image
the entire process, at more than 8oo0C
by him and blown by Layne Rowe; it shows
5). The mixed colour parison Is worked on a
(i4720F) in a 'gloryhole' (image 10).
some of the weaith of techniques used by the
marvering tabie and cherry wood formers are
London Glassblowing studio team.
used to create a uniform and stable shape.
The spiralling pattern within the glass can
on the punty enables the glassblower to
now been seen (image 6). The glass parison,
develop the shape further; by forming,
A small piece of white glass is attached to the
which has now been transferred to a blowing
pulling a stem or flattening it on a cork table,
end of a punty together with a 'gob' of clear
iron, is dipped into the crucible in the furnace
for example. In this case the glassblower is
glass (image 2). The white giass is heated
and a'gather'of clear glass forms a coating
making a bowl and so needs to expand the
to around 8oo0C (i4720F) and is worked on
over the pattern, which is worked in a wood
diameter of the rim. This is achieved with
a 'marver'table into a long thin rod. At this
block or former (image 7),
pucellas, which are used to draw out the hot
point a gob of molten red and clear glass is
in and out of the gloryhole to maintain the
over the white glass (image 3). Overlaying
glass on the end of the blowing iron to start
required working temperature. Once the
coloured glass builds up strata that add visual
blowing (image 8). The blowing process
bowl is finished, he cracks it off the end of the
depth to the final piece.
expands the gob of glass, magnifying the
punty and it is transferred to an annealing
pattern as it does so. While the parison is
kiln for controlled cooling over a period of 36
marvering table and then swung, which
blown it is continuously rotated and worked
hours (image 13).
exploits gravity to elongate it. A thin stream
with damp paper pads to coax the glass into
of molten blue glass is then trailed across (image 4). At this stage it is difficult to differentiate the colours, as they are all glowing red hot. At this point, the glass gob comprises a white core, with overlaid red and clear
glass and a trailed blue spiral. To enhance the pattern even further, the molten
Tooling costs are high for mechanized production methods, but are low to non¬
COMPATIBLE MATERIALS
existent for studio glassblowing, where
Soda-lime glass is the most commonly
equipment costs are low. For different
used for high-volume production, it
products, studio glassblowing often
is made up of silica sand, soda ash,
utilizes the same tools, which include
limestone and other additives. Light
metal tongs, paper formers, cherry wood
shades, tableware, cut glass, crystal glass
paddles and cork tables.
and decorative objects are typically made
Cycle time is governed by the
from lead alkali glass. Borosilicate glass
preparation and annealing required in
is used for laboratory equipment, high temperature lighting applications and
glass production. Mechanized molding
cookware.
Clark produce in excess of 15,000 glass
cycles are extremely fast. Beatson containers every 24hours (see case study,
Featured Manufacturer
London Glassblowing www.londonglassblowing.co.uk
page 159). Studio glass, on the other hand.
glass (image 12). All the time he 1s moving it
repeated 2 or 3 times, until there Is sufficient
the surface of the overlaid gob In a spiral
labelling lines.
The process of gathering and forming is
gathered onto a punty and allowed to run
The overlaid glass is worked on the
COSTS
Once blowing is complete, the parison is transferred onto a punty (image 11). Working
preheated in a small gas-fired kiln (image 1).
The 'punty' and biowing irons are
into conventional production,filling and
the desired shape (image 9). The temperature
Peter Layton is renowned for his use of colour
to produce dynamic and engaging works in
o CO CD (X)
Machine Glassblowing Process
is a much slower process that requires
Machine blow and blow method
great skill and experience. Each product could take between 5 minutes and 2
Stage 3
of stages required.
Stage U
Stage 5
mechanized methods and are relatively
main raw ingredient, silica sand, comprises
dispense them on a conveyor belt that
higher in studio glass, due to the high
about 70% of the final product and is piled
transfers the hot glass products (5500C/
level of craftsmanship needed,
up inside the factory (irnage 1). The various
io220F) to a gas-fired lehrfor annealing.
ENVIRONMENTAL IMPACTS ideal for packaging that will be refilled, especially for food an d beverag es, which greatly extends a product's useful life. Successful refilling systems, such as the
Finnish drinks bottles and British milk bottles, are refilled tens of times before Stage 3
Stage 5
Finished Stage 6 container
they need to be recycled. All scrap glass material can be
TECHNICAL DESCRIPTION The mechanized glassblowing process
injected through the mold into the formed
begins in the mixing department, where
neck. In the press and blow method, all
the raw materials are mixed together.
of this is done by a plunger. In stage U,
is injected through the neck to blow the
so there have been many developments
to form a homogenous, molten mass.
vessel into its final shape. The glass cools
in recent years to reduce energy
Glass is drawn through the furnace and
against the sides of the mold before it
consumption. Improved furnace design
opens and releases the part. The vessels
and production techniques reduce energy usage and thus reduce the price
(2100°F|. This process takes up to 24
surface treatment process to apply an
ofproduction.The raw ingredients
hours.
external coating, which helps the glass
of glass can affect its environmental
maintain its strength during its working
credentials because they are mainly
life. The vessels are fed by conveyor belt
oxides, which will find their way into the
through the annealing lehr to remove
atmosphere during production.
is then subject to rigorous inspections,
pressed or blown. The press and blow
including sidewall and base scans,
method is more suited to wide-mouth jars,
pressure tests, bore tests and the flatness
whereas the blow and blow technique is
of the sealing surface.
Robotic arms invert the parisons through
cn (T) cd
180° as the freshly blown bottles are
z:
cd
Glassblowing is energy intensive and
are then passed through a 'hot end'
that the parison (pre-form) Is either
O
the blowing mold (image 4) in tandem.
landfill every year in the UK alone.
conditioned (slowly cooled) to its working
lehr to improve the product's resistance to
and the neck is formed. These formed
parisons (image 3) are then transferred to
tonnes of container glass still make it to
temperature of approximately 1150°C
scratching and scuffing. Every container
and are fed into an automated packaging machine (image 9).
molds, into which the molten glass settles
the surface of the cool mold (image 6).
1500°C (2730°F) where they fuse together
processes are essentially the same, except
The gobs are fed along tracks to the
degradation. Even so, more than 1 million
to the second blow mold. In stage 6, air
treatment is added at the 'cold end' of the
forehearth and is cut into 'gobs' (image 2).
remanufactured many times without
the glass-melting furnace with cutlet at
press and blow or blow and blow. The
the production line as a single stream
air, which forces the molten glass onto
180°. In stage 5, the bottle is transferred
molding methods that are used, either
areas (image 8). The finished bottles leave
glass flows from the bottom of the
recycling because it can be melted and
to make clear glass. They are fed into
any stress build-up. A second surface
the glass-melting furnace the conditioned
and the bottles are filled with compressed
the mold opens and a partially formed
machine below. There are 2 different
are moved towards testing and inspection
removed (image 5). The split mold closes
vessel is released and inverted through
'gobs'. These are fed into a bottle-making
Having left the lehr, the bank of bottles
molten glass, and after sufficient time in
recycled directly in the manufacturing
with additives, or a decolourant is added
bottom of the forehearth and is cut into
continuously all year round (image 7) and
ingredients are mixed and melted to form
process. Glass is an ideal material for
At this stage they are either coloured
The conditioned glass flows from the
All 16 blowing molds produce bottles
made using the blow and blow method. The
Glass is along-lasting.material. It is
| Gob
A 500 ml (0.88 pint) beer bottle can be
Labour costs are relatively low for
Finished Stage 6 bottle
Machine press and blow method
Stage 1 Stage 2
Mechanized glassblowing a beer bottle
hours to blow, depending on the number
T Stage 1 Stage 2
Case Study
used for containers with a narrower neck. In stage 1, the molten glass gob is guided along tracks into a parison mold.
In stage 2 of the blow and blow method, a plunger rises and presses a neck into the molten glass, and in stage 3, air is
Featured Manufacturer Beatson Clark www.beatsonclark.co.uk
Lampworking Operations Workpiece: sealed glass tube
Localized heating . upto 1000oC
Localized heating up
Blowing
Hole boring (18320FI
to 1000oC (18320F)
Forming Technology
Lampworking
Rubber bung Air blown in by lampworker
Glass is formed into hollow shapes and vessels by lampworking, also known as 'flameworking', by a combination of intense heat and manipulation by a skilled lampworker. Products range from
Stage 2: Forming
INTRODUCTION Hot glass forms easily
The process of lampworking has been
Cold glass remains unchanged
around since the development of the Bunsen burner around 150 years ago. It is currently used to shape glass into
jewelry to complex scientific laboratory equipment.
functional and decorative objects.
Localized heating up
to 1000oC (18320Fl
Bending
Mandrel forming
Workpiece: glass tube
Cooling glass maintains shape Mandrel rotated
Thisis ahotforming process: borosilicate glass is formed at 800-
• Typically no tooling costs • Moderate to high unit costs
Typical Applications
Suitability
i2000C (i472-2i920F) and soda-lime
• Artwork • Jewelry • Laboratory equipment
• One-off to batch production
glass is formed at 500-700^
Workpiece glass tube or rod gradually heated up to working temperature
(g32-i2920F). A great deal of skill and experience are required to work hot glass
Quality
Related Processes
Speed
• Very high quality, but depends on the skill of the lampworker
Glass press molding • Glassblowing
• Moderate to long cycle time, depending on the size and complexity of part
intimately, and therefore this is one of
the few industries that still
Cold glass remains unchanged
trains apprentice workers. Applied pressure
Hot glass forms easily Stage 2: Forming
Lampworking is carried out in i of 2 ways: benchwork or lathework.
TECHNICAL DESCRIPTION
Benchwork can be used to create
Although benchworking and latheworking
complex, intricate and asymmetric
are carried out in different ways, they
if needed. The tools used are similar to
shapes, whereas lathework is suitable
use the same basic techniques such
those for glassblowing; various formers
for parts that are symmetrical around an
as blowing, bending, hole boring and
shape the workpiece and 'marver' the hot
axis of rotation (or at least partly so).
mandrel forming.
glass. Tungsten tweezers are used to pull
Benchwork is generally limited to 30 mm (1.18 in.) diameter tube; it is
impractical for the lampworker to hold anything larger and manipulate it at the same time. Latheworking is suitable formuch largertube diameters (upto 415 mm/16.34 in.).
A mixture of natural gas and oxygen
desired shape - with very fine tolerances
glass across a surface or to bore holes.
are burnt to generate the heat required
Trails of coloured glass can be pulled
for lampworking. Alternatively, propane
across the surface or metal leaf feathered
is used instead of natural gas, but it
onto the hot glass.
burns much hotter and so reduces the
Everything made in this way has to be
temperature range at which the glass
annealed in a kiln. For borosilicate glass
can be formed. The working temperature
the temperature of the kiln is brought
is 800-1200°C |U72-21920F| for
up to approximately 570°C (1058°F) and
borosilicate glass, at which stage it has
then maintained for 20 minutes, after
TYPICAL APPLICATIONS
the flexibility of softened chewing gum.
which it is slowly cooled down to room
Lampworking is the only way to make
All parts of the workpiece must be kept at
temperature. This process is essential to
certain specialized scientific apparatus
a similar temperature to avoid cracking.
andprecision glassware.When combined
with casting and grinding, lampworking
The workpiece can then be rolled,
blown, twisted, bent or shaped into the
relieve built up stress within the glass. Some very large pieces, such as artworks, can takes several weeks to anneal.
2 "D
s
o
aj
Case Study
Benchworking a total condensation stillhead A total condensation stillhead (variable
twist and seal the end of the glass tube
the previously formed part. Once in place,
takeoff pattern) is a piece of scientific
(image 3). From the cool end, air is then blown
the 2 parts are heated simultaneously, which
apparatus used for a specific distillation
into the part, forcing the hot end of the tube
causes the glass to fuse and join (image
process. This case study demonstrates some
into an even bubble (image 4). At each stage
11). A tight bend is achieved at the neck by
of the techniques used to produce it. Like any
of the process the accuracy of the parts are
blowing into the tube - air pressure acts like
other lampworking, a stillhead starts as a
checked against the drawing (image 5).
series of glass tubes that are cut to length in preparation for the flamework itself. The lampworker uses a technical drawing
a mandrel, which stops the walls collapsing
The blown tube is placed back into the
- and by forming the bend by hand (image 12).
flame and tungsten picks are used to form
This relatively simple subassembly (image 13)
a hole (image 6), which is opened out with a
will form only a small section of the stillhead.
(BS 308) to ensure that the product is to be
tungsten reamer (image 7). In the meantime
constructed to close tolerances (image 1).
the second part of the stillhead is brought
The first part of the stillhead is brought up
up to temperature (image 8) and drawn out
to working temperature and starts to glow
without reducing the wall thickness (image
cherry red (image 2). When hot enough the
9). It is heated around its circumference and
glass can be pulled and manipulated like
the hot glass is pushed back on itself to create
chewing gum. Tungsten picks are used to
a rib (image 10). This will help to locate it in
is used to produce everything from test tubes to complex process glassware.
Many industries utilize the versatility of lampworking in glass for prototyping and plant equipment. It is also used in
the jewelry industry to make beads and other decorative pieces. Architects and
artists alike have applied this process to lighting, sculptures andfunctional parts of their designs.
forming, cutting and joining action. Even tiny stresses in the part will cause the
RELATED PROCESSES
glass to shatter or crack. Annealing the
Lampworking needs a great deal of
parts after lampworking ensures they
skill; even simple shapes can be time-
are stabilized and stress free.
consuming to produce. Geometries that
are suitable for glassblowing (page 152)
DESIGN OPPORTUNITIES
or press molding (page 176) will therefore
The size, geometry and complexity of a
be made in that way as soon as the
part are limited only by the imagination
volumes justifythetooling costs.
of the designer. Lampworking is equally
3
suitable for precise functional objects
QUALITY
and decorative fluid artefacts.
The quality of the part is largely dependent on the skill of the lampworker.
DESIGN CONSIDERATIONS
During operation, the parts have to be
Everything made in this way comes from
carefully heated and cooled for each
a combination oftube and rod glass. 4
JdV ¦pj
to temperature it is carefully bent by hand
it out and into the profile that will neatly fit
coated mandrel. The glass must reach its
(image 16) to form the final bend (image 17).
the hole (images 21 and 22). The 2 parts are
optimum temperature just before it is formed
J 1
A glass spiral Is created using a graphite-
M
the other hand, can be found in domestic
suitable for automation. Where possible,
expansion (COE) to be compatible. COE is the rate at which the glass molecules
applications such as packaging, bottles,
glassblowing and press molding are
windows and lighting. It is known as 'soft
used to produce standard parts that are
expand and contract during the heating
glass', because it has a lower melting
finished or assembled with lampworking,
and cooling process. A part made up of
temperature. Soda-lime glass is less
to reduce cycle time andlabour costs.
glass with different COE values will crack
expensive; unlike borosilicate, however,
or shatter because of the build-up of
it cannot be mended or reformed once
stress within the material.
it has been annealed. One of the most
Glass scrap is recycled by the supplier, so
common artistic glasses is Morettl Glass,
no glass is wasted during the process.
The various ranges of glass are
idiosyncratic; they have different colour
manufactured in Murano, Italy.
fuses (images 23 and 24). A complete stillhead
complete, so assembly can start.This process
stretch rather than bend. Such an operation
comprises heating and boring holes and then
(image 25) takes 4,A hours to create from start
requires a great deal of skill and experience.
joining the parts together with a flame. To
to finish.
The glass tube may sag very slightly just
do this, a very small area is heated (image 18)
before it is formed over the mandrel
and then blown, forcing the glass to stretch
(image 14).
until it can be removed with the tungsten picks.The hole is opened out to the correct
section, using a much larger area of heat
diameter with a tungsten reamer (image
(image 15). Spreading the heat out makes
19). The extension that will be joined to the
sure that the U-bend will be even across a
assembly is prepared by cutting it to length
large diameter. As soon as the glass is up
with the flame (image 20) and then opening
20
21
22
23
ENVIRONMENTAL IMPACTS
A great deal of heat is required to bring the glass up to working
options, operating temperatures and prices.The lampworker will advise the
COSTS
designer as to which is most suitable for
There are usually no tooling costs, while
and oxygen are burnt to produce heat.
their particular application.
cycle time Is moderate, but depends
The combustion is non-toxic, but the
on the size and complexity of the part.
glass becomes so bright when it is heated
temperature. A mixture of natural gas
COMPATIBLE MATERIALS
The annealing process Is usually run
that protective eyewear must be worn.
All types of glass can be formed by
overnight, for up to 16 hours, but can
The glasses are fitted with didymium
lampworking.The 2 main types are
take a lot longer depending on material
lenses, which filter the bright yellow
borosilicate and soda-lime glass.
thickness.Very thick glass may take
sodium flare and prevent cataracts.They
Borosilicate glass is a'hard glass'known
several months to anneal, because in
also enable the lampworker to see what
underthe leading trade names Pyrex®,
such cases the temperature is lowered by
he or she is doing.
Duran® and Simax®. It is very resistant
only i.50C (2.70F) per day.
to chemicals, so is ideal for laboratory
brought together and heated until the glass
over the mandrel; if it is too hot, the glass will
A U-bend is then worked in another tube
The glass must have equal coefficient of
The stillhead parts are then almost
Labour costs are high due to the
equipment, pharmaceutical packaging
level of skill required-lampworking
and preservation jars. Soda-lime glass, on
being complex and therefore not
Featured Manufacturer
Dixon Glass www.dixonglass.co.uk
— ,
¦
Case Study
Latheworking the triple walled reaction vessel A lathe can be used to form large and smal)
a hole is opened out using another profiled
parts very accurately. The only requirement
carbon bar (image 3). These form the first 2
Once all 3 jackets of the reaction vessel are brought together, an extension tube is fused
is that they are rotationally symmetrical up
reaction vessel jackets, which are assembled
onto the bottom, using the heat of the gas
to a certain point (the final part may have
off the lathe (image 4). Throughout the
torch in much the same way as benchworking
additions that are not symmetrical).
process the assembly has been spinning to
(image 8). Some extra touches are added by
The operation starts with a large tube section being heated gently to raise its
ensure even heat distribution.
A rod of glass is used to pick hot glass from
temperature while spinning at approximately
the melt zone (image 5) and to bore a hole
5o rpm (image i).The neck of the innermost
(image 6). The hole Is opened out and the 2
jacket is formed with intense localized heat
parts are fused together using the profiled
and a profiled carbon bar (image 2). The 2
carbon bar (image 7). The process is repeated
halves of the tube section are separated, and
for the third and final jacket.
boring and joining onto the outer jacket of the reaction vessel (images 9 and 10) to create the semi-finished product (image n).
> CO CO
o o m >
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Featured Manufacturer Dixon Glass www.dixonglass.co.uk
TECHNICAL DESCRIPTION
Throwing Process
In stage 1 for wheel thrown pottery,
the clay body is 'pugged' in a pug mill.
Electric motor
This process has 2 main functions: it
thoroughly mixes and conditions the
Forming Technology
Air pocket
Clay Throwing
clay for throwing, and it removes some
_ Mixing paddle
of the air pockets. Some pug mills
Drive shaft
are equipped with a vacuum pump to remove even more air. Pugging is
Ceramic products that are symmetrical around an axis of rotation
INTRODUCTION
can be made on a potter's wheel. The style, shape and function of
Throwing (also known as turning) is used to produce sheet and hollow shapes that
each piece can be as varied as the potter who creates it, and each
frequently carried out at the beginning of the day, for 1 hour or so, in order to
produce sufficient pugged clay for a day's throwing. Prior to throwing the
are rotationally symmetrical. It is often
clay is 'wedged' by hand to improve the Rotating clay pot
combined with other processes to make
studio adapts and develops their own techniques.
working consistency of the material.
more complex products, with handles
In stage 2, the predetermined
and feet, for example.
quantity of clay is 'thrown' onto a 'bat',
Clay throwing has been used for Costs
Typical Applications
Suitability
centuries all over the world to create a
1 No tooling costs 1 Low to moderate unit costs
• Gardenware • Kitchenware • Tableware
• One-off and low volume production
diversity of products. The process relies
Quality • Variable, because handmade
Related Processes • Ceramic slip casting • Press molding ceramics
which is then placed on the potter's Extruded clay plug
wheel. The ball of clay is centred on the spinning wheel, which is generally
Potter's wheel
on the skill of the potter to create high
powered by an electric motor but can
quality and uniform pieces.
be driven by a kick wheel.
TYPICAL APPLICATIONS
gradually draws the clay vertically
While the wheel turns, the potter
Speed • Moderate cycle time (15-45 minutes), depending on size and complexity • Long firing process (8-12 hours)
upwards, to create a cylinder with an
Generally clay throwing is used to
Stage 1: Pug mill
Stage 2: Throwing
produce one-off and short production
even wall thickness. Clay throwing must always start In this way, to ensure
runs of gardenware such as pots and
parts will be rotationally symmetrical.
but depends on the complexity and size
fountains. Kitchenware and tableware,
To create asymmetric shapes, other skills
of the part. For example, simple shapes
such as pots, jugs, vases, plates and bowls,
such as handwork, carving and pressing
can be produced within 15 minutes or so,
are also manufactured in this way.
are combined with clay throwing. Knobs,
whereas tall or particularly 1 arge parts
feet, spouts and other embellishments
may have to be formed in stages, which
can be added post-throwing.
air dried together for about an hour,
weather and ambient temperature
RELATED PROCESSES
even wall thickness and distribution of stress, even though the shape can
subsequently be manipulated into a variety of geometries.
The bat and thrown part are then
press molded ceramics (page 176)
DESIGN CONSIDERATIONS
prolongs cycle time.The firing time can be quite long and is determined by whether the parts are biscuit fired and
use molds and so are more suitable
The size of part is restricted by the skill of
then glaze fired, or are once-fired only.
for making identical parts than clay
th.e potter, the quality of the wheel, the wall thickness and the size of the kiln.
each potter requires a high level of
At this point the part is trimmed, to
Wall thickness ranges from 5 mm (0.2 in.)
technical ability to throw accurate pieces.
remove any excess material, and
Slip casting ceramics (page 168) and
throwing.
QUALITY
Labour costs are moderate because
ENVIRONMENTAL IMPACTS COMPATIBLE MATERIALS
pots tend to have a variable quality that depends on the skill of the potter and on
Clay materials including earthenware,
this pottery-forming process. Any scrap
the material itself. Earthenware is the
stoneware and porcelain can be thrown
produced during the throwing process
most commonly used pottery ceramic.
on a potter's wheel. Porcelain is the
can be directly recycled. Once fired,
It is brittle and porous and has to be
most difficult material to throw and
discarded pieces are not reworked into
sealed with a glaze to be watertight.
earthenware the easiest, because it is
thrown clay unless special effects are
Earthenware garden products are prone
more robust and forgiving (see ceramic
required. Some studios,for example, mix
to crack in freezing conditions because
slip casting).
'green'and fired clay with fresh clay to
they absorb water.
There are no harmful by-products from
affect how long clay takes to dry out.
as feet, handles or stands.
The firing process can be carried out in the same way as with ceramic
slip casting and press molding ceramics, or it can be done in a single operation, known as 'once-fired'. Parts
produce speckled and decorative effects.
COSTS
or until the clay is leather-hard. The
assembled with any other parts such
for small parts up to 25 mm (1 in.).
Because they are handmade, thrown
removed from the potter's wheel, and
The firing process is energy intensive.
DESIGN OPPORTUNITIES
There are no tooling costs for the clay
Therefore the kiln is fully loaded for each
By the very nature of this process all
throwing process. Cycle time is moderate.
firing cycle.'Once-firing'reduces energy
with delicate features, such as cups
with handles, are biscuit fired first to minimize the risk of breaking during glaze firing.
Case Study
Hand throwing a garden pot Although premixed day is supplied to the
in i throw, as here, a second level of day
first until it is the same diameter and wall
studio (image i), it still has to be pugged in a
needs to be added. Potters have developed
thickness at the top (image 10). It does not,
pug mill and 'wedged'by hand.The extruded
a technique that enables them to build a
however, have a solid base. It is turned upside
pug of day is weighed into predetermined
pot higher than 1 throw would usually allow,
down and placed carefully on top of the first
quantities and worked by hand into the
but it takes a great deal of skill because the
part (image 11). The clay parts are aligned
correct consistency for throwing (image 2).
lower part has to match the additional piece
and joined together. Once the bat has been
Pummelling the clay levels the density of the
very accurately.
removed from the base of the top part, the
material and makes it supple for shaping. The predetermined quantity of day is then
The sides of the first part are smoothed (image 5) and then the top is finished with
thrower smooths the joint line and continues to shape the pot upwards (image 12).
thrown down onto the bat. This action makes
a level top, achieved using a flat blade. Its
the clay denser at the base, which helps to
height and diameter are checked (image 6)
give it strength.The lump of clay is rotated
and it is fired with a gas torch, which hardens
is to be once-fired, the glaze is applied before
and 'centred' by hand, until the mass of the
the clay very slightly and just enough for it to
the pot has been biscuit fired. The wet glaze
clay is rotationally symmetrical and can be
be self-supporting (image 7). Once the clay is
is painted on using a small pipette (image
shaped. The potter then makes a doughnut
sufficiently green-hard, the top is trimmed for
13). The pot is placed in the kiln for firing at
shape (image 3), which is drawn up into a
a second time (image 8).
lyoo'C (3092°?) for 8-12 hours (image 14),
cylinder with even wall thickness (image 4). Once the cylinder has reached the desired
For the second part of the pot, the potter's
wheel is prepared (image 9) and another ball
height the part can be shaped. However, if the
of clay is thrown onto the bat. The second
day pot being made is too high to be shaped
part is thrown in much the same way as the
Featured Manufacturer S. & B. Evans & Sons www.sandbevansandsons.com
The completed pot is left to air dry until it is green-hard throughout. Because this pot
after which the finished pot is removed from the kiln (image 15).
Slip Casting Process
Preprepared
Flash lines to be removed i Molds : separated
Forming Technology
Ceramic Slip Casting
1 Part ready for trimming, assembly and firing
Identical hollow shapes with an even wall thickness can be
molded in several pieces and assembled, or be formed in a multiple-part mold.
produced with this versatile ceramic production technique. It is
Assembly operations are preferably
used in the manufacture of many familiar household items and
avoided because of their cost, but they are sometime unavoidable. It is very
remains a largely manual operated process.
important that the product is designed
Stage 1: Fill with slip Stage 2: Ceramic deposit forms
Stage 3: Demolding
with consideration forthe process.
TECHNICAL DESCRIPTION 1 Low tooling costs Moderate to high unit costs
Quality
I
• Surface finish determined by mold, glaze and skill of the operator
Typical Applications
Suitability
DESIGN CONSIDERATIONS
In stage 1, the mold is prepared so It Is
• Bathroom whiteware • Kitchen and tableware • Lighting
• Low volume and batch production
The slip casting process relies on a
clean and free from any previous slip
carefully removed from the mold and
porous plaster mold drawing moisture
contamination. For intricate molds and
fettled to remove any flash.
small details a fine dust can be used to
Related Processes
Speed
• Clay throwing • Press molded ceramics
• Moderate cycle time (0.4-4 hours), depending on size and complexity • Long firing process (up to 48 hours)
from the slip by capillary action.The slip must be exactly the right consistency and the plaster mold sufficiently dry so that they work in harmony.
taken to ensure that the molds are
can withstand manhandling. The length
The design and construction of the
plaster mold will have an impact on the
INTRODUCTION
cream ware (a type of earthenware made
QUALITY
quality of the slip casting. Plaster molds
Ceramic slip casting is ideal for the manufacture of multiple identical
from white Cornish clay combined with
The overall quality of the final piece is
are generally produced directly from
a translucent glaze), and stoneware and
largely dependent on the skill of the
the master, which can be made of clay,
products. A permanent plaster mold can
operator.The materials used in slip
wood, rubber or other modelmaking
casting are generally quite brittle and
material.The parting lines are worked
replacing, and automated slip casting
porcelain (fine, high quality materials that can be fired at high temperatures to enhance their shiny white and
porous, which means that they are not
techniques can make many thousands of
sometimes translucent qualities).
very tough and tend to fracture rather
produce up to 50 pieces before it needs
parts. Numerous household objects and
than deform underload. Earthenware,
In stage 3, the 'leatherware' is
The next stages of processing depend
ensure that the slip casting and molds
on the surface treatment that is going
release cleanly. The molds are fastened
to be used. The parts are left to air dry
together with rubber bands - care being
so that they are self-supporting and
secure and can withstand the appropriate
of time Is determined by the weather
internal pressure, because slip is a
conditions, because hot weather will
relatively heavy material, about twice the
cause the clay to dry out more quickly.
weight of water.
Following cutting, assembly and
Meanwhile, the casting slip has been
sponging, the parts are further air dried
prepared by mixing together clay, silicate,
until the ceramic turns whitish in colour,
soda ash and water. The consistency of
known as 'greenware'. The parts are now
out to optimize production and reduce
the slip is essential for the success of the
ready to be biscuit fired, to remove all
assembly operations.
casting: It must be well blunged and free
remaining moisture. This takes place in
Shrinkage is in the region of 8%, but
from lumps. The mold is filled with the
a kiln over 8 hours. The temperature of
depends on the type of material. Draft
slip and left to stand for 5 to 25 minutes.
the parts is raised to 1125°C (2057oF) and
porous and so have to be glazed to be
angles are not usually a problem because
The length of time the slip is in the mold
retained at that level for 1 hour before
watertight. Stoneware and porcelain,
the molds are inward curving.
and the ambient temperature determines
cooling slowly.
tableware items are produced using this
TYPICAL APPLICATIONS
casting technique.
Slip casting is used to form a wide variety of household items such as basins,
is a finely ground (particle size around
lighting, vases, teapots, jugs, dishes,
on the other hand, have much better
1 micron/0.000039 in.) mixture of clay,
bowls, figurines and other utilitarian
mechanical properties, even though they
is limited for practical reasons such as
minerals, dispersing agents and water.
and decorative objects forthe bathroom,
are still quite brittle.
weight and fragility of the material.
moisture from the slip, causing the
Traditionally, the type of ceramic slip
kitchen and table.
However, large parts, such as shower
clay platelets to pile up around the
'biscuitware' is then glaze fired using
trays, are feasible for ceramic slip casting.
mold wall and create a ceramic deposit
the same cycle as biscuit firing. When
(shell). When the ideal wall thickness Is
the finished ceramic slip castings are
The ceramic slip (also known as slurry)
terracotta and creamware are the most
DESIGN OPPORTUNITIES
used was determined by the location of
the factory because the local clay would
RELATED PROCESSES
This process can be used to produce a
be incorporated in its production.
Clay throwing (page 168) is suitable for
range of both simple and complex 3D
Pottery is the general term used to describe ceramic materials that
The size of part that can be slip cast
COMPATIBLE MATERIALS
sheet geometries. However, it is generally
sheet and hollow geometries. Simple
Ceramic materials such as earthenware,
associated with one-off and low volume
shapes can be slip cast in a single
terracotta, creamware, stoneware and
are suitable for slip casting. Well-
production of idiosyncratic products.
operation, without any assembly: for
porcelain can all be slip cast.The main
known types of pottery materials
Press molding ceramics (page 176) is
example, a conical or straight-sided jug
ingredient for all of the compatible
include earthenware and terracotta
productive and repeatable like ceramic
with handle and spout can be molded in 1
pottery materials is clay, which is
(characteristically reddish orange but its
slip casting, but its application is also
piece. By contrast, objects with undercuts
a natural material that can be dug
colouring varies from country to country),
limited to sheet geometries.
or other intricate details may need to be
up from the ground. It can be mixed
the wall thickness. In stage 2, the plaster mold draws
Following the first firing all remaining surface decoration, such as glazing and hand painting, is carried out. The
achieved the slip Is drained (or poured)
removed from the kiln they are watertight
from the mold. The mold is left to stand
and rigid.
for anything between 1 and 1U hours to ensure that the ceramic shell is sufficiently leather-hard to be removed from the mold.
Case Study
Slip casting the puzzle jug A total of three molds are used in the
mold (image 3).The slip casting is left in the
production of the puzzle Jug. Each mold is
mold for 45 minutes while the plaster molds
even though they have been handmade.
cleaned and prepared and the bottom of the
continue to draw moisture from the slip and
A slip is used to join the parts together so
mold so that each jug will look very similar
mold and the locating points to the main
turn it leather-hard (image 4).The slip casting
they will become integral to the structure
body of the mold are checked (image 1). In
can then be demolded, but this has to be
during biscuit firing. The assembly process
turn each mold is filled to the brim with
carried out very carefully to make sure that
consists of inserting and fixing the inner skin
casting slip made from earthenware (image
it retains its shape (image 5). The casting is
(watertight) and outer skin together at the
2). The molds are left to stand for 15 minutes,
then left to air dry before any further work is
rim, using slip (images 8 and 9), and placing
or until a sufficient wall thickness has built
carried out (image 6).
the handle on the jug (image 10).
up as a deposit on the inside mold wall. The
The outer skin of the puzzle jug is then
remaining slip is poured from the mold into
pierced using a profiled punch (image 7).The
a bath, where it will be recycled for another
floral pattern is marked very lightly on the
After biscuit firing a cream glaze is applied (image 11). The glaze is blue so that the operator can see where the glaze has already
been applied. Finally the puzzle jug is placed into the kiln for glaze firing, which takes up
>
to 8 hours (image 12), after which the finished
o w
jug is removed from the kiln (image 13),
o > cn
with water and a number of different
Ideally, plaster molds comprise only 2 or 3
minerals to create various ceramic slips.
pieces in order to maintain cycle times.
Deflocculants are added to the slip to
Labour costs are moderate to high due
decrease the amount of water required
to the level of skill required, and they can
to make it fluid. This is achieved by aiding
be especially high in handmade pieces.
the suspension of the clay particles in
This is by far the 1 argest expen se an d it
water and reducing the porosity in the
determines the cost of the parts.
final product.
ENVIRONMENTAL IMPACTS COSTS
During slip casting there can be up to
Tooling costs arelow.The plaster molds
15% waste.The majority of this waste can
are generally produced from a rubber or
be directly recycled as slip. However, if the
clay master, which takes a great deal of
parts have been fired then the ceramic
skill to create.They must be engineered
is no longer suitable for recycling.There
not only to eliminate undercuts, but also
are no harmful by-products from these
to contain the least number of pieces.
pottery-forming processes.
Featured Manufacturer Hartley Greens & Co. (Leeds Pottery) www.hartleygreens.com
TECHNICAL DESCRIPTION
Jiggering Process
A plaster 'male' mold is used in the jiggering process and a 'female' one
for the jolleying process. In stage 1, the mold is mounted onto a metal carrier
Forming Technology
attached to an electric motor that spins
Press Molding Ceramics
at high speed. A charge of mixed clay is loaded onto the clean mold. In stage 2,
as the mold and clay spin, the jiggering
Ram pressing, jiggering and jolleying are all techniques for
arm is brought down onto the clay. A
manufacturing multiple replica ceramic parts with permanent
which is different for each mold shape,
profiled former with a shaping blade, forces the clay to take the shape of the
Stage 1: Open mold, loading and unloading
molds. They are used in the production of kitchen and tableware,
rotationally symmetrical mold. The
Finished part trimmed and removed on the mold for support
profiled former determines 1 side of
including pots, cups, bowls, dishes and plates.
the clay part and the mold determines the other side. The process is very rapid and takes less than a minute.
Costs
Typical Applications
Suitability
• Low to medium tooling costs • Low to medium unit costs, depending on level of manual input
• Kitchen and tableware • Sinks and basins • Tiles
• Low to high volume production
Once the final shape is complete and the edges have been trimmed, the Pressure applied to shape the clay over the plaster mold
Quality
Related Processes
Speed
• High quality finish
» Ceramic slip casting » Clay throwing
• Rapid cycle time (1-6 per minute], depending on level of automation • Long firing process (up to 48 hours)
Plaster mold rotates at high speed — Metal carrier
mold and clay are removed from the metal carrier intact. The clay part is
left on the mold until it is sufficiently 'green' to be removed. If the part is
demolded immediately It will deform Stage 2: Closed mold
because the clay is still very supple.
The length of time is determined by
INTRODUCTION
and tableware vessels), sinks and basins,
DESIGN OPPORTUNITIES
In this process, clay is forced into sheet
jewelry andtiles.
COSTS
Jiggering and ram pressing can be used
andprofiling tool to shape the clay.This means that jiggering is more suitable for
Tooling costs for jiggering are relatively
the weather conditions and ambient temperature: a hot environment will cause the clay to dry out more
to produce most shapes that can be
prototyping and shot production runs.
low because a single sided mold is used.
Parts are compressed and have an even
RELATED PROCESSES
slip cast in a 2 part mold. Using molds
For volume production multiple tools are
wall thickness. Press molding is often
Clay throwing (pagei68) and ceramic
increases repeatability and uniformity
The heat of the ram press molds 1 e ath er h arden s th e cl ay duri n g th e
required because the clay has to be left
piercing or assembly, then the clay
em ployed for the mass production of
slip casting (page 172) are used to make
of part, so even tall objects are easily
pressing cycle, which means that the
on the mold to air dry.
part Is transferred onto a 'female'
popular ceramic flatware andtiles.
similar products and geometries.
produced with minimum skill. Manual
part can be removed from the mold
Press molding differs from them by
operations, such as adding handles and
immediately. Jiggered parts, on the
are in the region of 10-20 times the cost
press ceramics are jiggering (known as
specializing in high volume and the rapid
spouts, ten d to require a hi gher 1 evel of
othex hand, have to be left to air dry on
of jiggering molds. However, they have a
jolleying if the mold is in contact with the outside surface of the part rather than
production of identical parts.
operator skill.
the mold. This causes a problem, in that
higheryield than jiggering molds, more
many molds have to be used to form
rapid turnover and they last many more
waste caused by inconsistency.There
the inside surface) and ram pressing.
OUALITY
being able to produce shapes that are
multiple products and these take up a
cycles (approximately 10,000).
are no harmful by-products from these
Although both of these processes can be
The pottery materials used in press
not rotationally symmetrical. Many
large amount of storage space.
automated, jiggering andjolleying are
molding are brittle and porous (see
design features (handles and decoration,
often carried out as manual operations
ceramic slip casting), so the surface is
for example) can be pressed directly onto
and can be used only on geometries
often made vitreous by glazing, which
the part to reduce or eliminate assembly
that are symmetrical around an axis of
provides a watertight seal.
and cutting operations.The part is
COMPATIBLE MATERIALS
pressed and cut in a single operation,
Clay materials including earthenware,
operations, but for automated
thereby reducing cycle time dramatically.
stoneware and porcelain can be pressed.
techniques they are relatively low.
geometries using permanent molds,
The 2 main techniques used to
Ram pressing has the advantage of
Shrinkage is in the region of 8%, but does depend on the type of material.
Ram pressing uses split molds, which
Cycle time is rapid for ram pressing
and slightly slowerfor jiggering.
quickly, if there are secondary operations to be carried out, such as
support mold.
pottery forming processes. The firing process is energy intensive,
Automated processes accelerate
so therefore the kiln is fully loaded for
production of press moldings.
each firing cycle.
Labour costs are higher for manual
rotation. Ram pressing can be utilized to
A very high surface finish can be
make symmetrical shapes as well as oval,
achieved with both jiggering and ram
square, triangular and irregular ones.
pressing techniques. When compared to ceramic slip casting and clay throwing,
DESIGN CONSIDERATIONS
not watered down for these processes.
ENVIRONMENTAL IMPACTS
TYPICAL APPLICATIONS
press molding has the advantage of
The 2 part mold used in ram pressing has
However, it is essential that the material
In all pressing operations scrap is
Uses for press molding ceramics include
producing parts that are uniform and
to be made to tight tolerances to ensure
i s suffi ci ently m oi st to fl ow duri n g th e
produced at the 'green' stage and so
flatware (such as plates, bowls, cups
compressed and therefore less prone
accurate and uniform reproductions. By
pressing cycle. The clay used for ram
can be directly recycled. Using molds to
and saucers, dishes and other kitchen
to warpage.
contrast, jiggering uses a single mold
pressing is slightly stiffen
reproduce the parts accurately reduces
Unlike ceramic slip casting, the day is
Case Study
Jiggering a plate If numerous identical parts are being made
profiled former shapes the outside surface
the plate is transferred onto a female support
biscuitware is then placed in specifically
with this process, then multiple plaster molds
while the mold shapes the inside surface
mold. The rim can then be pierced without
designed 'setters' and glaze fired using
are required (image i) because the parts have
(image 4). While the part is still spinning
forcing it out of shape (image 7). The part is
the same cycle (image 9). When the
to be left on the molds while they harden to a
on the mold, the edge is trimmed, to form a
then ready to be biscuit fired, to remove all
finished ceramic plates are removed from
'green' state. Each mold is made individually.
perfectly symmetrical shape (image 5). The
remaining moisture. This takes place in a kiln
the kiln they are watertight and rigid
mold and clay part are removed intact, so that
over 8 hours. The temperature of the parts is
(image io).
the clay can air dry and harden sufficiently
raised and then soaked at i^s'C (2057°F)fon
out to form an even and uniform 'pancake' of
before it is removed from the mold for biscuit
hour before cooling slowly.
clay (image 2). The pancake is then transferred
firing (image 6).
To press mold each part, a charge of mixed
clay is spun on a jiggering wheel so it spreads
onto the plaster mold (image 3). The jiggering arm is brought down onto the day and a
In this case the piece of flatware is to be pierced and so after a few hours of air drying
Following the first firing, all remaining surface decoration is carried out such as
glazing (image 8) and hand painting. The
I
Featured Manufacturer Hartley Greens & Co. (Leeds Potteryl www.hartleygreens.conn
TECHNICAL DESCRIPTION
Ram Press Process
This is an automated process that forms parts by hydraulic action. Each product
will be identical and manufactured to fixed tolerances. The molds are typically made of plaster, although these have
Metal die casting
a limited lifespan. The die casings can be made to accommodate either 1 large
Cutting edge
part or several smaller objects. In stage 1, a charge of mixed clay is
Charge of clay Hydraulic ram
Metal die casting
loaded into the lower mold. In stage 2,
Porous lower mold
the upper and lower molds are brought together at pressures from 69 N/cm2 to
276 N/cm21100-A00 psi). The pressure
Stage 1: Open mold, loading and unloading Finished part removed and trimmed
is evenly distributed across molds and through the clay, which produces even
Upper platen
and uniform parts. During the pressing cycle the warm plaster molds draw moisture from the clay, to accelerate
Excess flash
the hardening process. The perimeters
Pressed flatware
of each mold cavity on the upper and Lower platen
lower section come together to cut the excess flash from the clay part. The
Stage 2; Closed mold
ram pressing process is more rapid that
jiggering and can produce up to 6 cycles every minute.
Once the pressing cycle is complete, the molds separate and the parts are instantly released by steam pressure that is forced through the porous molds. The clay parts are self-supporting and
can be demolded immediately after they have been ram pressed.
Case Study
Ram pressing 2 dishes The day used in ram pressing needs to be slightly stiffer than for jiggering. Some
The molds are separated and any excess
flash is quickly removed for reprocessing
measured charges of mixed clay are cut from
(image 5). The clay parts are instantly ejected
the pug roll (image i).The charges of clay
by steam pressure, which is forced through
are placed into the lower mold cavity (image
the porous plaster mold (irnage 6). The
z) and the 2 halves of the mold are brought
parts are self-supporting as soon as they are
together (image 3). The pressure forces the
demolded because the ram pressing process
clay to flow plastically through the mold
dehydrates the clay during the pressing cycle,
cavity and to squeeze out as flash around the
and this hardens it sufficiently for immediate
edge (image 4).The flash is cut as the molds
biscuit firing. Ram pressed clay parts take
come together and the edges of the mold
glaze and other decoration very well, as the
cavities make contact.
surface is compressed and uniform.
Featured Manufacturer Hartley Greens & Co. (Leeds Pottery) www.hartleygreens.com
TECHNICAL DESCRIPTION
CNC Machining Process
Among the many different types of
Track for Dust extraction unit
CNC machinery, CNC milling machines
O
Forming Technology
yand zaxes
CNC Machining
and CNC routers are essentially the same, CNC lathes, on the other
hand, operate differently because the workpiece is spun rather than the tool.
The woodworking and metalworking Track forx- and y-axis movement
Using CNC machining, CAD data can be transferred directly onto the workpiece. The CNC process is carried out on a milling
Guard
INTRODUCTION CNC machining encompasses a range
traced back to when these materials Chuck and spindle
milling, routing, lathe turning, drilling Vacuum clamp
(boring), bevelling, reaming, engraving
quality end product.
1 • Low tooling costs 1 • Low unit costs
Suitability
materials. The terminology and use
• Automotive • Furniture • Tool making
• One-off to mass production
of CNC machining is related to the
a z-axis track (vertical). Some older versions, or reconditioned machines, Track for z-axis movement
traditional material values of each
Track forx- and y-axis movement
particular industry. For example, CNC
1
Quality
Related Processes
Speed
• High quality finish that can be improved with grinding, sanding and polishing
• Electrical discharge machining • Electroforming • Laser cutting
• Rapid, but depends on size and number of operations
specific tools and equipment.
x- and y-axis tracks (horizontal) and
3-axis CNC with tool carousel
industries for shaping metal, plastic, Typical Applications
were hand worked using material-
Most modern CNC machinery has
and cutting out. It is used in many wood, stone, composite and other
Costs
names for similar tools and operations - the names and practices can be
of processes and operations including
machine, lather or router, and results in a rapid, precise and high
industries will probably use different
have an x- and y-axis table Instead.
Beyond this, there are CNC robotics in development that will occupy a space and move freely within it, rather than
woodworking is affected by grain,
being fixed to a table with tracks. The
greenness and warpage. By contrast,
new technology relies on data for each
CNC metalworking is concerned with
part to be preprogrammed, so that it
Pivoting head
can locate machining and assembly
Pivoting router
operations for each individual piece as it comes across them.
Chuck
Many different tools are used in the cutting process, including cutters (side
Cutting tool
or face), slot drills (cutting action along the shaft as well as the tip for slotting
Table
and profiling), conical, profile, dovetail and flute drills, and ball nose cutters 5-axis CNC with interchangeable tools
(with a dome head, which is ideal for 3D curved surfaces and hollowing out). By contrast, CNC lathes use single-
1 ubri cation, m inute tol eran ces an d th e
rotation are vertical and horizontal, to
point cutters because the workpiece
heat-affected zone (HAZ).
achieve 360° of possible movement.
is spinning.
The number of axes that the CNC
The principles of CNC manufacturing
machine operates on determines the
can be applied to many other processes
geometries that can be cut. In other
such as ultrasonics, fusion welding and
words, a 5-axis machine has a wider
plastic molding.
examples. The 3-axls CNC machine has a tool carousel with an array of cutting tools and drills. This accelerates
range of motion than 2-axis one.The
\ - * a*
There are several ways to change
the cutting tool and here are two
the cutting process dramatically
type of operation can also determine the
TYPICAL APPLICATIONS
number of axes. For example, a lathe has
Almost every factory is now equipped
only 2 possible axes of motion (the depth
with some form of CNC machinery. It is
of cut and position along the length of
an essential part of both prototyping
be changed by hand, but this Is rare.
the workplace), whereas a router can
and mass production lines.Therefore,
In most cases there Is a separate
operate on all 5 axes of possible motion
applications are diverse and widespread
magazine that Is loaded with a set of
(x,y and z axes, and 2 axes of rotation).
across the manufacturing industry.
tools that the CNC head will locate and
The x andy axes are typically horizontal an d th e z axi s i s vertical. Th e 2 axes of
CNC machining isusedfor primary operations such as the production
and tool changes are instant. The 5-axis machine has a single tool. On both CNC machines, the tools can
use automatically.
Case Study
CNC carving the Ercol Windsor chair CNC machining can be used to cut and
With a slot drill, the 3-axis CNC machine
shape a wide range of materials. In this
cuts the external profile of the seat (image
case study, it is used to make the various
3), after which the tool carousel is rotated
components that comprise the beech Erco)
and the edge is profiled with a separate
Windsor chair, Ercol is a manufacturer of
cutting tool (image 4),Then, material is
traditional and contemporary wooden
removed from the top side of the seat
furniture, and they mix craftsmanship
by a dish-shaped cutter, to produce the
with new technology. This combination is
ergonomic profile required (image 5). The
very interesting as it illustrates the vast
process takes less then 2 minutes before
possibilities of CNC machining working
the seat is removed from the vacuum
alongside other processes,
4
3
clamp. A seal runs around the periphery of the vacuum clamp and it maintains the
CNC ROUTING THE SEAT
vacuum within the grooves incised across
A plank of wood is prone to warping and
its surface (image 6). This is a very quick and
buckling. For this reason, the planks used
effective method for clamping continuous
in the seat of the chair are first cut into
runs of the same parts. Because the seat
small widths, which are flipped and glued
is not quite finished it is stacked up for
back together with butt joints (image i).
secondary operations (image 7).
Each section of wood in the plank will then balance the forces of its neighbours. The
Holes are required for assembly, but the 3-axis CNC machine is capable only
planks are cut to size and loaded onto the
of profiling vertical holes. The seats are
CNC machine table (image 2). The parts
therefore loaded onto a 5-axis CNC, which
are pushed firmly onto the vacuum clamp,
drills holes at the correct angle for the legs
which is activated to hold the piece in place.
and back to be assembled.
QUALITY
In operation, there is no difference
This process produces high quality parts
between simple and complex shapes,
with close tolerances. CNC machining
and straight or curved lines.The CNC
is accurate across 2D and 3D curves and
machine sees them as a series of points
straight lines. Depending on the speed of
that need to be connected.This provides
operation, a CNC machine leaves behind
limitless design opportunity.
telltale marks of the cutting process. These can be reduced or eliminated of prototypes to minute tolerances, toolmaking and carving wood. More often, however, it is utilized for secondary operations and post-forming, Including the removal of excess material and boring holes.
RELATED PROCESSES CNC machining is versatile and widely used, competing with many other processes. For toolmaking, it is the most
cost effective method of production up to approximately 1 m3 (35 ft3). Any larger and electroforming (page 140) nickel becomes more cost effective.
Laser cutting (page 248) is suitable for profiling and shaping metals apd plastics as well as other materials. It is rapid and precise and more suitable for certain
applications, such as profiling sheet poly methyl methacrylate acrylic (PMMA). Electrical discharge machining (EDM) (page 254) is used to profile and shape metals. It is used for concave shapes that are not practical for machining.
CNC machining is also used to prototype and manufacture low volumes
of parts that can be formed by steam bending (page 198), die casting (page 124), investment casting (page 130), sand casting (page 120) and injection molding.
DESIGN CONSIDERATIONS
by, for example, sanding, grinding or
Most CNC machining is almost
polishing (page 376) the part.
completely automated, with very little operator interference.This means that
DESIGN OPPORTUNITIES
the process can run indefinitely once
CNC machining can be used to produce
started, especially if the CNC machine
3Dforms directlyfrom CAD data.This
is capable of changing tools itself. The challenge for the designers is to utilize the equipment available; it is no good
is very useful in the design process,
especially for prototyping and smoothing the transition between design and production of apart.
Some CNC machining facilities
designing a part that cannot be made in the identified factory. For parts with geometries that need
are large enough to accommodate a
different cutting heads or operations,
full-scale car (and larger, up to 5 x 10 x
multiple machines are used in sequence.
5 m/16.5 x 33 x 16.5 ft) for prototyping
Once up and running, the CNC process
purposes. Many different materials can
will repeat a sequence of operations very
be machined in this way, including foams
accurately and rapidly. Changing the set¬
and other modelmaking materials.
up is the major cost for these processes,
1,
CNC LATHE TURNING THE CHAIR LEGS The legs and spokes for the chair back are rotationa)ly symmetrical and produced on a CNC lathe. Cut and profiled timber is loaded into the automatic feeder (image 8). This in turn is loaded onto the lathe centres (image 9), which are 'alive'
and rotate with the workpiece (they are known as dead centres when they are
stationary). Each workpiece is spun between the headstock andtailstock of the lathe at high speed (image 10). Parts with large cross-section are spun more
slowly because the outside edge will be spinning proportionately faster. The cutting action is a single, smooth arc made by the cutting head, which carves the workpiece as a continuous
shaving (image 11). These images depict the profiling of a chair leg, which requires a second cutting operation to form a 'bolster' (shoulder) in the top for locating the leg within the seat (image 12). Vertical holes are drilled for the cross bars, which make up the leg assembly (image 13). The profiled legs are loaded into crates for assembly in batches (image 14). They still have a'handle' attached to the top end, which is waste material removed prior to assembly.
and subcontractors often charge set-up
Cycle time is rapid once the machines
time separately from unit costs. As a rule,
are set up. There is very little operator
larger parts, complex and Intricate
involvement, so labour costs are minimal.
shapes and harder materials aremore expensive to machine.
ENVIRONMENTAL IMPACTS This is a reductive process, so generates
COMPATIBLE MATERIALS
waste in operation. Modern CNC systems
Almost any material can be CNC
have very sophisticated dust extraction,
machined, including plastic, metal, wood,
which collects all the waste for recycling
glass, ceramic and composites.
or incinerating for heat and energy use.
The energy is directed to specific parts
COSTS
of the workpiece by means of the cutting
Tooling costs are minimal and are limited
tool, so very little is wasted. Dust that is
to jigs and other clamping equipment.
generated can be hazardous, especially
Some parts will be suitable for clamping
because certain material dusts become
in a vice, so there will be no tooling costs.
volatile when combined.
ASSEMBLING THE ERCOL WINDSOR CHAIR Each chair is assembled by hand because wood is a'live'material which will move and crack and so parts need to be
individually inspected. Adhesive is used in all the joints and soaks into the wood grain to create an integral bond between the parts.
Adhesive is added to each joint with a cue tip (image 15).The legs and cross bars are then carefully put together and the joints 'hammered home' (image 16).The legs come right through the seat and a wedge is driven into the legs' end grain to reinforce the joint (image 17). Once the adhesive is dry the excess material is removed from the seat with a belt sander and a shaped sanding block (image 18). Sanding also improves the cut finish left by the CNC machining. Meanwhile, the backrest for each chair will have been steam bent, the vertical spokes profiled to shape on a CNC lathe, and the relevant parts glued together. After the legs and seat have been assembled the backrest is put in place (image 19), the joints being glued and reinforced in the same way as the legs.
Once the legs have been cut to the same length, the assembled chair is ready for surface finishing (image 20). Featured Manufacturer Ercol Furniture 17
www.ercol.com
Wood Laminating Processes Adhesive applied to inside surfaces
In this process, a series of parallel cuts
Kerfing 1 Parallel
are made in one side of the workpiece.
UIMIMUT IMJUlfUMr
Forming Technology
TECHNICAL DESCRIPTION KERFING
This can be done with a band saw, table saw or router. The kerfs are usually
Grain runs perpendicular to cuts
Wood Laminating
Parts bent by hand or over a mold
between one-third and three-quarters
of the depth of the workpiece. Locally reducing the thickness of material
Multiple sheets of veneer or solid timber are formed using molds and bonded together by very strong adhesives, to produce rigid, lightweight structures.
makes It more pliable, and a smooth
INTRODUCTION There is nothing new about the process
bend can be achieved if the kerfs are
Solid wood lamination
cut close together. In the diagram 2
of bonding 2 or more layers of material
matching kerfed boards have been
together to form a laminate. However,
bent and bonded together to hide the
as a result of developing stronger, more water-resistant and temperature durable
kerfing. Kerfing can also be concealed Wood will be bent along the grain
Adhesive applied to inside surfaces
Wood clamped onto single sided mold
with thick veneer.
adhesives, lighter and more reliable
SOLID WOOD LAMINATING
structures can now be engineered in Costs
Typical Applications
Suitability
laminated wood and so greater creative
• Low tooling costs • Moderate unit costs
• Architecture • Engineering timber • Furniture
• One-off to medium volume production
opportunities have arisen in design and
Plug (upper mold)
be formed using solid wood laminating.
Therefore this process is generally
architecture.There are 3 main areas of
used to strengthen a section of timber
wood lamination: solid wood, wood chip Quality
Related Processes
Speed
and veneer lamination.
• High
• CNC machining • Steam bending
• Medium to long cycle time (up to 24 hours)
Solid wood bending is a cold press process generally limited to a single
Only gradual and large radii bends can
by cutting it into sections and bonding them back together in the desired shape. Laminating reduces shrinkage,
Adhesive applied to inside surfaces
Veneers forced together under pressure
axis. It consists of bending sections of
twisting and warpage, which may be critical to a building project, for
wood and laminating them together with adhesive. It is typically used to
Breuer and the Eames, and more recently
constructions and metal processes. For
form structural elements for buildings.
the Azumis and BarberOsgerby, Veneers
example, light aircraft were once made
To make a tighter bend radii possible,
are laminated onto a single mold, with
from laminated veneers and are now
the wood can be kerfed, that is slots
the addition of a vacuum or split mold.
produced in high tech composites of
can be cut into the inside of the bend,
The adhesives are cured by low voltage
carbon, aramid, glass and thermosetting
perpendicular to the direction of bend.
h eatin g, radi ant h eati n g, radi 0 frequen cy
resins, as developments in technology
VENEER LAMINATING
Laminating then acts as a means of
(RF) or at room temperature,
have made this economically possible.
This is carried out in a number of
example. To maintain the balance
For certain applications, CNC
locking the bend in place. Kerfing is a
between tension and compression, the sections must be inverted on one another if they are cut from the same log, to avoid warpage post-forming.
ways, such as onto a single sided mold,
useful modelmaking technique, as bends
TYPICAL APPLICATIONS
machining (page 182) is an alternative to
with the addition of a vacuum, or in
can be formed in solid sections of wood
Depending on the adhesive, wood
wood laminating. Steam bending (page
a split mold. All use the same basic
or in plywood without high pressure or
laminating processes can be used to
198) can be used to form solid timber.
principle of laminating an odd number
even tooling. Sheets precut with kerfing
produce articles, such as furniture and
A combination of these 2 processes is
of veneers (plies) perpendicular to
already exist for this purpose,
architectural products, for use both
frequently employed to achieve greater
each other, as seen in plywood, with
indoors and outdoors.
flexibility in manufacture.
Wood chip techniques are often used
adhesive under pressure. The wood
is the matrix for the adhesive, which
Wood chip and solid timber
to produce engineering timbers (page 465) for architectural applications such
applications include engineering timber
QUALITY
as load bearing beams, trusses and eaves.
products such as trusses, beams and
The quality of afinished wood laminated
The products are manufactured using
eaves, while veneer laminating and
article is high, although the parts
high pressure and penetrating adhesives
kerfing are used to produce an array of
to bond the wood chips permanently.
products that include seating, storage
often require finishing operations and sanding. The integral quality of the parts is determined by the grade of timber and strength and distribution of the
essential to ensure that the part does
adhesive. Working with timber requires a
not warp. Sheets are laminated this
Veneer lamination is an exciting
and room dividers.
process for designers, and over the years
determines the lamination strength.
Adhesive is applied to the face of each veneer as it is laid on top of the last. The lay-up is symmetrical, with a core made up of an uneven number of plies and face veneers of a similar material and equal thickness. This is
it has been used a great deal in the
RELATED PROCESSES
furniture industry by designers such
Veneer laminating has been replaced
skilled workforce, and these processes are
way to improve their resistance to
as A1 var Aalto, Walter Gropius, Marcel
over the years by other composite
no exception.
shrinkage, warpage and twisting.
Case Study
Veneer laminating preparation The method of preparation is the same for all of the veneer laminating processes. Face veneers are 'bookmatched' or
The core veneers, which are often birch
of a lower grade, are rotary cut (peeled) from a log. Much larger sheets can be
'slipmatched', depending on the grain of the
produced this way than by slicing across
wood. Slipmatching means taking veneers
the width of the log. They are cut to size
from the log and placing them next to one
on a guillotine (image 3). Each layer of
another. In bookmatching the veneers are
veneer is coated with urea-formaldehyde
opened next to one another (like a book) to
(UF) glue (image 4) and then stacked in
create a symmetrical and repeating pattern.
preparation for laminating.
Complex and curving grain is generally bookmatched to avoid it looking too 'busy', whereas straight grained wood is often slipmatched. In this case study the face veneers have
been bookmatched (image i).They are
o o The minimum internal radius is
COSTS
side with a continuous glass filament
developed a unique bending and layering technique that makes it possible
determined by the thickness ofthe
Toolin g costs are 10w to moderate for
coated with a hot melt adhesive (image 2).
to produce much deeper dish profiles.
individual veneers, rather than by the
wood laminating. Wood-based products,
number of veneers or thickness ofthe
such as oriented strand board (OSB)
then stitched together on their reverse
This join needs to hold in place only until the veneers are permanently bonded during lamination.
Cur ve d form s m ade by 1 am in ati n g have minimal spring-back, unlike
Cutting wood into strips, or veneers, and bonding it back together
build.This means that even parts with
and plywood, as well as solid timber can be used to produce molds, which often
greatly improves its strength and
large wall thicknesses can be formed
resistance to shrinkage, twisting and
to tight internal radii. Each veneer is
last for several hundred products. For
warpage. Applying a simple curve
typically between 1 mm and 5 mm
high quantities the wooden molds are
to a structure further improves its
(0.04-0.2 in.) thick,
replaced with aluminium or steel ones.
COMPATIBLE MATERIALS
depends on the adhesive curing system,
Although cycle time can be long, it
strength characteristics.
those made by steam bending, and are
z
The pulp stock is a mixture of 1.4%
In stage 3, the pulp shell is demolded
machine than aluminium. The transfer
pulped paper and water. In stage 1, it is
tool places the pulp shell, which is now
stirred constantly to maintain an even
only 75% water and self-supporting, onto
mixture as the tool is dipped in it. The
a conveyor belt. The shell is then warmed
molding is formed over the tool by a
and dried in an oven for about 15 minutes.
The primary use of paper pulp molding
vacuum, which draws water from the pulp
Alternatively, it is pressed into a hot tool
is for packaging. There are a couple of
stock, and in doing so begins to dry out
that dries it out rapidly.
exceptions, including biodegradable
the pulp shell that forms over it. The tool
flowerpots and even a lampshade.
is dipped in the stock long enough for it to
RELATED PROCESSES Molded expanded polystyrene (page 432), thermoforming (page 30) and die-cut corrugated card (page 266) are all used
pulp moldings are generally accurate to
tools to accommodate the progressively
within o.i mm (o.oo4in.).They can also
shrinking pulp molding.
for similar applications. As well as its
be made resistant to grease and water
environmental benefits, paper pulp has
with an additive known as 'beeswax'.
many other advantages; it is lightweight,
The smoothness of the molding is
DESIGN OPPORTUNITIES The main advantage of paper pulp
improved by wet pressing or hot pressing
molding compared to the related
molded (increases versatility) and
in the drying cycle. With such techniques
processes is its environmental impacts.
relatively inexpensive.
logos and fine text can be embossed
Essentially, paper pulp packaging is
into the molding. Alternatively, parts
board formed into sheet geometries. It
cushioning and protective, anti-static,
steel mesh.
Above Cull-U N packaging is UN certifiedforthe transportation of
Middle
The contents, in a
Top The face oftilis tool is covered with stainless
hazardous chemicals.
QUALITY
can be hot pressed in the final stage
is therefore typically not an added value
The tool is covered with
cardboard box, can be
Paper pulp is made up of natural
of air drying.This technique is a cost
material. However, it can be coloured
holes, for water to be
ingredients and so by its very nature
effective alternative to conventional hot
and printed, foil blocked and blind
is a variable material. Even so, paper
pressing, which requires up to 4 sets of
embossed. It is naturally grey or brown.
drawn through it and a pulp molding to form.
dropped onto a steel plate from 1.4m (4.6ft), without breaking.
Case Study
Molding paper pulp packaging The corrugated card waste produced in
pulp shell is demolded into a transfer tool.
1 side of Culler Packaging's facility is raw
The role of the transfer tool is to place
material in the paper pulp production
the fragile pulp shell carefully onto the
plant (image i). A predetermined quantity
conveyer (image 6).
is loaded into a vat, mixed with water and
The pulp moldings are fed into a gas
pulped gradually with a rotating paddle.
heated oven (image 7). Hot air (2000C/
The process is carried out slowly to avoid
392°F) is gently circulated around the
shortening the fibre length of the pulp.
moldings to dry them out. After 15 minutes
The pulp stock, which is 4% water, is
or so, the completed pulp shells are stacked
fed through a series of vats that remove
onto a pallet for shipping (image 8).
contamination and condition it in preparation for molding (image 2), The tools are mounted on a rotating arm, and usually work in tandem (Image 3). It is important that the tools all require roughly the same mass of pulp to
for the part when it is both wet and
maintain even distribution of pulp in the
dry. This is especially important for air
stock. The tools are dipped into the stock
dried moldings, which have to be self-
for about 1 second (image 4), after which
supporting within seconds of forming,
they emerge coated with a rich brown
because they are deposited onto a
layer of pulp (image 5). The partially dry
conveyor belt while still having at least 75% water content.
When fully dry, any ribbing provides depending on the stock. Brown pulp is
added support for the package contents,
typically made up ofhigh quality craft
including cushioning, strength and a
paper, whereas grey pulp is composed of
friction fit.
recycled newsprint and is not as sturdy or resilient as brown pulp.
Air dried moldings will have 1 smooth side (the tool side) and 1 rough one.The rough side will not show fine details that
Material thickness can range from i mm to 5 mm (0.04-0.2 in.), depending on the design needs. Pulp moldings can be up to 400 x 1,700 mm (15.75 x 66.92 in.) and 165 mm (6.5 in.) deep. Vertical
have been reproduced on the smooth
dipping machines can make products
side. Wet pressing improves surface
deeperthan 165 mm (6.5 in.).
COMPATIBLE MATERIALS
require additional tooling. As the pulp
ENVIRONMENTAL IMPACTS
Draft angles are especially important
This process is specifically designed for
molding dries it shrinks, and so for
This process for disposable packaging has
finish and reduces permeability. Logos,
for this process.The tools come together
molding paper pulp. It can be industrial
hot pressing several sets of tools are
admirable environmental credentials,
instructions and otherfine details can be
along a single axis and there is no room
or post-consumer waste, or a mixture of
sometimes required. Each set of tooling
because it uses ioo% recycled material,
pressed into a partially dry molding.
for adjustment. The molded part must
both of these.
roughly doubles the initial costs.
which can be recycled again and is fully
finish. And hot pressing improves surface
therefore be extracted along that axis.
DESIGN CONSIDERATIONS
It is possible to mix in other fibres,
Cycle time is rapid. Some machines
biodegradable. In the above case study
Draft angles are usually 50 on each
such as flax, with the waste paper
can operate at up to 10 cycles per minute.
from Cullen Packaging, the paper pulp
Paper pulp is made up of cellulose wood
side,but will depend on the design of
material, to reduce further the
However, it is more common to mold
is made up of by-product from their
fibres bonded together with lignin (the
the molding. It must be remembered
environmental impact of the product.
around 5 parts per minute.The drying
corrugated card production facility next
2 main ingredients of wood itself). No
that, when extracted from thetool,the
Additional fibres will affect the aesthetics
time extends the cycle time, adding
door, diverting it from landfill.
additional adhesives, binders or other
molded part comprises up of 75% water
and strength of the part.
ingredients are added to strengthen this
and so is very supple.
natural composite material.Therefore,
The parts are typically stacked onto a
COSTS
the wall thickness is increased and ribs
pallet and,because of the draft angle, the
Tooling costs are generally low but
are designed in for added strength.
parts can be packed more densely, saving
do depend on the complexity of the
The ribbing provides added strength
on costly transportation expenses.
roughly 15 minutes to the process. Hot pressing is quicker.
molding. Wet pressing and hot pressing
Labour costs are relatively low because most operations are automated.
Waste produced by th e process can be directly recycled and averages 3%. Water used in production is continuously recycled to reduce energy consumption.
Featured Manufacturer
Cullen Packaging www.cuUen.co.uk
Forming Technology
Composite Laminating Strong fibres and rigid plastics can be amalgamated to form ultra lightweight and robust products, using composite laminating. A range of material combinations is used to produce parts that are suitable for the demands of high performance applications.
INTRODUCTION
are used to apply heat and pressure
Composite laminating is an exciting
during the curing phase.
range of processes that are used in the
Pre-preg is the most expensive
construction of racing cars, aeroplanes
composite laminating process, and
and sailing boats alike.
therefore is limited to applications
There are 3 main types of laminating:
where performance is critical. It is made
wet lay-up, pre-preg (short term for
up of a mat of woven reinforcement
o o
pre-impregnatedwith resin) and resin
with resin impregnated between the
T3
Costs
Typical Applications
Suitability
transfer molding (RTM) (also known
fibres. The quantity of resin is precise, so
• Moderate to high tooling costs • Moderate to high unit costs, determined by surface area, complexity and performance
• Aerospace • Furniture • Racing cars
• One-off to batch production
as resin infusion).The resins used are
each layer of the lamination provides
Quality • High performance lightweight products
Related Processes • DMC and SMC molding • Injection molding • Thermoforming
Speed • Long cycle time (1-150 hours), depending on complexity and size of part
2:
O
structural framework in aeroplanes,
typically thermosetting and so will cure
optimum performance.This reduces the
satellite dishes, heat shielding, bicycle
at room temperature. In wet lay-up they
weight and increases the strength of the
frames, motorcycle parts, climbing
are soaked into woven mats of fibre
product, which is cured under pressure in
reinforcement, which is draped into a
an autoclave.
mold. For precision products, autoclaves
equipment and canoes.
Top left
strength to weight
Nomex® honeycomb
properties.
core is used to increase
the strength and bending stiffness of
Above
composite laminates.
aerodynamic racing
Above Left
car spoiler is made by CNC machining PUR
A lightweight
RELATED PROCESSES
Nomex® honeycomb
foam and encasing it in
manufacturing. Unit price is reduced
Composite laminating is unequalled in
core is laminated into
carbon fibre reinforced epoxy resin.
by accelerated production as a result of
its versatility and performance. Processes
Kevlar® aramidfibre epoxy for exceptional
using split molds, heat and pressure and
that can produce similar geometries
dividing the labour force into specialized
include dough molding compound
resistance and rigidity. Laminates cured
(DMC) and sheet molding compound
under pressure have the least porosity.
RTM is used for larger volume
areas of production.
(SMC) (page 218), injection molding
TYPICAL APPLICATIONS
(page 50) and thermoforming (page 30).
Processes other than RTM use single
sided molds, which produce a gloss finish
Until recently composite laminating
Metalworking processes that are used
on onlyi side. However, by joining two 3D
was limited to low volume production.
to produce the same geometries include
sheet geometries together a 3D hollow
However, since the development of RTM
part is made with an all over molded
finding application in the production of
panel beating, superforming (page 92) and metal stamping (page 82). DMC and SMC bridge the gap between injection molding and
automotive parts and bodywork and in
composite laminating.
it is now possible to make thousands of identical products.These processes are
finish. The surface finish of wet lay-up
and RTM products is improved by using a gel coat.
DESIGN OPPORTUNITIES
the aerospace Industry.
QUALITY
These versatile processes can be used
The mechanical properties of the product
for general-purpose glass fibre products
products, due to high costs. However,
are determined by the combination of
or high performance application with
designers have long craved the immense
materials and lay-up method. All of them
carbon and aramid fibre.The materials
potential of carbon fibre and other
produce products with long strand fibre
and method of lamination are selected
Manual laminating processes are
generally limited to high performance
composites, and so occasionally it is used
reinforcement.The resins used include
according to the budget and application,
for domestic products such as furniture.
polyester, vinylester, epoxy, phenolic and
which makes these processes suitable
Fibreglass is much cheaper and often the
cyanate.They are all thermosetting and
for a wide range of prototyping and
material of choice for such applications.
so have cross-links in their molecular
production applications.
High performance applications
structure. Thismeanstheyhavehigh
Fibre reinforcement is typically glass,
include the production of racing cars,
resistance to heat and chemicals as well
carbon, aramid or a combination. Various
boat hulls and sailing equipment.
as very high fatigue strength, impact
weaves are available to provide different
ffi H m
r~
>
§
Z CD
Lay-Up Processes Wet lay-up Single sided tool
Combination of fibre reinforcement and thermosetting resin
of 4.H bar (60 psi) and a temperature of
mold. When closed, resin is Injected under
balance of resin to fibre reinforcement.
120°C (2^8°F) for 2 hours. The pressure
pressure. Alternatively, the resin can be
are wet lay-up, pre-preg and resin transfer
Rollers are used to remove porosity.
and temperature are lowered when core
drawn through the mold under vacuum
materials are used.
(resin infusion) or it can simply be poured
All types of weave and thermosetting
framework
Demolding
Molding
Pre-preg lay-up Intermediate layer: breathable
is needed because this would Increase
known as 'double A side'. The molds are
process, gel coats are required for glass
methods. The mold is single sided and is
weight; Instead, the carbon fibre Is cut to
typically made from metal. Small molds
fibre products. For high volume production
made up of a skin of the composite material
predetermined patterns, which are laid Into
are machined from solid. Molds larger than
a thermoplastic-thermosettlng combination
supported by a rigid framework. It is
the pre-preg mold. Because the fibres are
1 m3 (35.31 ft3) are typically electroformed
is used, which produces a very high quality
essential that the mold Is not only strong
sticky, they can be rubbed together to form
because at this size this process Is less
finish because as the thermosetting resin
and supportive during lay-up, but is also
a lamination that is free of porosity.
expensive than machining and is capable of
cools and shrinks the thermoplastic takes Its
producing parts with a surface area up to
place and forms a Tow profile' surface finish.
the Intermediate layer Is a breathable membrane. These 2 are sealed in with a
prior to lamination. Gel coats are anaerobic;
These layers ensure that an even vacuum
in other words, they cure when not in the
can be applied to the whole surface area,
presence of oxygen, which is ideal for the
because if a vacuum was applied under 1
thermosetting resin is painted or sprayed
Finished workpiece
a blue film, which is permeable, while
hermetic film, and a vacuum is applied.
are laid onto the gel coat, and then
Air escapes through split line
with 3 layers of material. The first is
or sprayed onto the surface of the mold
Mats of woven fibre reinforcement
Moving platen
After lay-up the whole mold Is covered
(the same as in lamination), which is painted
mold face.
Resin transfer molding
areas that need density of material, such as surrounding a racing driver's head. Surface area is limited to 16 m2
(172 ft2), although it is possible to make larger products in more than i piece. Molding
Demolding
Monocoque boat hulls,for example, are made in stages-each area being
Because RTM Is basically a wet lay-up
16 m2 (172 ft2). The molds are preheated, then the
fibre reinforcement is laid into the open
layer of film It would stick and air pockets would be left behind.
ItiWi
The pre-preg lay-up is placed into an autoclave, which is raised to a pressure
Left above fibre chop strand mat is
Right above Unidirectional glass fibre weave has
used in wet lay-up and
specialized uses.
General purpose glass
Static platen
In prior to molding.
is the least precise of all the laminating
coat. The gel coat is a thermosetting resin
Demolding
RTM uses matched molds to produce
parts with a high quality finish on both sides,
Wet lay-up is typically started with a gel
Molding
precise and expensive. It Is most commonly used to form carbon fibre. No gel coat
be removed post-curing.
Skin of 6-8 mm j (0.236-0.315 in.) '
Pre-preg lay-up is more time-consuming,
resin can be applied by wet lay-up, which
sufficiently flexible to allow the molding to Valves
Pre-preg carbon fibre
onto it. It is important to achieve the right
The 3 main types of composite laminating molding (RTM).
Rigid j
Inner layer: permeable blue film"
TECHNICAL DESCRIPTION
resin transfer molding.
Right below Left below Carbon fibre twill is a high performance
very good resistance to
weave material.
high temperatures.
Kevlar® aramid and
epoxy composite has
laminated and cured one at a time. Manual lay-up methods are labour strength characteristics.The direction
DuPont™ Nomex® honeycomb (their
intensive and expensive. Each product
time-consuming process.To maximize
include plain (known as 0-90), twill
of weave will affect the mechanical
trademark for aramid sheet), foam and
may have between 1 and 10 layers of
strength, each layer of the lamination is
and specialist (see image, above right).
available only as spun fibres or sheet
properties of the part. For high
aluminium honeycomb (see images,
fibre reinforcement, and each layer is
overlapped at a different point to create
Forlarge surface areas chopping and
material because there is no other
performance products this is calculated
page 207). Cores make step changes in
applied by hand. A complex product may
astaggeredlap joint.
wall thickness possible.
be constructed from 10s of parts, which
using finite element analysis (FEA) prior
makes it very expensive.
to manufacture. Certain weaves have better drape and so can be formed into
DESIGN CONSIDERATIONS
Molds should be made from the same
COMPATIBLE MATERIALS Fibre reinforcement materials include
trademark name Kevlar®. Aramid is
spraying the glass fibres directly onto
practical way to make it. It has very high
the mold's surface produces a similar
resistance to abrasion and cutting, very
material to chop strand mat.
high strength to weight and superior
Carbon fibre has higher heat
temperature resistance.
Carbon and aramid fibres are very
materials as the part to be laminated.
fibreglass, carbon and aramid.
resistance, tensile strength and durability
is critical; just 50 of movement will
expensive, so every effort should be taken
This will ensure that the molds have
reduce its strength by 20%.
the same coefficient of expansion as
Glass fibre is a general purpose laminating material that is heat
than glass fibre. When combined with a
to minimize material consumption while
precise amount of thermosetting plastic
automotive industry there have been
Core materials are used to increase
maximizing strength. Wall thickness
the materials. Wall thickness is typically
resistant, durable and has good tensile
it has an exceptional strength to weight
many significant improvements in
the depth of the parts and thus increase
is limited to 0.25-10 mm (0.01-0.4 in.)
6 mm to 8 mm (0.236-0.315 in.).
deeper profiles. However, fibre alignment
When the mold parts are joined
Since composite laminating has become more important in the
strength. It is relatively inexpensive and
ratio, which is superior to steel. Carbon
materials such as a material that is made
can be used for a range of applications.
fibre twill (see image, below left) is the
up of glass fibres and polypropylene
most common weave.
torsional strength and bending stiffness.
(any thicker and the exothermic reaction
The role of the core material is to
can be too dangerous). Carbon fibre is
together, the fibre reinforcement is
Non-woven materials are the least
maintain the integrity of the composite
generally between 0.5 mm and 0.75 mm
overlapped.The case studies illustrate
expensive and known as chop strand
skin. Examples of core material include
(0.02-0.03 in.) and is only ever built up in
2 methods for doing this skilful and
mat (see image, above left). Weaves
Aramid fibre (see image, below right) is commonly referred to by the DuPont™
(PP) woven together.The composites are loaded into a heated mold and pressed,
which causes the PP to melt and flow
Far left PP and glass fibre have been woven together
Left Rigid molded glass fibre reinforced PP panels
into a novel composite
such as this have begun
material, which can
to replace sheet metal in
then be formed into rigid, lightweight panels
the automotive industry.
using resin transfer
molding technology.
around the glass fibre reinforcement (see
hour or so, whereas a large one with
contact with the materials and potential
images, page 216, above).
lots of undercut features and cores may
health hazards.
require as many as 150 hours.
COSTS
Labour costs are high because
Material developments are reducing the environmental impact of the process.
Tooling costs are moderate to high,
composite laminating is a skilful and
For example, hemp is being researched
as moldmaldng is a labour intensive
labour intensive process.
as an alternative to glass fibre, and in
complexity of the product. The tooling is
ENVIRONMENTAL IMPACTS
thermosetting materials.
done in the same way as the laminated
Laminated composites reduce the
process. Cost depends on the size and
some cases thermoplastics are replacing
product. Therefore, a master (pattern)
weight of products and so minimize
has to be made. However, it is possible to
fuel consumption. However, harmful
form th e m ol d from al m ost any m ateri al
chemicals are used in their production
and then fill, spray paint and polish the
and it is not possible to recycle any of the
surface to produce the required finish.
offcuts or scrap material.
Cycle time depends on the complexity of the part. A small part might take an
Operators must wear protective clothing in order to avoid too much
Case Study
Wet lay-up for the Ribbon chair The Ribbon chair (image 1) was designed This agent stops the gel coat bonding with by Ansel Thompson in 2002. It is the surface of the tool. constructed with vinylester, glass and The flanges are taped to enable the mold aramid reinforcement, and a polyurethane to be closed (Image 4), then the gel coat foam core, in a lengthy process that takes is applied and the masking tape removed approximately 1 day. The sequence of events (images 5 and 6). are; mold preparation, release agent, gel coat, lamination, cure time, demolding and
then finishing. The mold is prepared before each molding (image 2). Because the chair is a complex shape, the mold is designed to come apart to make demolding easier.
Particular care is taken in preparing the surface finish because it will be reflected on the outside surface of the part. Once the parts have been assembled, a wax release
agent is applied with a soft cloth (image 3).
The glass and aramid fibre mat is cut
The molds are then brought together
into patterns to fit the chair, using i of
and bolted along the flange (image 12).
2 different types of fibre reinforcement
Excess resin squeezes out as the bolts
(image 7). Sheets of fibre are laid onto the
are tightened. The design of the mold
gel coat, and vinylester is applied to the
means that an overlap of material forms
back (image 8). Air is then removed with a
a strong joint. While clamped shut an
paddle roller (image 9).
expanding polyurethane (PUR) foam is
The layers are gradually built up, and
injected into the mold cavity. This forces
care is taken to ensure that joints do not
the lamination against the surface of
overlap and cause weaknesses (image 10).
the mold, in order to improve the surface
An area of aramid is then applied to the
finish. It also increases the strength of the
inside of the seat, to increase resilience
chair by supporting the thin composite
and strength (image n).
wall sections.
After about 45 minutes the vinylester is fully cured and the mold is separated (image 13). it is trimmed and polished to complete the process (image 14).
9
Featured Manufacturer Radcor IO
11
www. rad cor. co.uk
Case Study
Case Study
Racing car design with carbon fibre
Pre-preg carbon fibre lay-up for the roll hoop trailing edge
Pre-preg carbon fibre is used in the
This case study demonstrates the production
roll hoop trailing edge, which is made with
like an x-y plotter (image 2).The carbon fibre
production of high performance racing
per gram (0.035 oz) of carbon fibre. The
of a small piece of the Intersport Lola B05/40
a simple split mold, so is relatively simple.
is coated with plastic film on either side. This
cars such as the Lola B05/30 Formula 3 car
image shows how the carbon has shattered
racing car (image 1). In total, this car is made
Parts such as the monocoque structure (see
Is peeled off just prior to lay-up (image 3).
{image 1), which is manufactured by Lola Cars.
into fragments. Each of the fragments is
up of hundreds of carbon fibre components.
opposite) comprise many different pieces,
The mold is In 2 parts (image 4), which are
Production starts when the designers
cured at different stages and incorporates
laid up separately. The carbon fibre patterns
Success is measured in energy absorption
Construction (image 2) is closely tied into
absorbing a small amount of the Impact;
design and engineering. High performance
so the smaller the fragments, then the
complete the 'lay-up handbook', which
core material. The lay-up handbook ensures
are aligned on the part with the rubbed side
products have to be engineered to take
more successful the engineering design.
outlines the production requirements of
that each part is made according to the
downwards (image 5). Each i Is trimmed
Exact replicas of the cars, Including
each part, including pattern profile, number
design requirements.
carbon fibre wheels, are tested at 50%
of laminations and sequence of production.
scale in a wind tunnel (image 6). This
This case study covers the production of the
the maximum load,yet be as lightweight as possible. It is the role of a carbon fibre engineer to push carbon fibre to its limits. The process of designing and producing a car takes approximately 8 months. By using detailed design, FEA and controlled testing, parts can be produced directly from the CAD drawing. In the CAD drawing of the monocoque chassis on
the car (image 3), FEA software is used to determine the stresses and strains
on the structure (image 4). This helps the engineer to calculate the optimal structure within set parameters.
Critical parts are molded and tested to ensure that the calculations are correct. A crash test is simulated on the nose cone of the car-the average deceleration
being 25G during impact (image 5). The aim of this part is to deaccelerate the car in a head-on collision.The nose cone is
coloured yellow and is attached to the monocoque structure.
Featured Manufacturer Lola Cars International www.lolacars.com
The patterns of carbon fibre are fed through to a kit cutter, which functions much
(image 6), leaving a small overlap to make a stronger joint interface, before the next layer is applied.
helps to solve issues of aerodynamics, balance and tuning.
o o
a pale pink hermetic film (image 13). The
produce the complete car. All of the parts are
in exactly the same way. Each pattern of
resulting 'sandwich' enables a vacuum to
finally brought together and assembled to
carbon fibre is cut to fit the mold like a dress
be applied on the mold, which forces the
make up the complete car (image 18).
(image 7). Profiled 'dobbers' are used to rub
laminate onto its surface (image 14).
The second part of the mold 1s kid up
the weave into tight corners (image 8). Three
The vacuumed mold is then placed in
layers of carbon fibre are applied to each
an autoclave (image 15), which cures the
surface, and the 2 halves of the mold are
resin with heat and pressure. The size of the
brought together (image 9). The layers are
autoclave limits the size of part - larger parts
carefully overlapped in the joint with another
are restricted to oven or room temperature
dobber (image 10).
curing methods.
When all the layers are in place the entire molding and tool are covered with
Many molds are placed in the autoclave at 1 time because curing is a 2 hour process.
a permeable blue film (image 11). This is
When finished, the part is removed (image
overlaid with a layer of breathable membrane
16). At the Lola Cars workshop (image 17), up
(image 12). The mold is then placed inside
to 20 laminators may be working at 1 time to
Compression Molding DMC Process
Hydraulic ram
Compression molding is used to form dough molding compound Locating pin
(DMC) and sheet molding compound (SMC) into structural and
Static platen
lightweight parts. These processes bridge the gap between
Ejector pins
composite laminating and injection molding.
Typical Applications
Costs • Moderate tooling costs • Low unit costs (3 to 4 times material
• Automotive • Building and construction • Electrical and telecommunication
Stage 1: Load
RELATED PROCESSES
TECHNICAL DESCRIPTION
• Medium to high volume production
Similar products can be made by
The diagram illustrates compression
process that ensures even distribution of
injection molding (page 50) and
molding DMC. SMC is a similar
material throughout the die cavity.
composite laminating. Reinforced
process, except that it is used for sheet
injection molded products are
profiles as opposed to bulk shapes.
Related Processes
Speed
• High strength parts with long fibre length
• Composite laminating • Compression molding • Injection molding
• Cycle time between 2-5 minutes
structurally inferior because the length
The molding compound is a mixture of
cured when it reaches 150°C (302°F)(
fibre reinforcement and thermosetting
which takes 2-5 minutes. In stage 3, the
resin; DMC is made up of chopped fibre
parts of the mold separate in sequence.
QUALITY
reinforcement, whereas SMC contains
If necessary, the part is relieved from the
sheets of woven fibre reinforcement.
lower or upper tool with ejector pins.
SMC: the raw materials are available
fatigue.These qualities make DMC
Combined with compression molding,
with different weave patterns for
and SMC very useful in electrical and
DMC and SMC have been used to replace
different structural applications.This
telecommunication applications. Some
to the materials such as heat resistant
steel and aluminium in applications
has significant mechanical advantages,
examples include enclosures, insulating
and electrically insulating polyester or
such as automotive bodywork and
similar to those of laminated composites
panels and discs.
phenolic.Thermosetting plastics are
(page 206).
The high volume, high strength and lightweight characteristics of DMC and
more crystalline and as a result are more acids and other chemicals.
A similar process, called pultrusion,
This is a very high quality process. Many of the characteristics can be attributed
resistant not only to heat, but also to
reinforced thermosetting materials
is used to produce continuous
SMC make them suitable for automotive
such as polyester, epoxy and phenolic
lengths of fibre-reinforced plastic.
parts. Examples include body panels,
resin. DMC is also referred to as BMC
Instead of compressing the materials,
seal frames and shells, engine covers
detail is very good. The compression, rather than injection, of material in the
Surface finish and reproduction of
(bulk molding compound).There are
pultrusion draws fibre through abath
and structural beams. Electric cars are
thermoplastic alternatives such as GMT
of thermosetting resin, which cures
making use of these materials because
die cavity produces parts with reduced
(glass mat thermoplastic), which is a
to form a continuous profile similar
they combine mechanical strength with
stress that are less prone to distortion.
DESIGN OPPORTUNITIES
fibre reinforced polypropylene (PP). Other
to extrusion. Pultrusion is the bridge
types of reinforcement include aramid
between filament winding (page 222)
high dielectric strength. In the building and construction
and carbon fibre. In recent years natural
and extrusion for continuous profiles.
sector, DMC and SMC are suitable for door pan el s, fl oorin g an d roof coverin g
TYPICAL APPLICATIONS
materials.They are very durable and so
the requirements of the application.This
to reduce the environmental impact of
These materials can be mass-produced
are suitable for public space furniture
helps to reduce weight and maximize the
these materials.
and so are suitable for application in a
and signage.
efficiency of the process.
as hemp, have been trialled in an attempt
DMC is compression molded to form bulk shapes. In contrast, SMC is
range of industries. Thermosetting composite materials
compression molded to form lightweight
have high resilience to dielectric
sheet components with a uniform
vibration, high mechanical strength
wall thickness. Fibre length is longer in
and are resistant to corrosion and
The sequence of operation is the same
for both and includes loading, molding
Metal inserts and electrical
It is a simple operation but is suitable for the production of complex parts.
and de-molding. In stage 1, a measure of
It operates at high pressure, ranging
DMC or SMC is loaded into the die cavity in
from AO to 400 tonnes UA-WI US tons),
the lower tool. Metal inserts with locating
although 150 tonnes (165 US tons) is
pins are loaded into slots. They are in
generally the limit. The size and shape
line with the direction of ejection because
of the part will affect the amount of
otherwise the part would not release
pressure required. Greater pressures
from the mold.
will ensure better surface finish and
In stage 2, the upper tool is gradually
reproduction of detail.
forced into the die cavity. It is a steady
DESIGN CONSIDERATIONS The type of fibre reinforcement and length of strand can be modified to suit
materials with suitable properties, such
Thermosetting material plasticizes at approximately 115°C (239° F) and is
of the fibre is considerably shorter.
INTRODUCTION
DMC and SMC are typically glass
Stage3: Finish
Suitability
Quality
structural electronic enclosures.
Stage 2: Mold
The size of the part can be 0.1-8 kg
Colours are applied by spray painting (page 350) because the thermosetting resins in DMC and SMC have a limited
the pressure that can be applied across
colour range.
the surface area, which is affected by part
(0.22-17.64 lb) on a400 tonne (441 US
ton) press.The dimensions are limited by
As with injection molding, there are
g eom etry an d design. An oth er m aj or
many design considerations that need
factor that affects part size is venting
to be taken into account when working
gases from the thermosetting material
components can be over-molded.This
with compression molding. Draft angles
as it cures andheats up.This plays an
reduces secondary operations.
can be reduced to less than o.50,if both
important role in tool design, which aims
the tool and the ejector system are
to get rid of gasses with the use of vents
designed carefully.
and clever rib design.
Step changes in wall thickness are not
a problem with DMC molding.
o > z a en 2 o S o r* a
Case Study
Compression molding 8-pin rings This is a DMC compression molding
After curing, the molds separate to reveal the
operation. In preparation, the metal inserts
fully formed part (image 5). The locating pins
are screwed onto locating pins (image 1). The
attached to the metal inserts remain on
surface of the metal inserts are knurled to
the part as it is removed (image 6).
increase the strength of the over-molding. The
from the metal inserts (image 7) and
Inserts are also loaded into the lower tool.
the workpiece is de-flashed by hand
A pre-determined weight of polyester and
(image 8). The finished moldings are
glass based DMC is loaded into the die
stacked (image 9).
(images 3 and 4). The 2 halves of the die come together to force the polyester to fill the die cavity.
Wall thickness can range from i mm to 50 mm (0.04-1.97 in.)-It is limited by the
COMPATIBLE MATERIALS
COSTS
Thermosetting materials molded in
Tooling is generally less expensive than
i7o0C and i8o0C (338- 3560F). It is not
molding temperatures, typically between
exothermic nature of the thermosetting
this way include polyester, epoxy and
for injection molding because less
possible to recycle them directly due
reaction because thick wall sections are
phenolic resin.Thermoplastic composites
pressure is applied and the tooling tends
to their molecular structure, which is
prone to blistering and other defects as a
are generally polypropylene; the molding
to be simpler.
cross-linked.This means that any scrap
direct result of the catalytic reaction. It is
process for these is different because
generally better to reduce wall thickness
they have to be plasticized and formed.
and minimize material consumption, so
Fibre reinforcement can be glass,
Cycle time is 2-5 minutes, depending
on the size of the part and length of time
produced, such as flash and offcuts, has to be disposed of.
it takes to cure. Labour costs are moderate because
bulky parts are hollowed out or inserts
aramid, carbon or a natural fibre such
are added. However, some applications
as hemp, jute, cotton, rag andflax. Other
the process requires a great deal of manual input.
require thick wall sections such as parts
fillers include talc and wood.The various
that have to withstand high levels of
fibre reinforcement and filler materials
dielectric vibration.
are used to increase the strength,
ENVIRONMENTAL IMPACTS
durability, resistance to cracking,
The main environmental impacts
dielectric resilience and insulating
arise as a result of the materials used.
properties of the part.
Thermosetting plastics require higher
The locating pins are unscrewed
pins are loaded into the upper tool (image 2).
Featured Manufacturer Cromwell Plastics www.cromwell-plastics.co.uk
Forming Technology
Filament Winding Layers of carbon fibre monofilaments, coated in epoxy resin, are wound onto a shaped mandrel to give the ultimate strength characteristics. The mandrel is either removed and reused, or permanently encapsulated by the carbon fibres.
Costs
Typical Applications
INTRODUCTION
There are 2 main types of winding,
Filament winding is used to produce
'wet'and'pre-preg'. Wet winding draws
continuous, sheet and hollow profiles
the fibre tow through an epoxy bath
for applications that demandthe high
prior to application. Pre-preg winding
performance characteristics of fibre
uses carbon fibre tow pre-impregnated
reinforced composites.They are produced
by winding a continuous length of fibre
with epoxy resin, which can be applied directly to the mandrel without any
around a mandrel.The fibre 1s coated
other preparation.
Suitability
with thermosetting resin to produce
high strength and lightweight shapes.
TYPICAL APPLICATIONS
The fibre (typically glass, carbon or aramid) is applied as a tow that contains
in high performance applications in the
• Low to moderate tooling costs, depending on size • Moderate to high unit costs
• Aerospace • Automotive • Deep sea submersibles
• One-off to batch production
Quality
Related Processes
Speed
• High gloss surface finish • High performance, lightweight products
• 3D thermal laminating • Composite laminating • DMC and SMC molding
• Moderate cycle time for small parts (20-120 minutes); large parts may take several weeks
Fil am ent woun d products can be foun d
a set number of fibre monofilaments. For
aerospace, deep sea and automotive
example,i2l< tow has 12,000 strands,
industries. Some examples include
while 24k has 24,000 strands.
blades for wind turbines and helicopters, pressure vessels, deep sea submersibles, suspension systems, torsional drive
has an aluminium liner
Top CNC machining after filament winding
filament wound with
produces very accurate
RELATED PROCESSES
carbon fibre composite.
surface dimensions.
Filament winding is used to produce
Left The gloss surface finish is a gel coat resistant to
tapers on the outside surface are applied in
Above
shafts and structural framework for
This pressure vessel
aerospace applications,
Channels, recesses and
low volumes of cylindrical parts. Higher volumes can be produced by DMC and
this way.
heat or chemical attack.
SMC molding (page 218). Composite laminating (page 206) is used to produce similar profiles. The benefit of
filament winding is that the direction
QUALITY There are 4 main types of finish.These
Winding is computer guided, making it precise to 100 microns
of the strand can be adjusted precisely
are 'as wound', taped, machined and
(0.0039 in.). The angle of application
throughout production from almost
epoxy gel coat.'As wound'finishes have
will determine whether the layer is
o0 up to 90°. In composite laminating,
no special treatment. Taped finishes
filaments are woven into mats with
produce a smooth surface finish.The
providing longitudinal, torsional (twist) or circumferential (hoop) strength. Layers
intertwined warp and weft.
principle is the same as vacuum bagging
are built up to provide the required
The 3D thermal laminating (3DL, page 228) developed by North Sails is similar to filament winding.The difference is that
in composite laminating, but the surface
mechanical properties. Products cannot
finish is more controllable. Surfaces are
be interchanged between applications
machined where precise tolerances are
filaments are laid onto a static mold in
required (see image,top). Smooth, glossy
because their properties will be designed specifically for each.
a process known as tape laying. In this
finishes can be achieved with epoxy gel
case the molds can be very large and up
coat (see image,left).
to 400 m2 (4,305 ft2). 3DL is best suited to sheet parts, where as filament winding is more suitedto hollow parts.
Stiffness is determined by the thickness of lay-up andtube diameter.
DESIGN OPPORTUNITIES Opportunities for designers are limited to cylindrical and hollow parts. But they need not be rotationally symmetrical;
Filament Winding Process
Supply reel of carbon fibre
Guide head
Continuous length of carbon fibre tow
TECHNICAL DESCRIPTION The carbon fibre tow is applied to the
reinforcement is loaded. This is the wet lay-
several different angles of tow. depending
rotating mandrel by a guide head. The head
up process; the fibre reinforcement is coated
on the requirements.
moves up and down along the mandrel as it
with an epoxy resin by a wheel rotating in a
rotates, and guides the filament into the geodesic overlapping pattern.
bath of the resin.
A complete circuit is made when the
Bulges can be made by concentrating the tow in a small area. These are used either to create localized areas of strength or to build
guide head has travelled from 1 end of the
up larger diameters that can be machined
to the material being used and the layer
mandrel to the other and back to the starting
for accuracy.
thickness required.
point. The speed of the head relative to the
The width of the tow is chosen according
The fibre is continuous and only broken when a new supply reel of fibre
COMPATIBLE MATERIALS Types of fibre reinforcement include
The winding process is computerguided. Even so,there is ahigh level
speed of mandrel rotation will determine the
glass, carbon and aramid. An outline of
of manual input, so labour costs are
angle of the fibre. A single circuit may have
their particular qualities is given under
moderate to high.
composite laminating.
Resins are typically thermosetting and
ENVIRONMENTAL IMPACTS
include polyester, vinylester, epoxy and
Laminated composites reduce the
oval, elliptical, sharp edged and flat-sided
DESIGN CONSIDERATIONS
These products are typically used for
phenolics.Thermosetting plastics have
weight of products and so reduce fuel
profiles can be filament wound (see
This is a high cost process for low
demanding applications, so the liners
cross-links in their molecular structure,
consumption.
image above).
volumes. Increasing the volumes reduces unit cost. Even so, the materials are
are typically produced by electron beam welding (page 288) high-grade
which means they have high resistance to heat and chemicals. Combined with
clothing to avoid the potential health
can be removed and reused, while
expensive and so every effort is made
aluminium or titanium.
carbon fibres these materials have very
hazards of contact with the materials.
3-dimensional hollow products that
to reduce material consumption while
are closed at both ends can be made by
maximizing strength.
high fatigue strength, impact resistance and rigidity.
recycled, so scrap and offcuts have to be
Parallel-sided and conical mandrels
winding the filament tow over a hollow
Parallel-sided parts can be made
Winding over a hollow liner produces parts that have inward and outward facing corners such as a bottleneck
Operators have to wear protective
Thermosetting materials cannot be disposed of. However, new thermoplastic
liner, which remains as part of the final
in long lengths and cut to size.
profile. Even though it is possible, it is
COSTS
systems are being developed that will
product (see image, page 227, above).This
Conventional filament winding is
generally not recommended to wind over
Tooling costs are low to moderate.
reduce the environmental impacts of
technique is known as bottle winding
typically limited to 3 m (10 ft) long and up
outward facing corners with a radius
Encapsulating the mandrel will increase
the process.
and is used to produce pressure vessels,
to 1 m (3.3 ft) in diameter. However, much
of less than 20 mm (0.8 in.) because
the cost.
housing and suspension systems.
larger forms are produced by filament
product performance will be affected.
winding, such as space rockets, which
There is no lower limit on the radius for
minutes for small parts, but can take
may take several weeks to make.
inward facing corners.
several weeks for very large parts. Curing
Other than shape, the benefits of winding over a liner include forming a water, air and gas tight skin.
Winding over a liner will increase the cost of the process because a new liner is manufactured for each cycle.
Filament winding cycle time is 20-120
time is typically 4-8 hours, depending on the resin system.
Top
Above
Non-circular profiles
Ibis flywheel is made up of 3 parts: the inner lining is glass fibre and
are suitable for filament winding. Examples
include the blades for wind turbines and helicopters.
the other 2 layers are carbon fibre.
Case Study
Filament winding a racing propshaft These are used in cars to deliver power from
(image 1). Carbon fibre tow is supplied from
the engine to the wheels. Traditionally these
a spool (image 2). Many different spools can
(image 5). In this case the carbon fibre is
components are made from metal, but when
be running simultaneously for multifibre
sealed onto the mandrel with a plastic tape
problem when tow is laid at or close to go0
carbon composite is used it is possible to
composites or if more than 1 mandrel is
(itnage 5). The tape squeezes excess epoxy
mate weight savings of up to 65%, Finite
being wound at the same time.The fibres are
resin from the carbon and ensures a high
element analysis is used to determine
coated with epoxy resin as they pass over the
quality, smooth finish. The excess is cut off
the stress and strain on the product prior
wheel (image 3).
while it is uncured (image 7). This is so that
to manufacture.The results, seen in the
The angle of application ranges from go0
computer generated images, indicate the
to almost o0. The mandrel ends are tapered so
required angle of tow and number of layers.
that adequate tension can be pulled on the
They are a parallel section tube and so are made on removable and reusable mandrels
the mandrel can be removed once the composite has cured.
The filament wound assemblies are
tow without it slipping along the mandrel
placed into an oven, which cures the resin at
(image 4) at shallow angles; this is not a
up to 2000C (3920F) for 4 hours. The whole curing process takes 8 hours because the
temperature inside the oven is ramped up and down gradually. Small droplets of resin form on the surface of the tape
during curing (image 8).This is removed when the tape is peeled off. The cured composite is removed from
the mandrel (image 9). It is possible to remove long cylinders from mandrels because metal expands and shrinks more
than carbon fibre, so is slightly smaller once it has cooled.This provides just enough space to remove the mandrel.
The ends of the shaft are cut off to precise tolerances, and machined metalwork is assembled onto the ends
(image io). These are bonded in with adhesives, which are heat cured.
1. .
Hi r.^
Continuous
Bend
Bulk
Internal
Forming Technology
3D Thermal Laminating This technology was developed by North Sails to make ultra lightweight, seamless 3-dimensional sails. The fibre reinforcement is continuous over the entire surface of the sail,
Fibre layouts Any combination of
fibre include aramid,
The first 3-dimensional laminating (3DL)
performance fibres can
carbon,polyester and
sail was constructed by Luc Dubois and
be laminated by the
other advancedyarns.
3DLand3Dr processes.
Above, from left to right,
The quantity, type and direction of fibre is adjusted to suit the
and 800 series. Left,
from left to right, 900
level of performance
series andTFi series.
INTRODUCTION
J, P. Baudet at North Sails in 1990. Since
then the process has been adopted by
replacing traditional methods of cutting, stitching and gluing.
nearly every racing boat in the Volvo Ocean RaceandAmerica'sCup-2major
application.Types of
600 series, 800 series
demanded by the
sailing grand prix.
1 Very high tooling costs ' Very high unit costs
Typical Applications
Suitability
• Sailing
• One-off and small batch production
Quality
Related Processes
Speed
• Very high strength to weight properties
• Composite laminating • Filament winding • Stitching
• Cycle time up to 5 days
Sails have a 3D 'flying shape'. In conventional sailmaking, cut patterns
TYPICAL APPLICATIONS
are stitched or glued together to produce
Although these laminating technologies
Th e thermally formed PET maintains the position ofthe fibres, which are laid
the optimum shape. In 3DL,the sails are
are currently limited to sailmaking, there
down in alignment with the direction of
molded in the optimum flying shape and so eliminate cutting and joining. This
is potential for them to be developed
stress across the sail.
tension.Therefore, this process is not
produces sails that are up to 20% lighter
for application in a variety of products such as high altitude balloons, dirigibles,
DESIGN OPPORTUNITIES
require resistance to compression.
than conventional equivalents.They are
tension structures, temporary structures
At present, opportunities for designers
The sails are not molded with a
also stronger and seamless.
and inflatable structures.
are limited because these processes are
uniform wall thickness; the thickness
restricted to sailmaking. In the future
varies with the Intended application.
The 3DL process combines the benefits
A %
performance applications. Sails are designed to be strong under
suitable for use in applications that
of composite laminating (page 206) with filament winding (page 222).The
RELATED PROCESSES
there is potential for application of these
Minimum wall thickness Is limited
The only processes capable of producing
techniques In other Industries.
by the thickness of PET film and fibre
3-dimensional sheet geometries are
very large and seamless shapes are 3DL
formed over computer-guided molds.
and 3Dr. Circular, conical, elliptical and
provide varying levels of performance
The fibre reinforcements (aramid and
similar shapes, however, can be produced
(see Images, above).The 600 series is
COMPATIBLE MATERIALS
carbon) are laid down individually along
by filament winding, composite
made up of high-modulus aramid fibres
The 2 outer films are PET coated with a
pre-determined lines of stress. They are
laminating and stitching (see upholstery,
andlaid down along the lines of stress
special adhesive.The fibre reinforcement
sandwiched between thin sheets of
page 338). Filament winding Is generally
to maintain shape and durability.The
is of carbon, aramid, polyester or a
polyethylene terephthalate (PET) coated
limited to structures no larger than
flowing shape produced In the catenary
combination ofthe 3 materials.
with a specially developed adhesive.
3 m (10 ft) in length andi m (3.3 ft) in
curves joins areas of stress with smooth,
diameter, but this is not always the case.
flowing lines of fibre reinforcement.
COSTS
The 800 and 900 series combine
Tooling costs are high. The male molds
3DLmanufacturing is along process,
and demand within the industry is very
wMwi lb
and therefore are limited to high
Specific fibre layouts and composites
reinforcement.
high.Therefore,3-dimensional rotary
QUALITY
carbon fibre with the aramid to reduce
are computer guided and adjusted to the
laminating (3Dr) was developed as a
These sails are bui'lt to perform a very
weight and stretch. Different films
flying shape of sail being made.They are
method for continuous production.
specific function. They are required to
can be used on the outside surfaces to
also very large, up to 400 m2 (4,306 ft2).
lnsteadofmanylarge3-dimens1onal
hold their shape, even in strong winds,
protect against tearing and chafing
molds, 3Dr sailmaking is carried out
be durable and lightweight and produce
and provide UV stability. Plain weave
on a single rotating drum.The shape
minimum resistance to the flow of air
polyester, known as taffeta, is used on
of the drum is manipulated as the sail
over the surface.
the outside surface ofthe TFi series to
of skill required to make reliable products
increase durability
for high performance applications.
Is constructed over it.The process is a very recent development and so is still
Aerospace vacuum and pressure
Cycle time is up to 5 days because of the lengthy curing process.
Labour costs are high due to the level
techniques are used to cure the laminates on the mold.This ensures
DESIGN CONSIDERATIONS
ENVIRONMENTAL IMPACTS
that the composite will not delaminate,
The materials and manufacturing
These sails minimize material
even when extreme loads are applied.
processes used In 3DL are expensive
consumption and reduce weight.
Three-Dimensional Laminating Process I3DLJ
Case Study
3DL sails on a TP 52 type racing boat The TP 52 type racing boat (rmage i) has here
laminate surface (image 6), or an infrared
been fitted with North Sails 3DL composite
heating system that travels above the
sails. The process starts with a bespoke sail
laminate surface (image 7), depending on the
design (flying shape), because each boat
fibre in the sail. The finished laminate is
requires a slightly different shape. There are a
Inspected after curing and left for a
range of sizes possible from 10 m2 to 500 m2
further 5 days to ensure that the adhesive
(108-5,382 ft2). The shape of the molds is
has reached its full bond strength.
computer guided, so they can be adjusted for many different sail shapes (images 2 and 3). The PET film is laid across the mold
Supply reel
Three-Dimensional Rotary Laminating Process (3Dr)
Rotating drum
Heat and vacuum pressure applied
Pneumatic rams
When the sail has fully cured, corner reinforcements, batten pockets, eyelets,
TECHNICAL DESCRIPTION
and other details are applied by sail
Each sail has an individual 3D shape. The
a computer controlled overhead gantry. It
and brought to the curing floor for a further
(image 2) and pulled tight with tensioning
makers using traditional cutting and
designer produces a CAD file, which is
operates on 6 axes, so can follow the profile
5 days to ensure the adhesive is fully cured
straps. The 6-axis computer controlled gantry
sewing techniques.
transferred onto the surface of the mold by a
of the mold exactly. The fibres follow the
and will not delaminate.
lays down the strands of carbon fibre
series of pneumatic rams. The shape of the
anticipated 'load lines'. Adhesive is applied
The 3Dr process is carried out on a
(image 4). An operator in a hang-gliding
mold will determine the 'flying shape' of the
to the fibres as they are laid down onto the
rotating drum as opposed to the static
harness inspects the sail (image 5).
sail when it is made.
mold, which helps to keep them in place.
horizontal mold used in 3DL. This enables
The PET and fibre are vacuum bagged
A PET film is laid over the mold and put
A second layer of film is laid on top of the
and held under pressure. An operator
under tension. It is coated with a specially
fibres and forced to laminate under pressure
quickly. The composite sail is formed as
then moves over the sail applying heat to
developed adhesive, designed for North
at approximately 8.6 N/cm2 (12.5 psi) from a
the drum rotates and leaves the drum
thermally form the composite over the
Sails by its industrial partners for the 3DL
vacuum bag. Heat is then applied with a
completed. The shape of the drum is
mold surface, using either a conductive
process. Strands of fibre reinforcement are
blanket to cure the adhesive. After curing,
computer controlled to produce 2-directional
heating system in contact with the
applied by a fibre placement head guided by
the composite sail is removed from the mold
curvature; the flying shape of the sail.
nuiwuiii!"''-
the sails to be put together much more
Case Study
3Dr sails on a Melges 24 A more recent development at North
Sails has been to make sails using rotary molds (sDr), which is a more rapid and cost effective process for sailmaking.The
Melges 24 racing boat is fitted with a 3Dr laminated sail (image 1). The rotating drum contains about 2000 actuators, which shape the surface into complex curvatures describing the
flying shape of a sail. The shape of the drum is manipulated to accommodate
the change in shape along the length of the sail. The drum surface is shaped to curve in 2 directions simultaneously,
using the principals of Gaussian curvature (images 2-4).
Fibre reinforcement is applied to the Featured Manufacturer
bottom PET film, which rotates on the drum (image 5). The sail leaves the drum
North Sails www.northsails.com
fully formed in 3 dimensions. Finishing touches are applied by skilled sail makers.
Featured Manufacturer
North Sails www.northsails.com
Forming Technology
Rapid Prototyping These layer building processes can be used to prototype one-offs or to direct manufacture low volume production runs from CAD data. There is no tooling involved, which not only helps to reduce cost, but also has many advantages for the designer.
INTRODUCTION Rapid prototyping is used to construct simple and complex geometries by fusing together very fine layers of powder or liquid. The process starts with
metal laser sintering (DMLS). SLA is the most widely used rapid prototyping technique and produces the finest surface finish and dimensional accuracy. These processes are utilized
a CAD model sliced into cross-sections.
mainly for design development and
Each cross-section is mapped onto the
prototyping, in order to reduce the
surface of the rapid prototyping material
time it takes to get a product to market.
Costs
Typical Applications
Suitability
by a laser, which fuses or cures the
• No tooling costs • SLS is the cheapest and DMLS the most expensive process
However, they can also be used to
• Automotive, FI and aerospace • Product development and testing • Tooling
• One-offs, prototypes and low volume production
particles together. Many materials such
direct manufacture products that have
as polymers, ceramics, wax,metals and
to be precisely reproduced with very
even paper can be formed in this way.
accurate tolerances.
Quality
Related Processes
Speed
• High definition of detail and surface finish
• CNC machining • Electrical discharge machining • Investment casting
• Long process, but turnaround is rapid because there is no tooling and data is taken directly from CAD file
This description will concentrate on 3
main processes: stereolithography (SLA), selective laser sintering (SLS) and direct
TYPICAL APPLICATIONS The high tolerances of the SLA process mean that it is ideal for producing fit-form prototypes that are used to
test products before committing to the chosen method of production.
The SLS technique is often selected to produce functional prototypes and
Electrical discharge machining (page 254) is another reductive process.
Material is removed by sparks that are generated between the tool and
Top PP mimic part with live hinges and snap fits has been produced by stereolithography.
electric seat adjustment cogs for use in the automotive industry. Above
test models because the materials
workpiece.This process is mainly used
have similar physical characteristics to
to form concave profiles that would be
Direct metal laser
This carbon strand filled nylon impellerhas been manufactured by
injection molded parts.
impractical to CNC machine.
sintering is suitable for
selective laser sintering.
DMLS is suitable for injection and
Investment casting (page 130) has
Above left
making nickel-bronze
blow molding tooling, wax injection and
many of the geometry advantages of
press tools.This process is typically used
rapid prototyping because the ceramic
in layers, contours are visible on the
to produce functional metal prototypes
molds are expendable.'
surface of acute angles. All of the parts
and low volume production runs of parts
As a result of manufacturing 3D forms
therefore require finishing when they
for the automotive, Fi, jewelry, medical
QUALITY
come out of the machine. It is possible
and nuclear industries.
SLA techniques produce the highest
to acquire a very high 'glass-like' surface
surface finish and dimensional accuracy
finish on the water clear SLA epoxy resin,
RELATED PROCESSES
of all rapid prototyping ones. All these
by polishing.
Conventional CNC machining (page 182)
layer-building processes work to fine
operations remove material, whereas
tolerances: SLS builds in o.i mm (0,004
produce intricate and precise parts (up to 77 x 61 x 230 mm/3.03 x 2.40 x 9.05 in.).
Micro modelling can be used to
rapid prototyping builds only what is
in.) layers and is accurate to ±0.15 mm
necessary. Machining produces very
(0.006 in.); SLA forms in 0.05-0.1 mm
This process builds in 25 micron (0,00098
accurate parts, but is a slow, energy
(0.002-0.004 in.) layers and is accurate
in,) layers, which are almost invisible to
intensive process. Rapid prototyping
to ±0.15 mm (0.006 in.); and DMLS builds
the naked eye and so eliminates surface
can produce complex internal shapes
in 0.02-0.06 mm (0.008-0.0024in.)
finishing operations.
by undercutting, which would be time-
layers and is accurate to ±0.05 mm
consuming and expensive to machine.
(0.002 in.).
DIRECT METAL LASER SINTERING
Selective Laser Sintering Process
Stereolithography Process
Direct Metal Laser Sintering Process
A considerable amount of heat is generated
CO2 laser
during this process because a 250 watt CO2 laser is used to sinter the metal alloy
SLA part
powders. An expendable first layer of the
Paddle to break surface tension
part is anchored to the steel plate to stop distortion caused by differing rates of
r
contraction. Such a layer also means that Solid state UV laser
the part is easier to remove from the steel
plate when the build is complete. During the sintering process, the delivery chamber
1'
rises to dispense powder in the path of
'i
the paddle, which spreads a precise layer over the build area. The build platform is incrementally lowered as each layer of Honeycomb support structure
metal alloy is sintered onto the surface of
UV sensitive liquid epoxy resin
the part. The whole process takes place in an
Build platform progresses downwards in steps of 0.05 mm to 0.1 mm (0.002-0.004 in.)
inert nitrogen atmosphere at less than 1% self-supporting = forming a nonsintered "cake-
Multiple SLS parts Build platform progresses downwards in steps of 0.1 mm (0.004 in.)
Delivery chambers progress upwards, supplying powder to the roller
oxygen to prevent oxydization of the metal powder during the build.
TECHNICAL DESCRIPTION STEREOLITHOGRAPHY
sweeps across the surface of the resin
computer-guided mirror. The build platform
All of these rapid prototyping processes
with each step downwards, to break the
progresses downwards in layer thickness
start with a CAD drawing sliced into cross-
surface tension of the liquid and control
steps. The delivery chambers alternately
confined to parts of 250 x 250 x 185 mm
at the same time and fine undercuts are
(9.84x9.84x7.28 in.).
more difficult to achieve.
polypropyl en e/polyethyl en e (PP/ PE) mimic and water clear polybutylene terephthalate (PBT)/ABS mimic. Materials
sections. Each cross-section represents a
layer thickness. The part gradually develops
rise to provide the roller with a fresh charge
layer in the build, generally between 0.05
below the surface of the liquid and is kept
of powder to spread accurately over the
mm and 0.1 mm (0.002-0.004 in.) thick for
off the build platform by a support structure.
surface of the build area. Non-sintered
its m ech ani cal properti es - stran d fill ed
COMPATIBLE MATERIALS
that can withstandtemperatures up to
SLA modelling. The model is built 1 layer
This is made in the same incremental way,
powder forms a 'cake', which encapsulates
materials having better strength in
The SLS process is compatible with a
2000C (3920F) have been developed for
at a time by an UV laser beam directed by a
prior to building the first layer of the part.
and supports the model as the build
certain geometries.The orientation of
variety of nylon-based powders. The
the SLA process,
progresses. The whole process takes place
SLS parts in regular nylon powders has
tough Nylon 11 is heat resistant up to
„ The DMLS process is compatible
with specially developed metal alloys: 2 examples are nickel-bronze, which is
computer-guided mirror onto the surface of
The orientation of the part can affect
the UV sensitive liquid epoxy resin. The UV
SELECTIVE LASER SINTERING
in an inert nitrogen atmosphere at less than
to be considered, to maintain accuracy.
1500C (3020F) and so can be used to
light precisely solidifies the resin it touches.
In this layer-additive manufacturing
1 % oxygen to stop the nylon oxydizing when
For example, a tube is built vertically to
produce functional prototypes that are
Each layer is applied by submersion of the
process, a CO2 laser fuses fine nylon powder
heated by the laser beam.
keep it round; if built horizontally the
suitable for working situations. Carbon
slightly harder wearing than aluminium
build platform into the resin. The paddle
in 0.1 mm (0.004 in.) layers, directed by a
tube would be very slightly oval. A large
filled and glass filled materials have been
tooling, and steel alloy, which has similar
flat plane should be manufactured at an
developed to build structural parts. The
characteristics to mild steel,
incline because if it is built flat there will
carbon filled material Windform™ XT
DESIGN OPPORTUNITIES
The SLS technique forms parts with physical characteristics similartothat
advantage of DMLS is that it produces
be too much stress in the part, which will
was designed specifically for use in wind
COSTS
There are many advantages to using
very accurate parts (±0,05 mm/0.002
result in warpage.
tunnels. It has good resistance to wind
There are no tooling costs.
rapid prototyping technology such as
of injection molded polymers. Because
in.) with fine surface definition
load and vibration, superior mechanical
reducing time to market and lowering
parts can be made with live hinges
(0.02 mm/0.0008 in.layers),andthe
product development costs. However,
and snap fits, this process is ideal for
final product is 98% dense metal. As a
the most desirable qualities of this
functional prototypes.
process for designers are not cost savings, they are that complex, intricate
The SLA technique is suitable for water clear, translucent and opaque parts.
properties and high surface finish, which
The cost of rapid prototyping is largely dependent on build time. Cycle
makes this an ideal material for Fi and
time is slow, but these processes reduce
result, DMLS parts have good mechanical
that the hinge is on the horizontal plane, for strength; if it was built vertically the layers would be too short to withstand
aerospace applications. Recent material
the need for any preparation or further
strength and so are suitable for tooling
the stress of opening and closing, and
developments for the SLS process include
processing and so turnaround is very
and functional metal prototypes.
wouldfail.
powders with rubber-like qualities and
rapid. Individual part cost is reduced if
In the SLS system, multiple parts can be built simultaneously and on different
those with integral colour, to reduce post¬
multiple products are manufactured
DESIGN CONSIDERATIONS
processing operations.
simultaneously,The SLS powders are
A live hinge is always constructed so
and previously impossible geometries
The surface finish can be improved with
can be built with these processes to
polishing and painting, SLA materials
fine tolerances and precise dimensions.
mimic conventional thermoplastics,
The main restriction for these processes
planes because the non-sintered powder
There is no tooling and so changes to the
which means SLA is good for making
is the size of the machine: SLS is limited
supports the sintered parts. By contrast,
resin polymers that are categorized
of components can be built around and
design cost nothing to implement.The
parts with the visual and physical
to parts of 350 x 380 x 700 mm (13.78 x
parts made by SLA and DMLS processes
by the thermoplastics that they are
inside one another to reduce cost.
combination of these qualities provides
characteristics of the final product.
14.96 x 27.56 in.); SLAis restricted to parts
need to be supported and undercuts
designed to mimic. Some typical
ofsoox 500x500 mm (19.69x19.69
must be tied into the build platform.This
materials include acrylonitirile
choice of process and layer thickness:
x 19.69 in.); while the DMLS process is
means that fewer parts can be formed
butadiene styrene (ABS) mimic.
typically SLS machines build 2 mm to
limitless scope for design exploration and opportunity.
DMLS provides an alternative to machining aluminium parts.The
The SLA process uses liquid epoxy
self-supporting and so large numbers
The build times are affected by the
Case Study
Building an SLA part of PE mimic The rapid prototyping machine works
tank to break the viscous surface tension
and any other contamination (image 9) and
automatically, overnight. The CAD data from
and ensure that the correct depth of layer is
the parts are then fully cured under intensive
a .stl file guides the UV laser (image ij.The
in place to be fused (image 5). The finished
UV light for 1 minute (image 10). The build
SLA parts appear as ghost-like forms in the
parts are left to drain and then removed
strata are Just visible in the finished part
clear epoxy resin (image 2). Each pass of
from the build tank along with any uncured
(image 11) and can be removed with abrasive
the laser fuses another 0.05 mm to 0.1 mm
epoxy resin residue (image 6). The parts are
blasting,polishing or painting.
(0.002-0.004 in.) to the preceding layer by
separated from the build platform (image
constructing the 'skin' (image 3) and then
7) and the support structure that separated
filling in the'core'material (image 4).The
them is carefully detached (image 8). An
build platform moves down 1 step, and the
alcohol-based chemical (isopropinol alcohol)
paddle sweeps across the top of the build
is used to clean off the uncured resin liquid
3 mm (0.079-0.118 in.) per hour in o.i mm (0.004 m) layers; SLA machines build 1.2 mm to 12 mm (0.047-0.47 in.) per hour;
and DMLS machines build at a rate of 2-12 mm3 (0.00012-0.00073 in*3) Per
hour. One drawback with SLS is that parts | have to be left to cool, which can increase
cycle time by up to 50%. Labour costs are moderate, although
they depend on finishing required. SLS parts are generally less expensive than SLA ones because they needless post-
building processing. DMLS parts are typically cut from the steel plate by EDM wire cutting and are then polished. This can be a 1 en gthy process, but it depen ds 4
'V
on the product and application.
ENVIRONMENTAL IMPACTS
f ¦
All the scrap material created during rapid prototyping can be recycled, except the carbon filled powders.These processes are an efficient use of energy and material, as they direct thermal
energy to the precise point where it is required.
Featured Manufacturer
CRDM www.crdm.co.uk
5
IP
V'
Case Study
Building an SLS part The SLS process takes place in a sealed, nitrogen rich atmosphere that contains less than 1% oxygen. The temperature
inside the building chamber is maintained at i700C (338^), Just below the melting point of the polymer powder, so that as soon as the laser makes
contact with the surface particles they are instantly fused (image i) by the i20C (220F) rise in temperature. Following the sintering process the delivery chamber moves up to deliver powder to the roller, which spreads it across the surface of the build area (image 2), coating the part with an even layer of powder (image 3). The building process can take anything from 1 hour to 24 hours. Once
it is complete, the build platform is raised (image 4), pushing the mixture of non-sintered powder and sintered parts
is disposed of in aThe clean-up I intoofapowder clear acrylic container. block booth and work begins to excavate the parts (image 5). The non-sintered'cake'
encapsulates the parts and has to be carefully brushed away so that individual parts can be removed for cleaning (image 6). Once most of the excess powder has
been removed (image 7), the parts are blasted with a fine abrasive powder (image 8).The final partis an exact replica of the computer model, accurate
to 150 microns (0.0059 in.) (image g).
Featured Manufacturer
CRDM www.crdm.co.uk
Building a DMLS part The DMLS process builds a metal part from
A steel build plate is set precisely inside
data within a .stl file. To make the process
the build chamber (image 2). Its thickness is
more efficient, each layer of the build is not completely filled in by the laser, The part is broken up into 3 main elements, which are
is guided across the surface layer by a CNC
This part will be used as an insert in
mirror (image 5). After each pass of the laser,
an injection molding tool. Some 20,000-
13-45 mm (0.51-0.77 in.), depending on the
a new layer of powder is spread over the build
30,000 components can be produced
depth of part to be built on it.
area (image 6).
with the part before any significant wear
The fine metal powder used to form this
Once building is complete, the build
occurs. Harder metal alloy powders will
the outer skin, the inner skin and the core. For
part comprises spheres of nickel-bronze alloy,
platform is raised (image 7), the excess
produce 100,000-200,000 parts from a
every 3 layers of metal powder that are spread
20 microns (0.00078 in.) in diameter.The
powder is brushed away (image 8) and
single impression tool.
the outer skin is sintered 3 times, the inner
powder is sieved into the delivery chamber
the steel plate removed with the part still
skin is sintered twice and the core is sintered
and then spread evenly across the build area
attached (image 9). The part is eventually
only once. A cross-section of atypical DMLS
in preparation for the first pass of the laser
removed from the steel build plate by
part shows the outer skin, inner skin and core,
(image 3). When the build area is ready for
EDM wire cutting (see electrical discharge
visible in the different tones (image 1).
sintering to begin (image 4), the CO2 laser
machining, page 254).
Featured Manufacturer
CRDM www.crdm.co.uk
Cutting Technology
TECHNICAL DESCRIPTION
Photo Etching Process
In stage 1, the metal workpiece Is carefully prepared, because it Is essential that It is clean and grease free to ensure good adhesion between
Cutting Technology
the film and the metal surface. The
Photochemical Machining
photosensitive polymer film Is applied by hot roll laminating or dip coating (page 68). In this case it Is being hot
Unprotected metal is chemically dissolved in photochemical machining. Masks are designed so that components are cut out and engraved simultaneously. The results are both decorative
roll laminated onto the metal. The
INTRODUCTION
coating Is applied to both sides of the
This chemical cutting process, which is
workpiece because every surface will
used predominantly to mill and machine
be exposed to the chemical machining
thin sheet metals, is also known as
process.
chemical blanking and photofabrication. and functional.
1 Very low tooling cost 1 Moderate to high unit costs
Stage 1: Applying photosensitive resist film
In stage 2, acetate negatives (the UV light source
Decorative chemical cutting is known as
photo etching (page 392). Photochemical machining has 3 main
are printed from CAD or graphics applied to either side of the workpiece,
Typical Applications
Suitability
functions: weight reduction, scoring
• Aerospace • Automotive • Electronics
• Prototype to mass production
and cutting out (known as profiling). It
software files. The negatives are Unexposed areas remain soft
Acetate negative
Exposed film hardens
can chemically remove surface material,
Related Processes
Speed
• High: accurate to within 10% of material thickness
• Abrasive blasting • CNC machining and CNC engraving • Laser cutting
• Moderate cycle time (50-100 microns/ 0.002-0.00/i in. per hour)
different on each side, so where they
cutting action is precise to within 10% of material thickness and so is suitable
do not meet up, the cut will only go
1} 1} ^
fortechnical application. Profiling is achieved by attacking the material from
half way through the sheet. The soft and unexposed photosensitive resist
film Is chemically developed away. This
both sides simultaneously.Therefore, this
process exposes the areas of the metal
Stage 2: UV exposure
process is limited to foils and thin sheet
that are to be etched.
metal between 0.1 mm and 1 mm (0.004-
In stage 3, the metal sheet is
0.04 in.) thick. However, accuracy can be Oscillating nozzles
maintained only in sheet materials up to 0.7 mm (0.028 in.) thick.
TYPICAL APPLICATIONS The technical aspects of this technology are utilized in the aerospace, automotive
Metal dissolves . in acid
-1 x 1 irr
Exposed film protects metal surface
the plastic (typically polycarbonate)
passed under a series of oscillating nozzles that apply the chemical etch. The oscillation ensures that plenty of oxygen is mixed with the acid to accelerate the process. Finally, the
protective polymer film is removed
Ferric chloride etchant
XXX X-
and electronics industries.
Circuit boards are made by coating
then both sides of the combined workpiece - resist film and negative - are exposed to UV. The patterns are
andean mark lines on most metals. The Quality
tool) are prepared in advance and
from the metalwork in a caustic soda mix to reveal the finished etching.
L Stage 3: Chemical cutting
board with a thin layer of copper. Areas of the metal are then chemically removed in order to create the positive image of the circuit board.
Other products include modelmaking nets, control panels, grills, grids, meshes, electronic parts, micro metal components and jewelry.
lillfe I
RELATED PROCESSES Laser cutting (page 248) and engraving
which can cause distortion in very thin
QUALITY
metal structure. The surface finish is
matt, but can be polished (page 376).
metals. Lasers are typically suitable for
This process produces an edge finish free
thicker materials, which are impractical
from burrs, and it is accurate to within
for photochemical machining.
10% of the material thickness. Another
DESIGN OPPORTUNITIES
advantage of photochemical machining
Photochemical machining is used to
engraving (page 396) also produce a heat-affected zone (HAZ), which can
is that there is no heat, pressure or tool
score lines, mill holes, remove surface
contact, and so the process is less likely
result in distortion in the workpiece.
to cause distortion, and the final shape is
material and profile entire parts (blanking).These different functions
CNC machining (page 182) and CNC
Photochemical machined engravings
are used to produce similar products.
have the same finish as an abrasive
However, lasers heat up the workpiece.
blasted surface (page 388).
free from manufacturing stresses. The chemical process does not affect
the ductility, hardness or grain of the
are applied simultaneously during machining.The type of cut is determined by the design of the protective mask.
Case Study
1
--*
Photochemical machining a brass screen The design for the negatives is prepared
brass sheet is degreased in a bath of 10%
using graphics software (image i )„ which
hydrochloric add. It is washed and dried, and
(image 7), the process is repeated until the
shows how the chemical machining process
a photosensitive film is laminated onto both
chemical has etched through the entire
works-The left hand drawing is the reverse
sides (image 3). The process takes place in a
thickness of material (image 8). This can take
and the right hand drawing is the front
dark room, to protect the film.
up to 25 minutes for 0.7 mm (0.028 in.) brass.
of the workpiece.The 2 sides are etched
The coated workpiece is placed into an acrylic jig (image 4). The negatives are aligned
out on both sides will be cut through
and mounted onto each side of the jig. The
the brass sheet and the tabs that connected
(profiled). Areas that are black only on 1 side
assembly is placed under a vacuum and
the workpiece are trimmed (image gi
will behalf etched.
exposed to UV light on both sides (image 5),
The negatives are printed onto acetate
t
mI
Ferrous metals will take longer.
simultaneously, so the areas that are blacked
(image 2).Then a 0.7 mm (0.028 in.)
.y
Afterthe first stage of chemical machining
Finally, the brass screen is removed from
1 ^iMi
I
Unexposed photosensitive film is washed off
I
in a developing process (image 6)
g
s 78,v (CMYK/Pieviewl
that is, by the photosensitive polymer resist film. Score lines can be machined to act as
foldlines.Changing the width of score will determine the angle of fold, and this
a.T. \.u,
w*** 1 • * • * ***
0*3. X-uJ. _i
is particularly useful for modelmaking and other secondary operations.
Profiling entire parts is achieved by chemically cutting the sheet from
> o X
X S** I • Ar-C* I** * J ^
rv *•*'* " • 7. A
Hi
*•¦
mate aa ÿ;
I a"-
both sides. Lines that do not match up on both sides will become surface
li, i, J TF
markings on 1 side.Therefore, sheets can
S zi W- J-l
be profiled and decorated (or scored) in a -fidop. e|.g> •Sgjopt
single operation.
Photochemical machining is suitable for prototyping and high volume production.Tooling costs are minimal:
the negatives can be produced directly from CAD drawings or artwork and will last for many thousands of cycles.
radii, holes, slots and bars is 1.5 times the thickness of the material.
Although any thickness of sheet
operations such as electroplating (page 364) andforflat sheet packaging.The
aluminium, copper, brass, nickel,tin and
Labour costs are moderate and
silver. Of these, aluminium is the easiest,
depend on the complexity and duration
shape of the tabs -V-shape or parallel - is
and stainless steel is the hardest and so
of photochemical machining process.
takes longer to etch.
This means that small changes are
material can be photo etched, only sheets
determined by the secondary operations.
inexpensive and adjustments can
and foils between 0.1 mm and 1 mm
A V-shape tab is for manually breaking
be made to the design. For these
(0.004-0.04 in.) can be profiled using
out, whereas a parallel tab is for parts
Glass, mirror, porcelain and ceramic
ENVIRONMENTAL IMPACTS
are also suitable for photo etching,
During operation, metal that is removed
reasons this process is suitable for
photochemical machining. Materials
that are punched or machined. V-shaped
although different types of photo resist
from the workpiece is dissolved in the
experimentation during design.
more than 1 mm (0.04 in.) thick will have
tabs can be sunk within the profile of the
and etching chemical are required.
chemical etchant. However, offcuts and
a visible concave or convex edge profile
part so that when removed there is no burr. The tabs can be half the material
COSTS
very few rejects because photochemical
thickness and a minimum of 0.15 mm
The only tooling required is a negative that can be printed directly from CAD
machining is a slow, controllable process.
DESIGN CONSIDERATIONS The intricacy of a pattern is restricted by the thickness of the material: any
left by the chemical process. Tabs are an essential part of the
other waste can be recycled. There are
The chemical used to etch the metal is
design for profiling. They connect the parts to the workpiece and hold the
(0.006 in.) each.
as the smallest details are larger than
parts in place as they are being cut out.
COMPATIBLE MATERIALS
the material thickness.The minimum
Tabs make handling easy, especially if
Most metals can be photo etched
multiple parts on the same sheet reduces
Both of these chemicals are harmful, and
dimension for internal and external
the parts are very small or in secondary
including stainless steel, mild steel.
cycle time considerably.
operators must wear protective clothing.
configuration can be machined, as long
data or a graphics software file. Cycle time is moderate. Processing
one-third ferric chloride. Caustic soda is
Featured Manufacturer
needed to remove spent protective film. Mercury Engraving www.mengr.com
Laser Cutting Process technical description
I I «
Mirror
CO, and Nd:YAG laser beams are guided
.
to the cutting nozzle by a series of fixed mirrors. Due to their shorter wavelength,
i
Cutting Technology
Laser Cutting
Nd;YAG laser beams can also be guided to the cutting nozzle with flexible fibre optic cores. This means that they can cut along 5 axes because the head is free to rotate in any direction. The laser beam is focused through a lens
This is a high precision CNC process that can be used to cut, etch,
that concentrates the beam to a fine spot,
engrave and mark a variety of sheet materials including metal,
between 0.1 mm and 1 mm (0.000^-0.00^ in).
The height of the lens can be adjusted
plastic, wood, textiles, glass, ceramic and leather.
to focus the laser on the surface of the material. The high concentration beam melts or vaporizes the material on contact. The
pressurized assist gas that blows along the path of the laser beam removes the cutting Typical Applications
Suitability
• Consumer electronics • Furniture • Model making
• One-offs to high volume
Quality
Related Processes
Speed
• High quality finish • Precision process
• CNC machining and engraving • Punching and blanking • Water jet cutting
• Rapid cycle time
1 No tooling costs 1 Medium to high unit cost
debris from the kerf.
Vacuum bed
INTRODUCTION
blanking (page 260) can all be used to
without reducing strength or distorting
The 2 main types of laser used for this
produce the same effect in certain
the part. Therefore very thin and delicate
thin sheet materials down to 0.2 mm
(PA),polyoxymethylene (POM) and polystyrene (PS). Of the metals, steels
process are CO2 and Nd:YAG. Both work
materials. However, the benefit of the
materials can be cut in this way.
(0.0079 i11-); it15 possible to cut sheets up
cut betterthan aluminium and copper
to 40 mm (1.57 in.), but thicker materials
alloys, for example, because they are not
greatly reduce processing speed.
as reflective to light and thermal energy.
by focusing thermal energy on a spot
laser cutting process is that it cuts
0.1 mm toi mm (0.0004-0.004in.) wide
thermoplastics so weill that they require
Raster-engraving methods can be used to produce logos, pictures and fonts
This process is ideally suited to cutting
to melt or vaporize the material. Both
no finishing; the cutting process leaves a
on the surface of materials with cuts of
Different laser powers are required for
operate at very high speeds to precise
polished edge. Laser cutting can also be
various depths. Certain systems are very
different operations. For example, lower
COSTS
tolerances and produce accurate parts
used to score and engrave, so competes
flexible and can be used to engrave from
powered lasers (150 watts) are more
There are no tooling costs for this
with very high edge finish. The main difference between them is that CO2
with CNC engraving (page 396), abrasive blasting (page 388) and photo etching
a variety of file formats.
suitable for cutting plastics because they
process. Data is transmitted directly from
leave a polished edge. High-powered
a CAD file to the laser cutting machine.
lasers produce a 10 micron (0.00039 in-)
(page 392) for some applications.
DESIGN CONSIDERATIONS
lasers (1 to 2 kilowatts) are required to
These are vector-based cutting systems:
cut metals, especially reflective and
m ateri al thi ckn ess. Thi cker m ateri al s take
QUALITY
the lasers follow a series of lines from
conductive alloys.
considerably longer to cut. However, suitable CAD files must be
infrared wavelength and Nd:YAG lasers produce a more versatile 1 micron
Cycle time is rapid but dependent on
The choice of material will determine
point to point.The files used are taken
the quality of the cut. Certain materials,
directlyfrom CAD data, which is divided
COMPATIBLE MATERIALS
TYPICAL APPLICATIONS
like thermoplastics, have a very high
generatedforthe laser cutting machine,
surface finish when cut in this way.
multitude of materials including timber,
which may increase initial costs.
modelmaking, furniture, consumer
Laser processes produce perpendicular,
up into layers that determine the depth of each cut. It is important that all lines are 'pedited' (joined together) so that the
These processes can be used to cut a
Applications are diverse and include electronics, fashion, signs and trophies,
smooth, clean and cuts with a narrow
laser cuts on a continuous path. Replica
marble,flexible magnets, textiles and
point of sale, film and television sets, and
kerf in most materials.
lines also cause problems because the
fleeces, rubber and certain glasses
Careful planning will ensure minimal
laser will treat each line as another cut
and ceramics. Compatible plastics
waste, but it is impossible to avoid
and so increase process time.
Thermoplastic scrap, paper and metal
(0.000039 It1-) infrared wavelength.
exhibition pieces.
DESIGN OPPORTUNITIES
The process requires very little labour.
RELATED PROCESSES
These processes do not stress the
CNC machining (page 182), water jet
workpiece, like blade cutting, so small
an d. DWG. Any oth er fil e form ats m ay
include polypropylene (PP), poly methyl methacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate
cutting (page 272) and punching and
and intricate details can be produced
need to be converted.
glycol (PETG), carbon fibre, polyamide
Compatible file formats include .DXF
Above
veneers, paper and card, synthetic
ENVIRONMENTAL IMPACTS
offcuts that are not suitable for reuse.
can be recycled,but not directly.
Laser cutting produces a polished edge on certain thermoplastics and so eliminates finishing operations.
:ase Study
Laser cutting, raster engraving and scoring LASER CUTTING PLASTIC
LASER RASTER ENGRAVING
The pattern was designed by Ansel Thompson
Adjusting the strength and depth of the laser
In this case the laser is being used at only
for Vexed Generation in 2005. This series
cutter can produce interesting finishes. Raster
3% of its potential. Scoring produces 'edge glow' effect in the cut detail (image 4) I his
LASER SCORING
of samples demonstrate the versatility of
engraving uses only a small percentage of
the laser cutting process. The strength and
the laser's power and produces engravings
is caused by light picked up on the surface of
depth of the CO2 laser can be controlled to
up to 40 microns (0.0016 in.) deep (image 3).
the material being transmitted out through
produce a variety of finishes.The laser is used
This form of engraving can be carried out
the edges. The scoring acts like an edge and so
to cut translucent 3 mm {o.n8 in.) thick poly
on a variety of materials and surfaces. For
lights up in the same way.
methyl methacrylate (PMMA) (image i).This
example, anodized aluminium maybe raster
is a relatively thin material, so the laser can
engraved to reveal the bare aluminium
LASER CUTTING WOOD
work rapid ly even though it is a complex and
beneath, instead of being printed. The sample
In this example 1 mm (0.04 in.) thick birch
intricate profile. The result (image 2) took only
took approximately 25 minutes to complete,
plywood is being cut and scored to form
12 minutes to complete.The laser leaves a
which is considerably longer than for a simple
part of an architectural model. The first pass
polished edge on PMMA materials and so no
cutting operation.
scores surface details laid out in the top
finishing operations are required.
More powerful lasers can engrave deeper channels in materials. However, when the
layer of the CAD file. Secondly, the laser cuts internal shapes and finally the outside profile
depth exceeds the width, problems with
(image 5). The entire cutting and scoring
material removal result in a poor quality
process takes only 8 minutes. The parts are
finish on the cut edge.
removed and assembled to form a building facade in relief (image 6).
Case Study
Laser cutting the Queen Titania Alberto Meda and Paolo Rizzatto designed the
(image 4). The parts on this sheet do not
The assembled structure is anodized (page
Queen Titania for Luceplan in 2005 (Image 1),
necessarily make up an entire light. Many
360) before the electronic and lighting
It is a modified (1.4 m/4.6 ft long) version of
lights are made in each batch, and so the
components are added. The reason for
the Titania, which was first manufactured by
parts are nested to optimize production and
anodizing is to ensure longevity of the
Luceplan in 1989.
reduce waste.
finish of the light. The surface of untreated
The cut parts do not have to be de-burred
aluminium Is less stable and more likely to
of an aeroplane wing.The parts are laser cut
or treated in any other way, which Is a major
change over time.The surface finish is grey,
from a sheet of aluminium and assembled to
advantage of laser cutting. Each part is
and light filters produce the vibrant colours.
The structure of the light is reminiscent
form a lightweight and rigid structure. The process starts by loading a sheet of aluminium into the laser-cutting machine (image 2). This is an Nd:YAG and oxygen cutting process operating at 5oo watts.
The machine is capable of cutting sheet steel up to 25 mm (0.98 in.) thick and aluminium up to 5 mm (0.2 in.) thick (image 3). Aluminium produces a larger HAZ (heat-affected zone) and so is trickier to laser cut.
The laser cutting process is rapid: each sheet takes only 8 minutes to process
removed from the sheet and hung up ready for assembly (images 5 and 6). The light is assembled in 2 halves, which are joined by riveting (images 7 and 8).
' Cutting Technology
Electrical Discharge Machining High voltage sparks erode the surface of the workpiece or cut a profile by vaporizing the material, making this a precise method of machining metals. Material is removed from the workpiece and a texture is applied simultaneously.
INTRODUCTION
and die-sink complex geometries deep
Electrical discharge machining (EDM)
into metal parts. Wire EDM is similar in
has revolutionized toolmaking and metal
principle to hot wire cutting polymer
prototyping. It is extremely precise and
foams and is used to create internal and
can be used to texture metal surfaces as
external profiles with either parallel
well as machine them.This makes it ideal
ortapering sides. Combined, these
for toolmaking for injection molding
processes provide metalworkers with
(page 50) and other plastic forming
unlimited versatility.
Costs
Typical Applications
Suitability
processes, which is the largest area of
• Low tooling costs for EDM; no tooling costs for wire EDM; very high equipment costs • Moderate to high unit costs
• Precision metalwork in the aerospace and electronics industries • Tool making
• One-offs and modifications to existing metalwork • Low volume production
application for this process.
Quality ¦ • Very high control of surface finish and
r
Related Processes
Speed
• CNC machining • Laser cutting • Water jet cutting
• Long cycle time
TYPICAL APPLICATIONS
There are 2 versions of the EDM
EDM equipment is very expensive, so
process: die sink EDM (also known as
its use is limited to applications that
spark erosion) and wire EDM (also known
demand the very high levels of precision and the ability to work hardened steels
as wire erosion). Die sink EDM can be used to bore holes, texture surfaces
and other metals that are impractical
for CNC machining (page 182). It has been widely adopted by the toolmaking 1 n dustry for i n j ecti on m ol din g, m etal
Alternatives to wire EDM include
casting and forging. It is also used for
water jet cutting (page 272), laser
modelmaking, prototyping and low
cutting (page 248) and the power beam processes (page 288) for certain profiling and drilling procedures. All of these
volume production of typically no more than 10 parts.
processes have high equipment costs,
RELATED PROCESSES
so the choice is often determined by available facilities. Wire EDM is suitable
EDM is generally used in conjunction with CNC machining.The electrodes
for parts up to 200 mm (7.87 in.) thick
Top On these die sfnlc EDM tools, the patination of black vaporized metal shows the cutting area.
Above right This very small die sink EDM tool was cut out using the wire EDM process. It is too small and intricate to
Above left The VDI scale is used to
produce by conventional machining.
measure the texture of the surface.
The quality of the finish and resulting
(tools) for die sink EDM are machined by
that require high dimensional accuracy,
conventional metalworking techniques
parallel kerf walls and a controlled
speed and voltage. High voltage and high
(see image, top). However, complex
surface texture.
cutting speed produce a rough texture.
using wire EDM, which combines the
QUALITY
and more passes produce finer surface
2 processes (see image, above right).
The quality of EDM parts is so high they
textures. Parts can be manufactured
can be used to manufacture tooling for
accurate to 5 microns (0.00019 in-)-
and intricate tools are sometimes cut
Die sink EDM has replaced CNC
texture are determined by the cutting
Lower voltage, slower cutting speeds
machining in applications that require
injection molding without any finishing
accurate and intricate internal features.
operations. Surface finish is measured
DESIGN OPPORTUNITIES
EDM is used because it can produce
on the Association of German Engineers'
A major advantage for designers is the
geometries that are not feasible with
VDI scale (see image, above left).The
ability of this process to cut metals and
any other process. Internal features,
VDI scale is comparable with roughness
apply a texture simultaneously.Textures,
especially in hard metals, are not
average (Ra) 0.32-18 microns (0.000013-
including matt and gloss, are usually
practical for CNC machining because
0.00071 in.). Many of the plastic products
applied after machining operations
they would require very fine cutting tools,
surrounding us today have been molded
using abrasive blasting or photo etching
which would wear out rapidly.
in tools shaped and finished by E DM.
techniques. EDM produces accurate
TECHNICAL DESCRIPTION
Die sink EDM Process
D
Die sink EDM takes place with the
Case Study
electrode (tool) and workpiece
Die sink EDM
submerged in light oil, similar to paraffin. This fluid is continuously
Movement in x, y and z axes
running and so both maintains the temperature of the workpiece and
Copper electrode
(tool)
dielectric, which insulates the working area and sustains the static discharge
The copper electrode (tool) and metal
¦=>
proximity, which initiates the spark Dielectric fluid in continuously running bath
erosion process. High voltage sparks Spark erosion
leap from the electrode to the workpiece
Workpiece
and vaporize the surface of the metal.
Clamp (+]
The electrical discharges jump between the closest points on the electrode and
even surface material removal. There is no pressure required in operation. The electrode is lowered into the workpiece very gradually,- the speed of the process is dependent on
the finish required and can range from 2 mm3 (0.00012 in.3) per minute to over 400 mm3 (0.024 in.3) per minute for very
rough finishes. As the tool is sunk into the workpiece it is continuously agitated
(image 7), This is a very shallow impression;
was once used as the insulating fluid, until
cavity directly into the surface of high-carbon
this oil was developed.
deep cavities.
Sparks and fumes are given off during
complex and intricate cavities into hard
rough cutting (image 4). The copper electrode
metals like this, other than by using EDM.
is charged with an electric current, which
The copper alloy electrode (tool) is inserted
when they come into very close proximity.
the computer guided tool head (image 2).
There are several thousand sparks per
The EDM machines are programmed to the
second. Each spark vaporizes a small piece
settings required forthe tool.The black areas
of surface material. The arcs will jump
show the parts of the tool that have been
across the shortest distance between the
exposed to spark erosion. Each tool may last
electrode and workpiece, which ensures
for only 5 uses before it has to be replaced.
evenly distributed surface removal. In this
radius is also affected by the thickness
If extreme levels of precision, to within
case the process is vaporizing around 400
the workpiece, creating sharp corners
of the wire electrode, which is typically
5 microns (o.oooig in.), are required, new
mm3 (0.024 in.3) per minute. The resulting
and complex features that would
50 microns (0.0020 in.) to 300 microns
tools are machined for each EDM operation.
surface finish is very rough (image 5).
otherwise be impractical.The erosion of
(0.012 in.) in diameter.
The thickness of material that can be cut by wire EDM ranges from o.i mm
(0.1%), so small internal radii and
(0.004 in.) up to 200 mm (7-87 i^-).
flushes vaporized material away from
Wire EDM can be used in much the same way as hot wire cutting polymer
foam, although it is considerably more precise andmuch slower,The equipment
(black powder) can be flushed away, so maximum depth is affected by the depth
requires a high level of skill to operate.
to diameter ratio. Very deep profiles are
Stress is not applied to the electrode
machine settings, eliminating the need
(tool or wire) or workpiece during
for further finishing operations.
processing because the metal is not
o > r~ o
cs
possible, but may require extra flushing, which will increase cycle time.
COMPATIBLE MATERIALS
produce geometries that are not possible
being shaped by force, but in stead by high voltage sparks that vaporize the
Many metals can be shaped by EDM
with conventional machining. For
surface. Other than the obvious, this
techniques.The hardness of the material
instance, the guide heads on many wire
has many processing advantages. For
does not affect whether it can be
EDM machines can move independently
example, multiple thin-walled parts can
processed in this way. Metals including
during the cutting process.The
be stacked up and cut by wire EDM to
stainless steel, tool steel, aluminium,
advantage is that complex tapers, up to
reduce processing time.
titanium, brass and copper are
30°, can be cut with extreme precision,
m o
jumps to the oppositely charged workpiece
into a tool holder that is registered with
negative electrode (tool) is reproduced in
slower than the erosion of the workpiece
(0,003 in.3) per minute (image 6), This produces a much finer surface texture die sink EDM can also be used to form very
applications.The minimum internal
the copper electrode (tool) is considerably
much slower, in this case as low as 50 mm3
similar to paraffin (image 3). In fact, paraffin
that are not suitable for cavities.The
the cutting area and ensures even and
commonly shaped in this way.
which is not possible with any other
DESIGN CONSIDERATIONS
machining technique.
Although these processes can produce
COSTS
internal radii as small as 30 microns
Wire EDM does not require tooling.
Die sink EDM can be used to produce
emboss surface textures and graphics. In this
The second stage of machining is
case study, Hymid Multi-Shot are forming a
larger than 500 microns (0.02 in.) in most
but depends on the capabilities of
These processes can be used to
submerged in a dielectric fluid, which is
electrode can be machined into shapes
the equipment.The depth that can be produced by die sink EDM is limited by the ease with which vaporized metal
textures, which are determined by the
tools. It can also be used to bore holes or
However, these do not need to be any
complex features are reproduced to the
efficient material removal.
The tool and workpiece are inserted and
This is because a negative copper
same precision as simple geometries.
and descends in a spiral. This action
separate tool for finishing.
steel (image 1). It is not practical to machine
workpiece are brought within close
the workpiece, forming continuous and
including a tool for roughing out and a
well as machining entire cavities for injection molding, it is often used to modify existing
flushes out vaporized material. It Is also
within In It.
This process is widely used for tool-making. As
Featured Manufacturer
internal geometries on parts that are not
(0.0012 in.), it is always better to use
However, it does consume wire electrode
Hymid Multi-Shot
possible with conventional machining.
larger radii to avoid stress concentration.
continuously, which must be replaced.
www,hymid,co,uk
CD
o X >
O > O
in
TECHNICAL DESCRIPTION
Wire EDM Process
Case Study
In this process the wire electrode, which is usually copper or brass, is fed
Wire EDM
between the supply spool and take up Supply spool!-)
spool. It is charged with a high voltage, which discharges as the wire progresses
through the workpiece. Similar to die sink EDM, the spark occurs in the smallest gap between the metals. There are many thousand sparks per second, which vaporize very small amounts of the metal surfaces. The wire electrode
Unlike die sink EDM, which is used to form
workpiece and wire electrode are submerged
where the wire has cut from the pre-drilled
internal relief cavities, wire EDM is used to cut
in deionized water, which acts as an insulator
hole to the cutting profile (image 7): on the
internal and external profiles. The wire is held
(image 3). Once submerged, the cutting
left are the parts prior to cutting, in the centre
under tension to cut straight lines. The guide
process begins (image 4). It is a long process;
is the finished workpiece and on the right the
heads move in tandem along x and y axes to
in this case the 36 mm (1.42 in.) workpiece is
material that has been removed.
produce profiles and independently along x
cut at 1.5 mm (0.059 in.) per minute. This will
andy axes to produce tapers. The wire acts
produce the desired finish.
like the copper tool used in die sink EDM and
is not recycled; instead it is replaced
is usually a copper alloy.
continuously, which maintains the
There are many cutting operations in
accuracy of the process.
This process is submerged in deionized water, which is maintained at
measured on a micrometer (image 6). On the
illustrates one of those operations, the
finished article you can just make out the kerf
other wire EDM operations.The partly
running to flush spent material and
Clamps 1+)
recycled through a filtration system. Static wire guide
The upper wire guide can be moved
Take-up spool (-)
machined high-carbon steel workpiece (image 1) is loaded into a jig and clamped in place. A small hole is drilled in
along x and y axes to enable cutting
preparation, which the wire electrode is
angles up to 30°.
automatically fed through (image 2). The guide heads are brought close to the workpiece for precision and both the
Die sink EDM tools are typically made
(0.012- 0.024 in.3) per minute. As the
from a copper alloy, which can be shaped
term suggests, this will produce a rough
by conventional machining processes
finish. After this a new tool is used at a
or wire EDM.The tooling is relatively
much slower cutting rate, which can be
inexpensive, but for precision parts new
as low as 2 mm3 (0.00012 in.3) per minute,
tools are required for each operation.
to produce a very fine finish. Therefore,
Different factors affect cycle time for wire and die sink EDM. In wire EDM applications, cycle time is affected by
very fine surface textures are best suited to small surface areas. Labour costs are moderate due to the
the thickness of the material.Thicker
high level of operator skill required and
materials require higher power and
the length of the process.
consume more wire electrode. As a rough guide, a piece of 36 mm (1.42 in.)
ENVIRONMENTAL IMPACTS
hardened steel can be cut at 1.5 mm
This process requires a great deal of
(o.osgin.) per minute.This will produce
energy to vaporize the metal workpiece.
an even, matt finish. Slowing the process
However, it does eliminate the need for
down, or using multiple passes, will
any further processing, such as abrasive
produce a finer texture. Speeding the
blasting (page 388) or photo etching
process up will produce a rougher
(page 392). The electrically insulating fluids are
surface finish.
Similarly, the cycle time of die sink EDM is determined by the size of the
continually recycled for reuse. The metal
cutting area and desiredfinish.Typically,
Fumes are given off during operation,
internal geometries are roughed out
which can be hazardous.
at between 200 mm3 and 400 mm3
(image 5). The accuracy of the part is
this case study. This collection of images principles of which can be applied to all
20oC (680F). The water is continuously
After cutting, which takes approximately 2 hours, the part is removed and cleaned
electrodes are also suitable for recycling. Featured Manufacturer
Hymid Multi-Shot www.hymid.co.uk
Cutting Technology
Punching and Blanking Circular, square and profiled holes can be cut from sheet materials using a hardened steel punch. Tooling is either dedicated or interchangeable, depending on the geometry and
INTRODUCTION Punching and blanking are shearing processes used in metalworlc.They are essentially the same, but the names indicate different uses: punching refers
complexity of design.
to cutting an internal shape (see images,
below and opposite) and blanking is cutting an external shape in a single Costs
Typical Applications
Suitability
• Low to moderate tooling cost • Low to moderate unit costs
• Automotive and transportation • Consumer electronics and appliances • Kitchenware
• One-off to mass production
Quality ¦ • High quality and precise, but edges require 1 de-burring
Related Processes
Speed
• CNC machining • Laser cutting • Water jet cutting
• Rapid cycle time (1-100 per minute) • Tooling changeover is time consuming
operation.
Above left Above
multiple punches around the perimeter
RELATED PROCESSES
removing large areas of material from
of the cut string together in a process
These processes can only be used for
the centre of the workpiece (punching)
known as 'nibbling'.
thin sheet materials up to 5 mm (0.2 in.).
and leave ahole of on a rotating die to
Water jet cutting (page 272) andlaser
exactly the same shape. accommodate its profile.
Cutting out large parts (blanking), or
becomes impractical with a single tool
Another operation, known as
These figures are The perforation on the
punched from Alessi Max Le Chinois colander stainless steel products is punched in 2 stages
above 85 mm (3.35 in.) diameter because
'notching', is the removal of material
cutting (page 248) are suitable for a
it would be too expensive. In such cases
from the outside of the workpiece.
wide range of materials and thicknesses.
will increase investment cost. It may also
Small cuts can be made more quickly by
have to be carried out in several stages
referred to as punching.They are often
punching because each cycle removes
because punching can only occur in the
combined in a production line such as
a chunk of material, whereas laser and
vertical position.Thus, Max Le Chinois
progressive dies in metal stamping (page
water jet have to trace the outline.
(see image, above), the Alessi colander
82). In other applications, punching may
CNC machining (page 182) of
designed by Philippe Starck, requires 2
These processes are generically
be the core process, in which case the
holes and profiles is more precise,
punches: 1 forthe perforations on the
operations are carried out on a punch
but consequently more expensive. A
side and 1 for the base. The product is
press, or turret punch. A punch press uses
machining operation, such as drilling
punched and rotated in stages until the
a single tool and is typically set up for a
or milling, will produce perpendicular
full circumference is complete.
repetitive operation. A turret punch is
walls without burr, but cycle time is
coijiputer controlled, and is loaded with
con si derably longer.
multiple tools that can accommodate
Turret punches can be used to
prototype parts without investing in expensive tooling. A typical
complex and varied operations, including
QUALITY
metalworking factory will have many
nibbling. Flypressing is a manually
The shearing action forms'roll over'on
tools for cutting a range of profiles
operated spinning press.
the cut edge andfractures the edges
guided by computer.
of the material.This results in burrs,
Punching tends to be used to
TYPICAL APPLICATIONS
which are sharp and have to be removed
Some typical products include
by grinding and polishing (page 376).
perforations orfixing points. It is also
kitchenware, such as Alessi colanders,
Problems are minimized by careful tool
used for decorative applications because
bowls and plates, consumer electronic
design and machine set up.
a punched hole, for example, does not have to be circular or square.
and appliance enclosures,filters, washers, hinges, separators, general metalwork
add function to a metal part such as
DESIGN OPPORTUNITIES
Selective material removal will reduce
It is not just flat sheet that can be
weight but may not reduce strength too
punched. Stamped, deep drawn (page
much.Therefore, it is sometimes practical
in low volume and prototype production
88), roll formed (page no) and extruded
to carry out functional punching and
of parts that will ultimately be shaped by
metal parts are also suitable. Specialized
selective material reduction on an item
processes such as stamping.
tooling is required for 3D parts, which
in the same operation.
and automotive body parts. These processes are used a great deal
ro Os
DESIGN CONSIDERATIONS
Punching and Blanking Process
The first consideration is the width of material being removed or left behind. Punch diameter or width should be not
Hydraulic ram i or fly press
smaller than material thickness. Also, the
width of material left behind should be greater than the thickness of material. Fixing points should be inset as far as possible for maximum strength.
Workpiece
n I l
Case Study
Punch pressing the Alessi Tralcio Muto tray Punch
1 Stripper
Scrap or workpiece
1 Die
move about during production, but are
sufficiently fragile to allow the parts
Cutting edge Roll over and burr Scrap or workpiece
to be broken outby hand. The burr left it is concealed in a recess.
Stage 1: Loading
to 0.75 mm (0.01- 0.03 in.). Therefore,
carried out on a turret punch, punch press
the sides of the hole are not exactly
Almost all metals can be processed in
or flypress. It is possible to punch a single
perpendicular to the face.
this way. It is most commonly used to
hole, multiple holes simultaneously, or
cut carbon steel, stainless steel and
many holes with the same punch.
Other materials, including leather, also be punched, but metalworking machinery is not suitable. These materials are softer and easier to cut than metal. Punching in this case is
punched again to produce the complete
Sansoniin 2000.
pattern (images 7 and 8).
In stage 1, the workpiece is loaded onto the roller bed. In stage 2, the
surface. This is to ensure that the tray can
be polished to a very high finish. If it were
at a time (image 4). The design is such that
punched from the front, the edges of the
the punching operation is carried out in 2
holes would have a slight radius from the
stages.There is too much cutting for a single
impact and so could not be polished to
stroke on this 150 tonne (165.35 US ton) press.
such a high level.
Once cut, the punch retracts and the
free. Either the punched material or the surrounding material is scrap, depending
stripper and die clamp the workpiece.
on whether it is a punching or blanking operation. In both cases the scrap is
causing the metal to fracture between
collected and recycled.
the circumferences of the punch and die.
Dedicated tooling may be made up
The die is slightly larger than the punch
of many punches joined together. They
to allow for roll over and burr caused
operate simultaneously in a punch press.
typically referred to as die cutting (page 266), which is the process of making all
by the shearing process. The offset is
Complex and intricate shapes are more
determined by the type and thickness
easily achieved with these tools such as
the cuts in a single stroke.Thin metal
of material and ranges from 0.25 mm
in the Alessi case study.
sheet is also suitable for die cutting.
COSTS Standard and small tools are inexpensive.
ENVIRONMENTAL IMPACTS
Specialized and 3D tools can be more
Parts can be nested very efficiently on
expensive but are suitable for small
a sheet to minimize scrap. Any scrap is
batch production. Cycle time is rapid. Between 1 and 100 punches can be made every minute,
but this depends on loading time
collected and separated for recycling, so there is very little wasted material. The de-burring process is abrasive and so produces some waste.
and continuity of production.Tooling changeover time can be expensive. Labour costs are moderate to high because these processes require skilled operators to ensure high quality cuts. Machine set up determines the quality and speed of cut.
so that the burrs are on the flat front
Trays are loaded into the tool (image 3) one
stripper ensures that the metal comes
The hardened punch stamps through it,
The tray is punched from the back
part is coated in a thin film of oil (image 2).
TECHNICAL DESCRIPTION The operation is the same whether it is
textiles, plastic, paper and card, can
which was designed for Alessi by Marta
Stage 2: Punching
COMPATIBLE MATERIALS
aluminium and copper alloys.
and the product is rotated through go" and
edges are trimmed, de-burred and rolled. The
n n 1 1
These ensure that the part does not
behind will have to be polished off, unless
The first punch is made (images 5 and 6)
production of the Tralcio Muto tray (image l),
The tray is stamped in stainless steel; the
Parts that are cut out have to be tied into the sheet of material by tabs.
This case study illustrates a stage in the
Featured Manufacturer
Alessi www,ales5i,com
The final part is removed from the too! and taken to be polished (image 9),
Case Study
The turret punch is loaded with a series of
Each cycle produces a small piece of scrap,
The cut out part is inspected and cleaned
matching punches and dies (image i).The
which is siphoned into a collection basket for
up (image 5). Tabs maintain the blank in the
orange surround on the punch is the stripper,
recycling (image 4). In a blanking operation,
sheet until it is further processed (image 6).
which makes sure the punch can retract from
these pieces of metal are the workpiece. Many
In this case, the metal blanks are formed into
the wofkpiece.
of the pieces, such as squares and circles, are
enclosures by press braking (page 148).
The die set is loaded into the turret and
from straightforward punching operations.
their location programmed into the computer
The crescent shaped part was produced by a
guiding software (iinage 2). Optimization
nibbling operation, in which a circular punch
software ensures that the punch selected
makes a larger diameter hole with many
is the most efficient for each cut. Many
overlapping cuts,
different tools may be used for a single part, all of which are pre-loaded into the turret.
Changeover time can be lengthy, and all the while the machine is not working it is losing money.
Parts are nested together on a sheet to minimize scrap. The punching operation takes less than 2 minutes for these parts (image 3). The sheet is moved around on the roller bed and the turret rotates to select the die set for each operation.
Featured Manufacturer Cove Industries www.cove-industries.co.uk
ttm Cutting Technology
Die Cutting Using die cutting, thin sheet materials can be cut through, kiss cut, perforated and scored in a single operation. It is a rapid process and is utilized a great deal in the packaging industry for mass producing cartons, boxes and trays.
Low tooling costs Low unit costs
INTRODUCTION
The depth and shape of each steel rule
This process, which is also referred to as
determines whether it cuts through,
blanking, is a stamping process in which
kiss cuts (in which the top layer is cut
shapes are cut from sheet material using
through and the support layer is left
steel knives mounted on wooden tools.
intact), scores or perforates the material.
It is the opposite of punching (page 260),
Typical Applications
Suitability
• Packaging • Promotional material • Stationery and labels
• Low to high volumes
Quality
Related Processes
Speed
• High quality edge finish
• Laser cutting • Punching • Water jet cutting
• Very rapid cycle time (up to 4,000 per hour)
which is the removal of material from the
TYPICAL APPLICATIONS
workplace by a similar action.
This process is primarily used in the
Die cutting, which is carried out as
packaging industry. The number and
a linear or rotary operation, is the most
angle of lines does not affect the
cost effective way to cut complex net
operating cost, so it is ideal for packaging
shapes from most non-metallic sheet
systems that have intricate details or
materials,including plastic, paper,
complex shapes and are not based on
card,felt andfoam. It combines many
right angles. Many boxes, cartons and
operations into a single stamping action.
trays are made in this way. A major area of application is cutting out labels, including pressure Other stationery applications are
Top This is the steel rule wooden die used for
plastic and paper folders, envelopes and
the Libellule light
promotional material. Lighting products
(page 269).
sensitive and adhesive backed ones.
are also made using die cutting. This process lends itself to low volume production, as low as 50 parts, because of its relatively inexpensive tooling.
Above
The foam pads that surround the sharp
blades eject the cut or perforated material.
RELATED PROCESSES
over large volumes.The cutting action is
Testing is essential to eliminate such
Die cutting is the process of choice for
between a sharp cutting rule and a steel
aesthetic defects.
most non-metallic and non-glass flat
cutting plate, and therefore results in
sheet cutting applications. Sheet metals
clean, accurate cuts. Scoring, kiss cutting
DESIGN OPPORTUNITIES
are cut into similar shapes by punching,
and perforating are equally precise, and
The complexity of a design does not
water jet cutting (page 272), laser cutting
the depth of cut is accurate to within
affect the cost of die cutting -unlike
(page 248) or simply with a guillotine. Sheet glass is typically scored (page 276)
50 microns (o.ooig in.). Accuracy also
many mass production techniques in the
depends on the material being die cut:
packaging industry such as the printing
or water jet cut.
for example, corrugated materials have
and rotary slotting machines used to
a unidirectional core pattern that may
produce cardboard boxes.Therefore,
affect scored bends.
designers are free to explore innovative
QUALITY The tools used in die cutting are
Some materials resist certain cutting
structures such as closures, handles and
typically laser cut and so precise. The
techniques, especially kiss cutting.
display windows in packaging without
steel knives wear very slowly and have
Cutting such materials may result in
fear of ramping up the cost.
a long lifespan.The quality of the cut is therefore very high and repeatable
a halo around the perimeter, or cause laminated materials to delaminate.
The size of the product is also
insignificant because multiple small
TECHNICAL DESCRIPTION
Die Cutting Process Sheet material
Die cutting consists of 3 main elements: Perforated cutting rule
the steel rule wooden die, the press
Cutting rule
Score rule
Case Study
Angle score rule with lower die
Die cutting the Libellule light
either side of it and the sheet material to be cut.
Support plate
Steel rules are mounted in a
u Ju n
I Steel rule I wooden die
wooden die. The slots for the rules are
typically laser cut. If the blades wear
| Cutting plate
out then they can be easily replaced.
This Libellule pendent light was designed
which the cut shapes are easily removed
by Black & Blum (image 1). Because the
from the sheet (images 5 and 6), which
volumes for this product do not justify
becomes scrap material (image 7).
fully automated production, it is made on a manually operated die cutting machine
The steel rules pass right through the i Hydraulic ram
wooden die and press against the steel
Foam pads
(image 2). To reduce weight and maximize production efficiency, 2 shades are produced
support plate. This ensures that all of
on each piece of polypropylene sheet, which
the energy produced in the hydraulic
is cut to size (image 3).
Stage 1: Loading
rams is directed Into the cutting or
Each cycle requires the operator to load
scoring action.
and unload the cut sheet (image 4), after
The pressure required for cutting is determined by the thickness and type of material. It is also sometimes
possible to cut through multiple sheets simultaneously. Generally, the pressure
required to die cut is between 5 and 15 tonnes (5.5-16.5 US tons), but some
die cutters are capable of ^00 tonnes (441 US tons) of pressure. In stage 1, the sheet is loaded onto Stage 2; Die cutting
the cutting plate, which rises up to meet the steel rule wooden die. In stage 2, the
sharp steel rules cut right through the shapes can be mounted onto a single die,
operating on x andy axes.This same
pads either side of each cutting rule
maximizing output. Cutting beds can
process is used to cut fabric patterns
apply pressure to the sheet material to
typically accommodate sheet materials
for upholstery (page 338) andfibre
prevent it from jamming. The cutting
up to 1.5 x 2.5 m (5 x 8 ft).
reinforcement for composite laminating
sheet material, while foam and rubber
action is instantaneous, each sheet
A multitude of materials can be die
being processed within a few seconds.
cut. This means that an entire packaging
However, particularly tight and complex
system can be shaped in this way,
(page 206).
DESIGN CONSIDERATIONS
geometries can clog up the die, in which
including the card enclosure and foam
Thetypeofmaterial will determinethe
case the operator may have to remove
padding, for example.
thickness that can be cut.
material manually.
Multiple operations are performed
Possible shape, complexity and
It Is possible to score certain
simultaneously. Materials can be cut
intricacy are determined by the
materials, such as corrugated card
to specific depths in increments only
production of the steel rule dies. Steel
microns apart, such as in kiss cutting,
rule blades can be bent down to a 5 mm
and plastic, using different techniques, including perforating and creasing, and by adding a ribbed strip on the cutting plate. The type of steel rule used to score the material is determined by the angle and depth of score required.
which is used for the production of
(0.2 in.) radius. Holes with a smaller
self-adhesive labels on a backing
radius are cut out using a profiled punch.
film. Because these operations have
Sharp bends are produced by joining 2
to be extremely precise (within 50
steel rules together at the correct angle.
microns/o.ocng in.), they take longer to
The width between the blades is
set up and require skilled operators to
limited to 5 mm (0.2 in.); any smaller and
control the tools.
ejection ofmaterial becomes a problem.
Prototyping in sheet materials is
Thin sections should be tied into thicker
generally an inexpensive process. Most
sections to minimize ejection problems.
cutting operations are carried out on a
Nesting parts is essential to reduce
CNC x- andy-axis cutter, which transfers vector based CAD data to a cutting head
material consumption, cycle time, scrap material and costs in general.
Featured Manufacturer
PFS Design & Packaging www.pfs-design.co.uk
Case Study
Die cutting and assembling a crashlock box This crashlock cardboard box (image i) is
with the adhesive fully cured, flat and ready
produced in very large numbers and so
to ship (image 8).
production is fully automated. It is called
This particular set-up is not dedicated,
a 'crashlock' because the base is glued
and most of the mechanisms are computer
together in such a way that It unfolds as
controlled. Therefore atthe click of a button
the box is opened up.
they move into place ready for the next
Die cutting is the most effective method
sequence of events. However, setting up the
of manufacturing the box because there
process for the first time is still a long and
are angled cuts and scores that cannot
highly skilled job.
be produced on printing and slotting machines. Very simple boxes that are scored
and cut at right angles can be produced economically with rotary cutters on the end of the print line. However, as soon as there is an angle to score, such as on
the base of the crashlock box, die cutting techniques are used.
Large quantities of card are needed for this production process that requires 4,000 feeds per hour (image 2). The card is die cut in an enclosed production line, after which is it fed onto the folding production line (image 3).This is an incredible and rapid process, which is hypnotic to stand and watch. The combination of levers, arms,
rollers and glue dispensers gradually assemble the boxes (images 4-7). The finished boxes emerge from the press,
COMPATIBLE MATERIALS
more parts, which means a cycle time of
the material supplier. In some cases
Many materials can be cut by die cutting,
16,000 parts per hour.
the offcuts can be recycled by the
Labour costs are low in automated
manufacturers themselves, such as In
sheet, plastic film, self-adhesive films,
systems. Manually operated production
thecaseofCullen Packaging, who use
cardboard, corrugated card, board, foam,
is restricted to low volume parts and is
the scrap material from their cardboard
including corrugated plastic, plastic
rubber, leather, veneer, felt, textile, very
slightly more expensive, but operation is
packaging facility as raw material in their
thin metals, fibreglass and other fibre
rapid and needs little adjustment or
paper pulp production plant (page 204).
reinforcement, flexible magnets, cork,
maintenance. Set-up can be expensive in
vinyl and DuPont™Tyvek®.
both automated and manually operated versions, due to the machine down time.
COSTS Tooling costs are low.Tools are usually
ENVIRONMENTAL IMPACTS
wooden based and wear out very slowly.
Die cutting does produce offcuts.
Cycle time is very rapid. Automated
However, scrap can be minimized
systems can operate at up to 4,000 feeds
bynesting the shapes together on a
per hour. Each feed may produce 4 or
sheet. Most scrap can be recycled by
Featured Manufacturer
Cullen Packaging www.cullen.co.uk
7
I
Abrasive Water Jet Process High-pressure water feed
4 A high-pressure jet of water, which is typically mixed with
thickness. For example, polymer foam
abrasives, produces the cutting action. It will cut through almost
100mm (3.94 in.) thick will cut with very little drag, but the maximum thickness
any sheet material from soft foam to titanium, and is capable of
for stainless steel is 60 mm (2.36 in.) and the cycle time is considerably longer.
cutting stainless steel up to 60 mm (2.36 in.) thick.
One-off to medium volumes can be accommodated because there are no tooling costs. Also, the scale of the
1 No tooling cost Moderate unit cost
Typical Applications
Suitability
workpiece does not dramatically increase
• Aerospace components • Automotive • Scientific apparatus
• One-off to medium volumes
costs.Therefore, this process is ideal
Nozzle
for prototyping and experimentation. Materials can be changed and tested
Quality
Related Processes
Speed
• Good quality
• Die cutting • Laser cutting • Punching and blanking
• Moderate cycle time, depending on the type and thickness of material
without any start-up cost because the main cost factor is time. External and internal profiles can be cut in the same operation. Entry holes are unnecessary, except in materials that are
INTRODUCTION
industries were the early adopters.
QUALITY
This is a versatile process for cold cutting
However, this process is now an
One of the main advantages of water
The process does not create stresses in
sheet materials. It has been used for
essential part of many factories. Specific
jet technology is that it is a cold process;
the workpiece, so small, intricate and
commercial industrial applications since
applications include cutting intricate
therefore it does not produce a heat-
complex profiles are possible.
the 1970s andhas continued to develop
glass profiles for scientific apparatus,
affected zone (HAZ), which is most critical
at a rapid pace. It is carried out as either
titanium for aerospace and carbon
in metals. This also mean s that there is
DESIGN CONSIDERATIONS
TECHNICAL DESCRIPTION
water only cutting or abrasive water jet
reinforced plastic for motor racing.
no discolouration along the cut edge and
Reducing cycle time reduces the cost of
This is only a small part of the equipment
pre-printed or coated materials can be
the water jet process. Sharp corners and
required to produce water jet cutting. Tap
or increasing the water pressure. The
tight radii slow down the process; the water jet cutter will slow down to avoid
water is supplied to the cutting nozzle
same techniques will reduce drag and
at very high pressure from a pump and
other cutting defects, which are especially
intenslfler combination. In the pressure
prominent on internal and external radii.
cutting. Water only cutting is ahighvelocity jet of water at pressures up to
RELATED PROCESSES
4,000 bar (60,000 psi).The supersonic jet
This process competes with a diversity
of pure water erodes the materials and produces the cutting action. In abrasive
of machining operations as a result of
the diversity of compatible materials.
cut this way. Pure water jet produces a much cleaner cut than abrasive systems. In both operations, there is no contact
likely to delaminate or shatter on impact.
drag, which inadvertently increases cut taper on curves. Also, holes with
chamber the water reaches up to 4,000
decreased by reducing the cutting speed
The difference between this process
bar (60,000 psi). At this high pressure It
and pure water jet cutting Is the addition
Is forced through a small opening In the
of abrasive particles. Without the mineral
water jet cutting small particles of sharp
Laser cutting (page 248), die cutting
between the tool andworkpiece and so
material are suspended in the high-
there is no edge deformation. However,
velocity jet ofwaterto aidthe cutting
(page 266), punching and blanking (page 260) and glass scoring (page 276) are all
process in hard materials. In this case the
alternatives for profiling sheet materials.
due to reduced pressure and so produces
water jet cutting vary in size much like
cutting action is executed by the abrasive
Laser cutting is suitable for a range of
a rougher finish. The process is slowed
sandpaper (120,80 and 50). Different
particles as opposed to the water. Both
materials, but produces a heat-affected
down to accommodate this in harder
This water Is continuously sieved, cleaned
zone (HAZ). Die cutting and punching
materials, which increases cycle time.
grit sizes affect the quality of the surface finish; finer grit (higher number) is
mineral particles (often garnet! are fed
are very accurate and work to tolerances
Into the mixing chamber and come Into
and recycled.
of less than 500 microns (0.02 in.).
and blanking are used to cut a wide
slower and produces a higher quality
contact with the supersonic water, which
surface finish.
propels them at very high speed towards
TYPICAL APPLICATIONS
the flow of water drags in deep materials
range of thin sheet materials. Glass
DESIGN OPPORTUNITIES
scoring is only suitable for thin materials.
This process cuts most sheet materials
a diameter smaller than the depth of material should be drilled. The sharp particles used in abrasive
The final accuracy of the part is
'orifice' (0.1 to 0.25mm In diameter). This
particles it Is the water alone that erodes
Is also sometimes called a jewel because
the workpiece.
It Is made of diamond, sapphire or ruby.
In abrasive jet water cutting the sharp
the workpiece. The abrasive particles
Applications for this process are diverse.
between 0.5 mm and 100 mm (0.02-
determined by a combination of many
create a beam 1 mm (0.04 in.) In diameter,
As with most new technology, the
3.94 in.) thick. The hardness of the
factors including material stability,
which produces the cutting action. The
aerospace and advanced automotive
material will determine the maximum
thickness and hardness, accuracy of
taper left by the cutting process can be
The high velocity jet Is dissipated by the bath of water below the workpiece.
Water jet cutting glass The water jet cutter is CNC, so every
operation is programmed into the machine from a CAD file (image i). The discs are being cut from 25mm (0.98 in.)
plate glass.The cutting nozzle progresses slowly around the workpiece to achieve a clean cutting action. As it progresses,
the operator inserts wedges to support the part as it is being cut (image 2). This image clearly shows the drag on the high-velocity jet of water as it erodes the material. The faster the cutting process, the greater the effect of drag and subsequent drop in quality. After cutting, the part is carefully removed. The cutting programme is
designed to overrun at the start and end of the process to ensure a perfectly symmetrical disc (image 3). The surface finish that is left by the abrasive water jet cutting action (image 4) is improved by polishing, which takes place on a diamond encrusted polishing wheel (image 5). Finally, a small chamber is ground onto the cut edge (image 6).
the cutting bed, consistency of water
but it is possible to cut wood and other
process does not cause these problems.
ENVIRONMENTAL IMPACTS
pressure and speed of cut.
natural materials.
Even printed and coated materials can
The kerf is quite narrow and so very little
be cut without any detrimental effects to
material Is wasted during operation.
the surface.
Offcuts In most materials can be recycled
Very thin materials may break before
Mild steel, stainless steel and tool
the cutting process has finished due to the weight of the part on the uncut
Titanium, aluminium, copper and brass
steel can all be cut with high accuracy.
or re-used. Computer software Improves
material. Tabs can be designed in to avoid
are suitable for complex profiles and
COSTS
efficiency by nesting parts together to
this, or wedges inserted to support the
can be cut rapidly with this process
There are no tooling costs.
produce minimal waste. Water jet does
part.Tabs mean secondary operations
compared to other cutting technologies.
because they will have to be removed afterwards.
Marble, ceramic, glass and stone can
be cut into intricate profiles even though they are quite brittle.
COMPATIBLE MATERIALS
Laminates and composite materials
There are very few materials that cannot
(including carbon reinforced plastic)
be cut in this way. The first water jet
can be cut very effectively. Laminated
cutting was developed to machine wood.
parts tend to delamlnate under stressful
Cycle time can be quite slow but
not produce a HAZ or distortion, so the
depends on the thickness of material and
parts can be nested relatively closely and
quality of cut.Thin sheets of material
as little as 2 mm (0.079 ,T1-) apart.
can be stacked up and cut In a single operation to reduce cycle time. Labour costs are moderate due to the skilled workforce that Is required.
There are no hazardous materials created In the process or dangerous vapours off-gassed. The water is usually tapped from themains andis cleaned and recycled for continuous use.
Featured Manufacturer Instrument Glasses www.instrument-glasses.co.uk
Very little wood is now cut in this way.
cutting conditions, and the water jet
TECHNICAL DESCRIPTION
Glass Scoring Process
Glass scoring can be carried out by hand or on a computer-guided x-y plotter. This diagram shows computer-guided scoring.
Attached to the rotating head is a
Cutting Technology
Rotating head
tungsten carbide cutting wheel. Low
Glass Scoring
pressure is applied to the cutting wheel as it runs across the surface of the glass. Glass workpiece
This is a precise method for cutting sheet glass materials. The
INTRODUCTION
cutting wheel is guided along x and y axes at high speed from a
Class scoring is the most widely used
Cutting wheel
just ahead of the cutting wheel. This crack is known as a median or vent crack and is
typically less than 1 mm (O.O^i in.) deep.
technique for shaping and sizing
CAD file to produce one-offs or high volumes of parts.
Stage 1: Score
sheet glass from 0.5 mm to 20 mm (0.02-0.8 in.) thick. It is used for both
Applying pressure to the glass forces the Median crack
manufacturers and craftsmen alike Suitability
1 No tooling costs 1 Low unit costs
• Furniture • Glass panes and tiles • Stained glass
• One-off to high volume production
Quality
Related Processes
Speed
• Good quality cut edge, but with some lateral cracking
• Laser cutting • Water jet cutting
• Rapid cycle time (roughly 100 m/328 ft per minute)
shallow crack to extend through its depth and the parts are broken out.
utilize this process for general sheet Typical Applications
Once the operation is complete, the glass sheet is removed from the cutting bed.
industrial and decorative applications:
Costs
This produces a flaw that forms as a crack
This method produces a good quality
cutting operations.
cut edge. The median crack caused by the
cutting wheel is a different texture to the
Carried out on a computer guided x-y
plotter, this is a high speed and precise
Stage 2: Breakout
break (see image, opposite).
cutting technique. Handheld scoring tools are also widely used, especially for simple, long and straight cuts.
TYPICAL APPLICATIONS
DESIGN OPPORTUNITIES
COMPATIBLE MATERIALS
Display screens,tabletops, lenses, filters,
The main advantage for designers is
All types of sheet glass can be cut such as
protective glass covers and glass signage
the speed and versatility of this process.
float glass, textured, coloured, mirrored
are just a few of the wide range of
Designs can be prototypedfreehand,
and dichroic glass.
products made in this way.
with a compass, or around a profile. In
This is the main technique for cutting out stained glass designs.
production, the design is cut from sheet
COSTS
by a computer guided cutting wheel.
There are no tooling costs.
Small shapes are possible in thin
RELATED PROCESSES
materials. For example, disks down to
Waterjet cutting (page 272) andlaser cutting (page 248) are also used to profile
5 mm (0.2 in.) in diameter are feasible.
sheet glass materials. They are both
DESIGN CONSIDERATIONS
slo,werthan scoring for simple external
This process is limited by what can
Cycle time is rapid, and cutting speeds
Of loo m (328 ft) per minute are typical. Labour costs are low for automated operations and high for manual processes such as stained glass.
profiles, but are capable of cutting
be broken out of the glass sheet. It is
ENVIRONMENTAL IMPACTS
through a wide variety of materials and
possible to cut simple straight or curved
No glass is wasted in this operation: all
thicknesses. Class scoring is suitable for
lines of any length, but internal shapes
offcuts can be recycled.This is a verylow
materials up to 20 mm (0.8 in.) thick. By
cannot be made, only external profiles.
impact process, which requires very little
contrast, waterjet cutting is capable of
Each score must run from edge to
energy in operation. Unlike waterjet cutting, this process
cutting sheet glass up to 70 mm (2.75 in.)
edge, or as a continuous shape.Therefore
thick. Laser cutting produces a very high
it is ideal for cutting out disks, rectangles
does not remove a kerf width from
surface finish on the cut edge with less
and simple irregular shapes. But designs
the material.Therefore, parts can be
defects than other cutting methods.
with indents in the profile, such as a
n ested closer together, further reducing
crescent shape, cannot be easily made.
material consumption.
QUALITY
Also, acute angles and complex shapes
The scoring technique produces a clean
are not practical because it may not be
break. However, if the cut edge is exposed
possible to break them out of the sheet in
in application, it should be polished.
a single piece.
I
I U»W^'V*»v\ÿv'»xv"1 v"• V1'V'SVV'
Case Study
Glass scoring dichroic lenses The discs are cut out on a computer guided
shallow. Gentle pressure is applied, which
x-y plotter. A small amount of lubricant is
causes it to 'run'. Straight edges can be broken
sprayed onto the cutting wheel and glass
out by hand (image 3).
prior to cutting (image i). A small median crack forms under the
Circles and other shapes are broken out using 'running pliers' (image 4), These break
tungsten carbide cutting wheel (image 2).The
the glass outside of the desired shape, causing
amount of pressure is adjusted according to
it to fail along the median crack.The shallow
the thickness of material. For example, 20 mm
cracking caused by the wheel is visible in
(0.8 in.) thick glass needs a relatively high
contrast with the 'run'fracture (image 5).
level of pressure to form a median crack large
Scoring causes small amounts of lateral
enough to enable the shape to be broken out
cracking. To give a sense of scale, this sample
afterwards. At this point the crack is very
is only 3 mm (0.118 in.) thick.
Joining Technology
TECHNICAL DESCRIPTION
Manual Metal Arc Welding Process
MMA welding, also known as stick welding, has been in use since the late 1800s, but has seen major Consumable electrode
development in the last 60 years.
Joining Technology
Modern welding techniques use a
Arc Welding
Weld pool Evolved gas shield —
Arc welding encompasses a range of fusion welding processes. These processes can only be used to join metals because they rely on the formation of an electric arc between the workpiece and electrode to produce heat.
No tooling costs Low unit costs
Quality • High quality
Suitability
• Containers • Fabrications • Structures
• One-off to mass production
• Friction welding • Power beam welding • Resistance welding
Speed • Slow to rapid cycle time
Core wire
coated electrode. The coating (flux)
melts during welding to form the protective gas shield and slag. There are several different types of flux
Slag —
and electrode, which improve the
The most common types of arc welding
versatility and quality of the weld.
are manual metal arc (MMA), metal inert
MMA welding can only produce
gas (MIG) and tungsten inert gas (TIG), which are respectively called shielded
short lengths of weld before the electrode needs to be replaced. This
metal arc welding (SMAW), gas metal arc welding (GMAW) and gas tungsten arc
Typical Applications
Related Processes
INTRODUCTION
Weld metal
Flux covering
is time consuming and stresses the welded joint because the temperature
welding (GTAW) in the US. Arc welding
is uneven. The slag that builds up on
also includes submerged-arc welding
top of the weld bead has to be removed
(SAW) and plasma welding (PW). The joint interface and electrode (in
before another welding pass can take
some cases) melt to form a weld pool,
or large volume production, and the
which rapidly solidifies to form a bead of
quality of the weld is largely dependent
weld metal. A shielding gas and layer of
on the skill of the operator.
place. It is not suitable for automation
slag (in some cases) protects the molten weld pool from the atmosphere and encourages formation of a'sound'joint.
MMA, MIG andTIG welding can all be operated manually. PW and SAW are more suited to mechanized systems due
to the bulkiness and complexity of the equipment, but there is a microplasma variant that is suited to manual work.
MIG welding is also very well suited to automation because it uses continuousfeed consumable electrode and separate Above left
Above
An operator uses
An arc is formed
for certain automated applications such
MMA welding to join
as orbital welding of pipes.
steel plate.
between the coated electrode and
shielding gas.TIG welding is only suitable
workpiece.
Left Joining steel pipes with MMA welding.
TYPICAL APPLICATIONS Arc welding is an essential part of the fabrication process, used extensively in the metalworking industries.The various processes are suited to different uses, determined by volumes, material type and thickness, speed and location.
Top A steel joint that has been MMA welded.
Above Coated electrodes are used in MMA welding.
MMA welding is the most portable of the processes, requiring relatively little equipment; it is used a great deal in
«
the construction industry andfor other site applications such as repair work.
Featured Manufacturer
TWI www.twi.co.uk
TECHNICAL DESCRIPTION
Metal Inert Gas Welding Process
a process. Deposition rate is measured
MIG welding is also referred to as semi-
as kg/hour (Ib/hr), and duty cycle as a
automated welding. The principle is the
percentage. MMA has a deposition rate
same as MMA welding; the weld is made
of approximately 2 kg/hr (4.4 Ib/hr) and duty cycle of 15-30%;TIG has a deposition
by forming an arc between the electrode
and the workpiece and is protected by
Gas nozzle
rate of approximately 0.5 kg/hr (1.1 Ib/hr)
a plume of inert gas. The difference
is that MIG welding uses an electrode
Weld pool
continuously fed from a spool and the
and duty cycle of 15-20%; MIG has a
Contact tube
deposition rate of approximately 4 kg/hr (8.8 Ib/hr) and a duty cycle of 20-40%; and SAW has a deposition rate of
Gas shield
shielding gas is supplied separately.
Weld metal
Therefore, MIG welding distinguishes
Consumable electrode
itself from MMA welding through higher
approximately 12.5 kg/hr (27.5 Ib/hr) and
productivity rates, greater flexibility and
duty cycle of 50-90%. Certain metals, such as titanium, can
suitability for automation.
only be welded to like metals. In contrast,
The gas shield performs a number of
functions, including aiding the formation
carbon steel can be welded to stainless
of the arc plasma, stabilizing the arc
steel or nickel alloys, and aluminium
on the workpiece and encouraging the
alloys to magnesium alloys.
transfer of molten electrode to the weld
MIG welding Is limited to materials
pool. Generally the gas is a mixture of
provides an alternative to conventional
welded joints. MIG welding produces a
between 1 mm and 5 mm (0.039-0.2 in.)
argon, oxygen and carbon dioxide. MIG
TIG welding; the equipment is bulkier
neat and continuous weld bead, as can
thick. PW can accommodate the largest
but the weld is more penetrating.
be seen on aluminium alloy metal ship
range of materials, from 0.1 mm upto
Keyhole welding has the advantage of
decks. Steel ship decks are SAW.
10 mm (0.0039-0.39 in.) thick.
speeds.This means it is suitablefor sheet
DESIGN OPPORTUNITIES
processes, arc welding produces a HAZ.
material up to 10mm (0.39 in).
As well as being suitable for batch and
All welding produces residual stress in
is also known as metal active gas (MAG) in the UK when CO2 or O2 are present in the shielding gas. Non-ferrous metals
deep penetration and high welding
require an inert argon-helium mixture.
Due to the nature of SAW it is only suitable for horizontal welding positions.
RELATED PROCESSES
Modified MMA technology can be used
Top
Featured Manufacturer
TWI www.twi.co.uk
Above
An operator uses MIG
Cross-section of a MIG
welding to seal the end of a steel pipe.
welded overlapping joint profile.
Above left Example of a MIC welded tee joint profile.
Opposite MIG consumable
mass production of actual parts, these
HAZ weld area and beyond.The problems
processes make it possible to realize
are caused by a change in structure
complex metal assemblies without
leading to change in properties and
expensive tooling costs. Combined with
susceptibility to cracking.
More recent fusion welding technologies,
profiling operations such as gas,plasma,
including laser and electron beam
or laser cutting (page 248), welding can
workpiece to be connected to an earth
welding (page 288), are providing an
be used to fabricate accurate prototypes.
return to the power source, so that the
alternative to the conventional processes,
MMA is especially useful for quickly
electrical current passes through the
especl ally for thi cker m aterial s th at
fabricating steel structures, whereas TIG
electrode and creates an arc with the
require deep penetration.
welding can be used to produce Intricate
weld pool. If the metalwork is painted or
Other welding processes, such as
and delicate metal fabrications.
All of these processes require the
coated in any way, this will insulate the
for wet underwater welding of pipes and
friction welding (page 294), resistance
other offshore structures.
welding (page 308) and gas welding,
welding can be used in horizontal,
or impossible. Also, assemblies and
are alternatives for certain applications.
vertical and inverted positions, making
fabrications may contain other elements
of all welding operations and is used in
Adhesive technologies are becoming
these versatile for manual operations.
th at coul d be dam ag ed by th e el ectri cal
many Industries, it is used extensively for
more sophisticated, providing Increased
car assembly because it is rapid and
joint strength with no heat-affected zone
DESIGN CONSIDERATIONS
metal contact close to the weld zone to
produces clean welds.
(HAZ), which is sometimes preferable.
MIG welding accounts for about half
•lOOnim-
As with all thermal metal fabrication
The quality and slower speeds of TIG
Theequ1pmentforMMA,MIG andTIG
metal contact and make welding difficult
current, so It is important to mount the Welding Is aline-of-slght process.
create a path of least resistance avoiding
Therefore, parts need to be designed so
the vulnerable parts of the assembly,
welding make it ideally suited to precise
QUALITY
that a welder or robot can get access to
and demanding applications. It may be
The quality of manual arc welding is
manual or fully automated.
largely dependent on operator skill.
the joint.The geometry of the joint will affect the speed of welding. Deposition
Precise and clean weld beads can be
rate and duty cycle (how much welding
steel,iron andnlckel alloys.There are also
formed with MMA, MIG and TIG welding.
is achieved in an average hour, allowing
for set up, cooling, jigging and so on) are
electrodes for welding copper alloys. MIG andTIG welding, PW and SAW can be
used as a measure of the efficiency of
used on ferrous and non-ferrous metals.
There are 3 main types of PW, which
electrode, which also
have different applications. Microplasma
acts as a filler wire during welding.
welding Is suited to thin sheet and mesh materials. Medium current welding
Automated welding operations produce the cleanest and most precise
COMPATIBLE MATERIALS MMA welding is generally limited to
TECHNICAL DESCRIPTION
Tungsten Inert Gas Welding Process
Plasma Welding Process
Plasma welding is very similar to TIG welding. This means that the process
is versatile and capable of welding everything from meshes and thin sheets to thick materials in a single pass. Plasma nozzle
There are 3 main categories of Optional filler material Weld metal
plasma welding, which are microplasma,
Gas nozzle
medium current and keyhole plasma.
Microplasma is operated with relatively
Plasma gas Weld pool ,
Tungsten electrode
low electrical current, so is suitable for Gas shield
Weld metal .
materials as thin as 0.1 mm (0.0039 in.)
Arc
mi
and meshes. Medium current techniques
Tungsten electrode
Shielding gas
are a direct alternative to TIG welding but with deeper penetration. Keyhole
v
welding can be achieved with plasma because of its powerful, small diameter.
The temperature of the plasma is estimated to be between 3000°C and
TECHNICAL DESCRIPTION
6000°C (5432-10832°F). This is capable of penetrating material up to 6mm
TIG welding Is a precise and high quality
amounts of hydrogen can be added to
welding process. It is ideal for thin sheet
produce a cleaner weld that has less
materials and precise and intricate work.
surface oxidization. Hydrogen makes the
The main distinction is that TIG welding
arc burn hotter and so facilitates high
does not use a consumable electrode;
welding speeds, however, it can also
instead, it has a pointed tungsten
increase weld porosity. Helium is more
electrode. The weld pool is protected by
expensive, but helps the arc burn hotter
a shielding gas and filler material can be
and so facilitates higher production rates.
used to increase deposition rates and for thicker materials.
(0.236 in.) in a single pass.
Top Detail ofTIG welded butt joint profile.
Above Automated TIG welding
Submerged Arc Welding Process TECHNICAL DESCRIPTION
in operation.
SAW, like MIG welding, forms the
The shielding gas is usually helium, argon or a mixture of both. Argon is the
Middle
Below
An arc is formed
Joining metal pipe by TIG welding.
between the tungsten
most common and is used for TIG welding
weld by creating an arc between the continuously fed electrode and Flux recycling
workpiece. However, there is no
electrode and workpiece,
steels, aluminium and titanium. Small
need for a shielding gas because the
and the filler material melts into the weld pool
electrode is submerged in a layer of
flux fed to the joint from a hopper. There are many associated benefits
TIG is widely used on carbon steel,
Labour costs are high for manual
of submerging the arc, including the
stainless steel and aluminium, and it is
operations, due to the level of skill
the main process for joining titanium.
Tequired. Some automated versions can
MIG welding is commonly used to join
run almost completely unattended and
steels, aluminium and magnesium.
so labour costs are dramatically reduced.
the joint, the flux is laid down in front
on very thin sheets, meshes and gauzes.
ENVIRONMENTAL IMPACTS
The weld pool is not visible and it is a
COSTS
A constant flow of electricity generates a great deal of heat during the welding
There are no tooling costs unless special
process, and there is very little heat
jigs or clamps are required.
insulation, so it is relatively inefficient.
absence of a visible arc light, spatterLayer of flux
As the welding torch passes along
Certain PW technologies can be used
Cycle time is slow for MMA welding, especially because the electrode needs
to be replaced frequently. MIG welding is rapid, especially if automated, andTIG
and collected for recycling behind. complex operation, so it is generally
SAW insulates the arc in a layer of flux,
producing 5o% thermal efficiency, compared with 25% for MMA welding. This process produces very little waste
Featured Manufacturer
TWI www.twi.co.uk
welding falls somewhere in the middle.
free weld area and very little heat loss.
material; slag must be removed.
Right
mechanized. The flux will affect
In submerged arc
the depth of penetration and metal
welding asolidfluxis used, which limits the
deposition rate, so the workpiece must
process to horizontal
be horizontal to maintain the layer of
joints including lap,
flux. However, overlapping, butt and
butt and tee profiles.
tee joint profiles are all possible and frequently used.
Of the powerful welding processes, electron beam welding
are no processes that compete with them in this area.
is capable of joining steels up to 150 mm (5.91 in.) thick and
Arc welding (page 282), however, is an alternative to power beam welding
aluminium up to 450 mm (17.72 in.) thick, while laser beam
for thin sheet applications. For plastics,
welding is mainly used for materials thinner than 15 mm (0.6 in.).
ultrasonic welding (page 302) is an alternative to LBW. LBW can be combined with arc
Costs
Typical Applications
• No tooling costs • Very high equipment costs • High unit costs
• Aerospace • Automotive • Construction
Suitability
welding to increase opportunities for
• Specialist to mass production
production. For example, large structures
leaving absolutely no trace of the process
often have varying joint gaps that
on either surface.
Above
A dear plastic printer ink cartridge laser welded using
cannot be avoided. Because power beam Quality • High strength joint
Related Processes
Speed
• Arc welding • Ultrasonic welding
INTRODUCTION
technologies are not suitable unless
DESIGN OPPORTUNITIES
accurate joint configurations are lined
Power beam welding has many
• Rapid cycle time
metals and thermoplastics from 1 mm to
Clearweld®.
up precisely with the laser or electron
advantages such as increased production
beam, laser-arc hybrids developed for
rate, narrow HAZ and low distortion.
shipbuilding have been used instead.
Another major advantage for designers
TYPICAL APPLICATIONS
These can accommodate variations
is the ability to join dissimilar materials:
has potential applications in waterproof
in joint gap. The combination of high
for example, EBW can be used to fuse
clothing,for example.
Like arc welding, power beam welding
15 mm (0,04-0.59 in.).The many different
LBW is used on a wide range of industrial
joins materials by heating and melting the joint interface, which solidifies to
types of laser technologies include CO2,
applications,including aluminium
powered laser welding with versatile
a range of different metals. As well as
direct diode and Nd:YAG, as well as Yb
car frames (such as the Audi A2),
metal inert gas (MIG) welding increases
joining dissimilar metals, LBW can weld
which until recently has meant that
form a high integrity weld.The difference
disc and Yb fibre lasers. Besides welding,
construction, shipbuilding and airframe
the quality of joints and improves
a range of different thermoplastics to
the workpiece size is restricted by the
is that power beam processes do not
lasers are used to cut and engrave (see
structures. Since the 1970s, it has been
production rates.
one another. Factors that affect material
size of the vacuum chamber. However,
choice include relative melting point and
mobile EBM has been made possible by
reflectivity.
reduced pressure techniques developed
rely on the formation of an electric arc
laser cutting, page 248), and fuse layers
developed for plastics and utilized for
between the welding electrode and
of particles (see rapid prototyping,
joining thermoplastic films, injection
QUALITY
m ol ded parts, textil es an d tran sparent
Both LBW and EBW processes form
components in the automotive, packaging and medical industries.
workpiece to generate heat. Heat is produced by the concentration of energy in the power beam. Both laser and electron beam
page 232). Electron beams are generated in a high vacuum. Electrons are energized using a cathode heated to above 20000C
technologies are capable of establishing
(36320F) and up to two-thirds the speed
a'keyhole'in the workpiece to deliver
of light for normal industrial electron
heat deep into, or through, the joint.
beam guns.The high velocity electrons
Indeed, this ability means they can be
bombard the surface of the workpiece,
It is now possible to weld clear
EBW is carried out in a vacuum,
in the 1990s. It is now feasible to apply
rapid and uniform high integrity welds.
plastics and textiles using a technique
a local vacuum in a small EBW unit that
They have superior penetration and
known as Clearweld®.The Clearweld®
travels aroundthe joint.This has many
so produce a relatively smaller heat-
process was invented and patented
advantages, including on-site welding
th e 19 60s an d h as been used for m any
affected zone (HAZ) than arc welding. A
by TWI, and is being commercialized
of parts too large or unsuitable for the
years in Japan for welding heavy duty offshore and underground piping.The ability of this process to penetrate thick
major advantage of power beam welding
by Centex Corporation.This process is
vacuum chamber.
is its ability to make deep and narrow
particularly useful in applications that
welds. However, this means there is a
demand high surface finish (see image,
DESIGN CONSIDERATIONS
above). The principle is that an infrared
These processes require expensive equipment and are costly to run,
EBW has been in development since
used to cut, machine and drill materials
causing it to heat up and melt, or
materials makes it ideal for construction
huge temperature differential between
as well as weld them together.
vaporize in an instant.The focused
and nuclear applications.
the melt zone and parent material, which
absorbing medium is applied to the
electrons create power densities as high
can cause cracking and other problems
joint region, either printed or film. This
especially EBW which is carried out
focused to achieve power densities above
as 30,000 W/mm2 (1 mm2 = 0.039 in-2)
RELATED PROCESSES
in certain metals, especially high
causes the joint to heat up on exposure
in a vacuum. Both EBW and LBW
loo W/mm2 (i mm2 = 0.039 in.2). At this
in a localized spot. Thus electron beam
Although they are specialized processes,
carbon steels.
to the laser beam. Without the infrared
are automated, and need careful
absorbing medium the laser would
programming prior to any welding.The
high quality joints. In overlapping
pass right through clear materials and
cost and complexity of power beam
Lasers produce light waves that are
LBW in plastics produces extremely
power most engineering materials melt
welding (EBW) produces rapid, clean
LBW and EBW are gradually becoming
or vaporize, and laser beam welding
and precise welds in materials between
more widespread for joining parts in a
(LBW) is therefore suitable for welding
0.1 mm and450 mm (0.004-17.72 in.)
single pass, which would previously have
geometries the laser penetrates the top
textiles. Hermetic seals can be achieved
processes means that they are suitable
been almost impossible to achieve.There
part and affects only the joint interface,
in plastics and fabrics, so this technology
only for specialist applications and
a range of materials, in eluding most
thick, depending on the material.
m 1— o
TECHNICAL DESCRIPTION
Laser Beam Welding Process
In LBW, the COz, Nd;YAG and fibre laser
Laser beam delivered via mirrors or fibre optic cables
beams are guided to the workpiece by a series of fixed mirrors. Nd:YAG and fibre laser beams can also be guided to the
welding or cutting head by fibre optics, which has many advantages. These
laser technologies typically weld at 7 kW, which is suitable for fusion welding 8 mm (0.315 in.) carbon steel in a single pass at up to 1.5 m (5 ft) per minute. These processes can be used for many
different welding operations, including
Workpiece
profile, rotary and spot welding. Spot welding processes have been recorded at rates of up to 120,000 welds per hour.
A shielding gas is used to protect the melt zone from oxidization and contamination. Because of their shorter
Above
Above right A robot manipulates
wavelength, Nd:YAG laser beams can
to 100 mm (3,94in.) thick. Nor are these
COSTS
also be guided with fibre optics. This
processes limited to very thick materials;
There are no tooling costs, but jigs
means that they can cut along 5 axes, as
they are also used to join thin sheet and
and clamps are necessary because of
Right
the head is free to rotate in any direction.
film materials with extreme precision.
the precision required for the welding
The process of NchYAG laser beam welding
The laser beam is focused through a lens that concentrates the beam to a fine spot, between 0.1 mm and 1 mm (0.004-0.04 in.) wide. The height of
the lens is adjusted to focus the laser
process to be successful. Equipment
COMPATIBLE MATERIALS
costs are extremely high, especially for
Many different ferrous and non-
processes that involve EBW.
ferrous metals can bejoined by power
Cycle time is rapid, but set-up will
An operator checks the CO2 LBW equipment.
the Nd:YAG lasers.
commences.
Far right This detail shows the Nd:YAC laser beam welding head while it
beam welding. The most commonly
increase cycle time, especially for large
welded metals include steels, copper,
and complex parts. For EBW each part
melting the workpiece on contact, which
aluminium, magnesium and titanium.
has to be loaded into a vacuum chamber
Below
resolidifies to form a homogenous bond.
EBW, however, is limited to metallic
and a considerable vacuum applied,
Detail of the finished
materials because the workpiece must
which can take up to 30 minutes. Mobile
NdrYAG laser weld.
on the surface of the workpiece. The
high concentration beam is capable of
be electrically conductive.
Aluminium is highly reflective but can be welded with both lasers and electron beams. Certain alloys are more suitable
massproduction.Thep ayoff i s th at th ey
than others for power beam welding,
are very rapid: EBW can produce high
such as 5000 and 6000 series'.
integrity welds at up to io m/minute
Titanium can be power beam welded,
reduced pressure techniques have lowered set-up time and increased cycle time considerably. Labour costs are high.
ENVIRONMENTAL IMPACTS Power beam welding efficiently
(33 ft/minute) in thick sections. For an effective butt weld the joints have to fit tight tolerances and align
but it is highly reactive to oxygen and
transmits heat to the workpiece, EBM
nitrogen.This means that it is more
typically requires a vacuum, which
difficult and therefore more costly to
is energy intensive to create. Recent
with the beam very accurately. As a
weld.Tungsten inert gas (TIG) welding
developments have made it possible to
result, preparation can also be costly and
is used as an alternative but is up to 10
weld steels up to 40 mm (1.57 in.) thick.
time-consuming, especially for large and
times slower than laser welding.
cumbersome parts. Material thickness is much greater for power beam welding than with arc welding. High power EBW can be used to join steel from 1 mm up to 150 mm (0.04-5.91 in.) thick, aluminium up to 450 mm (17.72 in.) thick and copper up
LBW can be used to join most thermoplastics, including
polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polyoxymethylene (POM) acetal and poly methyl methacrylate (PMMA).
However, weld quality and width to depth ratio are diminished.
is in operation.
l
TECHNICAL DESCRIPTION
Electron Beam Welding Process
Electrons are emitted from a heated tungsten cathode. They are pulled and accelerated into the gun column High voltage cathode
at up to two-thirds the speed of light.
Magnetic focusing coils concentrate the
w
beam into a fine stream, which impacts , Electron particles agitated between electrodes
on the surface of the workpiece. The
. Anode
electrons' velocity is transmitted into heat energy on contact, which
11
vaporizes a localized area that rapidly penetrates deep into the workpiece.
Magnetic focus coil
EBW is carried out in a vacuum of lO'MO"2 mbar 10.000000U5-0.000U5 psi). The level of vacuum determines
the quality of the weld because the High velocity beam of electrons Vacuum
IB
atmosphere can dissipate the electron
o
beam, causing it to lose velocity.
aJ CD
Reduced pressure EBW is carried out
at 1-10 mbar 10.0145-0.145 psil, which requires considerably less energy and Workpiece
O z o
time. As the fusion welding is carried Melt zone
out in a vacuum there is very little contamination of the melt zone, which
ensures high integrity welds.
Above
The scale of this electron beam welded gear is shown by the ruler beneath it. Below This cross-section of
NV? Left Apiece of electron beam welding
electron beam welded
joint demonstrates the integrity of a deep weld.
Above
Electron beam welding in progress.
equipment.
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Linear friction welding
Rotary friction welding
Friction Welding Processes
CLamps Workpiece
Stage 1: Load
Stage 1: Load
Interface plasticizes
Forge welding processes are used to form permanent joints in
Plasticized metal Reciprocating motion
metals. There are U main techniques: rotary friction welding
(RFW), linear friction welding (LFW), orbital friction welding (OFW) and friction stir welding (FSW). Stage 2: Friction through \ j Axial pressure rubbing
Stage 2: Friction through rotation
Typical Applications
Suitability
• Aerospace • Automotive and transportation • Shipbuilding
• High volume production
Quality
Related Processes
Speed
• High integrity hermetic seal • High strength joint that can have similar characteristics to base material
• Arc welding • Power beam welding • Resistance welding
• Rapid cycle time that depends on size of joint
RFW. LFW and OFW: No tooling costs FSW: Inexpensive tooling costs Low to moderate unit costs
INTRODUCTION
In the automotive industry, RFW is
The 4 main friction welding techniques
usedfor critical parts including drive
can be separated into 2 groups:
shafts, axles and gears. LFW is utilized to
conventional techniques including LFW,
join engine parts, brake discs and wheel
OFW and RFW processes; and a recent
rims. OFW has not yet found commercial
Weld flash
Weld flash
Stage 3; Axial pressure
Stage 3: Axial pressure
Axial pressure
Olufsen aluminium speakers (see
TECHNICAL DESCRIPTION
images, page 297, above left and left).
The use of RFW Is limited to parts where at least 1 part Is symmetrical around
RELATED PROCESSES Even though the welds are of similar
Another technique uses stored energy and is known as inertia friction welding.
an axis of rotation. In stage 1, the 2
In this process the spinning workpiece
workpleces are secured onto the chucks.
is attached to a flywheel. Once up to
In stage 2,1 of the parts is spun while
speed, the flywheel is left to spin freely.
the other is stationary. They are forced
The parts are brought together and the
derivative, FSW.
application in metals, but is utilized
quality, friction welding is not as widely
LFW, OFW and RFW operations weld materials with frictional heat generated
in the plastics industry (see vibration
used as arc welding (page 282) and
welding, page 298). FSW is used to join
resistance welding (page 308).This
together, and friction between the 2
stored energy in the flywheel spins the
flat panels, formed sheets, alloy wheels,
is mainly because it is a more recent
faces causes the metal to heat up and
parts sufficiently for a weld to form. The
fuel tanks and space frames.
development: for example,TWI patented
plastlclze. In stage 3, after a specified
process Is similar to RFW, except that a
The first commercial application of
friction stir welding only in 1991. It is also
time - a minute or so - the spinning
mandrel Is used to maintain the Internal
The rotary technique (see main image)
FSW was in the shipbuilding industry,
because friction welding is a specialized
stops and the axial force Is Increased to
diameter of the pipe.
was the earliest and is the most common
for welding extruded aluminium
technique, and the equipment costs are
20 tonnes or so. Flash forms around the
of the friction welding techniques.
profiles into large structural panels.
extremely high.
circumference of the joint and can be
principles as RFW. However, instead of
polished off afterwards.
rotation, the parts are oscillated against
by rubbing the joint interface together. The joint plasticizes and axial pressure is applied, forcing the materials to coalesce.
In FSW the weld is formed by a
This has benefits for many industries:
Friction welding does not take the
LFW and OFW are based on the same
rotating non-consumable probe (tool),
for example, the railway one, in the
weld zone above melting point, so this
one another. In stage 1, the 2 workpleces
which progresses along the joint mixing
construction of prefabricated structural
process can join metals that are not
are clamped. In stage 2, the joint Interface
the material at the interface (see image,
components in train carriages (see
suitable for fusion welding by arc or
page 396, above left).
above right). FSW is suitable as it causes
power beam welding (page 288). Friction welding plastics is known as
TYPICAL APPLICATIONS
very little distortion in the welded parts,
vibration welding (page 298).
Application of these processes is
even across long joints in thin sections.
concentrated in the automotive,
Recently, FSW has been introduced
transportation, shipbuilding and
into the consumer electronics industry,
Friction welding produces high integrity
aerospace industries.
such as in the fabrication of Bang &
welds. Butt joints are fused across the
images, page 297, above, top right and
QUALITY
Above
Right
is heated by rubbing the parts together.
This titanium blistc (i-piece bladed disc) for ]et engines is made by linear friction welding.
These beech blocks have been joinedby linear
In stage 3, axial force Is Increased and
friction welding.
maintained until the joint has formed. LFW typically operates at frequencies up to 75 Hz and amplitudes of ±3 mm 10.118 in.). These processes were developed for parts that are not suitable for rotary techniques.
TECHNICAL DESCRIPTION
Friction Stir Welding Process
This process is similar to RFW, LFW
Rotating chuck
and OFW because the metals are
welded by mixing the joint interface. Likewise, there is no consumable wire, shielding gas or flux. However, FSW
differs from the other friction welding techniques because it uses a non-
Backing bar
Probe
consumable probe to mix the metals.
The probe is rotated in a chuck at high speed, pushed into the joint line and progresses along the joint interface, plasticizing material that comes into contact with it. The probe
softens the material, while the Shoulder Plasticized metal
shoulder and backing bar prevent the plasticized metal from spreading. As the probe progresses, the mixed material cools and solidifies, to
Left above and left Bang & Olufsen BeoLab
Above, top right and
aluminium speakers
Lightweight and
consumable, they can run for only up to
were designed by David Lewis and launched
structural aluminium
1000 m (39.4 in.) before they need to be
during 2002.
stir welding, are needed
produce a high integrity weld. Even though FSW tools are non-
above right
panels, made by friction in the production of
replaced. Some techniques run more
train carriages.
than 1 tool in parallel, for a broader
on the equipment and development for the application.
Cycle time is rapid for RFW, LFW and OFW. FSW is the slowest of the friction welding processes because it runs along
the entire length of the joint. Using
weld or for a weld from either side to
FSW, 5 mm (0,2 in.) aluminium can be
form a deeper joint.
welded at approximately 12 mm (0.472
L
DESIGN CONSIDERATIONS
COMPATIBLE MATERIALS
in.) per second.Thick materials will take
Because they are comparatively new, the
Most ferrous and non-ferrous metals
con siderably 1 on g er.
equipment costs for friction welding are
can be joined in this way, including low
still very high.Therefore it is expensive to
carbon steel, stainless steel, aluminium
ENVIRONMENTAL IMPACTS
develop products with these processes
alloys, copper, lead, titanium, magnesium
Friction welding is an energy efficient
in mind unless there are high volumes
and zinc. It is even possible to weld metal
process for joining metals; there are
of production to justify the investment.
matrix composites.
no materials addedto the joint during
This is partly why friction welding is Above left This aluminium butt joint profile is being
Pipes can be joined in a process known
as radial friction welding, which is a
shielding gas.This process generates no
The tool (probe) and
shipbuilding industries and only to a
development on RFW.The difference is
waste; the exception is run-offs in FSW,
buttjoint have been formed in aluminium by friction stir welding.
limited extent elsewhere.
that in radial friction welding an internal
wh ere th e wel d run s from edg e to edg e.
Above right
integrity. Useful material combinations
state welding processes. In other words,
include aluminium and coppe'r, and
theyweldmetalsbelowtheirmelting
aluminium and stainless steel.
point.The heat-affected zone (HAZ) is
from 1.2 mm up to 50 mm {0,047-1.97 in.)
relatively small and there is very little
It is also possible to join materials of dissimilar thickness. Multiple layers
in non-ferrous metals. It is possible to
made it possible to join certain woods,
shrinkage, and thus distortion, even in
stacked up can be welded in a single pass
weld joints up to 150 mm (5.91 in.) deep if
including oak and beech (see image, page
long welds.
with FSW.
welded from both sided simultaneously.
295, right). Although TWI assessed the
Recently, microfriction welding
process in 2005, it is still in the very early
made using friction stir welding.
Use of RFW, LFW and OFW is limited
FSW is suitable for materials ranging
mandrel is used to support the weld area. Recent developments in LFW have
DESIGN OPPORTUNITIES
to parts that can be moved relative to
producing butt, lap, tee and corner joints.
techniques have been developed that are
stages of development. In the future
As the friction welding techniques are
one another along the same joint plane.
It is particularly useful in the fabrication
capable of welding materials down to
this process has the potential to replace
relatively new processes, especially FSW,
FSW, on the other hand, can be computer-
of parts that cannot be cast or extruded
0.3 mm (0.012 in.).
conventional wood joining techniques.
many commercial opportunities have yet
guided around circumferences, complex
such as large structural panels made up
to be fully understood.
3D joint profiles and at any angle of
of several extrusions.
Joint size in RFW, LFW and OFW techniques is limited to less than
COSTS
advantages such as the ability to join
can fuse almost any joint configuration
gravity, and so can be carried out upside
FSW requires tooling, the cost of which depends on the thickness and type of
dissimilar materials without loss of weld
and part geometry. FSW is also capable of
down if necessary.
material; even so, it is inexpensive,The
operation. Combined, these processes
welding such as flux, filler wire or
used extensively in the automotive and
entire joint interface. These are solid
Friction welding offers important
cost of this process is largely dependent
These processes are not affected by
2,000 mm2 (3.1 in.2).
Featured Manufacturer
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Vibration Welding Process
Joining Technology
Vibration Welding Homogenous bonds in plastic parts can be created using
INTRODUCTION
RELATED PROCESSES
vibration welding. Rapid linear or orbital displacement
Vibration welding is based on friction
Linear friction welding metal and linear
welding (page 294) principles.The
vibration welding plastic are the same
generates heat at the interface, and this melts the joint material and forms the weld.
Low to moderate tooling costs Low unit costs
Quality
parts are rubbed together to generate
process; both join parts by rubbing them
frictional heat, which plasticizes the
together using linear motion, under axial
joint interface. The process is carried out
force. Ultrasonic welding (page 302) and
as linear or orbital vibration welding.
certain adhesive technologies are
Linear vibration welding uses transverse,
frequently an alternative, especially for thin walled and delicate parts.
Typical Applications
Suitability
reciprocating motion - the vibration
• Automotive • Consumer electronics • Packaging
• Medium to high volume production
occurs in only 1 axis. Orbital vibration welding uses constant velocity motion
Related Processes
Speed
• Friction welding • Hot plate welding • Ultrasonic welding
• Very rapid cycle time (up to 30 seconds]
Ultrasonic welding transfers energy
through the part to thejoint interface.
- a non-rotating offset circular motion
By Contrast, the Vibration process
in all directions.The vibration motion
transfers energy directly to thejoint
occurs equally in both the x andy axes
interface, so does not rely on the ability
and all axes in between.
of the part material to transmit energy.
Stage 2: Closed mold, welding and clamping
Fillers, regrind, colour additives and
TYPICAL APPLICATIONS
contamination all affect a material's
Although this process is typically utilized
ability to transmit energy and so reduce
TECHNICAL DESCRIPTION
in the automotive industry, it is now
the effectiveness of ultrasonic welding
In stage 1 of linear vibration, 1 part Is
but not vibration welding.
placed in the lower platen and the part
speed, identical for all points on
to which it is to be joined is positioned
the joint surface. The movement's
in the upper platen. In stage 2, the heat
orbital character Is produced by three
necessary to melt the plastic is generated
electromagnets arranged horizontally at
steadily becoming more widespread in, for example, medical, consumer
Recent developments include heating
electronics and white good appliances.
the joint interface prior to welding, in a
process similar to hot plate welding
ssisr
(page 320). Combined, these processes
create neat and high strength welds with much less debris, especially important for such applications as filter housings.
QUALITY Vibration welding produces strong
The orbit Is continuous and of constant
by pressing the parts together and
relative angles of 120°. These magnets
vibrating them through a small relative
Influence the movement of the fixture
displacement from 0.7 mm to 1.8 mm
and generate a harmonic movement.
(0.028-0.071 in.) at 240 Hz or a 4 mm
Compensation for the decreasing force
(0.016 in.) peak to peak at 100 Hz in the
of one electromagnet is provided by
plane of the joint under a force of
attraction of the next electromagnet,
1-2N/mm2 (0.69-1.37 psi).
together with a change in direction. This
Heat generated by the resulting
causes rotary vibration of the fixture,
bonds. It is possible to form hermetic
friction melts the plastic at the interface
which ensures a controlled relative
seals for automotive and packaging
within 2-3 seconds. Vibration motion
movement in a frequency between
applications. When certain material
is then stopped and the parts are
190 Hz and 220 Hz and an amplitude
combinations are joined in this way a
automatically aligned. Pressure is
range between 0.25 mm and 1.5 mm
complete mixing of the materials occurs,
maintained until the plastic solidifies
(0.1-0.59 in.) peak to peak.
resulting in a homogenous bond.
to bond the parts permanently with a
Further variables to influence weldability include moisture content and the addition of resin modifiers.
strength approaching that of the parent material itself.
During orbital vibration welding, each point on the joint surface of the moving part orbits a different and distinct point on the joint surface of a stationary part.
Case Study
Linear vibration welding an automotive light In this case study Branson Ultrasonics
case the red reflectors) rises to meet the
parts are held under a measured clamping
are producing a short production run
upper platen (image 5), forcing the parts
force for another 2 to 15 seconds and the
of automotive sidelights. A pair of right-
together at a pressure of 103-207 N/cm2
melted polymer in the joint interface cools
and left-hand sidelights is being molded
(150-300 psi) (image 6). Either hydraulic or
to form a continuous weld. Finally the mold
simultaneously. The red reflectors (image i)
electromagnetic drivers are used to create
platens part to reveal the welded parts held
are placed into the lower platen (image 2),
the vibration in the upper platen. This is
by vacuum in the upper platen.The vacuum is
then the sidelight housings (image 3) are
mounted onto a resonant spring assembly to
released, dispensing the sidelights (image 7).
positioned into the upper platen, where they
ensure that the parts align accurately once
These are quality checked (image 8) and
are held by vacuum (image 4).
the vibration sequence concludes and the
packed for shipping.
During the welding cycle, the lower
polymers resolidify. The welding process lasts
platen holding the stationary part (in this
no more than 2-15 seconds, after which the
DESIGN OPPORTUNITIES
DESIGN CONSIDERATIONS
for products with thin wall sections or
COMPATIBLE MATERIALS
Both linear and orbital vibration welding
Vibration welding is most suitable for
long unsupported walls because they
Thermoplastics (Including amorphous
(ABS), poly methyl methacrylate (PMMA) acrylic and polycarbonate (PC), which can
and semi-crystalline) are suitable for
be welded to one another.
will flex unless supported by the tooling.
when fully automated or Integrated Into a production line.
provide a fast, controlled and repeatable
injection molded and extruded parts.
m eth od of ach 1 evln g a perm an ent stron g
However, 2 essential requirements must
bond between 2 plastic parts.They also
be taken Into account when considering
requires less clamping pressure than
composite m aterl al s, therm opl asti c
COSTS
There are no materials addedto the joint
eliminate the need for mechanical
the process. Firstly, the design must allow
linear methods and so can be used for
films andfabrics can also be welded
Tooling has to be designed and built
to form the weld, which means that this
fastenings and adheslves.
for the required movement between the
more delicate products. It is currently
in this way. Vibration welding Is particularly useful for materials that
specifically for each part, which Increases
process does not generate any waste.
the start-up costs of the process,
are not easllyjoined by ultrasonic welding or adhesive bonding such
especially if the product is made up of multiple parts that need to be joined In
These processes can accommodate
Orbital technology, on the other band,
ENVIRONMENTAL IMPACTS
this process, and some polymer based
parts to generate sufficient frictional
suitable for relatively small parts, up to
parts with complex geometry, whether
heat; the plane of vibration must be flat,
250 mm (9.84in.) in diameter.
large or small, and can be used to create
or at least within 10°. Secondly, the parts
perimeter and internal welds. As long
must be designed so that they can be
applications where the workpiece cannot
as polyoxymethylene (POM) acetal,
this way.
as the parts can be moved relative to
gripped adequately to ensure sufficient
be vibrated, for Instance, as products
each other along the same joint plane,
energy transmission to the joint.
polyethylene (PE),polyam1de (PA) nylon, and polypropylene (PP). Plastic welding is limited to joining like materials. There
between 2 and 15 seconds and clamping
time Is the same. Welding multiple parts
to weld parts up to 500 x 1,500 mm
are a couple of exceptions to the rule
simultaneously can reduce cycle time.
(20 x 59 In.), but It Is not recommended
such as acrylonltrlle butadiene styrene
Labour costs are relatively low, especially
vibration welding can be used.
Linear vibration welding can be used
Vibration welding Is not suitable for
with moving parts in the top section.
Cycle time Is rapid: welding Is typically Featured Manufacturer Branson Ultrasonics www.branson-plasticsjoin.com
Joining Technology
Ultrasonic Welding This process forms permanent joints using ultrasonic waves in the form of high-energy vibration. It is the least expensive and fastest plastic welding process and so is the first to be considered in many welding applications.
Typical Applications 1 Low tooling costs 1 Low unit costs
• Consumer electronics and appliances • Medical • Packaging
INTRODUCTION
TYPICAL APPLICATIONS
Ultrasonic technology includes welding,
Ultrasonic welding in used for a vast
swaging, staking (page 316),inserting,
range of products in many different
spot welding, cutting, and textile and
industries.The packaging industry
film sealing. Welding is the most widely
uses ultrasonics for joining and sealing
used ultrasonic process and is employed
cartons of juice and milk, ice cream tubs,
by a ran g e of in dustri e s, in cl udin g
toothpaste tubes, blister packs, caps and
consumer electronics and appliances,
enclosures.
Suitability
automotive, medical, packaging,
• Batch and mass production
stationery andtoys. It is fast, repeatable and very
Applications in consumer electronics include mobile phone covers and screens, watch bodies, hairdryers, shavers and
controllable.The conversion of electrical
printer cartridges. Applications in the
Quality
Related Processes
Speed
energy into mechanical vibration is
textile and non-woven industries include
1 High quality permanent bond 1 Hermetic seals are possible
• Hot plate welding • Power beam welding • Vibration welding
• Rapid cycle time (less than 1 second) • Automated and continuous processes can form many welds very rapidly
an efficient use of energy. No fillers
nappies, seat belts, filters and curtains.
are required, and there is no waste or contamination. It is safe to use for
RELATED PROCESSES
toys, medical applications and food
Ultrasonic welding is often the first
preparation. Ultrasonic cutting is used
joining process to be considered. If it
to cut cakes, sandwiches and other
is not suitable then hot plate welding
foods without squashing them: the
(page 320, vibration welding (page 298),
high-energy vibrations effortlessly cut through both hard and soft foods. It is
Top and opposite
Above
freedom. For example, products like
TheTSM6 mobile phone by Product Partners
Triangular beads,
mobile phones and MP3 players are
uses ultrasonic welding
directors, are molded
laser welding (see power beam welding,
made up of material combinations that
on the front assembly.
onto each side of
page 288) may be used.
may not be possible with multi-shot injection molding (page 50), or other
also used to seal drinks cartons, sausage skins and other food packaging.
This diversity gives greater design
Above left Ultrasonic welding
known as energy
the joint interface, perpendicularto one another, to maximize
produces hermetic seals
the efficiency of the
in extruded plastic tube,
welding process.
QUALITY
processes. Parts that cannot be molded in
Ultrasonic welding produces
a single operation can be ultrasonically
for instance, those for
homogenous bonds between plastic
joined to produce complex, intricate and
cosmetic packaging.
parts. Joint strength is high andhermetic
otherwise impossible geometries.
The energy director is raised bead
seals are possible.
DESIGN CONSIDERATIONS
of material on one side of the joint. It is
but this can be minimized with careful
The main considerations for designers
design such as housing the joint out of
are type of material (ease of welding) and
generally triangular and is molded inline with the joint or perpendicular to it (see
geometry of the part. There are 3 main
image, above).The role of the triangular
A small amount of flash is produced,
sight or with the provision of flash traps.
types of joint design: straightforward
bead is to minimize contact between
DESIGN OPPORTUNITIES
overlapping material, energy director
the 2 surfaces and therefore maximize
The advantage of ultrasonic technology
and shear joints (see images, page 304).
the energy transferred to the joint. This
is the range of welding processes
The difference is that energy director
reduces the amount of energy needed
and techniques that are available. For
and shear joint techniques have molded
to produce the weld, reduces flash and
example, as well as conventional joining
details to aidthe ultrasonic process.
minimizes cycle time.
ultrasonic welders can spot weld, stake,
Overlapping joints, such as extruded
embed metal components (known as
tube packaging sealed at one end, are the
works on the same principle of reducing
inserting), swage and form joints.
least strong, but are suitably effective for
surface area in the joint to maximize
the application (see image, above left).
efficiency.The difference is that instead
The alternative method, shear joint,
TECHNICAL DESCRIPTION
Ultrasonic Welding Process
Ultrasonic welding works on the principle
to the joint by the workpiece. This generates
into high-energy vibration by means of
frictional heat at the Interface, which causes
piezoelectric discs. Electricity is converted
the material to plastlcize. Pressure Is
from mains supply (50 Hz in Europe or
applied, which encourages material at the
60 Hz in North America) into 15 kHz, 20 kHz,
joint Interface to mix. When the vibrations
30 kHz or 40 kHz operating frequency. The
stop, the material solidifies to form a strong,
frequency Is determined by the application;
homogenous bond.
20 kHz Is the most commonly used frequency Inserting
Energy director
V
FO
fl fi
4
A
Spot welding
Shear joint
The ultrasonic vibrations are transferred
that electrical energy can be converted
The horn in the diagram is shaped to
because It has a wide range of application.
apply vibratory energy to selected areas of
The converter consists of a series of
the joint. Other joining techniques include
piezoelectric discs, which have resistance
energy director, inserting, shear joint and
to 15, 20, 30 or 40 kHz frequencies. The
spot welding. In each case, the red area
crystals that make up the discs expand
Indicates the weld zone. This is barely visible
and contract when electrically charged. In
from the surface, but clear In a microscopic
doing so, they convert electrical energy Into
view (see Image, belowl.
mechanical energy with 95% efficiency.
33
> in o
The mechanical energy Is transferred to the booster, which modifies the amplitude Into vibrations suitable for welding. The horn transfers the vibrations to the workpiece.
o o
2
The size and length of the horn are limited because it has to resonate correctly.
of a triangular bead, the joints are
field welded, meaning the joint is within
Textile and non-woven materials,
Labour costs are generally low. Tooling
5 mm (0.2 in.) of the contact point.
including thermoplastic fabrics,
changeover Is quick and the process is
composite materials, coated paper and
highly repeatable without the need for
to a thin line of contact. As the parts
COMPATIBLE MATERIALS
mixed fabrics, can be joined.
operator intervention.
are pressed together, the shoulder
All thermoplastics can be joined in this
progresses down the joint until the
way. Many amorphous thermoplastics
designed with a shoulder or step.This detail concentrates the vibratory energy
entire interface is welded.
such as acrylonitrile butadiene styrene
Some metals can be joined in this way. However, the technology is more
ENVIRONMENTAL IMPACTS
specialized and less widespread. It is
Ultrasonic welding is an efficient use
(ABS), poly methyl methacrylate (PMMA),
also known as 'cold welding'because
of energy; almost all of the electrical
because the horn has to resonate at the
polycarbonate (PC) and polystyrene (PS)
energy is converted into vibrations at
correct frequency and withstand high-
can be joined to themselves and in some
the parts are joined below their melting point. It is similar in principle to diffusion
the joint interface, so there is very little
vibration energy. Horns are typically no
cases to one another. Semi-crystalline
bonding, which is aform of brazing (page
heat radiation. It is rapid and there are no
larger than 300 mm (11.81 in.). Longer
312). However, no flux or other surface
other materials added to the joint. There
welds can be made in more than a
thermoplastics such as polyamide (PA), cellulose acetate (CA),polyoxymethylene
preparation is required as long as the
is no risk of contamination, which makes
single step, with multiple heads or as a
(POM),polyethylene terephthalate (PET),
joint fits properly.
this process suitable for food packaging,
continuous process.
polyethylene (PE) and polypropylene (PP)
Horn (tool) size and shape is limited
Joints must be designed with consideration for transmitting sufficient
can only be joined to themselves. There are many factors that affect the
toys and medical products.
COSTS
Welding reduces mixing materials,
Horns have to be made from high-grade
weight and cost by eliminating the need for mechanical fasteners or adhesives.
requires a new horn
Above Ultrasonic welding is a precise and neat Joining
Cycle time is very rapid. Welding time is typically less than 1 second. Loading
which means parts cannot be easily
to be mactiinedfrom
process,ascan be seen
disassembled for recycling. However, if
high-grade aerospace
in this microscopic
and unloading will increase cycle time
only like materials are joined, this is not
aluminium ortitanium.
image of a shear joint.
a problem.
energy to the interface.The tool has
ability of a material to weld to itself or
aerospace aluminium or titanium. Even
to be within a certain distance of the
another plastic. For example, a material
so, tooling costs are generally low.
joint. Generally, amorphous materials
has to be sufficiently stiff to transfer
dampen the vibrations less and so can
vibratory energy to the joint interface.
be far field welded, meaning the joint is
Amorphous materials are more
more than 5 mm (0.2 in.) from the horn
suited to energy directing joint designs,
slightly. Automated and continuous
contact point. However, semi-crystalline
whereas semi-crystalline materials are
operations are very rapid and can
and low stiffness parts have to be near
best welded with shear joints.
produce several welds per second.
This Is a permanent joining method,
Top Each application
Case Study
Ultrasonic welding a shear joint This case study illustrates the equipment
or 40 kHz. This application requires 30 kHz.
used in ultrasonic joining and a simple shear
The converter, booster and horn are screwed
part and the welding process is completed
joint in a small impellor.
together and inserted in a vertical pillar
in less than a second (image 6).The finished
assembly (images 2 and 3).
part is removed from the anvil with a
This product is suitable for ultrasonic joining because a shear joint is used, housed in the lower part. This provides a clean finish
The parts that are going to be joined
permanent hermetic joint (image 7).
(image 4) make up a small impellor. There
with very little flash. It is a 3-dimensional
is a small step on the blades of the impellor,
shape, but tooling is made for every
which provide the interference for the shear
application, so this does not increase costs.
joint. The lower part is placed in the anvil,
Boosters are anodized aluminium and
The horn is brought into contact with the
which provides support (image 5). The upper
coloured to indicate the frequency at which
part, which is over-molded onto a metal bar,
they operate (image 1), which is 15,20,30
locates on top and is self-aligning.
Branson Ultrasonics www.branson-plasticsjoin.com
TECHNICAL DESCRIPTION
Projection Welding Process
In projection welding, the weld zone is localized. This can be done in 2 ways; either projections are embossed onto 1 side of the joint, or a metal insert is used.
Electrode (+] j
This process is capable of producing
Joining Technology
Resistance Welding
multiple welds simultaneously because
unlike spot welding the voltage is directed by the projection or insert. The electrodes
These are rapid techniques used to form welds between 2 sheets
do not determine the size and shape of the
INTRODUCTION
weld. Therefore, they can have large surface
All of the resistance welding techniques
of metal. Spot and projection welding are used for assembly operations, and seam welding is used to produce a series of
are based on the same principle: a high
area that will not wear as rapidly as spot Electrode (-)
welding electrodes.
voltage current is passed through 2 Stage 1: Load
sheets of metal, causing them to melt
overlapping weld nuggets to form a hermetic seal.
Stage 2; Clamp and weld
Stage 3: Unload
and fuse together. As the name suggests, these processes rely on metal's resistance to conducting
Costs • Low tooling costs, if any • Low unit costs
Typical Applications • Automotive • Furniture and appliances • Prototypes
^ Quality Related Processes
Suitability
electricity. High voltage, concentrated
• One-off to mass production
between 2 electrodes, causes the metal to heat and plasticize. Pressure applied during operation causes the melt zone to
Speed
coalesce and subsequently form a weld. The 3 main resistance welding
h • High shear strength, low peel strength 'Arc welding I • Hermetic joints possible with seam • Friction welding I welding • Riveting
• Rapid cycle time
processes are projection, spot and seam.
These are used in many sheet metal
Above Left The ring is placed onto a
industries, but most importantly in
lower electrode, which
automotive construction,They have
locates it to ensure
repeatable joints.
been fundamental in the development
It is clamped into the upper electrode.
Right Projection welding takes a second or so.
of mass produced cars: operating at high
Above
Both welds are formed
speeds they are suitable for both manual
The second part has protrusions that
simultaneously and are
and automated application. A single car
localize the voltage.
full strength almost immediately.
may have up to 4,000 spot welds holding its metalwork together.
Spot and projection welded products include car chassis and bodywork,
TYPICAL APPLICATIONS
appliance housing, electronic circuitry,
Applications are widespread, including
mesh and wire assembly.
the automotive, construction,furniture,
Seam welding is used on products
appliance and consumer electronic
such as radiators, gas and water tanks,
industries.These processes are used for
cans, drums and fuel tanks.
prototypes as well as mass production.
TECHNICAL DESCRIPTION
Spot Welding Process
TECHNICAL DESCRIPTION
Seam Welding Process
Spot welding is the most versatile of the
Seam welding is a continuous process in
resistance welding processes. The weld zone
which the welding occurs between rolling
is concentrated between 2 electrodes that Electrode (+) .
I f I
i
1
!
i
j
®
joints in sheet metal using this technique.
Electrode (+]
joint. Very high voltage plasticizes the metal
1}
I
electrodes. It is possible to form hermetic
c?=C>
are clamped onto the surface of the metal
An alternative technique is used to apply multiple spot welds in a line. This is done
and pressure is applied, forcing it to coalesce
1
and subsequently form a weld nugget.
by replacing the rolling electrodes with
i Because the weld is concentrated
wheels that have a single electrode on the
between the electrodes only 1 weld can
perimeter, which produces a spot weld when
be produced with each operation. Multiple
the upper and lower electrodes are aligned.
This technique is used for high volume
welds are produced in sequence.
Electrode I-) i BB BH Stage 1: Load
Stage 2: Clamp and weld
Stage 3; Unload
Electrode (¦
Equipment is generally not dedicated,
production of metal radiators, for example.
so this process is the least expensive and
the most suitable for prototyping and low volume sheet metal work.
QUALITY
vertical axis, so weld points must be
ENVIRONMENTAL IMPACTS
Weld quality is consistently high. Joints
accessible from above and below. Even so,
No consumables (such as flux,filler or
have high shear strength, but peel
it is possible to weld in confined spaces
shielding gas) are required for most
strength can be limited with small and
with offset or double bent electrodes,
resistance welding processes. Water
localized weld nuggets,
is sometimes used to cool the copper
COMPATIBLE MATERIALS
electrodes, but this is usually recycled
DESIGN OPPORTUNITIES
Most metals can bejoined by resistance
continuously without waste.
These are simple and versatile processes.
welding, including carbon steels,
Above
Spot welding is widely available for
stainless steels, nickels, aluminium,
steel mesh with a hand
Heavy duty handheld welding guns like this
process itself, and spot welding does not
prototyping sheet metal work; it is
titanium and copper alloys,
require any preparatory or secondary
held welder and larger,
are used for general
relatively inexpensive and can be used on
static lower electrode.
sheet metal assembly
a range of materials,
Lett Spot welding stainless
work. Sophisticated
Dissimilarmetals can bejoined
operations that create waste.
COSTS Tooling costs are not always a
Below lett
computer-guided
The welded mesh covers
robotic systems are
together, although the strength of the
consideration: many joints can be welded
a paper pulp molding tool (page 202).
used for high volume
joint may be compromised. Also, different
with inexpensive standard tooling.
welding operations.
thickness of material can bejoined
Specially designed tooling maybe
together, or multiple sheet materials
required to weld contoured surfaces, but
RELATED PROCESSES
laid on top of each other. Assemblies up
is generally small and not expensive.
Resistance welding stands alone in
to 10 mm (0.4 in.) deep can bejoined
the welding techniques: it is simple,
with a single spot weld, but thickness is
standardelectrodes (tooling),which
consistent, low cost and de-skilled. Arc
generally limited to between 0.5 mm and
minimizes costs. However, certain
welding (page 282) and power beam
5 mm (0.02-0,2 in.).
applications, including contoured
welding (page 288) require ahigh level of skill to operate with such efficiency. Formed and riveted joints require
Most assemblies can be welded with
surfaces, require dedicated electrodes.
DESIGN CONSIDERATIONS
Cycle time is rapid. Spot welding can
The position of the weld is limited
only produce 1 weld at atime and so islimitedtoabouti weldpersecond.
preparation. Resistance welding can
by 2 factors;the reach of the welding
be applied with very little surface
equipment and the shape of the
Projection welding can produce multiple
preparation. Weld nuggets are formed
electrode. Theform of atypical handheld
welds simultaneously, so is more rapid.
easily in most metals, regardless of
spot welding gun (see image, opposite,
The speed is affected by changes in
theirhardness. Slightly higher clamping
above) makes clear the constraints.
material thickness, welding through
pressures are required when welding
The weld point must be accessible
harder materials to achieve the same
from the edge of the sheet. Welding
level of coalescence.
equipment typically operates on a
There is no waste generated by the
coatings and variability in part fit up.
Soldering and Brazing Processes Conduction method
Torch method | Workpiece
J
Joining Technology
Soldering and Brazing
1 Small gap
Workpiece
Both these processes form permanent joints by melting a filler
Stage 1: Assembly
Stage 2: Applying heat and filler material
Capillary action
Stage 1: Assembly
Stage 2: Applying heat and filler material Heating elements
processes is the melting point of the filler materials, which is
Furnace method
TECHNICAL DESCRIPTION
lower for soldering than it is for brazing.
Workpiece
Soldering and brazing is made up of
Conveyor belt
the following main elements; joint preparation, flux, filler material and Costs
Typical Applications
Suitability
heating. These 3 diagrams illustrate
• No tooling costs, but may require jigs • Low unit costs
• Electronics • Jewelry • Kitchenware
• One-off to mass production
the most common methods for heating
DDDDDDD
a joint.
Stage 1: Assembly
There are many different techniques, Quality
Related Processes
Speed
• High strength bond, close to strength of parent material
• Arc welding • Resistance welding
• Rapid cycle time 11-10 minutes de¬ pending on technique and size of joint)
D D D D D D-
Stage 2; Applying heat and filler material
but the basic principle of soldering and brazing is that the workpiece is heated to above the melting point of the filler
INTRODUCTION
There are several techniques that
a process known as 'wave soldering'. In
These processes have been used in
employ different combinations of these
operation, the PCBs are assembled with
metalworking for centuries to join lead
elements to achieve a range of design
all the relevant components, preheated
material. At this point the filler becomes
CONDUCTION HEATING
The filler may be added as a pre-form, or
molten and is drawn into the joint by
Conduction heating is typically carried out
coating, which becomes molten under the
capillary action. The liquid metal filler forms
with a soldering iron. The diagram depicts
intense heat of the flames.
a metallurgical bond with the workpiece to
a through joint, which is common on circuit
create a joint that is as strong as the filler
boards. The alternative is surface mounting.
FURNACE HEATING
material itself.
In this case the filler material, solder, is fed
Both of the previous methods have been
frames in stained glass windows and
opportunities. For example, the filler
and dipped in a tank of flux, followed
into the joint separately as a rod or wire.
based on heating localized areas of the
copper sculptures, for example. More
material is drawn into the joint by
by a tank of solder. The solder wets the
of silver, brass, tin, copper or nickel,
Applying a fine coat of filler and flux to the
workpiece. Furnaces heat up the entire
recently, filler material shave been
capillary action, dipped, or inserted as
unmasked metal connections and forms
or a combination of these. The choice
workpieces prior to assembly is similarly
workpiece to the melting point of the filler
developed that are suitable for joining
a pre-form. Heating methods include
apermanent, conductive joint when it
of filler material is determined by the
effective; on heating, the filler material
material. This process is ideal for making
many metallic and ceramics materials.
induction, furnace and flame. Fluxes
is baked.
workpiece material because they have to be
coalesces to form the joint. On heating, the
multiple joints simultaneously, for mass
The most well known application is
protect the surface of the joint from
metallurgically compatible.
filler material coalesces to form the joint.
production and for materials that are brazed
soldering printed circuit boards (PCBs).
oxidizing. An alternative is to carry
An alternative method for massproducing soldered joins is known as
The filler material is typically an alloy
Fluxes are an essential part of the
in a protective atmosphere such as titanium.
TORCH HEATING
Traditionally, lead-based solders were
out the operation in a vacuum or in
'reflow soldering'. In this case, a paste
process. The type of flux is determined
used for many applications, including
the presence of an inert gas (such as
of solder and flux is screen printed onto
by the filler material. The role of flux is to
The next method of heating is using a gas
PCBs. As a result of the negative
hydrogen brazing).
the part and then baked. The advantage
provide a clean, oxide-free surface, so the
torch, usually oxyacetylene. However,
the flux and filler are screen printed onto the
filler can flow around the joint and form
soldering can be carried out with a cooler
joints. The baking process can take longer
a strong bond. This is also referred to as
burning gas such as propane. As with the
than other methods, but many parts can be
surface 'wetting'.
previous technique, the joint is heated to the
joined simultaneously.
environmental impacts of lead and other heavy metals, tin, silver and copper filler materials are now more commonly used.
The melting temperature of the filler
is that hundreds, or even thousands of
TYPICAL APPLICATIONS These are widely used processes. The most common use of soldering is joining
joints can be coated in a single pass of the squeegee. Soldering is also used a great deal in
Wetting is the coverage achieved by the filler material. It is hindered by surface
desired temperature and the filler material
apply heat using a shaped element, which
electronic components, such as surface,
jewelry, domestic plumbing (hermetic
is known as soldering, which is below
or through hole mounting onto PCBs. It is
seals in copper pipes), silverware and
45o0C (8400F), or brazing, which is above.
ideal for this because solder is conductive
food preparation items, restoration and
But the melting point of the workpiece is always higher than the filler material, so
and is suitable for joining delicate
repair work (re-soldering).
filler materials are non-ferrous.
assembled by hand using a soldering
soldering because the filler material
they are coated with metal by electroplating
may have many torches fixed in place
iron, especially for low volume parts.
has a higher melting point than solder.
(page 364), or vacuum metalizing for non-
and pointing at the workpiece such as in
High volume production is carried out in
Typical applications include industrial
conductive materials (page 372).
the production of certain bicycle frames.
There are 3 main elements to the process: heating, flux and filler material.
Brazing is generally stronger than
Instead of a furnace, it is possible to
is added. A small gap of approximately
material determines whether the process
components. Many electronic parts are
The filler material can be added as a pre¬ form, or as in the case of reflow soldering,
contamination and surface tension between
0.05 mm (0.02 in.) is necessary to facilitate
surrounds the part without touching it, to
the materials. In some instances, such as
capillary action. The gap can be larger, but
elevate the temperature of the joint area.
reflow soldering, fluxes are incorporated
this will affect the strength of the joint.
This technique is more commonly used for
into the filler to aid wetting. To encourage wetting on the surface of ceramic materials
This is not restricted to manual operations. Mass production methods
large volume production brazing.
pipework, bicycle frames, jewelry
out with brass filler, the colour can be
material will bridge the gap.This also
COMPATIBLE MATERIALS
pressure and very thin film of filler
The cycle time for furnace techniques
and watches. Brazing is also usedfor
adjusted to suit the parent material.
mean s very complex and intricate joints
Most metals and ceramics can be
coated onto the joint interface. When
may be longer, but is offset because
can be made because the molten filler is
joined with these techniques. Metals
the temperature is raised a very small
multiple products can be joined
drawn right through.
include aluminium, copper, carbon steel,
amount of pressure is applied, which
simultaneously.
stainless steel, nickel, titanium and metal
causes the molecules in the joint to
matrix composites.
mix and form a strong bond. Dissimilar
joining components in engines, heating elements, and parts for the aerospace
DESIGN OPPORTUNITIES
and power generation industries.
The main advantage of these processes is
Alternatively, the filler material can
that they do not affect the metallurgy of
be inserted into the joint as a pre¬
RELATED PROCESSES
the parent material. Even so, an integral
form. In such cases, it is possible to join
Like arc welding (page 282), brazing
metallurgical bond is made at the
multiple products, or multiple joints
and to metals. Many ceramics can be
uses thermal energy to melt the filler
interface by the molten filler material.
simultaneously.
joined, but brazing is generally reserved
material. But soldering and brazing do
Soldering and brazing are simple
Ceramics can be joined together
materials, such as metals and ceramics,
ENVIRONMENTAL IMPACTS
can be joined in this way.
Soldering and brazing operate at lower temperatures than are welding.There
for engineering materials due to the
COSTS
are very few rejects because faulty parts
sophistication of the process.
There are no tooling costs. But jigs may
can be dismantled and reassembled.
not melt the parent material, which is
processes, but there are many variations,
DESIGN CONSIDERATIONS
beneficial for thin, delicate and sensitive
which make them versatile and
The filler material determines the
components. Resistance welding (page
suitable for many different materials
optimum service temperature and
diffusion bonding, is suitable for joining
However, joints can be designed to locate
308) is used for similar applications but
and joint geometries. The range of
strength of soldered and brazed joints.
ceramic, glass and composite materials.
and therefore do not need to be jigged.
with different joint geometry.
techniques cover manual and automated
Butt, tee and scarf joint types are not
production, making these processes
generally suitable for these processes
QUALITY
equally suitable for one-off and mass
because joint interface must be as
Soldering and brazing do not heat the
production. One-off and small batch
large as possible.Therefore, whatever
joint above the melting temperature
production is typically carried out with
the configuration, the joint interface is
of the parent material and so there is
ahandheldtorchandfillerrod,whereas
designed to provide substantial surface
minimal metallurgical change, or heat-
mass produced items are fed through a
area. This may affect the decorative
affected zone (HAZ). The finish of the
furnace on a conveyor belt.
aspects of the product.
1 '' joint bead is usually satisfactory without
Filler material is drawn into the
the need for significant grinding. And
j oi nt by capill ary acti on. Th erefore, th e
the size of the products is limited by
even though brazing is usually carried
joints do not have to fit exactly; the filler
chamber size.
Case Study
Brazing the Alessi Bombe milk jug This is the Bombe milk jug (image 1). It was
There is very little finishing required.
designed by Carlo Alessi in 1945 and is still in
The brazed part is removed from the jig
production today. It was originally made by
complete (image 5). It is lightly polished
metal spinning brass (page 78), but is now
and cleaned before being packed
deep drawn stainless steel (page 88). Brazing
(image 6).
is used to join the spout and handle even though it would be quicker by resistance welding. Brazing is still used to maintain the integrity of the original design. First of all, the joint is checked and coated with flux paste (image 2). An overlap has been created between the spout and body to maximize the surface area to be joined.
They are mounted into a jig (image 3). The brazing process is very rapid, lasting 30 seconds or so (image 4). The craftsman
first warms up the join area with an oxyacetylene torch. When it is up to temperature, the filler material is added.
It flows into the joint interface and forms an even bead.
In furnace and vacuum methods
Labour costs are generally low.
A similar process to brazing, known as
This process joins materials in a vacuum chamber, using a small amount of
be necessary to support the assembly.
Cycle time is rapid and ranges from i-io minutes for most torch applications.
i/i
o o m
X)
Staking Process
Butt
1
Scarf
•
¦2 OJ
Hot air staking
Ultrasonic staking
Alternative profiles
°
f
Joining Technology
Staking Thermoplastic studs are heated and formed into permanent joints. This process is suitable for joining dissimilar materials
INTRODUCTION These are dean and efficient processes
used to assemble injection molded
such as plastic to metal. There are 2 main techniques: hot air and
thermoplastic parts with other materials.
ultrasonic staking.
They utilize the ability of thermoplastics to be heated and reformed without any loss of strength.
The joint configurations resemble 1 Low tooling costs Low unit costs
Quality • High strength joints with variable appearance
Typical Applications
Suitability
• Appliances • Automotive • Consumer electronics
• Medium to high volume production
Related Processes Hot plate welding Ultrasonic welding Vibration welding
Speed Rapid cycle time (0.5-15 seconds)
rivets. A plastic stud, injection molded onto the component, is heated and
DESIGN OPPORTUNITIES
formed into a tight fitting joint.
This is a simple process that eliminates
parts (page 50) and so large volumes.
Dissimilar materials can be joined, as
consumables such as screws and rivets.
These joints are usually internal
long as 1 is thermoplastic; staking is used
extensively to join metal circuitry into
The studs are injection molded into the part and add no cost to the
plastic housing.
forming process.
Staking is limited to injection molded
TECHNICAL DESCRIPTION The thermoplastic stud is softened with hot air or ultrasonic vibration. It
and so appearance is not a major
is then formed into a domed, knurled,
consideration. Due to the nature of the
split or hollow head. The shape of the
process joints are neat and clean, but the
tool is adjusted to fit the requirements
finish is not controllable.
of the application and stud diameter.
The largest areas of application are in the
snap fits. The advantage of staking is that multiple fixing points can be
COMPATIBLE MATERIALS
to 5 mm (0.02-0.2 in.). Rectangular
consumer electronics and automotive
molded in, as long as they are in
This process is limited to injection
and hollow studs can be much larger,
industries. In many instances, staking has
the same line of draw (tool action).
molded parts. Suitable materials include
replaced mechanical methods such as
Snap fits are more difficult to integrate
screws and clips.
onto a product's surface without
polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS) and
complextool actions.
poly methyl methacrylate (PMMA).
An alternative to staking is molded
TYPICAL APPLICATIONS
Applications in the automotive industry include control panels,
Round studs are typically 0.5 mm
Multiple studs can be heated and
as long as the wall thickness is thin enough for staking. Hot air staking is a 2 stage process.
In stage 1, hot air is directed at the stud. The temperature of the air is determined by the material's
dashboards and door linings. Staking is
formed simultaneously to form large
COSTS
ideal for joining electrical components
joint areas. It is possible to produce
Tooling costs are low. Aluminium jigs
stake with a profiled head presses
into plastic housing because the studs
watertight seals by sandwiching a
are required to support the part during
down onto the hot stud. This
are insulating.
rubber seal in the assembly.
assembly. Ultrasonic staking uses a horn
simultaneously forms and cools the
(tool). Hot air staking uses standard
stud and joins the materials.
There are no restrictions on the layout,
RELATED PROCESSES
pattern or number of studs. Pressure
tooling, which is laid out to suit the
If 2 similar materials are being joined
is applied during operation and so the
orientation of the studs.
then ultrasonic (page 302), hot plate (page 320), vibration (page 298) or other
joints are tight and free from vibration.
Cycle time is rapid. Ultrasonic staking
Low pressures are sufficient to form
can form joints in 0.5-2 seconds. Hot air
welding techniques can be used. Staking
the joints, so thin walled and delicate
stands alone in its ability to join plastics to metals without additional fixings.
parts that may not be able to stand up to vibration can be joined in this way.
staking cycle times are 5-15 seconds. Labour costs are low because these processes are generally automated.
plasticizing point. In stage 2, a cold
Ultrasonic staking is more rapid and takes only a few seconds. It is a single
stage operation in which the stud is heated up by ultrasonic vibrations. As the stud is heated up It softens and is formed by pressure applied by the tool. Ultrasonic welding is suitable for a range of other operations including
QUALITY
DESIGN CONSIDERATIONS
ENVIRONMENTAL IMPACTS
These are permanent joints.The
The principal consideration is that the
Staking eliminates consumables such as
strength of the jointis determined by the diameter of the stud and mechanical
studs should align in a vertical direction,
rivets, screws and clips.
otherwise they cannot be formed in a
properties of the parent material.
single stroke.
welding, sealing and cutting.
Case Study
Case Study
Hot air staking This case study demonstrates atypical
In this case, ultrasonic staking is used to join
studs (image 3). The ultrasonic vibrations
hot air staking application. The parts
a rubber seal onto an injection molded part.
form the studs very quickly. After a couple of
being assembled are the lamp housing
The 2 parts are assembled on a jig (image 1).
seconds the joint is complete and the horns
The studs are rectangular to provide a larger
retract (image 4).
and electrical contacts.
The lamp housing is placed into a tool and the pressed metal contacts are placed over the studs (images i and 2). A stream of hot air is directed at each stud for a few seconds (image 3). Cold dome-headed tools form the hot plastic studs (image 4).The stakes retract and
joint area. The ultrasonic horns are mounted onto a single booster and work simultaneously. The
inside of the horn forms the stud into the desired shape (image 2). The ultrasonic horns compress onto the
parts and apply vibrations to heat up the
the assembly operation is complete (images 5 and 6).
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Featured Manufacturer Branson Ultrasonics
Branson Ultrasonics
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4
Hot Ptate Welding Axial force applied
Joining Technology
Hot Plate Welding This is a simple and versatile process used to join materials. The joint interface is heated to above its melting point, causing it to plasticize. The parts are then clamped together to form the weld.
INTRODUCTION Hot plate welding is used to form joints in extruded and injection molded (page 50) thermoplastic parts. It is a very simple process: the joint interface is heated until it plasticizes andthen pressed together
Stage 1: Loading
Stage 2; Heating
until it solidifies. It is also a versatile process: size is restricted only by the Costs 1 Moderate tooling costs 1 Low unit costs
Quality High quality homogenous bonds Hermetic seals possible
Typical Applications • Automotive • Packaging • Pharmaceutical
Suitability • Batch to mass production
size of the heating platen, and the joint profile may be flat or 3D.The equipment can be either portable or fixed to a
required to form the joint, unlike these
production line.
delicate parts can be welded.
Related Processes Ultrasonic welding Vibration welding
• Variable cycle time (30 seconds to 10 minutes)
other processes, which means small and
TECHNICAL DESCRIPTION This process is made up of several
and Impractical for complex and
stages, which can be divided into 3 main
undulating joint profiles. PTFE coatings
operations; loading, heating and welding.
start to degrade above 270°C (518°F) and
TYPICAL APPLICATIONS
QUALITY
The automotive Industry is the largest
The strength of the weld Is affected
the tools, which generally operate on a
only be used for low melt temperature
user of hot plate welding.The process
by the design of the part and type of
vertical axis. They are held in place by a
plastics such as polypropylene |PP) and
is also usedfor some packaging and
material. Strength Is therefore very
small vacuum. The tools align the joint
polyethylene (PEl.
pharmaceutical products.
difficult to quantify because it varies according to the application. Flash
Interface, so that it can be heated and
RELATED PROCESSES Similar joint profiles are suitable for
produced by pressure in the welding operation is often left untrimmed. It is
vibration (page 298) andultrasonic (page
posslbleto conceal the joint flash with a
302) welding.This process is selected
flange around the weld area.
because only small levels of pressure are
Heating andplasticizlng is localized, up to i mm (0.04 in.) on either side, and so the process does not affect the structure of the workpiece.
In stage 1, the parts are loaded into
welded very accurately. A pre-heated platen is located between the parts. In stage 2, the parts are brought
into contact with the heated platen,
give off toxic fumes. Therefore, they can
The hot plate Is generally a flat plate of aluminium, but can be profiled to accommodate parts with a 3D joint Interface ias shown In the diagram). In stage 3, the parts separate from the
which raises the temperature of the joint
heated platen, which is withdrawn to allow
interface and plasticizes the outer layers
the parts to be brought together. Axial
of material. The temperature Is adjusted
pressure Is applied and the plastlcized
according to the plastic parts being
joint Interfaces mix to form a homogenous
welded. Generally, it Is set 50°C to 100°C
bond. A pre-determined amount of
(90-180°F) above the melting temperature
material Is displaced by the pressure,
of the polymer because it has to warm the
which produces small beads of flash.
DESIGN OPPORTUNITIES
plastic up enough for it not to fall below
The parts are held In place until
There are few restrictions on part size
melting point before the weld has been
the polymer has solidified and cooled
and geometry; the joint interface can be
made. Maximum temperature is around
sufficiently so that It can be removed.
very complex and have both internal and
500°C (932°F).
Small parts are typically heated for around
external welds.The only requirement
is that it can be accessed by a hot plate
The hot plate Is coated with a thin film
10 seconds and then clamped (welded) for
of polytetrafluoroethylene (PTFE), which
a further 10 seconds. Therefore, cycle time
along one axis. Joints on different axes
prevents the melting plastics from sticking
Is up to 30 seconds. Large applications
must be welded in a second operation.
during heating. For particularly sticky
may take considerably longer.
This process is not specific to any
plastics, heat Is applied without contact
thermoplastics material. In other words,
different materials can be welded with the same tooling. All that need to be adjusted Is the temperature of the heating platen.
(convection rather than conduction), but this can cause problems. The benefit
of contact with the tool Is that pressure can be applied for uniform heating. Non-contact heating Is less effective,
Case Study
¦ Hot plate welding an automotive part This product is a typical application for hot
is withdrawn. The parts are then brought
plate welding. It is part of a water-cooling
together and held under pressure until the
system for an automotive under-the-
joint interface has mixed and solidified
bonnet application. This process is ideal
(image 6). The whole process takes no more
because both internal and external welds
than 25 seconds.
can be made simultaneously. Only a small
amount of pressure is required to form
The tools part and leave the welded product in the bottom half (image 7). The
the weld, which is suitable for thin wall
part is removed and checked. A bead of
sections.
flash is typical with this process (image 8);
The part is made of 2 injection molded halves (image i).The top and bottom half
it builds up around thejoint as the pressure is applied.
are loaded into their respective jigs and are held in place by a small vacuum (linages 2 and 3). The required pressure,
heating and welding time have been established through tests and so the process is run automatically to ensure
accurate repeatability; the operator sets the programme for these particular parts (image 4). Heating takes place on a heated platen (image 5), which raises the temperature of the material to more than 5o0C (9o0F) higher than its melting point.This ensures that there is sufficient heat build up in the joint for welding to take place. After only a few seconds, the
tools separate and the heating platen
DESIGN CONSIDERATIONS
COMPATIBLE MATERIALS
This process is most commonly used to
Most thermoplastics can be joined in this way, although it is limited to injection
10 seconds. However, complex and large
weld butt joints. Lap joints are possible in simple parts and extrusions, but this is a
molded and extruded parts. Some
10 minutes.
much less common configuration.
materials, in eluding polyamide (PA), oxidize when they are heated to melting
orfully automated, so labour costs are
by increasing the surface area of the
point, which can decrease the strength of
relatively low.
weld. Incorporating a tee-shape or right
the weld.
The strength of the joint is improved
The maximum dimension of part
welds can take considerably longer; up to
Hot plate welding is either partially
ENVIRONMENTAL IMPACTS
angle at thejoint interface,for example, will increase the weld area.
Cycle time is generally rapid; around
COSTS
This process does not add any material to
Tooling costs are moderately expensive
thejoint and there is no waste produced
that can be welded is limited by the
because they are required to support the
during welding. Hot plate welding has a
size of equipment, which can be up to
part accurately during welding. Parts are
low environmental impact.
620 mm by 540 mm (24.41 x 21.26 in.) on
often supported with a vacuum, which
the heating pi aten an d up to 350 mm
further increases cost.
(13.78 in.) high.
Joint Configurations
Joining Technology
Joinery
•L
w
Contemporary furniture is constructed with both handmade and machine made joints. There are many different types, and it is up to the joiner to select the strongest and most visually pleasing
¦/ ,
for each application.
Costs
Typical Applications
Suitability
• No tooling costs; jigs may be necessary • Moderate to high unit costs depending on the complexity
• Construction • Furniture and cabinet making • Interiors
• One-off to high volume production
Related Processes
Speed
• Friction welding • Timber frame construction
• Cycle time depends on complexity
Quality
_
|
1 ' '¦]
TECHNICAL DESCRIPTION
INTRODUCTION Joinery remains an essential part of
sympathetic to the strengths and instabilities of this natural material.
construction, especially if the joints are on display. Buttimberframe
The diagram illustrates the most common
these is that they are concealed within the
joint types. They include handmade and
joint interface. These are widely used in high
perpendicular lengths of wood. The leg is the
machine made configurations, which are
volume production and flat pack furniture.
tenon and the mortise the hole. The tenon is
Joints can be seamless and almost
construction tends to be concerned with
used in furniture construction, house
industry have combined over the years
invisible, or they can provide contrast to
speed of operation and reliability of joint.
building and interior structures.
and as a result a standard selection
emphasize the joint.These are decisions
Metal fixtures are often used, rather than
There are U main types of adhesive,
of joint configurations have emerged.
made by the designer and made possible
which are urea polyvinyl acetate (PVA),
These include butt, lap, mitre, housing,
by a skilled joiner.
spending time cutting a complex joint. The advantage of gluing is that it spreads th e 1 oad over the entire joint and
formaldehyde (UF), 2-part epoxies and polyurethane (PUR). PVA and UF resins are
A lap joint increases the size of the
is not visible from outside.
the,least expensive and most widely used.
interface to include gluing to long grain on
PVA is water based and non-toxic, and
both sides. This increases the strength of the
welding (page 294) may compete with
excess can be cleaned with a wet cloth. PUR
joint and requires more preparation.
conventional gluing techniques.
and 2-part epoxies can be used to join wood
furniture and cabinet making. Craft and
mortise and tenon, M-joint, scarf, tongue and groove, comb,finger and dovetail.
TYPICAL APPLICATIONS
Additionally, butt joints are strengthened
Joinery is used in woodworking
with dowels or biscuits.
All of these joints can be further reinforced with screws and nails, but this
section is dedicated to joints that are
industries, including furniture and cabinet making, construction, interiors,
In the future, linear friction
Typical furniture includes tables,
QUALITY
usually cut on a band saw, and the mortise
joining 2 planks at right angles. It is more
on a mortiser, which is a machine with a drill
aesthetically pleasing than a butt joint
bit inside a chisel that cuts square holes in
because it ensures continuity of long grain
wood. Alternatively, the mortise can be cut
and avoids exposed end grain.
by hand. There are many different types
A comb joint (also called a finger joint)
including haunch, shoulder, blind, through (illustrated) and pegged. Scarf joints, tongue and groove, M-joints
and finger joints are primarily used to join planks of wood to make larger boards.
provides a much larger gluing area and is a
They increase the gluing surface between
ceramic, and are waterproof and suitable for
common joint for boxes or drawers in tables
2 planks in a butt joint configuration.
exterior use. They are rigid, so restrict the
and cabinets. It is made by a series of spaced
movement of the joint more than PVA.
cutters on a spindle molder, a spinning
for mass production. They are cut on a high¬
cutter for profiling lengths or ends of wood.
speed spindle molder.
to other materials, such as metal, plastic or
boat building andpatternmaking.
A mitre joint is a simple, neat method of
Mortise and tenon joints are used to join
M-joints are machine-made and suitable
secured only with adhesive. (For metal
chairs, desks, cabinets and shelves.
The quality of joint is very much
fixtures in timber frame construction,
Joinery is used in construction for timber
dependent on skill.There is very
see pages 344-7.)
roof trusses, gable ends, doors and
little room for error, but mistakes are
window frames. Interior applications
because the 2 planks are simply cut to
They are cut with re-entrant angles, which
designed to integrate lengths of timber
length. However, they are also the weakest
increase the strength of the joint In certain
into a continuous profile. It is designed to
because there is a relatively small interface
directions. They are especially useful for
maximize gluing area and joint strength.
for gluing and 1 face is end grain. End grain
drawers, which are repeatedly pulled and pushed from the front.
and decoratively.The art of joinery
for this process include floors, walls,
inevitable. Skilled cabinet makers differentiate themselves by their ability
is using wood to its strengths. It is
structures and stairwells.
to repair mistakes imperceptibly.
Joints have to work both functionally
Products made from wood have
ani sotropi c an d i s stron g er al on g th e
Butt joints are the simplest form of joinery. They are inexpensive to prepare
length of its grain. It is alsoproneto
RELATED PROCESSES
unique characteristics associated
is the least strong face for all fixing types,
shrinking or expanding as it dries or
Joinery and timber frame structures
with visual patterns (growth rings),
including adhesives, nails and screws.
(page 344) overlap. Simple joinery
smell, touch, sound and warmth. High
absorbs water from the atmosphere. Therefore, the joint design must be
is used a great deal in timber frame
quality woodwork is often left exposed.
Butt joints are reinforced with dowels, biscuits or metal fixings. The benefit of
Dovetail joints are modified finger joints.
A housing joint is a lap joint in the middle
The finger joint is machine-made and
There are many variations on each of
the above joints, including the angle of interception and whether the joint detail
of a workpiece. It is common for shelves and
penetrates right through the wood or is blind
cabinet making.
(not right through).
Case Study v.
Mortise and tenon and M-joints in the Home Table This is the Home Dining Table, which was designed by BarberOsgerby in 2000. It is
On the assembled table the mitre joint is almost invisible (image 7). The grain merges
on the front of the leg because the 2 halves of the leg are cut from the same plank of wood.
produced from solid oak with a range of different joints (image 1). The legs are mitred together (image 2). The legs and table frame are joined with a mortise and tenon, the traditional
and strongest joint for this application (images 3-5). The top is made by joining solid planks of oak with M-joints (images 6 and 7).
Materials like medium density fibreboard
using butt joints will be less expensive
(MDF) tend to be concealed under several
than finger or dovetail types. However,
layers of paint. A very high level offinish
glued butt joints may not provide such
can be achieved on these surfaces with
a large and strong joint interface as other methods.Therefore, very strong
repeated painting and polishing.
adhesives, dowels and biscuits are used
DESIGN OPPORTUNITIES
to maximize strength.
Joints have several primary functions, For example, the framework and legs
one-third the thickness of the workpiece.
COMPATIBLE MATERIALS
change of grain direction and joining
of a table are join ed together, partly
This will ensure that there is sufficient
The most suitable woodfor joinery is
shapes that cannot be made in a single
because the grain should run in different
material aroundthe joint to support it.
process orfrom a single piece.
directions for optimum strength.The
which include lengthening or widening,
The style of joint should minimize the
The choice of joint is determined
solid timbers, including oak, ash, beech, pine, maple, walnut and birch. Joinery is not limited to wood. These
most common joint forthis application is
by a balance between functional and
amount that wood will naturally twist
a mortise and tenon because it helps to
decorative requirements, and economic
methods can be applied to any material
and buckle, reduce weight and maximize
prevent twisting.
factors.There are types of joint that
as long as it is sufficiently hard to cut a
have been used traditionally for joining
joint into. Synthetic materials will not
gluing area.
Joinery is often combined with CNC
6
legs to tables and panels to doorframes
require such complex profiles because
of designing with timber. It is possible
machining (page 182), laminating (page 190), steam bending (page 198), timber
or making shelves and drawers, for
they are more stable than wood.
to make large flat surfaces, such as
frame construction and upholstery (page
example. For each application the joints
tabletops, of planks joined together
338).The joints maybe exposed and
are modified and adjusted.The case
COSTS
with M-joints or tongue and grooves
decorative or purely functional.
studies illustrate some of the most
Most applications do not require tooling.
ENVIRONMENTAL IMPACTS
common joint types and how they
Some machine made joints may need
Wood has many environmental benefits,
are used.
tool s cut for spindle molders or routers,
especially if it is sourcedfrom renewable
but these are generally inexpensive.
forests.Timber Is biodegradable, can be
Cycle time 1s totally dependent on the complexity of the job and the skill
reused or recycled and does not cause
Joinery maximizes the opportunities
and with 'bread board'ends of wood fixed across the ends of the planks to
DESIGN CONSIDERATIONS
prevent warping. Long and continuous
There is no limit on the size of plank
lengths can be made with M-joints and
orlength of wood that can be joined.
exposed joints. For example, a mitred
finger joints. Shelving and cabinets can
However, the type of joint and its size
be assembled with simple housing, lap
relative to the wood are important
joint will cover up end grain and provide a neat edge detail with continuity of
Aesthetics play an important role for
Labour costs tend to be quite high due to the level of skill required.
of the operator. A single joint may take
any pollution. Joints tend to be formed by cutting, so
or butt joints reinforced with dowels
considerations.There are guidelines
surface grain, whereas comb and dovetail
only 5 minutes to cut and assemble, but
or biscuits. Simple boxes can be made
to maximize retained strength in the
joints express craftsmanship and add
there might be 15 different joints on the
wood chips are often burnt to reclaim
with butt, mitred and lap joints, or more
timber that is cut to form the joint.
perceived value.
product. Generally, the same or similar
energy in the form of heating.
decorative comb and dovetail joints. Change of grain direction is especially useful for load bearing applications.
For example, mortises (mortise and tenon joint) and grooves (tongue and
groove joint) should be no wider than
Economic factors, such as cycle time and labour costs, often have a role to play. For example, a part that is being made
joints will be used as much as possible on a product to minimize set up and changeover time on the machines.
waste is unavoidable. Dust, shavings and
Featured Manufacturer Isokon Plus www.isokonplos.com
Case Study
Case Study
Mitred and biscuit reinforced butt joints in a bedside table
Dowelled butt joints in a table drawer
This is a simple, veneered bedside table.
This case study illustrates dowels used to
The 4 sides of the product are lipped with
strengthen butt joint configurations. The
solid oak edges, veneered, cut to size and
parts are drilled with the holes set apart to
materials (image 2).They are inserted into
mitred. Grooves are cut for the biscuit
exact measurements (image i).This is often
the joint with glue and hammered into
carried out on a drill with 2 heads, which are
place (image 3).
reinforced butt joints. To join the mitred joints, the parts are laid face up (joint down) on the table. The
The dowels are made from beech or birch, because they are suitably hard
set exactly the same distance apart for both sides of the joint.
faces are taped (irnage i) to keep the joint tight during assembly Prior to assembly, the biscuits (Image 2) are placed into precut grooves on the butt joint, and glue is applied to all of the joints (image 3). The 4 sides are assembled with the tape still in place (image 4).This keeps the joint tight and acts like a clamp (image 5).
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Windmill Furniture www.windmilLfurniture.com
Featured Manufacturer
Windmill Furniture www.windmiUfurniture.com
Case Study
Case Study
Comb jointed tray
Decorative inlay
Comb joints are traditionally used to
This is a simple form of wood inlay,
join the sides of trays and drawers. The
used visually to separate 2 veneers on a
joint is cut by spindle molder with a set
tabletop (image 1). The inner veneer is
of cutters separated by matched spacers.
bird's eye maple and the outer veneer is
Both sides are cut with the same set up to
plain maple. This type of decorative Inlay
ensure a perfect fit (image i), which can
is made up of layers of exotic hardwoods
be assembled by hand (image 2).
and fruitwoods, which are cut Into strips
The base of the tray, which is located
(image 2). The groove is cut by router, and
in a housing joint between the 4 sides,
the strips of inlay are bonded In with UF
holds it all square, and the finished
adhesive (image 3).
product is lacquered (image 3).
Featured Manufacturer
Windmill Furniture www.windmillfurniture.com
;ase Study
Housing joints in the Donkey This version of the Donkey was designed by Egon Riss in 1939. It is made from birch plywood (image 1). Housing joints are a simple and a strong way to fix the shelves into the end caps (image 2). This use of this joint means that the product can be assembled and glued in a single operation. The end caps are clamped
together, which applies even pressure to all the joints.
Featured Manufacturer
Featured Manufacturer
Isokon Plus
Windmill Furniture
www.isokonplu5.com
www.windmillfurniture.com
Joining Technology
Weaving Weaving is the process of passing strands or strips of material over and under each other to form an intertwined structure. Fibre strength and alignment can be adjusted specifically for each application, reducing weight and material consumption.
Costs • There are no tooling costs • Low unit costs, but dependent on the raw material
Typical Applications • Furniture • Interiors • Storage
INTRODUCTION
Machine made textiles are woven
Weaving is used across a wide range
as panels, which are then secured to a
of industries, including textiles, rug
structural framework.To make 3D profiles
making, sail making and architecture.
they are draped over molds and coated in
This section focuses on rigid textiles,
adhesive to retain their shape.
which are used in the construction and
Hand weaving techniques date back
upholstery of furniture, baskets, fences,
thousands ofyears and are very similar
screens and mats. Rigid textiles can be
today because many are not suitable
Suitability
made not only as flat panels, but also as
for mechanized mass-production.
• One-off to high volume production
3D, self-supporting structures.
There are 3 main types of rigid textile
Quality
Related Processes
Speed
• Depends on raw material
• Steam bending • Upholstery • Wood laminating
• Machine weaving is rapid • Hand weaving is moderate to slow, but depends on size and complexity of part
Nevertheless, there is a substantial market for hand woven products, which
weaving: plain (see image, opposite,
are made in large quantities in countries
above middle), twill (see image, opposite, top) and satin (in which either the warp
with enough labour to make production
or the weft bridges 5 perpendicular
economically attractive. Hand weaving is carried out either
strands or more). Satin has a slightly less
on a loom (in which case it can be
stable textile, a warp- or weft-rich surface
mechanized), between rigid elements
and a more densely packed weave. Other
(which do not have to be parallel as they
types of weaving, such as machine-made
are in machine weaving), or as a 3D self-
tri-axial 'strand caning' (see image,
supporting structure.There are many
opposite, above) and 'basket weaving'
techniques including plaiting (general
(see image,below), are combinations of
weaving), hand caning, lashing, splint
these techniques.
seat weaving and coiling.
TYPICAL APPLICATIONS Weaving is used in many different
Top
Above
areas of furniture construction. Typical
Twill, or herringbone,
Cane weave.This is the
products include stools, chairs, tables,
is a diagonal pattern created by overlapping
of caning, based on
sofas, beds, lights, storage boxes, blinds and screens.
2 strands ormore at a time.
Other products using similar techniques and materials include
Above middle
Above The Lloyd Loom Nemo chair, designed by Studio Dillon in 1998, is made up of a single
most popular method the traditional 7-step manual technique
steam bent ring, onto
to form an octagonal
which the woven
pattern
material is fixed.
Plain weave is a simple
baskets, fences and wall and floor panels.
'1 up, 1 down'pattern.
RELATED PROCESSES
CNC machined (page 182) wooden
advantage is that woven structures can
Alternatives to rigid textiles in furniture
support structure.
be shaped, for example onto a mold in
include upholstery (page 338) with
Wood and composite laminates
leather or'soft'textiles, wood laminating
rely on adhesives to hold the layers
(page 190) and composite laminating (page 206). Similar to upholstery,
together. By contrast, woven materials are maintained by friction.This means
the case of the Lloyd Loom Nemo (see image, above right).
QUALITY
woven 'rigid' textiles are often fixed
woven structures tend to be more
The quality of weave is determined
wonto a steam bent (page 198) or
flexible and deform permanently.The
by the combination of rawmaterial
Loom Weaving Process
Case Study
t #
Weaving upholstery This case study demonstrates weaving and
The metal is concealed in paper (image 4) and
The woven material is transferred onto a
the subsequent upholstery of woven material
is the structural element of the basket weave.
steam bent structural framework (image 8).
onto a steam bent wooden structure. The
Each of the looms is loaded with 664
The edge is stapled with a braid of twisted
example being made is the Lloyd Loom
bobbins of twisted paper warp (image 5). The
paper to secure the strands and prevent any
Burghley chair (image 1).
looms produce flat and continuous woven
fraying (image 9). Finally, the completed chair
material 2 m (6.6 ft) wide (image 6). The wire
is sprayed with a protective coating, which
based weaving material. The warp is made by
wefts are folded along the edge to lock the
ensures the longevity of the material.
twisting strips of Kraft paper into tight fibres
warps in place (image 7). Otherwise they
(images 2 and 3). It is coated with a small
would spread out and fall off the end of the
amount of adhesive to lock it in place. The
structural wefts.
Lloyd Loom manufacture their own paper-
weft has a metal filament along its centre.
TECHNICAL DESCRIPTION Weaving rigid textiles on a loom consists
are separated into 2 sets, which creates a
of 3 movements repeated many times;
basket weave pattern.
raising and lowering the heddle bars, feeding the weft and beating. Each strand of warp is fed through
A weft is fed into the space between the fibres and in front of the beater. The beater is a series of blunt blades that sit between
an eyelet in the heddle bar. The heddle
each fibre. They are used to 'beat' each
bars are operated individually or as a set,
weft tightly into the overlapping warp.
and are computer-guided or moved by
The weft is held in place by the beater
depressing a foot pedal. Moving them up
while the lower heddle bar moves up and
and down determines whether the warp or
the upper heddle bar moves down, which
weft will be visible from the top side. This
locks the weft between the warps. The
is how patterns are made, and they can be
process is repeated to form the next run.
very intricate. In the diagram the heddles
to drop without a parachute, saving valuable materials. Colours and patterns can be woven into rigid textiles. Like 'soft'textiles, they are treated as repeating modules. Alternatively, they can be printed on, or dyed in a solid colour.
Different types and thickness of material are combined to produce and pattern. Nearly all contemporary
DESIGN OPPORTUNITIES
structures with specific load-bearing
weaving is carried out on computer-
Woven structures tend to be
capabilities. For example, the weft can
controlled looms, which produce high
multifunctional, and there are
bind a structural warp together, as in the
quality, repeatable materials. The quality
many opportunities associated with
Lloyd Loom basket weave.
of handmade weaves depends on the
construction and application.
skill of the weaver.
Rigid textiles tend not to be as tightly
Each type of weave has a different
Handmade weaves illustrate a
major advantage, which is that a
appearance, drape and robustness.
woven structure can be designed and
woven as 'soft'textiles. Material is used
Combined with different materials,
constructed to suit a specific load
only where necessary and there is give
an endless number of structural
bearing application.
between the fibres, which makes them
properties can be achieved,This
lightweight and durable structures.They
makes woven structures suitable for
are breathable, which is advantageous
both self-supporting and reinforced
product. Laminated composites,filament
for applications such as beds and chairs,
applications. For example,food parcels
especially in hot and humid climates.
dropped in World War 11 were made by
winding (page 222) and 3D thermal lamination (page 228) exploit this
placing i woven basket inside another
property to huge advantages with 'soft'
for protection: this was durable enough
The continuity and direction of fibres directly affect the strength of a woven
fibres reinforced with rigid adhesive.
Featured Manufacturer
Lloyd Loom www.lloydloom.com
The benefits of weaving 'rigid textiles'
Case Study
according to strength requirements are weight reduction and an aesthetic that is
Strand caning
directly related to function.
The S32 was designed by Marcel Breuer and
formed. The seat back, which is the product
which applies even pressure (image 7) and
DESIGN CONSIDERATIONS
production at Thonet began in 1929 (image 1).
being made here, is steam bent and a groove
the finished seat backs are stacked ready
Hand weaving techniques, which
It is among most highly mass-produced
is cut around the front Into which the cane
for assembly onto the tubular metal frame
tubular steel chairs in history.
is fixed.
(image 8).
include rattan and wicker furniture, are time consuming and labour intensive.
The sheets of strand cane are pre-woven
The cane is hammered into the groove
Machine made weaves tend to be a
on a loom (image 2).There are many different
using a specially shaped tool (image 3).
standard pattern. Even so, there Is a wide
types and patterns, but this octagonal pattern
A spline of cane is then pressed into the
range to choose from.They are supplied
is the most popular. It is a reproduction of the
groove to secure the weave (image 4). They
as a fl at p an el. Th i s can be bent, but
traditional y-step hand caning technique.
are both locked in place with adhesive.
First of all the cane is cut into strips and
typically only tightly in i direction, or gently over a shaped mold. Forcing it into
complex profiles will push the fibres out of alignment and affect the strength and
The excess material is trimmed off and
soaked for at least 35 minutes. This is to
the spline finished off (images 5 and 6).
ensure that it is sufficiently pliable to be
The assembly is placed into a warm press,
aesthetics of the product.
The size of bend is determined by the type of material. Some materials, such as cane, can be bent to very tight angles.
Other materials arenotso pliable and may split.These shapes have to be woven
into a 3D shape by hand, or by joining panels of material.
Many of the materials used in rigid weaving are natural and so need to be protected from the elements. This is often done with a clear or coloured spray
coating (page 350).
COMPATIBLE MATERIALS Woven furniture was traditionally handmade using natural fibres such as rattan, willow and bamboo. Mass production methods can also produce
ENVIRONMENTAL IMPACTS
continuous woven materials from metal,
This process creates products with
paper, plastic and wood.
minimal materials. Hand weaving
methods traditionally use locally grown
COSTS
materials and so do not require the
There are no tooling costs unless the
transportation of raw materials over
weave is formed over a mold. Even then
large distances. However, these practices
the tooling costs tend to be low.
are becoming less common.
Cycle time depends bn size, shape
The mechanical join is formed by
andthecomplexityofthewe ave or 3 D
intertwining materials.Therefore, there
product.
are no chemicals, toxins or other hazards
Labour costs tend to be high because
ahigh level of skill is required. Weaves made by machine and then upholstered onto products require less labour, but still require highly trained operators.
associated with melting, fusing, or
otherwise altering materials to join and Featured Manufacturer
shape them.
Thonet
Most waste is either biodegradable or
www.thonet.com
capable of being recycled.
r
Machine Stitching Process Scarf
CD
t
Tee
1
Overlap Presser fool
Needle 1
Needle bar
Joining Technology
Upper thread
Upholstery
Layered textile or leather
Upholstery is a highly skilled process and the quality of Feed dog
craftsmanship can set products apart. It is the process of
Lower thread
Shuttle hook
bringing together the hard and soft components of a piece of
Bobbin
furniture to form the finished article. Stage 1: Pick-up Stage 2: Loop Stage 3; Finish
TECHNICAL DESCRIPTION
\ • \ Quality
I
• Very high quality that depends on the skill of the upholsterer and type of material
Related Processes • Steam bending • Weaving • Wood lamination
Speed • Moderate to long cycle time depending on size and complexity of product
\
\
^ X ^ \ \ ^
Machine stitching is a simple form of
The needle pierces the layers of material
mechanical joining that requires a complex
and stops momentarily. In stage 2, a spinning
process of making stitches from a single
series of operations to execute. There are
shuttle hook picks up the upper thread.
thread. The downfall of this method is that
3 main types of machine sewing: lockstitch,
The shuttle hook loops behind the lower
if the thread is broken at any point it readily
chain stitch and overlock. The diagram
thread, which is held under tension on the
comes apart.
illustrates lockstitching, which is used to
bobbin. In stage 3, as the shuttle continues
join the leather cover in the Boss Eye chair
to rotate, tension is applied to the upper
of finishing the edge of fabric with multiple
thread, which pulls it tight, forming the next
threads. It protects the fabric from fraying
case study.
INTRODUCTION Atypical upholstered chair consists of
Nowadays, the padding is polyurethane (PUR) foam. It is either
a structural frame, foam padding and a
molded using the RIM process (page 64)
textile cover. Sofas and lounge chairs may
or cut and glued tog ether. Modern foams
RELATED PROCESSES
also have a sprung seat deck. Springs are
have reduced the need for sprung seat
There are many processes used in the
mounted onto the frame or suspended
decks, and many contemporary sofas and
upholstery procedure. Wooden frames
within it.There are 3 main spring
lounge chairs no longer have springs.
tend to be laminated (page 190), steam
systems: 8-way hand-tied, drop-in and
Instead, foam density is designed to
sinuous springs.
provide maximum comfort.
Hand-tied springs are the most
The covering is fabric or leather and
seats and interiors, break out seating and padded walls.
by casting a net of interlocking stitches over
process. The needle and shuttle hook are
forward, catches the fabric and pulls it into
the edge.
synchronized by a series of gears and shafts,
place for the next drop of the needle. The
powered by an electric motor.
fabric is supported between the presser foot
In stage 1, the upper thread is carried
and feed dog. Industrial sewing machines
through the fabric by the needle, and
can repeat this sequence over 5,000 times
the lower thread is wound on a bobbin.
every minute.
bent (page 198) or CNC machined (page 182). Metal frames are bent (page 98) or cut and welded (page 308).The cover is
QUALITY
Right With a highly skilled
The look of the upholstery is largely
expensive and considered superior. Using
is permanently fixed to the padding and
cut out on a CNC x- andy-axis cutter, or
underlying framework.
by hand, sewn together and glued and
dependent on the skill of the upholsterer.
stapled onto the foam and framework.
The comfort is determined by the quality
accurately placed stitches per minute.
TYPICAL APPLICATIONS
The foam padding is either molded
Upholstery is used extensively in
over the framework, or cut and glued
of foam and springs, while the longevity of the product is affected by the rigidity
furniture and interior design. It is
onto it. The choice of RIM is not solely
and strength of the framework.
used to make 'soft'furnishings for the
dependent on quantities because certain
names suggest: drop-in springs are
automotive,marine, home, office and
shapes cannot be produced feasibly in
DESIGN OPPORTUNITIES
a prefabricated unit fixed into the
transport industries.The materials
any oth er way an d h ave to be m ol ded.
The density and hardness of foam can be
framework, and sinuous springs are
for each of these applications will
continuous lengths of steel wire bent
vary according to the likely wear and
mesh stretched over the framework,
or leather cover is adhesive-bonded to
into's' shapes and fixed at either end.
environmental conditions.
wooden, plastic or metal slats, injection
the foam, so undercuts and overhangs
stretched across it and the springs are hand-tied to the webbing up to 8 times. Drop-in and sinuous springs are machine-made.They are as their
The structural framework is generally
Typically, upholstered products
fabricated in wood or metal. Its strength
include lounge chairs, sofas, task and
determines the durability of the product.
office chairs, car seats and interiors, boat
Alternatives to upholstery include
Overlocking, or serging, is the process
stitch. Meanwhile, the feed dog progresses
Lockstitching is a mechanized
them increases cycle time considerably. A wooden box is fabricated, webbing is
Chain stitching, or loop stitching, is the
chosen to suit the application. The fabric
molding (page 50), weaving (page 332)
can be upholstered. Shape limitation
and wood lamination.
is determined by what can be cut and shaped in the textile; single axis curves
operator, an industrial sewing machine can produce over 5,000
Left The distinctive relief pattern of this button tufted Chesterfield
reduced due to increased buying power.
leather sofa is created
Labour costs tend to be high due to the
by pinning the leather cover to the support
level of skill required.
Batch production does not reduce the labour costs,but material costs may be
Upholstering with cut foam These images illustrate a technique for
This case study shows upholstering the
upholstering foam-padded chairs. An
Neo chair using the cut foam technique.
ENVIRONMENTAL IMPACTS
example of a chair produced in this way
The structure is laminated wood (image 2),
Upholstery is the culmination of
is the Sona chair, designed by Paul Brooks
onto which the foam is bonded (images 3
many processes and as a consequence
(image 1). Production began in 2005.This
and 4). The covering material is stretched over the foam and stapled onto the plywood
structure.
Fabrics come on rolls that are typically
Case Study
multiple axis curves require elastic
1.37 m (4.5 ft) wide. Leather comes in
a typical sofa will include many different materials that have varying
technique is suited to geometries that have a constant wall thickness; RIM is more
substrate. Each panel Is made up in this
material or 2 or more pieces of material
various sizes: for example, cow hides
environmental implications.
cost effective for complex and undulating
way and then fitted together to conceal the
stitched together.
range from 4 m2 to 5 m2 (43-54 ft2) and
shapes such as the Eye chair.
inner workings of the chair.
sheep skins can range from 0.75 m2 to
The choice of covering material will affect the environmental impact of
1 m2 (8-10 ft2).
the product. For example, the William
are easily covered with textile, whereas
Each product has to be upholstered individually and so manufacturers are often prepared to run single colours,
The choice of covering material is an
McDonough collection of fabrics
or short runs of colour. The textiles
important factor in determining the unit
available are as varied as the clothes you
price. High value materials, such as high
and manufactured in a closed loop
wear. Different weaves and materials
quality leather from a top supplier like
industrial process. Many leather
have varying levels of durability, andthe
Elmo Leather in Sweden, can double the
materials have to go through a series
toughness of the covering is determined
price of the product
of potentially environmentally harmful tanning and dying processes before they
example, a domestic lounge chair may be
COMPATIBLE MATERIALS
can be used in upholstery. By contrast,
used for only 3 or 4 hours on an average
The area of application, such as
Elmo Leather produce a chrome-free
day, whereas break out areas in offices
automotive, marine, domestic, office,
leather called Elmosoft.There are no
will see much heavier usage.
education, healthcare or public
hazardous substances used in the
Fabrics have varying levels of elasticity and bias. Slightly elastic fabrics reduce
transport, determines the specification
production process.
by the application of the product. For
the number of pieces required to cover
of uphol stery m ateri al. Contract grade materials suitable
produced by Designtex is biodegradable
upholstering with leather,! reason why
for high wear applications include
used on convex shapes because they will
polyamide (PA) nylon, thermosetting
shapes can be nested very efficiently on
bridge concave profiles.
and thermoplastic polyester, synthetic
fabric, producing only 5% waste, whereas
leather polyurethane (TPU), polyvinyl
leathermayhaveimperfectionsthat
it is so much more expensive.The net
in a number of different ways. Possible
chloride (PVC),polyproylene (PP) and
cause up to 20% waste. Offcuts can
details include button tufting, beading
other hardwearing fibres.
sometimes be used in furniture with
and twin stitching.
General upholstery materials for low
o
A lot more waste is produced when
a 3D shape. However, they can only be
Upholstered covers can be finished
c
~D nr
smaller pieces, or gloves.
wear applications include leather, flock,
DESIGN CONSIDERATIONS Whatever the design, it must be possible to cut and stitch a fabric shape that will
raffia, mohair, cotton and canvas.
Outdoor application materials have to withstand exposure to the elements
cover it.There are various techniques
and ultraviolet light. Examples include
used to conceal the open end of the fabric cover. Conventionally, the fabric
synthetic leather TPU and polycarbonate (PC) coated materials.
cover is pulled on and the edges stapled onto a single face, typically the bottom or
COSTS
back of the product. This is then covered
There are no tooling costs in this process,
with a separately uph ol stered pan el.
but there may be tooling costs in the
Concave shapes can be upholstered, but the cover will need to be secured in place with a panel, pins, ties or adhesive to maintain the cover in place.
RIM foam process and for any wood laminating or steam bending.
Cycle time is quite long but depends on the size and complexity of the piece.
Featured Manufacturer Boss Design www.bossclesign.co.uk
Upholstering a RIM foam chair The Eye chair was designed by Jackie Choi for
inside for additional strength. Many different
Boss Design and production began In 2005.
stitch patterns and details can be applied;
process requires a great deal of patience; the
It is covered with fabric or leather (irnage 1).
this is twin stitch. The patterns are carefully
heat from the steam softens and activates the
The polyurethane foam is made by Interfoam using the RIM process. The foam has a metal structure for support and plastic
designed so that the seams line up with the
adhesive, so that as the cover is gently pushed
corners of the chair.
into the desired shape, the adhesive bonds to
Once the leather patterns have been
or wooden panels to which the covering
assembled, the cover is pulled over the
material can be fixed.
foam inside out and sprayed with adhesive
Upholstering this product is a timeconsuming and highly skilled operation. First of all, the foam is coated in a thin film
(image 6). The adhesive is not sticky at this point because it is triggered by steam. The cover is removed and fitted onto the
of adhesive (image 2) and covered in soft
foam (image 7). It is stapled in place using the
polyester or down lining, which helps smooth
plastic panels molded into the product
over imperfections and gives the surface a
for this reason (image 8). Another panel,
better feel (image 3). Meanwhile, the leather is prepared by a pattern cutter (image 4), who carefully has to work out the least wasteful arrangement of
steam and a soft cloth (images 10 and 11). This
upholstered separately, snap fits onto the plastic panel to conceal the trimmed edges (image 9). The leather cover is now securely in
patterns on the sheet. If possible, the patterns
place. However, there are undercuts to
are cut from a single skin and stitched
which the cover must be bonded if it
together (image 5). A tape is sewn on the
is to retain its shape. This is done with
the foam overhang.
The final chair is inspected prior to packing and shipping (image 12).
Fixing Methods
TECHNICAL DESCRIPTION Various fixing methods are used
4
in timber frame construction to
accommodate different joint types and access to them. They are generally
Joining Technology
semi-permanent, and so can be
Timber Frame Structures
removed if necessary.
Nailing is used for tee and overlap joint configurations. It is always
Large-scale timber frame construction uses a variety of fixing methods. Softwood and engineering timber structures can span large gaps. Amongst other applications, they are used for house
preferable to nail through the thinner
INTRODUCTION Timber frame structures are used in
Straight nailing
Skew nailing
Nail plates
factory-made low-rise buildings, interior
advantages. Generally, two-thirds of
structures, roofs, large enclosures and
the nail shank should penetrate the
freestanding structures.There are
building because construction is fast and efficient.
Costs
Typical Applications
Suitability
• No tooling costs • Moderate unit costs, depending on complexity
• Temporary structures • Theatre and film sets • Timber frame housing
• One-off to medium volume production
lower material.
many standard products, including
The strength of a nailed joint is
roof and attic trusses, wall panels and
determined by the angle at which the
floor cassettes. Bespoke structures are
nail intersects the grain because wood
manufactured for each application,
is anisotropic. The nail shank parts the
which m ay h ave different fun ction al
grain as it is forced into the wood. The Bolts
and decorative requirements.
Framing connectors
Related Processes
Speed
• Lightweight and long lasting
• Joinery
• Moderate cycle time (5-30 minutes per frame)
grain contracts around it, forming a
tight grip. Nailing into end grain is the
Engineering timbers utilize the Quality
material and into the thicker material.
This provides obvious mechanical
strength and stability of laminated wood
and exhibitions), permanent and large-
of wood is harnessed and dimensional
weakest, and nailing across the grain
and include plywood, oriented strand
scale structures (including airports,
stability achieved by laminating
is strongest.
board (OSB), laminated strand lumber
government offices and residential
layers with strong adhesives to form
(LSL), parallel strand lumber (PSL) and
housing), and interior structures (such
composite I-beams. These materials
as stairwells, warehouse conversions and
are used in a variety of combinations
wide spanning floors and ceilings).
to produce lightweight structures,
engineering timbers (page 190). Like other natural materials, wood has unique characteristics associated with
visual patterns (growth rings), smell,
Nail plates are effective for tee and butt joints. They are steel plates that have been stamped to form a rack of short nails. Even though these do
not penetrate deep into the material they are strong due to the number
engineered to precise requirements.
RELATED PROCESSES
touch, sound and warmth. The finish can
A variety of softwoods are used, and
Joinery (page 324) and timber frame
be exposed to make use of its sensual
each piece is strength graded. Structural
structures overlap. Joinery tends to use
qualities, or concealed, depending on the
designers select timber strong enough
adhesives and wooden fixtures, whereas
requirements of the application.
preparation. They are not self-tapping,
for each application.
timber frames use metal fixtures for
DESIGN OPPORTUNITIES
pre-hole slightly larger than the shank.
Buildings and other large-scale structures are simulated in CAD
speed and ease of manufacture. There are 2 main housing alternatives
of nails. They eliminate the need for overlapping joints. Bolts tend to require more joint like screws and nails, so require a
There are many reasons for building
However, they tend to be stronger than
software. They are tested for load-bearing
in the UK construction industry, which
with timber: it has a low environmental
other fixing methods because they grip
stren gth an d 1 ocation -specifi c factors
are masonry and steel framework. The
impact, it is lightweight and strong, it
the joint from both sides.
such as wind speed.
choice of material will determine the
is inexpensive and each piece is unique.
method of construction. Timberframe is
It can be shaped using similar processes
to plastic and metal, but will always
As technology in this area progresses,
steadily becoming more popular in the U K due to its beneficial environmental
so does the range of applications.
impact and the speed of production.
APPLICATIONS
Approximately three-quarters of the
retain natural qualities. Timberframe construction is not limited to a range of standard products.
An alternative method for tee
joints in load-bearing applications is framing connectors. These are bent
metal fixings nailed in place to provide support in the critical areas and reduce stress on the joint. They are similar to
a housing joint (see Joinery).
world's housing construction is timber.
QUALITY
Many structural designs have been
Timber frame is the most popular form
Wood is a natural composite made up
refined to give optimum performance,
of construction in countries with cold
of lignin and cellulose.This has many
but this does not limit the designer with
climates because it is such afast and
advantages, but means that designs
regard to size or shape. Manufacturers
efficient method of building.
need to accommodate dimensional
have to accommodate a range of
applications, especially near the coast,
changes as a result of variation in
products, so there is little cost difference
stainless steel fixings should be used
constructed houses, theatre and film sets,
moisture content. In timberframe
between making 10 or 100 identical
to avoid corrosion, which can cause
temporary structures (such as pavilions
construction, the strength and lightness
products using this process.
staining and ultimately joint failure.
Some typical products include factory-
Metal fixtures come in a variety
of finishes. They tend to be made in carbon steel, which is galvanized for improved longevity. For exterior
DESIGN CONSIDERATIONS
Case Study
Designed properly, wooden structures
Constructing a timber frame building
can achieve large spans.They are capable of bearing significant loads, even in
iiii
The load bearing structure of this 4-storey
plates are placed on either side of the joint
rigidity to the framework and maximizes its
be taken to ensure correct support to
timber frame house (image 1) is the
(image 3). Each Joint is placed in a hydraulic
strength without adding too much weight.
reduce stress on load-bearing joints. For
woodwork. It is being clad with a masonry
press, which force the nail plates into the
example, there are guidelines for drilling
skin, which does not come into contact
timber (images 4 and 5). Once the joints are
lightweight I-beams, which are a composite
with the timber framework; there is a cavity
assembled they are pressed simultaneously.
of LVLandOSB (image 10). They can span
between them.
Each piece has been strength tested to verify
distances up to 7.5 m (24.6 ft). They are fully
its structural integrity and thus its location in
assembled in the factory and then dismantled
the framework (image 6).
into units for transportation.
cantilever configurations. Care must
holes, which weaken structures. Wood is anisotropic and is stronger
The structure of the building is
along the length of its grain than across.
manufactured as flat panels off-site in a
It can only be used for load-bearing
factory. The pine struts for the roof and
applications in low-rise construction,
although it is capable of carrying significant load and has been used in the UK for up to 7 storeys.
The wall panels are nailed together using
Floor cassettes are assembled using
The units are brought together on site
attic trusses are cut to length in preparation
pneumatic guns (images 7 and 8). Once again,
and assembled very quickly (image 11). Each
(image 2). They are assembled according to
all of the wood is cut to length and packaged
floor takes approximately 1 day to construct.
the requirements of the drawing, and nail
as a bundle for assembly. The assembly
Framing connectors are used to tie the
process is computer-controlled and
I-beams together (image 12). They are also
adjusts the bed and clamps to fit each
used to tie timber beams into masonry and
on the combination of the frame and
part.The operator and machine work
steel framework.
th e skin. Th erefore, pan el s ten d to be
together nailing the joints.
The strength of timber panels relies
con structe dflatandthenfixedtogether
The strength of these panels is
to form 3D structures.
achieved with a combination of timber
The size of mechanical fixture is
frame and an OSB skin, which is nailed onto 1 side (image 9). The skin contributes
calculated on CAD software to ensure adequate support. Generally, nails are
used for tee and butt joints, while bolts are used for overlapping joints.
COMPATIBLE MATERIALS All timber products Including softwoods, hardwoods, veneers and engineering timbers can be used.
COSTS There are no tooling costs: assembly can
be achieved with hand tools, but the industry is evolving more sophisticated CNC assembly operations. Cycle time is moderate. Each frame takes 3 to 30 minutes to construct. A typical timber frame house can be constructed on site at a rate of a floor per day, but large, complex or curved structures may take longerthan this.
Labour costs are typically high due to the level of skill and number of operators required for large construction.
over competing methods.Timber is a
embodied energy than steel and concrete
renewable material. It has lower levels of
equivalents. Timber is biodegradable,
'embodied energy'than alternatives -in
and it can be reused or recycled.
other words, it uses less energy to grow,
ENVIRONMENTAL IMPACTS
extract, manufacture, transport, install,
One of the main reasons for specifying
use, maintain and dispose of than other
timber frame construction is the
construction methods. In fact, timber
environmental advantage that it has
frame structures have up to 50% less
Finishing Technology
c o 0 U3 '¦P 03
S E
1 Q.
-I
Finishing Technology
Spray Painting Spray painting is a fast and efficient means of applying adhesive, primer, paint, lacquer, oil, sealant, varnish and enamel. The
surface determines the applicable finish and how long the process takes.
INTRODUCTION
propelled onto the surface of the base
Spray coating is the application of liquid
coat. This produces a topcoat that is
borne materials onto a surface.The
multilayered: it is rich with colour near
sprayed material generallyhasi ormore
the basecoat and almost clear on top.
of the following functions: filler, primer,
This promotes a glossy, rich and intense
colour, decoration and protection.
colour finish.
High gloss, intense and colourful
finishes are produced by a combination
The majority of spray painting is manually operated. However, there
Costs
Typical Applications
Suitability
of meticulous surface preparation,
are sufficiently high volumes in the
• No tooling costs, but may require jigs • Low to high unit costs, depending on size and paint
• Aerospace • Automotive and transportation • Consumer electronics and appliances
• One-off to mass production
basecoat and topcoat. The role of the
automotive, consumer electronics and
base coat is to supply a monotone
appliance industries to justify robotic
backdrop for the high gloss topcoat. The
spraying systems.
Quality
Competing Processes
Speed
topcoat is clear and contains platelets
• Variable because it depends on the skill of the operator
• Hydro transfer printing • Powder coating • Vacuum metalizing
• Variable cycle time, depending on size and drying or curing time
the basecoat, the platelets or flakes are
or flakes of colour. As it is applied to
TYPICAL APPLICATIONS Spray painting is used in a vast range of applications including prototyping, repairs, low volume and mass production. It is used in the automotive industry for painting metalwork, and in the consumer electronics industry to colour plastic injection moldings.
COMPETING PROCESSES Powder coating is a dry coating
technique (page 356) with a finish similar to 2-pack thermosetting paints
Above
(see technical description, page 353). It
aluminium.The aluminium is locked
These swatches are a
produces a uniform and glossy coating.
onto the surface of the workpiece by a
range of Kandy colours
Some techniques are electrostatic and
basecoat and topcoat that are sprayed.
so attract the coating particles to the
It produces a highly reflective finish that
a new range of slightly
surface of the workpiece. Combined
can be tinted or coloured.
different colours.
Each basecoat produces
Colours can also be
with collection and recycling of the dry
matched to Pantone or
powder, up to 95% material utilization
QUALITY
can be achieved with powder coating.
The quality of surface finish in this process depends on the skill of the
Hydro transfer printing (page 408)
over different basecoats.
RAL reference charts.
The level of sheen on the coating is
can produce effects that were previously
operator. Spray coatings are built up
categorized as matt or egg shell, semigloss, satin or silk and gloss.
spray painted with airbrushes and
in thin layers, typically between 5 and
masking. It is a dipping process and
100 microns (0.0002-0.004 in.) thick,
reproduces patterns and print much
with the exception of high-build systems
more rapidly than spray painting.
such as combined filler-primer. It is
surface. Protective paints form a barrier
Vacuum metalizing (page 372) is essentially spray painting with pure
essential that the surface is prepared to
between the workpiece and atmosphere,
a high finish.
to prevent rusting,for example.
The surface finish may not be critical if the role of the coating is to protect the
TECHNICAL DESCRIPTION
Spray Coating Process
Spray guns are gravity fed, suction
Topcoat or lacquer
Spray mist
Paint supply
Spray gun Manually operated
as quick drying, antifouling, anti-mould or
illustrates a gravity-fed gun. They all
depends on the type and viscosity of paint.
are made up of 2 parts, the resin and the
antimicrobial properties.
catalyst or hardener. They are thermosetting and bond to the surface in a 1 -way reaction.
painting. The first is similar to the above,
controls the valve through which the
surface is prepared with filler and primer.
They are also hazardous to use because they
except that it is a mixture of paint with a high
pressurized air flows. The atomized
The primer may provide a surface onto
contain isocyanates.
level of lacquer, which produces a high gloss
paint is blown out of the nozzle and
which paint will adhere such as an acidic
makes a cone shape. Pressurized air
etch primer used to make a good bond with
pigment and a binder of acrylic emulsion,
glass, which is bonded onto the surface of
is blown out of the cap onto the cone,
metallic surfaces. Some topcoats require
vinyl emulsion or polyurethane, dissolved or
the workpiece at high temperatures (above
which forces it into an elliptical shape.
a basecoat to provide a coloured backdrop.
dispersed in water. They are applied to the
the melting point of the glass]. This limits
This gives the operator more control
Opaque topcoats can be applied directly onto
surface and dry as the water evaporates and
the finish to materials with a higher melting
because the shape can be adjusted to
the primer.
the binder adheres to the workpiece. They
point ceramics and metal, for instance.
Paints are made up of pigment, binder,
Water-borne paints are made up of
thinner and additives. The role of the binder
wood and other materials that are likely to
the surface in overlapping strokes.
is to bond the pigment to the surface being
expand and contract In their lifetime.
coated. It determines the durability, finish,
Solvent-borne paints (also known as
pot on the underneath instead of
speed of drying and resistance to abrasion.
alkyd and oil-basedl are made up of pigment
on top. The paint is drawn into the
These mixtures are dissolved or dispersed
and a binder of alkyd resin dissolved in
jet of air by suction. Pressure feed
in either water (water bornel or a solvent
thinners. Solvent-based paints are slow
systems are supplied by a paint pot
(solvent bornel. The ingredients of varnish, lacquer and
flexible pipe. The paint is pressurized
paint are essentially the same. Lacquers and
to force it into the spray gun.
varnishes can be pigmented, tinted or clear.
material.They can be replaced or
surface and so is prone to peeling and
enhanced by platelets of metallic,
to produce a cracked topcoat. Crackle
flaking.This is often the result of pinholes
pearlescent, dichroic, thermochromic or
varnish is painted over a colour. Onto this
or porosity in the coating, which allows
photoluminescent materials.
is applied a contrasting colour, typically
There is even a varnish employed
sprayed in booths that are modified
drying and off-gas polluting and harmful volatile organic compounds (VOCs).
All surface coatings are left for at least
catches the overspray and transfers it
paints and varnishes will dry in 2-4
to a central well where it settles and
COMPATIBLE MATERIALS
hours. Solvent borne products will take
separates ready for treatment.
roughly 4-6 hours.
g ol d on top of bl ack. Th e crackl e varn i sh
Almost all materials can be coated with
allows the topcoat to crack but not peel
paint, varnish and lacquer. Some surfaces
a seamless finish. Otherwise, masks and
as it dries and contracts.The effect is
have to be coated with an intermediate
because these tend to be manual
'pebbling', 'orange peeling',runs and
templates can be used to create different
similar to antique gold leaf.
layer, which is compatible with both the
processes, and the skill of the operator
sags. Pebbling is caused by a coating that
colours, patterns, logos and text. Masks
workpiece and topcoat.
will determine the quality of the finish.
is too dry; the thinner evaporates before
and templates can be made from tape,
DESIGN CONSIDERATIONS
it has had a chance to settle and smooth.
paper or cardboard for example.
The opportunities for paint effects and
only suitable for high-melting-point
ENVIRONMENTAL IMPACTS
quality are heavily dependent on the
materials such as ceramics and metal.
Solvent borne paints contain volatile
Water borne paints are prone to orange
There are many different techniques
peeling. As the name suggests, it is when
used to apply decorative effects. For
skill of the operator. With the correct
the surface resembles orange peel. It is
example, overlaying colours and tones
preparation and basecoat almost any
caused by the coating not flowing on the
using different spraying techniques
surface, or improper paint thinning. Runs
will produce graduation, shading and
and sags occur when there is too much
mottling. Marbling is achieved by
spraying applies coatings in line-of-sight,
wet coating material.
draping materials over a wet topcoat,
so deep undercuts and recesses are more
which drags and smears it over the
difficult to coat evenly. Electrostatic
DESIGN OPPORTUNITIES
basecoat. Covering it with a clear topcoat
There is an almost unlimited range of
seals in the pattern with dramatic effect
colours and finishes for paints. Standard
(see image, page 350).
colour ranges include RALand Pantone.
Colour is supplied by pigments, which are solid particles of coloured
A flock finish can be achieved by
Labour costs are typically high
Enamel paints that contain glass are
organic compounds (VOC). Since the
COSTS
ig8os automotive manufacturers have
combination of materials can be coated.
Tooling is not required. However,]igs or
been making the switch to water-based
An important consideration is that
framework may be necessary to support
paint systems to reduce their VOC
the workpiece during spraying.
emissions. It was not until the late 1990s
Cycle time is rapid but depends on the
that water-based systems were capable
size, complexity, number of coats and
of producing a finish that equalled the
techniques draw more spray to the
drying time. A small consumer electronic
previous solvent-based technologies.
surface, but there is always overspray.
product may be complete within 2 hours;
There is no size restriction. If the part
One system uses running water, which
12 hours to harden fully. Water borne
aircraft hangers.
including different materials, to produce
Some aesthetic problems include
finish. The second Is applying a coating of
are flexible and so are suitable for painting
thickness. The coating is applied onto
However, paint is not integral to the
underneath.
There are 2 different types of enamel
up of more than 1 layer. If necessary the
that is connected to the spray gun via a
Entire surfaces can be painted,
Painted surfaces are nearly always made
the paint into a fine mist. The trigger
Suction feed guns have the paint
the surface of the workpiece to corrode
Additives provide specific qualities such
emerged. They are so called because they
suit the application and required film
Rotating table or support jig
Another type of paint, 2-pack, has
approximately 3.45 bar (50 psi). This
use a jet of compressed air to atomize Workpiece
Conventional spray guns operate at
fed or pressure fed. The diagram
in contrast, a car may take several days.
Water-based paints are less toxic and easily cleaned with water.
will not fit in a spray booth or cannot be
Automated spraying techniques are
spraying adhesive followed by fibres of
moved then it can be sprayed on site.
very rapid. The parts are sprayed as the
booth or cabinet to allow the paints
cotton, paper, silk or similar material.
For example, very large aeroplanes are
productis assembled to avoidmasking.
to be recycled and disposed of safely.
Spraying is usually carried out in a -
Case Study
Spray painting a Pioneer 300 light aircraft Thfs is the Pioneer 300 (image i).The kit
In total 3 coats are applied and left to
is masked and the second topcoat colour
dry (image 5). The length of the drying tie
is applied (images 10 and 11).The finished
Aviation, Italy (image 2). The fuselage is
depends on the cure system. Once the primer
fuselage is assembled (image 12), ready for
assembled prior to spray painting. The joints
is sufficiently dry, the fuselage is rubbed
the wings.
between components are filled and rubbed
down with abrasive paper (image 7). Painting
down to make a smooth surface for the
several coats and then abrading the surface
primer. Masking is used to protect the glass
produces a much smoother finish. More coats
components are manufactured by Alpi
hood and areas of the bodywork (image 3). A 2-pack polyurethane paint is used to prime the surface. All paint sprayed in this way has to be filtered to make sure that there are no lumps, dust or other contamination
of primer are required if the finish is not good enough at this stage because the topcoat will show up every imperfection.
In preparation for the topcoat the top layer of masking tape is removed
that might block the spray nozzle (image 4).
(image 8). Underneath is a second layer
The first coat is sprayed on in overlapping
of masking,whichmarkswhere the
strokes (image 5). Each stroke is overlapped
topcoat will be sprayed up to. The edges
by about 50% to ensure a uniform coating.
are staggered in this way to avoid a build
The whole process is carried out in a
up of paint; otherwise the primer would
spray booth that cleans and circulates the air
produce a visible white line along the
continuously. It takes only a few minutes for
masked edge.
the giant fans to remove and replace all the air in the booth.
The topcoat is applied (image 9) to each component. The 'racing' stripe
Fluidized Bed Powder Coating Process
Electrostatic Spraying Process
Layer of powder builds up
Finishing Technology
Powder Coating
r
\
Electrically grounded metal workpiece
r
I'
This dry finishing process is used to coat a range of metalwork
Electrically grounded workpiece
Spray guns
by either spray or a fluidized bed. The powder adheres to the
Airflow through powder
Charged spray nozzle (-) Layer of powder builds up
Plume of electrostatically charged powder
workpiece electrostatically and is cured in an oven to produce a
Voltage I
glossy protective coating.
1 No tooling costs Low unit cost
Typical Applications
Suitability
a uniform finish.This is because the
• Automotive • Construction • White goods
• One-off to mass production
airborne orfluidizedpowderis drawn
TECHNICAL DESCRIPTIONS ELECTROSTATIC SPRAYING
FLUIDIZED BED POWDER COATING
to and adheres to the surface of the
Powder coating materials are made by
The fluidized bed technique is used
workpiece electrostatically.There is
blending together the ingredients; resin,
to apply plastic coatings to parts
greater electrical potential difference
pigment, filler and binder. The mixture
both with and without the addition of
where the coating is thinnest, which
is then ground into a fine powder so that
electrostatic energy.
encourages the powder to build up in a
each particle contains the necessary
uniform manner.
ingredients for application.
Quality
Related Processes
Speed
• High quality, gloss and uniform
• Dip molding (as a coating) • Galvanizing • Spray painting
• Rapid application depending on size of part and level of automation • Curing takes 30 minutes or more
Thermoset coatings are the most
INTRODUCTION
The most common method of
RELATED PROCESSES
commonly used and have similar
Powder coating is primarily used to
application is electrostatic spraying
Powder coating is often used in
characteristics to 2-part epoxy, or
protect metalwork from corrosion and damage: the polymer forms a durable skin on the surface of the metal.
because it is more versatile. Fluidized
bed is limited by the size of the tank and colour batches, and is therefore
conjunction with other finishing processes for particularly demanding or outdoor applications. For example,
polyester paints.The baking process forms cross-links in the polymerthat increase hardness and resistance to acids
The most common powder coating
The fluidized powder is made up of the same ingredients as those used in
electrostatic spraying. In fluidized bed
technique is electrostatic spraying. In
coating, the powder is contained in a
this process the powder is suction fed
tank. Air is pumped through it to create
or pressure fed to the spray gun. Air
a powder-air mixture that is dynamic,
pressure forces it through the spray
similar to a liquid. The part is dipped into
nozzle, which applies a high-voltage
the fluidized powder, which adheres to its
negative charge to each particle. This
surface. For thermosets, the powder has
negative charge creates electrical
to be cured after dipping in the same way
potential difference between the particle
as electrostatic spraying.
Because it is a polymer there are many
most suitable for mass production
steelwork must be galvanized (page 368)
and chemicals. In contrast, thermoplastic
associated benefits such as a range of
applications such as wire rack shelves
prior to powder coating for a durable and
coatings do not cross-link when heated.
vivid colours and protective qualities that
in fridges and automotive parts. It is
long-term finish. Without galvanizing,
Instead, the dry powder coating melts
and electrically grounded workpiece. The
are engineered to suit the application.
more commonly used for thermoplastic
the steel would rust beneath the powder
and flows over the surface as it warms
electrostatic force draws the plume of
thermoplastic coatings. The workpiece
Furthermore, it is a dry process that has
powder coatings.
coating, causing it to blister and flake.
up. Cooling re-solidifies the polymer to
powder towards the workpiece, causing
is pre-heated to just above the melting
produce a smooth and even coating.
it to wrap around and lightly coat the
temperature of the thermoplastic and
reverse side. The negatively charged
dipped into the fluidized powder, which
DESIGN OPPORTUNITIES
polymer powder adheres to the workpiece
adheres to the surface of the workpiece
These processes are used to provide
with static energy. All parts of the
on contact. In this way, thick coatings can
alayer of protection, often with the
workpiece must be exposed to the stream
be applied in a single dip or with multiple
addition of col our. There are many
of powder to ensure a uniform coating.
dips. Thicker coatings provide a greater
low environmental impacts.
Alternatives to powder coating
TYPICAL APPLICATIONS
include wet spray painting methods
the 1960s for in-line coating aluminium
Powder coating is suitable for both
extrusions (page 360) such as window
functional and decorative applications.
(page 350), especially 2-part thermosetting paints which are
frames. Architects and designers enjoyed
Functional applications include
extremely durable.These techniques are
Powder coating was developed in
the possibilities of powder coating and so
products for abrasive, outdoor and
m ore suitabl e if a vari ety of m ateri al s are
demand increased for powder coating on
high-temperature environments
being coated, or if the materials cannot
other metal s, in cludin g steel. Currently, aluminium and steel are the most widely
such as automotive, construction and agricultural parts. Powder coating is also
withstand the high temperatures in the powder coating baking process.
associated benefits, especially for application in children's play areas or publ i c furn iture, for exam ple.Therange
powder coated materials, but many other
used in white goods that demand good
materials are being explored that could
temperature and chemical resistance.
QUALITY
speckled, textured and wood grain
benefit from a powder coated finish,
Other than that, it is used a great deal for
The polymer coating is baked onto the
finishes are possible.
including plastics and wood composites.
parts of indoor and outdoor furniture,
workpiece in an oven, which produces
The powder can be applied as an electrostatic spray or in a fluidized bed.
domestic and office products.
of colours is unlimited and even metallic,
As well as pigments, many other
a glossy, durable and tough finish. By its
additives can be mixed into the powder.
very nature, powder coating produces
Additives are used to improve the
The whole process takes place in a
spray booth. The parts are generally fed into and out of the booth on a conveyor
It is frequently used to apply
level of protection as well as smoothing over rough surfaces and joints.
This technique, without the addition of
belt, which provides the electrical
electrostatic energy, improves the coating
grounding. After spraying, the workpiece
of wire racks and other parts that cause
is baked in an oven at approximately
problems during electrostatic spraying
200°C (392°F) for 30 minutes or so.
due to the 'Faraday cage' effect.
Case Study
Electrostatic spraying a gate In this case study, Medway Galvanising are
the factory. The operator is protected as he
powder coating some previously galvanized
sprays a plume of electrostatically charged
steelwork. Preparation is key to the success
powder over the metalwork (image 4).
of the finish. First of all, the parts have been
The powder coated finish is very
galvanized (page 368) to protect the base
delicate at this point, so handling is kept
metal, which is then sanded to produce an
to a minimum. The part is loaded onto a
even higher quality finish (image 1).
conveyor that takes it through a camelback
The cleaning process consists of a series of 10 baths that progressively clean,
oven (image 5), The temperature inside the oven is 2000C (392°F).The part is heated
degrease and prepare the surface for
as it is conveyed up and over the heating
powder coating. A bath of zinc phosphate
compartment, hence the name. At this
(image 2) provides an intermediate binding
temperature the thermosetting polymer
layer between the clean galvanized surface
chemically reacts, forming cross-links
and the thermosetting powder.
between the molecular strands to produce
The metalwork, in this case part of a
a very durable and tough coating. It is a
steel gate, is loaded onto an electrically
gradual process and lasts 30 minutes or so.
grounded conveyor belt that delivers it
The cured part has a rich-looking red
into the powder-coating booth (image 3).
plastic coating (image 6). It is still very warm
This process is manually operated, due to
and is left to air dry for a short period while
the level of versatility that is required in
the thermosetting plastic fully hardens.
coating's UV stability, chemical
time consuming and less practical.Thin
not prepared effectively. Preparation
hardness and durability. Certain grades
resistance, temperature resistance and
films can be very difficult to achieve, especially with electrostatic methods
consists of anumber of cleaning and
offer added protection against UV.
durability, for example. Antimicrobial additives can also be incorporated, which
The choice of thermoplastic and
Thermoplastic powders include
and thermosetting powders.
for powder coating.These stages are essential to produce a sufficient bond
polyethylene (PE), polypropylene (PP), polyamide (PA), polyvinyl chloride (PVC),
DESIGN CONSIDERATIONS
between workpiece and coating to
fluoropolymers and many more. These
Part design will affect the choice
ensure its longevity.
coatings make up a small percentage
inhibit the growth of mould, mildew and bacteria on the surface of the coating.
etching baths, which ready the surface
thermosetting powders provides
of technique. Each technique is
designers and manufactures with a large
generally suited to different materials:
of the powder coating market. They
COMPATIBLE MATERIALS
scope of opportunity.The coating can be
thermoplastic powders are coated
Many metals can be coated in this
can be built up in thick layers using the fluldlzed bed method to provide superior
engineered with additives, binders and
using the fluldlzed bed technique and
way. However, the majority of powder
performance characteristics.
pigments to suit a specific application if
thermosets are electrostatically sprayed.
coating is used to protect and colour
the volumes justify It. Otherwise, there
But this is not always the case.
aluminium and steelwork,Technologies
COSTS
higher with powder coating than wet
are emerging that make it possible
There are no tooling costs, although
that can be utilized in standard powder-
and widely used process. Most parts
to powder coat certain plastics and
equipment costs are relatively high.
coated finishes.
can be coated in this way. Fluldlzed
composite wood panels, although they
bed coating offers improved coverage
Is a vast range of polymer characteristics
There is very little risk of powder
Electrostatic spraying is a versatile
coatings running into sags In either
on complex and intricate geometries,
technique, even when a heavy build up
especially if they will cause the 'Faraday
is required.The thickest coatings can be
cage' effect in electrostatic spraying.
achieved with fluldlzed bed techniques,
Surface finish is determined by the
ENVIRONMENTAL IMPACTS Material utilization tends to be much
spray painting methods. This 1s partly due to electrostatically charging the particles, but also because It Is possible
One coat is usually sufficient, so cycle
to collect and filter powder overspray.
are new and relatively specialist. It is
time is very rapid. The baking process to
Production lines powder coating with
also possible to powder coat glass by the fluldlzed bed method.
cure the resin adds approximately half
continuous colour can achieve over 95%
an hour to the cycle.
powder utilization.
The coating materials include
This is a simple process: powder is
Everything requiredforthe coating
th erm opl asti cs an d th erm osets. Typi cal
easy to spray and the potential electrical
is contained in each particle: resin,
which can be built up by dipping a hot
quality of the finish prior to coating,
thermosets Include epoxy, polyester,
difference actively encourages a uniform
pigment, filler and binder. Therefore It is
workpiece several times In thermoplastic
unless a very heavy coating is produced
acrylic and hybrids of these polymers.
coating to develop.Therefore, labour
not necessary to suspend the powder in a
powder. Electrostatic spraying can also
in a fluldlzed bed. Castings, for example,
They are characterized by good resistance
costs can be quite low.
solvent or water, which can be harmful to
produce thick coatings, but it Is more
will produce a textured finish if they are
to chemicals and abrasion, andtheir
Featured Manufacturer Medway Galvanising Company www.medgalv.co.uk
the operator and environment.
Anodizing Process
s
'{r
£ Cathode (-) Workpiece: anode
TECHNICAL DESCRIPTION
The surface of aluminium, magnesium and titanium can be
Anodizing has 3 main stages: cleaning
anodized to form a protective oxide layer. It is naturally light
Dilute sulphuric acid electrolyte
U
OOC COC
y
and etching, anodizing and sealing.
In stage 1, the cleaning and etching
grey, but can be electrolytically coloured, or dyed, with a range of
baths prepare the workpiece for anodizing. The surface is either etched
vivid colours including red, green, blue, gold, bronze and black.
Stage 1; Cleaning and etching
Stage 2: Anodizing
Stage 3: Sealing
or brightened in chemical baths. Etching produces a matt or dull finish and minimizes preparatory operations. Costs
Typical Applications
Suitability
Brightening (chemical polishingl
15 minutes to produce 5 microns
colour is produced by light interference.
• Tooling is not usually necessary • Low unit costs, but increasing with film thickness
• Architectural • Automotive • Consumer electronics
• One-off to high volumes
produces a very high gloss surface
(0.00019 in.) of anodic film.
An alternative technique uses tin instead
suitable for decorative applications. Alkali
Quality
Related Processes
Speed
• High quality, lightweight and very hard
• Powder coating • Spray painting
• Moderate cycle time (approximately 6 hours)
Hard anodizing produces films up to
of cobalt. This is popular, but the colour is
surface of the metal. In doing so, a small
less resistant to UV light than the Anolok™
neutralize each other.
amount of base material Is consumed
system. The third technique is known as
In stage 2, the anodizing takes place In
INTRODUCTION
Anodizing adds an anodic film to the
and acid baths are used in succession to
(roughly half the thickness of the anodic
'dip and dye'. In this, the colour is created by
an electrolytic solution, which is generally
film). This will affect the roughness of the
simply dying the anodic film prior to sealing.
dilute sulphuric acid. A current Is passed
surface. Only thin coatings will retain a high
This process can produce the widest range
between the workpiece (anode) and
gloss finish and these are therefore not
of colours, but it Is the least UV stable and
of these processes include building up
electrode (cathode). This causes oxygen
suitable for high-wear applications.
Colour is applied In 3 main ways. The
consistent, so is generally only used for
Anodizing refers to a group of processes
50 microns (0.0020 in.) thick. It is used for
thick layers, a wide colour range and how
to gather on the surface of the part, which
that are used to treat the surface of
more demanding applications because
easily they can be repaired.
reacts with the base metal to form a porous
Anolok™ system, recommended for outdoor
metals. The workpiece is made the
the thicker film Improves wear and
oxide layer (aluminium produces aluminium
applications, is an electrolytic colouring
Is sealed in a hot water bath. Sealing the film
oxide). The length of time in the bath, the
process. A range of colours are created by
produces the hardwearing and weather-
anode and submerged in an electrolytic
temperature resistance.
temperature and the current determine the
depositing cobalt metal salts in the porous
resistant characteristics that are associated
rate of film growth. It takes approximately
anodized surface prior to sealing. The
with anodizing.
are relatively expensive metals and are selected for their superior strength
solution.The process builds up the naturally occurring oxide layer on the
Aluminium, magnesium and titanium
TYPICAL APPLICATIONS
to weight ratio. Anodizing improves
surface of the metal.The film is hard,
Anodizing Is used to protect and enhance
the material's natural resistance to
protective and self-healing; aluminium
metal for both Indoor and outdoor use.
weathering without significantly
oxide is inert and among the hardest
Indeed, most aluminium in the
increasing weight, and is therefore the
certain colour systems are guaranteed
automotive, construction,leisure and
most popular surface technology.
for up to 30 years.
strength, so electrical components can be
The appearance of the finished piece is determined by the quality of the mill finish prior to anodizing. It is Important that the material is from the same batch
mounted onto them.
materials known to man. There are 3 main methods, which are natural anodizing, hard anodizing and chromic acid anodizing. Most
consumer electronics industries is treated this way.
Well known examples include the
Chemically colouring stainless steel Is a similar process: the naturally occurring passive film on the surface of themetal is enhanced.
decorative and indoor applications. In stage 3, the surface of the porous film
Anodic films have very high dielectric
Anodizing can be applied to all types of finishes and textures, Including satin,
architectural, automotive and general
Maglite, Apple IPod and G5 Powermac.
anodizing is carried out in sulphuric
Other products Include karabiners and
acid using the natural or hard anodizing
general climbing equipment,televisions,
methods. Chromic acid anodizing is a
telephones, appliances, control panels,
Anodizing is unmatched for surface
It is not possible to colour match to
removed by laser engraving (page 248) orphoto etching (page 292).This is
more specialized process.
picture frames, cosmetic packaging, shop
treating aluminium,magnesium and
specific swatches such as Pantone.
used to create patterns, text or logos by
fronts and structural products.
titanium. It Is light, very hard, self-healing
contrasting the colour of the anodized
BeoLab 4000 speakers
and resistant to weathering.The anodic
DESIGN OPPORTUNITIES
surface with that of the base metal.
are produced by
film is Integral to the underlying metal and so will not flake or peel like some
Anodizing has many benefits Including hardness, ease of maintenance, colour
DESIGN CONSIDERATIONS
coating processes. It has the same
stability, durability,heat resistance and
Anodizing adds a film thickness to the
melting point as the base metal and
corrosion resistance, and it is non-toxic.
dimensions of the product, but the
Natural anodizing produces finishes 5-35 microns (o.oooig- 0.0014 in.) thick and grey in colour.The finish can be
RELATED PROCESSES
coloured to range of vivid shades, such as the Bang & Olufsen BeoLab 4000
Painting (page 350) and powder coating (page 356) addalayer of material to the
speakers (see image,opposite).
surface of the metal.The advantages
if it Is used together because different
QUALITY
batches will have varying colour effects.
brushed, embossed and mirror polished.
The anodic film can be selectively Above
The vivid colours of these Bang & Olufsen
anodizing aluminium.
Case Study
> Anodizing automotive trims Heywood Metal Finishers use the Anolok™
hardwearing. After this, they are sealed in
colouring system. This technique is used to
hot water with additives at a temperature
anodlze parts for exterior and demanding
of 980C (208.4°F).
applications such as in the construction and
The anodic film is non-toxic and can
automotive industries. It is distinguished
be handled immediately after sealing.
from other processes by the colouring phase:
The parts are removed from the jig and
cobalt metal salts are deposited 1n the porous
packed (image 7).
film during colouring.The colours (grey, bronze, gold and black) are produced by light interference and so are more durable and less
prone to fading than other methods. In this case, aluminium extrusions are being anodized for automotive
application (image i).The lengths are loaded onto an adjustable jig, which is set up to accommodate different lengths of metal (image 2). The parts are mounted at a slight incline to allow the chemicals to drain off during dipping (image 3). There are 10 baths in the anodizing cycle and the whole process can take up to 6 hours
(images 4 and 5). At the other end of the plant some aluminium parts are being anodized.
They are dipped into the sulphuric acid electrolyte for between 15 and 5o minutes (image 6). Longer dip times produce thicker films, which are generally more
etching and cleaning process usually
Variation in the chemical composition
ENVIRONMENTAL IMPACTS
compensates forthis as it removes about
of the metal affects the colour. This is
Waste from anodizing production
the same amount of material. However,
a concern both for welded joints and
is non-hazardous. Companies are
this will depend on the anodizing
for fabrications containing metal from
monitored closely to ensure they do not
system and hardness of the material
different batches.
because softer material will etch more
allow contamination into wastewater
This is a dipping process and so liquids
or landfill. Although acidic chemicals are
rapidly.Therefore, it is essential that the
have to be able to drain from the parts.
used in the anodizing process there are
anodizing company is consulted for parts
The maximum size of part that can be
n o h azardous by-products.
that have critical dimensions.
anodized is limited by the capacity of
The colouring process will determine
the UV stability of the part.The AnoM™
The baths are continuously filtered
the baths, and fabrications can be up to
COSTS
and recycled. Dissolved aluminium
7 x 2 x 0.5 m (23 x 6.6 x 1.6 ft).
There are no tooling costs.but jigs may
is filtered from the rinse tanks as
colouring system, which applies cobalt
have to be made up to accommodate the
aluminium hydroxide, which can be
metal salts electrolytically,1s guaranteed
COMPATIBLE MATERIALS
parts in the anodizing baths. Cycle time is
safely recycled or disposed of.
for up to 30 years in architectural
Aluminium, magnesium and titanium
approximately 6 hours.
applications, but the colour range is
can be anodized.
limited to grey, bronze, gold and black.
This process is generally automated, so labour costs are minimal.
Anodized surfaces are non-toxic.
Electroplating Process
Connected to power source (-) Connected to power source (+)
Finishing Technology
Wire jig
Electroplating
Electrically charged workpiece
QUALITY
This is an electrolytic process used to apply a thin film of metal
Electroplated films are made up of
to another metal surface. A strong metallurgical bond is formed
Electroplated metal coating
pure metal or alloys. An integral layer
between the base material and coating. Electroplating produces
is formed between the workpiece and
a functional and durable finish.
forms a strong metallurgical bond with
metal coating because each metal ion
its neighbour.
Metals that will not plate to each Costs
Typical AppUcations
Suitability
other can be joined with intermediate
• No tooling costs, although jigs may be required to support parts • High unit costs, determined by materials
• Consumer electronics • Furniture and automotive • Jewelry and silversmithing
• One-off to high volume production
layers that are compatible with both the coating and base material. For
Quality
Related Processes
Speed
• Coating material is chosen for specific qualities such as brightness or resistance to corrosion
• Galvanizing • Spray painting • Vacuum metalizing
• Moderate cycle time, depending on type of material and thickness of coating
\
and corrosion resistance of a gold
TYPICAL APPLICATIONS
is used in critical applications to improve
Electroplating is used to produce
This process is used a great deal by
conductivity and ensure a tarnish free
jewellers and silversmiths, who can form
surface finish.
replenished by dissolution of the metal anodes. The anodes are suspended in the
The thickness of electroplating
degreaslng In a hot caustic solution. Then parts are Immersed in a dilute cyanide
depends on the application of the product
solution, to remove surface oxidization,
and material. For example, nickel
the workpiece prior to electroplating.
which is neutralized in sulphuric acid.
used as an intermediate levelling layer
up to 25 microns (0.0098 in) thick,
then coat them with silver or gold to give
Electroplating is the most reliable,
are deposited on the surface of the
a bright, inert and tarnish-free surface
repeatable and controllable method
DESIGN OPPORTUNITIES
workpiece in an electrochemical process.
finish. Examples include rings, watches
of metal plating.
The main benefit of this process is
beakers, goblets, plates and trays.
electrolyte In a perforated container.
The quality of surface finish is largely dependent on the surface finish of
have suitable mechanical properties,
a combination of the properties of the
The cleaning stage consists of
and protection to the brass.
The metal coating is too thin to cover
There are many other techniques
builds up on the surface of the workpiece the Ionic content of the electrolyte Is
onto a jig to support them through the
less than i micron (0.000039 in.)
and bracelets.Tableware includes
stages, which are cleaning, electroplating and polishing. The parts are mounted
electroplating process.
parts in less expensive materials that
Electroplated metals benefit from
As the thickness of electroplating
intermediate layer is used as a barrier
on metals.Thin layers of metal,from
RELATED PROCESSES
Electroplating is made up of 3 main
electroplating. Thereto re, a nickel and provides a strong inter metallic bond
INTRODUCTION functional and decorative finishes
example, brass will affect the strength
TECHNICAL DESCRIPTION
scratches and other imperfections.
tha,t it can produce the look, feel and
used to coat materials with metal,
benefits of 1 metal on the surface of another, allowing parts to be formed in materials that are less expensive or have
Electroplating occurs in an electrolytic solution of the plating metal held in
may be up 10 microns (0.00039 in.), while electroplated gold needs to be
suspension in Ionic form. When the
only 1 micron (0.000039 In.) thick for
workpiece is submerged and connected to
decorative applications.
a DC current, a thin film of electroplating
After electroplating the parts are
forms on its surface. The rate of
finely polished (buffed) In a process
deposition depends on the temperature
known as 'colouring over'.
and chemical content of the electrolyte.
brass combines the strength and reduced
pieces that will not come into prolonged
including spray painting (page 350) with conductive paints, galvanizing (page
cost of brass with the long lasting lustre
human contact can be plated with
368) and vacuum metalizing (page
suitable properties for the application.
of silver.
rhodium or nickel for an even longer
372). Spray painting technology has been
Electroplating then provides them with a metal skin that possesses all the
is hard, highly reflective and resistant to
18 ct is 75% gold by weight; 14 ct is 58.3%
most chemicals and acids. It is used for
gold; 10 ct is 41.1% gold and 9 ct is 37.5%
improving steadily.There are now paints
desirable aesthetic qualities.
decorative applications that demand
gold. Many national standards, including
superior surface finish such as medals
the US standard, allow 0.3% negative
and trophies.
tolerance: the British standard does not.
2 materials. For example, silver-plated
It is possible to plate certain plastics in an electrochemical process. However, this
Trophies, medals, awards and other
lasting and brighter finish. Examples of electroplated plastic
The most common electroplating
is not strictly electroplating. It is a slightly
include automotive parts (gear sticks,
with high metallic content. Finishes can
different process because the finish can
door furniture and buttons), bathroom
be polished and buffed like solid metal.
only be achieved by coating the plastic
fittings, cosmetic packaging and trims on
These processes rely on the polymer
nickel, silver, gold and rhodium. Each of
mobile phones, cameras and MP3 players.
carrier within which the metal platelets
these materials has their own particular
Electroplating has many important
are suspended. Like vacuum metalizing,
properties and benefits.
with an electroless intermediate layer. This provides a stronger base for the desired material to be plated onto, but it
functional roles, such as improved levels
these surface coatings do not form a
is difficult to produce a long lasting finish
ofhygiene, ease of joining (such as silver and gold soldering) and improved
metallurgical bond with the workpiece.
because there is no metallurgical bond between the coating and substrate.
thermal and electrical conductivity. Gold
materials include tin, chrome, copper,
Gold is a unique precious metal
Silver is less expensive than the
with a vibrant yellow glow that will not
previous metals. It is bright and highly
oxidize and tarnish.The alloy content of
reflective, but the surface will oxidize
Rhodium is a member of the platinum
the electrolyte bath will affect whether
more readily and so has to be frequently
family and is very expensive. It has a long-
it has a rose or green tint. The purity of
polished or'coloured over'to maintain its
lasting lustre that will not tarnish easily
gold is measured in carat (ct), or karat
brightness. Silver's tendency to oxidize is
in normal atmospheric conditions, and
(kt) in North America: 24 ct is pure gold;
used to emphasize details by'blackening'
it in a chemical solution and then
Case Study
polishing raised details back to bright silver. This technique is often used in
-> Silver electroplating nickel-silver cutlery
jewelry to emphasize relief patterns. Nickel and copper are often used as
The quality of the finish is largely dependent
To prepare the metal for electroplating it
The electroplated parts are cleaned and
intermediate layers.They help to produce
on the smoothness of the finish prior to
is immersed in a series of cleaning solutions,
dried (image 6). At this point the finish is
a very bright finish because they provide
electroplating.These nickel-silver spoons are
including a dilute cyanide solution, in which
not a high gloss. A brightening agent is
polished to a high gloss In preparation for
the surfaces of the spoons can be seen fizzing
sometimes added to the electroplating
silver electroplating (images i and 2).
(image 4). All traces of contamination, such as
bath to produce a more reflective finish. The
polishing compound and grease, are removed.
surface is improved and finished with a very
a certain amount of levelling. If they are
built up in sufficient quantities they will
They are being coated entirely with a
cover small imperfections and produce
In this case 25 microns (0.00098 in.) of
fine iron powder polishing compound, known
a smooth layer to electroplate onto.
thin layer of silver and so they are connected
As intermediate layers they provide a
to the DC current with a loose fitting wire
silver is being electroplated onto the surface
as 'rouge'. This is applied in a buffing process
(image 3). The parts are agitated in the
(image 5). This takes approximately an hour
known as 'colouring over'to produce the
electroplating bath so they receive an even
in the electroplating bath.The whole process
highly reflective finish (image 7).
coating. If they were jigged on aframe there
is computer-controlled to ensure maximum
would be a small area left unplated.
precision and quality of surface finish.
barrier between the electroplated metal and workpiece. This Is especially useful for metals that either contaminate each other, or are not compatible. Copper is an inexpensive material for
electroplating, but tarnishes very quickly and so Is rarely used as a topcoat.
33 -a
o
DESIGN CONSIDERATIONS Parts have to be connected with a DC
¦ current to be electroplated. This can be
wired' mounted a rigid 'loose jig. Loose I done in 2 or ways: they onto are either wiring is an effective way to hold parts forlowvolume electroplating. Jigs have
a fixed point of contact, which Is visible after electroplating.This Is minimized by contacting the workpiece between 2
The plastic that is most commonly electroplated is acrylonitrlle butadiene styrene (ABS). It is able to withstand the 6o0C (i4o0F) processing temperature,
small points, or on an inconspicuous part
and it is possible to etch into the surface
of the product.
to form a relatively strong bond between
It Is possible to mask areas with
it and the electroless plated metal.
special waxes or paint so they are not electroplated.This will increase unit cost. Chrome plating was used extensively in the automotive and furniture industries. It is still used a great deal but
4
COSTS There are no tooling costs, but jigs may
ENVIRONMENTAL IMPACTS
be required to hold the parts In the tank.
Many hazardous chemicals are used in
Cycle time depends on the rate
all of the electroplating processes.These
Is steadily being replaced, due to the
of deposition, temperature and
are carefully controlled with extraction
heavy metal content of the process. At
electroplated metal. It Is approximately
and filtration to ensure minimal
present there is nothing to compete with the brightness and durability of chrome
25 microns (0.00098 in.) perhourfor
environmental impact.
silver and up to 250 microns (0.0098 in.)
electroplate onto a nickel basecoat.
per hour for nickel.The rate of
microns, and these processes apply only
Similar levels of reflectivity can be
deposition will affect the quality of the
the necessary amount of material.
achieved with other metal combinations,
electroplating: slower processes tend to
but they may not be as durable.
produce more precise coating thickness. Labour costs are moderate to high
Coating thickness is measured in
Gold and silver are inert and suitable
for all types of products including medical implants, beakers,bowls and
COMPATIBLE MATERIALS
depending on the application. For
jewelry. Nickel should not be used in
Most metals can be electroplated.
example, silverware and jewelry has to
contact with the skin because it is
However, metals combine with different
be finished to a very high level because
irritating and can be poisonous.
levels of purity and efficiency.
appearance and durability are critical.
Featured Manufacturer
BJS Company www.bjsco.com
7
\
TECHNICAL DESCRIPTION
Hot Dip Galvanizing Process
There are typically 6 baths in the hot dip galvanizing process. The first U are in the cleaning and degreasing stage
Finishing Technology
of the process. The parts are dipped in
Galvanizing
hot caustic acid for degreasing. Next,
the parts are dipped in 2 progressive hydrochloric acid pickling baths to remove all mill scale and rust. Lastly,
In this process steel and iron are hot dipped In molten zinc that
they are washed at 80°C (176°Fj in
alloys to its surface metallurglcally and provides electrochemical
preparation for the zinc flux.
protection against the elements. It produces a bright, distinctive
dipped in a flux of hot zinc ammonium
During stage 2 the metalwork is chloride to condition the clean surface
pattern on the surface, which over time becomes dull and grey.
for galvanizing and ensure a good flow of zinc over the internal and external surfaces of the metalwork.
Costs
Typical Applications Architectural and bridges Automotive Furniture
Quality • Excellent protection • Appearance affected by quality of steel
Finally, the metal work is immersed
Suitability
The zinc will react with atmospheric
explosive design elements that include
in a bath of molten zinc, which is
elements more readily than iron and
sealed tubes and blind corners. All
maintained at 450oC |8/iO°F). The zinc
forms a deposit over the exposed area
weldingslag,grease an dp ainthaveto
bonds with the iron metallurgically to
be removed pre-treatment.
create a zinc-iron alloy that is inherent
One-off to mass production
that protects the base material from
Competing Processes
to the surface of the metalwork. Strata
further corrosion. Electroplating Spray painting Vacuum metalizing
INTRODUCTION Zinc and iron combine to produce a vety
effective alloy that increases the life of steelwork and ironwork substantially. Unprotected metalwork continuously corrodes and its structure is undermined, whereas galvanized metalwork is protected from the elements and so
• Rapid cycle time (typically complete within 10 minutes)
removes excess zinc and produces a more uniform, even coating.This is particularly useful for threaded fasteners and other small parts that require accurate coating. Galvanizing is resilient to aggressive handling and over the last 150 years has proven to provide a long-lasting, tough and low-maintenance coating.
The look of the zinc coating is also
QUALITY
affected by the quality of the steel.The final effect can appear bright and shiny
metallurgical bond, only steel and iron
to dull and grey; the latter is caused by
can be coated in this way.
The costs of this process are low,
clean finish. Over time and with exposure
This is a versatile process that can be
especially in the long term. No specific
to atmospheric conditions this becomes
used to protect small items such as nuts
tooling is required. Cycle time is rapid.
dull and grey. It is tough and protects the
and bolts as small as 8mm (0.315 in.)
of finish is affected by the skill of the operators, amongst other factors.
oxygen, water and carbon dioxide. Levels
to 12 m x 3 m (40 x 10 ft). Structures larger than this can be fabricated post-
Victorian steel roofre-galvanizedforthe
(0.0000039 in.) per year for indoor uses
galvanizing. Complex and intricate
ENVIRONMENTAL IMPACTS
first time (see image, opposite).
to 4-8 microns (0.00015- 0.00031 in.) per
shapes can be galvanized in a single
This process can increase the life of
year for outdoor applications near the
operation, including hollow and open-
steelwork to between 40 and 100 years.
coast. A typical coating is between 50 and
sided vessels.
Station, for example, has recently had its
During galvanizing, zinc bonds with
iron metallurgically to produce a layer of zinc-iron alloy coated by a layer of pure zinc. The coating is therefore integral to
Galvanized steel can be recycled and so has an almost indefinite lifespan.
TYPICAL APPLICATIONS Typical applications include architectural steelwork such as stairwells, walls, floors and bridges; agricultural hardware, automotive chassis and furniture.
the base material; the intermediate alloy layer is very hard and can sometimes exceed the strength of the base material. Galvanizing is carried out in 2 ways:
hot dip or centrifugal galvanizing.They are essentially the same, except that
in centrifugal galvanizing the parts are dipped in baskets and then spun after submerging in molten zinc. This
COMPETING PROCESSES Other techniques used to coat materials
with metal include electroplating (page 364), vacuum metalizing (page 372) and spray painting (page 350) with conductive paints. Unlike these processes, galvanizing is limited to coating steel andiron with zinc.
150 microns (0.0020- 0.0059 in.) thick
depending on the application technique. The thickness of the coating is normally determined by the thickness of the base metal.The exceptions are centrifugal galvanized coatings, which produce a
slightly thinner coating, or thicker coatings produced by roughening the surface of the part or adding silicon to the steel during production. By its very nature the zinc coating protects the steel, even if it is penetrated.
pure zinc. The dipping process can last up to 10 minutes, depending on
the depth of zinc coating required. The parts are gradually withdrawn from the zinc bath to allow excess zinc to drain off.
Labour costs are moderate; the quality
diameter, to very large structures up
of corrosion can vary from o.i microns
retains its structural integrity. Waterloo
process, and the outer layer is typically
COSTS DESIGN OPPORTUNITIES
base material against corrosion from
concentration are built up during the
Because galvanizing relies on a
steel with high silicon content.
When the steelwork is removed from the
galvanizing bath the zinc has a bright,
of zinc-iron alloy layers of varying
COMPATIBLE MATERIALS
It is widely accepted that half of all new steel produced is used to replace
DESIGN CONSIDERATIONS
corroded steel. In some countries this
Galvanizing coats the entire surface of a
costs up to 4% of GDP. Galvanizing
part with zinc. High temperature tape,
dramatically increases the longevity
grease or paint can be used to mask
of steel fabrications, reducing their
Above
environmental impact.
The roof ofWaterloo
areas. Certain hollow geometries can be
galvanized only on the outside, but this requires special coating techniques.
The galvanizing bath is maintained at
The process uses zinc efficiently to protect the surface of steelwork. After each dip the unused zinc drains back into
4500C (84O0F), so all parts must be able
the galvanizing bath for reuse. Zinc can
to withstand that temperature. Another
be recycled indefinitely without loss of
important consideration is potentially
any physical or chemical properties.
Station in London was galvanized nearly 100 years ago. It has not needed re-galvanizing
until recently and will probably last another century before any further treatment.
Case Study
Hot dip galvanizing steelwork First of all the parts are cleaned and checked
its temperature has by now been raised to
for any air or solution traps that may cause
8o0C (1760F). The parts are then dipped into a bath of
problems during the galvanizing process. The metalwork is then rigged onto beams at
molten zinc at 4500C (84O0F) (image 6).The
a 30° angle to facilitate draining {images i
zinc spits as it comes into contact with the
and 2). Drainage holes may have to be
cooler metal. During galvanizing the surface
designed into the product to ensure that
of the molten zinc is continuously skimmed
solution can drain off during the process.
to remove any contamination and flakes of
The metalwork is moved through to the galvanizing plant where it is dipped
metal that might affect the quality of the galvanized finish (image 7).
in progressive cleaning and pickling baths (image 3).The preparation, cleaning
The parts are removed from the molten zinc slowly to allow excess zinc to drain back
and base material content determines
into the bath (image 8). The use of zinc is
the quality of the galvanized part, so
very efficient; a ratio of roughly 1:15 of zinc to
this stage of the process is essential to
metalwork is usual. The parts are removed
ensure consistent levels of quality. The
from the bath and air dried or quenched,
penultimate bath (image 4) contains a flux
according to the customer requirements
that conditions the surface in preparation
(image 9) and they are loaded for delivery
for the hot dip galvanizing. The metalwork
(image 10).
is removed from the flux steaming in preparation for galvanizing (image 5);
3
4
Vacuum Metalizing Process
Vacuum pulled lO"'' millibars
Finishing Technology
Vacuum Metalizing Also known as physical vapour deposition (PVD) and sputtering, the vacuum metalizing process is used to coat a wide range of materials in metal to create the look and feel of anodized
INTRODUCTION
models in suitable materials can be
This process combines very high vacuum
coated to give the look and feel of a metal
and an electrical discharge that vaporizes
part. In contrast, mass produced metal
almost pure metal (most commonly
parts can be coated for added value.
aluminium) in a vacuum deposition
aluminium, chrome, gold, silver and other metals.
No tooling costs, but jigs are required Moderate unit costs
Typical Applications
Suitability
• Consumer products • Reflective coatings • RF. EMI and heat shielding
• One-off to mass production
application. Cosmetic finishes are
condenses onto surfaces, coating them
typically less than 6 microns (0.00024 in.)
with a high-gloss film of metal.
thick, with a metal film of less than
It is a means of coating many different
1 micron (0.000039 in.). For functional coatings, thicknesses of 10 to 30 microns
metal, with metal.There are no tooling
(0.00039-0.0012 in.) are producedusing
costs, and the process is controllable and
plasma vaporizing techniques, which can
build up film thickness indefinitely.
Quality
Related Processes
Speed
repeatable, making it suitable for coating
• High quality, high gloss and protective finish with similar characteristics to spray painted coatings
• Electroplating • Galvanizing • Spray painting
• Moderate cycle time (6 hours including spray painting)
mass produced items. Prototypes and
Outer frame also rotates
Coating thickness depends on the
chamber. The plume of vaporized metal
materials,including plastic, glass and
Workplece mounted onto rotating fixture, which in turn rotates on a spinning wheel
Vacuum chamber Vaporized metal disperses
everything from single prototypes to
TYPICAL APPLICATIONS
Electrodes
Wire spiral carriers
Vacuum metalizing is used equally for decorative and functional applications. Decorative uses include jewelry, sculptures, trophies, prototypes, kitchen utensils and architectural ironmongery. Coatings can be functional, providing electromagnetic interference (EMI) or
radio frequency (RF) shielding, improved
TECHNICAL DESCRIPTION The parts are first cleaned and coated
When the correct pressure is reached,
with a base coat by spray painting. The
an electrical discharge is passed through
base coat has 2 main functions; improving
the wire of aluminium (or other metal) by
surface finish and encouraging the metal
the electrodes. The combination of the
vapour to adhere to the workpiece. The workpieces are mounted onto
electric current and high vacuum cause the almost pure metal to vaporize in an
rotating holding fixtures (custom made
Instant. It bursts into a plume of metal
for each part), which are in turn rotated
vapour, which condenses on the relatively
reflection, an electrically conductive
on spinning wheels. The assembly
cool surface of the workplece. The
surface or a vapour barrier. Some typical
is suspended within a frame, which
condensing metal adheres to the base
products are torch and automotive light
also rotates. All in all, the parts are
coat on the parts In a thin, uniform layer.
wear resistance, heat deflection, light
reflectors, machine parts, metalized
being rotated around 3 parallel axes
pi asti c fil m s an d con sum er el ectron 1 cs.
simultaneously. This is to ensure an even coating with line-of-sight geometry.
RELATED PROCESSES
Before the vacuum metalizing can
The vacuum metalized film Is protected by the application of a topcoat. This Is water-clear, but can be coloured to mimic various metallic materials. The
Other processes used to coat materials
take place, a vacuum has to be generated
topcoat is then cured in a warm oven
with metal include electroplating (page
within the metalizing chamber. To reach
for 30 minutes or so. The end result Is
10' millibars (0.0000145 psi) takes
a metallic layer encapsulated between
approximately 30 minutes, depending
2 coats of lacquer, which is durable and
on the materials being coated. The
highly reflective.
364), galvanizing (page 368), and spray painting (page 350). Spray painting with conductive paints is also suitable for RF and EMI shielding,These processes are closely related; spray painting is used to apply abase coat pre-metalizing and seal in the delicate metal film with a topcoat. Spray painting and vacuum metalizing can coat the widest range of materials.
metalizing process can operate at a lesser
degree of vacuum, but the quality of the finish will be inferior.
Case Study
i
Vacuum metalizing brass hinges with aluminium The process starts with the application
(image 4). The whole assembly is loaded into
of a base coat lacquer (image i).This is
the vacuum chamber (image 5). It takes about
Everything that goes into the vacuum chamber emerges with a thin coating of
essential for a high-quality finish; not only
30 minutes or so to pull a sufficient vacuum.
vaporized metal. The unprotected metal
does it promote good adhesion between
An electrical discharge is passed through
film can be easily rubbed off at this stage.
the workpiece and metallic coating, it also
the wire, causing it to heat up and vaporize
Spraying a lacquer topcoat onto the
gives a smoother finish. Once applied, the
(image 6). It glows white-hot and a film of
workpiece secures the thin metallic film and
workpieces, which are mounted onto their
aluminium begins to form on the workpiece.
bonds it to the base coat. The parts before
jigs, are loaded into a warm oven to accelerate
The vacuum metalizing process takes only a
and after they have been vacuum metalized
the curing of the base coat (image 2).
few minutes. The chamber is brought back up
appear markedly different (image 7).
After 30 minutes or so, the jigs are loaded,
to atmospheric pressure and the door opened.
with the parts, onto the rotating holding fixtures (image 3). Loading the parts by hand means that they are individually checked, which limits waste. The parts are secured
to the holding fixtures by clips that will not affect the quality of the coating. Each design will require a different method for connecting it to the holding fixtures. The wire spiral holders that connect the positive and negative electrodes are loaded with 95% pure aluminium wire
QUALITY
smoother transition from prototyping
Vacuum metalizing is used to
to production, and also means that
increase the surface quality by
designers can explore the look and feel of
improving reflectivity, wear and
their objects in metal at an early stage.
corrosion resistance. It also improves
The coating produced by vacuum
colouring capability; the topcoat can
metalizing is fine and uniform. Passing
be impregnated with a wide range of metallic colours.The quality of the finish
the workpiece through the process more
Is determined by the quality of the
than once Increases the film thickness. Vivid colours can be used to replicate anodized aluminium, bright chrome,
by the vacuum chamber, but also by the
COSTS
silver, gold, copper or gunmetal, among
geometry of the part. Flat parts up to
There are no tooling costs, but jigs
products by increasing their resistance to
geometry.This means that the parts
others.The advantage of this is that
1.2 m x i m (3.94 x 3.3 ft) can be coated,
often have to be made to support the
corrosion and wear. Very little material
have to be rotated during metalizing to
relatively Inexpensive materials can be
where as 3D parts are limited to
workpiece in the vacuum chamber.
is needed for the metal coating because
surface priorto coating. The coating is applied on line-of-sight
encourage an even coating, and deep
formed and then vacuum metalizedto
1.2 m x 0.5 m (3.94 x 1.6 ft) because they
undercuts and recesses can escape the
give the look and feel of metal.
have to rotate as they are metalized.
Cycle time is moderate (up to 6 hours).
it is generally a very thin film, but this
It is quite a labour intensive process;
depends on the application.
the parts have to be sprayed, loaded,
coating process.The vacuum can be replaced with argon gas to encourage a
Metalizing extends the life of
DESIGN CONSIDERATIONS
COMPATIBLE MATERIALS
unloaded and sprayed again.This means
more vigorous coating, but this will be
The quality of the coating 1s affected by
Many materials are suitable, including
the labour costs can be quite high, but
more expensive to carry out because it is
the surface quality of the workpiece. In
metals, rigid and flexible plastics, resins,
depend on the complexity and quantity
a specialist process.
other words, the metal finish will only be
composites, ceramics and glass. Natural
of parts.
as smooth as the uncoated finish. If the
fibres are not suitable; it is very difficult
DESIGN OPPORTUNITIES
desired effect is distressed, this must be
to apply vacuum if moisture is present.
Vacuum metalizing is an inexpensive
achieved priorto metal coating.
and versatile metal coating technique.
The maximum size of the part that
There Is no tooling cost, which makes a
can be metalized is determined not only
Aluminium is the most commonly
ENVIRONMENTAL IMPACTS Featured Manufacturer
This process creates very little waste.
used metal for coating. Other metals that
Spraying the base coat and topcoat has
can be used include silver and copper.
Impacts equivalent to spray painting.
VMC Limited www.vmclimited.co.uk
Mechanical Grinding, Sanding and Polishing Techniques Wheel cutting
Belt sanding Table Workpiece
Rotating platen
Honing
Abrasive coating
Spinning axle
Workpiece
Finishing Technology
Grinding, Sanding and Polishing Workpiece
Surface cutting
Profiled honing stone Outside diameter
Surfaces are eroded by abrasive particles In these mechanical processes. The surface finish ranges from coarse to mirror,
and can be a uniform texture or patterned depending on the
INTRODUCTION Grinding, sanding and polishing cover
Abrasive coating
Abrasive Workpiece
a wide range of processes used to finish
Support plate
metal, wood, plastic, ceramic and glass products.The size andtype of abrasive
technique used and type and size of abrasive particle.
particle, combined with the method of finishing, will determine the range
Hollow Profiled workpiece honing stone
Costs
Typical Applications
Suitability
These terms are used to describe
• No tooling costs for many applications • Non-standard profiles may require tooling • Unit costs dependent on surface finish
• Automotive, architectural and aerospace • Cookware, kitchens, sanitary and medical • Glass lenses, storage jars and containers
• One-off to mass production
different techniques for surface cutting.
Quality • High quality finish that can be accurate to within fractions of a micron (0.000039 in.)
Related Processes • Abrasive blasting • Electropolishing
Lapping
Speed • Rapid to long cycle time, depending on size and type of finish
Abrasive 1 block
¦
1 Workpiece
fulfils a range of functions, including deburring metals, preparing surfaces forfurther processes, cutting into or right through materials, and precision
Cylindrical profile
finishes.There are many different
Abrasive pad Workpiece
grinding techniques, including wheel,
belt and platen grinding, honing and barrel finishing. Many different abrasive
Inside diameter
TECHNICAL DESCRIPTION
| Lap
Grinding is used to produce surface finishes on hard materials. The process
Linear
Edge cutting
of surface effects that can be achieved.
Table
materials are used, including metal, mineral, diamond and maize seed.
Sanding is used to describe the process of eroding surfaces with
abrasive-coated substrates.The abrasive
These are common techniques used for
They are not suitable for applying a
cutting surfaces in industrial applications.
super-bright finish. The diagrams
Each is capable of applying a range
Illustrate how they are set up to cut
of finishes, from super bright to very
different geometries of product. The
coarse, depending on the type of abrasive
rotary method is suitable for circular and
material. They all rely on lubrication,
Irregular tube and rod profiles; as the belt
which reduces the build up of heat and
spins, the platen rotates to produce an
wear on the cutting tool.
even finish around the outside diameter.
To achieve a highly reflective and super-bright finish, the material will pass through a series of stages of
of rotationally symmetrical parts. It Is
surface cutting, which will use gradually
a precise method of surface cutting;
finer grits of abrasive. The role of each
an example application Is finishing the
abrasive is to reduce the depth of surface
inside diameter of cylinder blocks in
undulation. In mirror polishing this Is
engines. The tooling for this can be made
measured in terms of Ra (roughness
up specially for each job. The abrasive
average); a mirror polish is less than Ra
surface wears away gradually as it is
0.05 microns (0.0000019 in.).
used, and therefore has to be replaced to
Wheel cutting is carried out at high
particles consist of sand, garnet,
speed. Either the outside edge or the
aluminium oxide or silicone carbide;
face of the wheel is coated with abrasive
each has its benefits and limitations.
The grade of paper (grit) is determined by the size of particle and ranges from 40 to 2,400. Lower numbers indicate fewer particles for the same area and so produce a courser finish. These processes are known as
Honing is suitable for grinding and polishing internal and outside diameters
retain accuracy.
Lapping is typically used to produce a very fine and super-bright finish on hard
particles, generally made from metal
metallic and glass surfaces. The abrasive
and so providing a hard surface to grind
Is not coated onto the pad or block, but
or polish. They are equally suitable for
is Integral to it. Blocks are rigid abrasive
coarse grinding and diamond polishing.
blocks, and pads are flexible rubbers
The set up of the wheel and table will
impregnated with abrasives of a defined
determine the precision of the finish. Belt sanding Is used in both woodworking and metalworking. There
grit size. The surface finish is therefore very controllable. Lapping can be carried
out at different speeds depending on the
polishing when they are used to produce a bright and lustrous finish on hard
are many different types of machine.
material being polished; mirror finishes
Including free standing and portable
on flat and cylindrical surfaces can take many hours to complete.
surfaces. Polishing is characterized by
types. Like wheel cutting machines, they
the use of compounds in the form of
operate at high speed and are designed
pastes, waxes and liquids in which the
to apply the desired finish very quickly.
Case Study
Case Study
Wheel grinding
Honing glass
Wheel grinding is used to produce a
in this case honing is being used by Dixon
perfectly into it (image 3). The glass stopper
very flat surface that is suitable for rapid
Glass to produce an airtight seal between
is finished in the same way.
prototyping onto using the direct metal
a glass container and a stopper.
laser sintering (DMLS) process (page 232).
The profiled metal honing stone is
The finished products (image 4) are used to store scientific specimens for
First the surface is milled to provide an
machined specially for this application.
many decades, and honed glass is the only
even surface for grinding (images 1 and 2).
It is loaded Into the chuck of a lathe and
material capable of this.
This speeds up the process.Then the
coated with a mineral based cutting
metal plate 1s placed onto the magnetic
compound (image 1). As the part is ground,
grinding table and carefully ground for
the coarseness of abrasive compound Is
up to 45 minutes to produce the desired
reduced to produce a finer finish (image 2).
Ra value (images 3 and 4).
Abrasive honing increases the size of hole very gradually until the glass stopper fits
Featured Manufacturer
CRDM www.crdm.co.uk
abrasive particles are suspended. Cloths
widespread and cover both Industrial
are commonly used to apply the abrasive
and DIY projects.
paste, elther by h and or spun at high speed on a wheel. Mixing water with abrasive-coated substrates, such as wet and dry paper,
Abrasive blasting (page 388) is
glass specimen jars (see case study) are
finish obtained with 80-100 grit will
ground with a honing tool to form a
be Ra 2.5 microns (0.000098 In.); a dull
metal castings. It is a versatile and rapid
hermetic seal capable of maintaining
buffed finish from 180-220 grit will be Ra
into or right through fibre reinforced
process, but produces a limited range of
the contents for more than icq years.
composites, metals and glass.This is
surface finishes, all of which are matt.
Mechanical polishing produces
especially useful for brittle materials.
Polishing and grinding of embossed patterns in metal will emphasize the
hygienic surfaces, suitable for catering
As well as finishing, grinding can cut
produces a similar effect.The water suspends abrasive particles that form
RELATED PROCESSES
during sanding, creating a paste that
Electropolishing (page 384) Is used to
commonly used to smooth and finish
depth of texture.
and medical applications. Polished metal finishes reflect over
1.25 microns (0.000049 i1"1-); dull polish from 240 grit will be Ra 0.6 microns
(0.000024 in.); and a bright polish produced with a polishing compound will be Ra 0.05 microns (0.0000019 in-)-
QUALITY
95% of the light that hits their surface. Finely polished stainless steel Is i of the
finishes on metal. It is not as accurate as
It is possible to grind and polish surfaces
most reflective metals and can be used
Polished surfaces are more hygienic
TYPICAL APPLICATIONS
these techniques and cannot produce
accurate to within fractions of a micron.
as a mirror.
and easier to clean, which makes them
contributes to a very fine surface finish.
produce bright, lustrous and burr-free
DESIGN OPPORTUNITIES
These processes are used in all
such a bright fin1 sh. The advantage of
Precision operations are considerably
Depth of surface texture at this scale
very suitable for high traffic areas and
manufacturing Industries both for
electropolishing is that part geometry Is
more expensive and time consuming,
is measured as a value of Ra (roughness
human contact. In contrast, satin and
surface preparation and as precise
not a significant consideration and will
but are sometimes the only viable
average). Approximate Ra values for
finely textured finishes are prone to
finishing operations. Applications are
not affect cost or cycle time.
method of manufacture. For example,
Featured Manufacturer Dixon Glass www.dixonglass.co.uk
metal finishes are as follows: a ground
fingerprints and other marks.
Case Study
Case Study
^ Rotary sanding
-> Vibratory finishing
This is a typical application for the
This is a method used for finishing high
rotary belt sanding method (image i).
volumes. It is especially suitable for deburring
is used to produce a very fine finish on
Crushed maize seed (image 2), which
It produces an even satin finish on the
metal, but is also used to cut back painted
hard surfaces, is the next stage in the
surface of stainless steel (image 2). It is
surfaces and a range of other applications.
abrasive process.
equally suitable for non-uniform profiles.
A deep drawn (page 88) metal part is placed into the vibrating barrel, which is filled with smooth, hard pellets (image 1). It works in much the same way as pebbles eroding
o
each other on the beach to produce smooth,
33
rounded stones. Many products can be in the barrel together.
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1 J D ¦) 1 1 ") 1 •)
desirable results.The hardness of the
material will affect how well It finishes, as well as how long It will take.
I
COSTS Much grinding, sanding and polishing
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Case Study
cn 3;
^ Manual polishing This is the most expensive and time-
The final stage is a buffing process,
consuming method of polishing. It is used
which uses the finest polishing compound
can be carried out with standard tooling.
to produce an extremely high surface
to produce a highly reflective finish. It is a
Consumables are a consideration for the
finish on the surface of parts that cannot
labour intensive process, but is nonetheless
unit price. Specific tooling can be very
be polished by mechanical means. This
used to finish a high volume of products
costly, but depends on the size.
polishing method can be used to work every
(image 4).
Cycle time is largely dependent on
surface of this colander (images 1-3). The
Featured Manufacturer
the size, complexity and smoothness of
size of spinning mop can be adjusted to fit
Plpecraft
surface finish. Brightly polished surfaces
smaller profiles such as spoons.The density
www.pipecraft.co.uk
can take many hours to achieve.
of the mop is adjusted for different grades
Labour costs are also dependent on
of cutting compound.
the size, complexity and smoothness
Repeating patterns can be polished into surfaces, like those found on cafe tables,These patterns reduce the visual effects of wear and dirt.
It is often more cost effective to polish stock material, such as sheet or tube, prior to fabrication. The joints can then be polished manually afterwards.
and rely on either rotating or moving back and forth. In contrast, cosmetic grinding and
of surface finish required. A dull polish will add about 10% of the raw material cost, a measured finish about 25% and a reflective finish about 60%.
polishing operations can be applied to most shapes because they can be carried out manually If necessary.
The hardness of the material will affect the surface finish. Stainless steel Is
ENVIRONMENTAL IMPACTS Even though these are reductive processes, there is very little waste produced in operation.
very hard and so can be polished to a very
DESIGN CONSIDERATIONS
fine surface finish; aluminium is a softer
The shape of the part will determine
metal and so cannot be polished to such
the effectiveness of these processes.
a bright lustre.
For example, precision grinding and
polishing operations are limited to flat,
COMPATIBLE MATERIALS
Featured Manufacturer
cylindrical and conical shapes.This is
Any material can be ground, sanded
Alessi
because the operations are reciprocal
or polished, but they may not produce
www.alessi.com
Case Study
Case Study
-> Lapping
-> Diamond wheel polishing Diamond particles are used to finish a range
The diamond cutting wheel is spinning at
Lapping is used to produce a range of
of materials that are too hard for other
high speed and produces a super fine finish
finishes, including reciprocal patterns, dull
polishing compounds.They are also used
in amatter of seconds (rmages 2 and 3). This
and super bright finishes. To polish a sheet of
prior to polishing (image 3) because a
for high speed finishing of plastics. This
is a mass-production method suitable
stainless steel to a bright finish, the polishing
protective plastic film is applied by the
acrylic box has been CNC machined. The
for finishing a high volume of products
compound is applied with a roller each time
machine directly after polishing. The
lid and base are paired up and then the 4
(image 4).
the lapping pad passes over the surface
circular pads that make the pattern
sides are cut on a circular saw (image i).This
(image i). Pressure is applied to maintain
(image 4) are impregnated with abrasive
produces an accurate finish, but it has an
a very accurate finish. Afterwards a lime
particles. The pattern (image 5) is a
undesirable texture. The workpiece is placed
substitute is spread over the surface of the
typical example of the finish that can be
stainless to remove any remaining moisture
achieved by this method.
on the cutting table and clamped in place.
When lapping to produce a patterned finish, the edges of the sheet are deburred
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Featured Manufacturer
Featured Manufacturer
Zone Creations
Professional Polishing
www.zone-creations.co.uk
www.professionalpoUshing.co.uk
TECHNICAL DESCRIPTION
Electropolishing Process
The electropolishing process is made up of 3 elements: the pre-cleaning (where
necessary), the polishing (see diagram) and the final cleaning to remove
Finishing Technology
chemical contaminants.
Electropolishing
The process takes place in a bath of electropolishing solution, which is made up of phosphoric and sulphuric acid. The
This is the reverse of electroplating; material is removed from the surface of the workpiece by electrochemical action to leave
bath is maintained between 50°C and
INTRODUCTION
90°C (122-194°F), depending on the rate
Electropolishing produces a bright
Electrically charged workpiece (+)
lustre on the surface of metals. It is an
more rapid the reaction. The workpiece
electrochemical process; surface removal
metal parts with a bright and clean finish.
is suspended on an electrically charged
takes place in an electrolytic solution, which can be very accurate. As well as deburrs, passivates and improves the
• No tooling costs, but jigs are required • Low unit cost (roughly 5% material cost)
Dissolved metal particles
jig and becomes the anode. The cathode
Heated electrolytic solution (phosphoric and sulphuric acid)
solution and is generally made of
is also placed in the electropolishing
polishing, this process cleans, degreases,
Costs
of reaction; the warmer the solution, the
the same material as the workpiece.
Typical Applications
Suitability
corrosion resistance of metal surfaces.
For electroplating, conversely, the
• Architectural and construction • Food processing and storage • Pharmaceutical and hospitals
• One-off to mass production
It is becoming more widely used because
workpiece becomes the cathode.
the environmental impacts are less
Microscopic detail
harmful than those of other processes. Quality
Related Processes
Speed
• High quality, bright, lustrous and hygienic surface finish
• Electroplating • Grinding, sanding and polishing
• Moderate cycle time (5-30 minutes)
When an electric current is passed between the cathode and the workpiece,
the electropolishing solution dissolves
Electropolished stainless steel has similar visual characteristics to chrome-
metal particles from the surface of
plated metals. Electropolishing is a
the workpiece. Surface dissolution
takes place more rapidly on the peaks simpler process than electroplating
driven by industry's aim to reduce the
chrome (page 364) and uses less water
consumption of chrome and other heavy
and chemicals, so is more cost effective.
metals (very toxic chromic acid is used for
As a result of the increase in use of
chrome plating). Electropolishing does
electropolishing, it is steadily becoming
produce chemical waste that must be
less expensive.
because that is where the power density is greatest. Low points are dissolved more slowly, and thus the surface of the material is gradually made smoother.
After electropolishing the parts are neutralized, rinsed and cleaned.
cleaned and pH neutralized, but it is less harmful than these other processes.
TYPICAL APPLICATIONS
Similar to mechanical polishing (page
Electropolishing has become a widely
376), electropolishing is a reductive
accepted finishing process for metals.
process. However, it is possible to
In architectural and construction
electropolish complex shapes that would
metal work, it is used for both aesthetic
be impractical by mechanical means.
andfunctional reasons (resistance
surface finish prior to electropolishing
to corrosion and reduced stress
QUALITY
concentration). In the pharmaceutical
The quality of finish that can be achieved
greater than 50 microns (0.002 in.), so a
and food industries it is used for
with electropolishing enhances the
rough finish will be smoothedbut not
mainly functional reasons (hygiene
surface of metalwork both aesthetically
completely removed. Even so, this process
and resistance to corrosion). Aesthetic
and functionally. Aesthetically, it
is frequently used for deburring as well
applications make up roughly 90% of its
increases the brightness and reflective
as polishing because burrs are like high
total use.
index by smoothing (polishing) the
points and so are dissolved very rapidly.
RELATED PROCESSES
level, the high points are dissolved
produces a finish that is clean, hygienic,
Electropolishing has been steadily
more rapidly than the troughs.The
less prone to stress concentration
replacing more ecologically harmful
result is reduced surface roughness
and more resistant to corrosion. The
processes such as chrome plating
and reduced surface area. However, the
electrochemical action removes dirt,
(see electroplating, page 364).This is
end result is largely dependent on the
grease and other contamination.
surface of the metal. On a microscopic
because material removal is usually no
Functionally, electropolishing
Case Study
Electropolishing architectural steelwork This case study demonstrates a recent
and rinse the parts. They are mounted onto
development in electropolishing technology.
a rotating frame which suspends them in
The equipment has been modified to reduce
each tank (image 4),
effluents and improve the environmental credentials of the process.
Throughout the process test pieces are checked to measure the rate of
They are dipped in the electrolytic solution for 10 minutes or so. As they are raised up, the green acidic mixture drains
back into the tank (image 5), The polishing
electropolishing accurately (Image i).
process is complete, and the rest of the
Electropolishing is generally used to remove
process neutralizes and rinses.
up to 40 microns or so: this sample shows a reduction of 30 microns (0,0012 in,).
they have been rinsed (image 6), and are
The sample indicates the amount of time
then washed a final time to remove any
required in the electrolyte to remove
remaining contamination.The parts are
sufficient materials.
then heated to dry (image 7), after which
These are investment cast stainless
steel architectural spiders (see page 133),
3
The spiders are hung to drain after
they are safe to handle and so are packed and shipped.
which are designed to hold panes of glass in buildings (image 2), They are jigged with electrical contact (image 3),This particular process requires only a small number of
baths to electropolish effectively, neutralize 5
It produces a more hygienic surface
not apply any mechanical stress to parts
COMPATIBLE MATERIALS
ENVIRONMENTAL IMPACTS
because potential microscopic bacterial
and so can be used to deburr andfinlsh
Most metals can be electropollshed,
The environmental Impacts of this
and dirt traps are opened up to allow
delicate parts that are not suitable for
but this process is most widely used for
process are threefold. Firstly, it Is
more thorough sterilization,The process
mechanical polishing techniques.
stainless steels (particularly austenitlc
replacing the use of chrome-plated steel,
grades). Generally, an electropolishing
which is a harmful material due to the chemicals used in its production.
dissolves iron more readily than other
This process is also useful in the
metallic elements, and this phenomenon
preparation of parts that will be used
plant will be set up for a specific material
means that electropollshed stainless
in applications that require contact
because different materials cannot be
Electropolishing uses less harmful
steels have a chromium-rich layer on
between surfaces.This method of
polished together or even In the same
chemicals, needs less water and Is
the surface,This layer protects the steel
polishing deburrs and so reduces
electrolytic solution. Other metals
simpler to operate. Secondly, It increases
from corrosion because it reacts with
friction between mated surfaces such as
that can be treated in this way Include
the longevity of stainless steel because it
oxygen to form chromium oxide, which
threaded assemblies.
aluminium and copper.
increases the material's natural
reactive to atmospheric elements. As well
DESIGN CONSIDERATIONS
COSTS
this process removes material, rather than coating with an additional material,
passivates the surface and makes it less
protection against corrosion. And thirdly,
as protecting the steel, the chromium-
The level of finish is determined by the
There are no tooling costs, but jigs are
rich layer can be so bright that It also
quality of the metal surface prior to
required for electrical contact.
gives the Illusion of chrome plating,
electropolishing, so preparation is key. Marks from blunt tools on the forming
the amount of material removal and
DESIGN OPPORTUNITIES
or cutting machine, deep scratches and
cleanliness of the part.
The entire process takes place
other imperfections will not disappear
submerged in baths of solution, which
with electropolishing. Instead,they
partially automated, so labour costs are
consumption of chemicals represents
has many advantages over mechanical
may be emphasized by the enhanced
relatively low. It adds only 5% to the cost
only a small proportion of the overall
operations,The process is equally
surface finish. Metalwork that requires
of the base material, as opposed to metal
costs. They tend to be far less hazardous
effective on small technical and large
preparation, such as a casting, Is abrasive
plating, which can add up to 20%.
to the operator, and the resultant residue
structural parts. Size and complexity
blasted (page 388) to produce a uniform
1s more easily treated than with other
Firma-Chrome Ltd
have no bearing on cycle time. It does
surface finish that will respond well.
metal finishing processes.
www.firma-chrome.co.uk
Cycle time is rapid, but depends on
This process tends to be either fully or
so reduces material consumption and eliminates delamlnatlon and other associated problems.
Approximately 25% of the chemical solution is replaced annually.The
Featured Manufacturer
Finishing Technology
Abrasive Blasting This is a generic term used to describe the process of surface removal by fine particles of sand, metal, plastic or other abrasive materials, which are blown at high pressure against the surface of the workpiece and produce a finely textured finish.
Costs • No tooling costs, but masks may be required • Low to high unit cost
Typical Applications • Architectural glass • Decorative glassware • Shop fronts
Suitability • High volume removal of surface material • Low to medium volume fine finishing
Quality
Competing Processes
Speed
• Very fine details can be produced by skilled operators
• Chemical paint stripping • Photo etching • Polishing
• Rapid cycle time, but slowed down by masking, layering and carving
INTRODUCTION Abrasive blasting encompasses sand
QUALITY
blasting, dry etching, plastic media blasting (PMB), shot blasting and bead blasting. All ofthesehave 2
With manual operations the success
of this process is largely dependent
main functions. Firstly, they are used
details can be reproduced accurately.
on the skill of the operator. Very fine
to prepare a surface for secondary
Material removal is permanent, so care
operations by removing contaminants
must be taken to etch the surface of the
andapplying a fine texture that will aid
workpiece in a controlled fashion.
TECHNICAL DESCRIPTION This is a simple process that can be used
glass bead, metal grit, plastic media and
can be used to apply a decorative texture
DESIGN OPPORTUNITIES
to attain extremely sophisticated results
ground walnut and coconut shells.
to the surface of a part such as affecting
This is afast and effective way of
on many different materials. Abrasive
Sand is the most commonly used
the transparency of glass or applying
removing surface material.The various
blasting can be either pressure fed. or
because it is the most readily available
a pattern. Other functions include
grades and types of blasting media mean
siphon (suctionl fed. Both can be used
and versatile. Metal grit abrasives include
deburring, cutting and drilling.
that a range of textures and effects can
inside a sealed booth (glove box) or a
steel and aluminium oxide. Steel grit
be achieved, from a very fine texture
walk-in booth. Alternatively, blasting
is the most aggressive and is used to
glass and shop fronts. It is the process
(similar to that achieved with acid
apparatus can be used on-site or
create a rough texture on the surface
of sculpting the glass with 3D relief
etching), to a more rugged sand-blast
outdoors if the workpiece is very large or
of the workpiece. Aluminium oxide is
impractical to move. With all operations,
gentler and less durable, resulting in a
the steady stream of compressed air
softer texture. Glass beads are the least
generally operates at pressures between
abrasive and reserved for more delicate
5.51 bar and 8.62 bar (80-125 psi), except
materials. Plastic media are the most
surface addition processes. Secondly, they
Glass carving is used in architectural
patterns, with and without the use of
look.The depth of texture will affect the
masking (see image, page 484, above
level of transparency in clear materials
right).
by increasing light refraction.This quality can be used to enhance the visual depth
some specialized systems such as PMB.
expensive blast materials and require
which operate at 2.76 bar (iOpsij.
specialist equipment. They are much
TYPICAL APPLICATIONS
of an image, which will also be affected
Typical surface removal operations
by layers of colour in the workpiece.
include the deburring and preparation of metal surfaces for further finishing
effective. The abrasive material is
shapes, from round to angular, can be
DESIGN CONSIDERATIONS
forced through the blasting gun from a
selected to suit the application. Certain
operations and removing damaged or
Like spray painting (page 350), this
pressurized tank, attached by a flexible
natural materials, such as walnut shells,
weak material from a surface such as
process is limited by line-of-site
pipe. Siphon fed systems are more
will not affect glass or plated material.
rotten wood from sound wood or paint
geometry.This also means that erosion
versatile because they suck the blast
This can be useful if, for example, the
and rust from metal.
will not occur under the edges of the
material through a feed pipe, which is
operator only wants to erode the metal
mask, but rather perpendicular to it.
simply inserted into a container of blast
part of a product made up of metal
include glassware, signage, awards and
The abrasive material must be matched
material. Both processes are controlled
and glass.
medals and art installations.
to the workpiece and it is advisable
by 5 main variables: air pressure, nozzle
to test the abrasives, pressure and
diameter, distance from workpiece.
distance from workpiece prior to full
abrasive flow rate and type of abrasive.
Typical decorative applications
COMPETING PROCESSES CNC engraving (page 396),photo etching (page 392) and laser cutting (page 248)
production.Textures can act as dirt traps,
emphasizing fingerprints on glass for
are all used to produce similar effects
example; to reduce visual degradation
on glass and a range of other materials.
they are often encased in a laminate or a
Textured plastic films laminated onto
clear, protective coating.
glass sheet produce similar effects to
Pressure fed systems are the most
The choice of abrasive material is
softer than other blast materials and the
Wax resists are used for decorative applications. The abrasive materials cannot penetrate 'slippery' materials and bounce off. leaving the masked area
crucial and will be affected by many
untouched. Wax resists are produced
factors, which include the material being
from artwork that has been generated in
etched, the depth, grade and speed of cut
2-tone and are applied to the surface of
and economics. The abrasives are graded
the workpiece using an adhesive backing.
in much the same way as abrasive papers. The choice of materials includes sand.
Case Study
Decorative sand blasting The glass vesse] being decorated here was
The product is held in a glove box with
surface has been built up in layers, in that
designed by Peter Furlonger in 2005. It was
protective gloves. The operator (artist)
the top layer has been fired with a blowtorch
shaped by glassblowing (see page 152). For
carefully etches away the unprotected areas
to produce metallic effect, the layer
this project, sand blasting has been used to
of the workpiece with virgin aluminium
underneath is non-metallic and the base
decorate the surface of the workpiece with
oxide, ranging from 180 grit to 220 grit
layer Is clear glass.
a multilayered artwork.The same principle
(image 4). Once the first stage of etching Is
can be used to apply decorative patterns to
complete, specific areas of the wax resist are
for the second stage of the etching process
surfaces, except the wax resist is replaced
removed, and other delicate areas have their
(image 6). Finally the wax resist and all other
with masking.
protection reinforced (image 5). This will
masking is removed to ready the workpiece
enable the artist to create a multilayered
for cleaning and polishing (image 7).
Firstly, the artwork or pattern is translated onto a wax resist, either by hand
etched image. This technique is particularly
or by printing (image 1) and applied to the
effective on this product because the coloured
The product is returned to the booth
workpiece (image 2). Negative etching is used to describe the process of etching the image and leaving the background intact. This case study is an example of
positive etching because the image is left intact and the background is textured.
Once the wax resist has been applied,
i
the inside surface is masked to avoid damaging it with the abrasive (image 3).
COMPATIBLE MATERIALS This process is most effective for etching metal and glass surfaces, but can be used to prepare and finish most materials such as wood and some polymers.
COSTS There are no tooling costs. However, masks maybe required, the cost of which
Is affected by the complexity and size of the area to be abrasive blasted. Cycle time is good, but is slowed down by complex masking and multilayerlng.
Automation of simple tasks will greatly improve cycle time. For manual operation labour costs are
relatively high. for spray painting (page 350) and other
ENVIRONMENTAL IMPACTS The dust that is generated during
hazardous finishing processes. Working in a sealed booth means that
abrasive blasting can be hazardous.
the blast materials can be reclaimed
Booths and cabinets can be used
easily for re-use. Attaching a vacuum
to contain the dust that Is created,
system to the blast head makes It
otherwise breathing apparatus will be
possible to reclaim spent material for
required, much the same as those used
field stripping applications.
Featured Manufacturer The National Glass Centre www.nationalglasscentre.com
JSi
Photo Etching Process
m
Laminating roller applies film Metal workpiece
Film adheres to metal surface
Finishing Technology
Photo Etching
r
This is surface removal by chemical cutting. It has a similar appearance to abrasive blasting. The surface of the metal is masked with a resist film and unprotected areas are chemically dissolved in a uniform manner.
=5 Costs Low cost tooling Moderate to high unit costs
Quality • Prolonged exposure to chemical attack will cause undercutting
Typical Applications • Jewelry • Signage • Trophies and nameplates
INTRODUCTION Photo etching, also referred to as acid
Laser cutting (page 248), CNC engraving
etching and wet etching,is the process of surface removal by chemical dissolution.
(page 396) and abrasive blasting (page 388) are used to produce similar effects
This process is precise andlow cost.
in a wide range of materials. However,
Phototooling is printed acetate, which is
lasers and CNC engraving heat up the
inexpensive to replace.The accuracy of
workpiece and can cause distortion in
the etching is determined by the resist
thin materials.
Suitability
film, which protects areas of the sheet
• Prototype to mass production
that will remain unchanged. Surface removal is slow, typically
Competing Processes
Speed
• Abrasive blasting • CNC machining and engraving • Laser cutting and engraving
• Moderate cycle time, typically 50-100 microns (0.002-0.0039 in.] per pass (5 minutes)
COMPETING PROCESSES
QUALITY
UV light source
Phototooling
. Unexposed areas remain soft 1 Exposed film hardens
A major advantage of photochemical
50-100 microns (0.0020-0.0039 in.) in
machining is that it is less likely to cause
a 5 minute pass. Depths of 150 microns
distortion because there is no heat,
(0.0059 in ) are suitable for decorative
pressure or tool contact; the final shape
applications. Patterns, text and logos can
is free from manufacturing stresses.
be filled with colour.
Stage 1: Applying photosensitive resist
Stage 2: UV exposure
The chemical process does not affect
the ductility, hardness or grain of the
TYPICAL APPLICATIONS
metal structure. . Oscillating nozzles
Applications include signage, control panels, nameplates,plaques and
DESIGN OPPORTUNITIES
trophies. Photo etching is also employed
This process is suitable for prototyping
by jewellers and silversmiths for
and high volume production.Tooling
decorative effect.
costs are minimal; the negatives can be produced directly from CAD drawings,
XX2x
. Exposed film protects metal surface
Stage 3: Etching Metal dissolved by acid
graphic software or artwork and last for
Ferritic chloride etchant
many thousands of cycles. Small changes are inexpensive and adjustments can be made to the design, so this process is
TECHNICAL DESCRIPTION
suitable for experimentation and trials
The material Is meticulously prepared;
during the design process.
it Is essential that the metal workpiece
Both sides of the part are exposed to
is clean and grease free to ensure good
ensure that the resist on the reverse is
adhesion between the film and the metal
fully hardened and protective. The soft,
Lines, dots and areas of etching can be
filled with colour if the etch is more than 150 microns (0.0059 in-) deep. Very small details can be coloured independently such as patterns,logos, text and
halftone images (visible dot pattern). It is possible to etch multiple layers with repeated masking and processing; layers significantly increase cycle time. Thin sheet materials, up to i mm
and negative are exposed to UV light.
surface. In stage 1, the photosensitive
unexposed photosensitive resist film is
polymer film is applied by dip coating
chemically developed away. This exposes
(page 68) or, as here, hot roll laminating.
the areas of the metal to be etched.
The coating is applied to both sides of the
In stage 3, the metal sheet passes
workpiece because every surface will be
under a series of oscillating nozzles that
exposed to the chemical etching process.
apply the chemical etch. The oscillation
Phototooling (acetate negatives) are
ensures that plenty of oxygen is mixed
printed in advance from CAD or graphic
with the acid to accelerate the process.
software files or artwork. In stage 2, the
Finally, the protective polymer film is
(0.04 in.), can be cut as well as etched (see
negatives are applied to either side of
removed from the metalwork in a caustic
photochemical machining,page 244).
the workpiece and the workpiece, resist
soda mix to reveal the finished etching.
Case Study
Photo etching a stainless steel plaque This case study illustrates the entire etching
negative is secured to 1 side of the workpiece
is likely that the chemical etchant will have
sequence where graphics are applied to only
and placed in the light booth, where it is
attacked them during processing.
i side of the metalwork. The part is a building
exposed to ultraviolet light on both sides
plaque for the British Embassy in Beirut.
(image 5). Unexposed polymer film is washed
2-stage process and usually takes no longer
The final product is a combination of photo
off in a developing process (image 6). Close
than 30 minutes. The colour is mixed, using
etching and colour fill (image i).
Filling the etched areas with colour is a
inspection often reveals minor blemishes in
cellulose-based paints, and squeegeed over
the protective film, which can be touched up
the workpiece surface (image 11). Multiple
negative (image 2). Each negative can be
with a liquid chemical resist that dries onto
colours can be applied to very intricate
used for a single etching process or multiple
the film instantly (image 7).This is a time-
patterns, but this takes considerably longer.
etchings; there is very little wear and tear, so
consuming process but it ensures a high
Each colour will require 20 minutes drying
they can last a very long time. In preparation,
quality finish.
time. Finally, excess paint is polished off and
The process begins with a printed acetate
the metal workpiece is carefully cleaned in
The workpiece now passes through
a series of baths. The first bath contains 10%
the etching process, which takes up to
hydrochloric acid and degreases the metal,
20 minutes (image 8). The depth of the
which is then washed in mild detergent and
etch is checked, 150 microns (0.0059 in-) is
water (image 3). The surface of the metal is
sufficient for filling with colour (image 9).
dried with pressurized air.
The remaining polymer resist and
The process takes place in a dark room to
protect the photosensitive film. The polymer
the plaque is finished (image 12). 6
chemical etchant are cleaned off with a caustic soda mix and then finally with
film is applied to both sides of the metal
pure water (image 10). It is desirable to
sheet by hot roll laminating (image 4). The
trim the edges at this stage because it
the film and phototooling are free from
although different types of photo resist
ENVIRONMENTAL IMPACTS
photo chemical machining and etching,
dust and other contamination because
and etching chemical are required.
In operation, metal that is removed
are generally limited to sheet materials.
this is large enough to be visible on the
It is possible to etch very thick materials,
finished workpiece.
Chemical cutting processes, including
or 3D surfaces using a paste. The stencil
Lines and large areas of surface
from the workpiece is dissolved in the
COSTS
chemical etchant. However, offcuts and
Tooling costs are minimal.The only
other waste can be recycled. There are
is applied in the same way, but instead
material can be removed without
tooling required is a negative that can
very few rejects because it is a slow and
of passing the workpiece under a series
causing any stress to the workpiece.
be printed directly from data, graphics
controllable process.
of oscillating nozzles, a chemical paste is
applied, which has a similar effect,
software or artwork.
COMPATIBLE MATERIALS
Cycle time is moderate. Processing
Most metals can be photo etched,
multiple parts on the same sheet reduces
DESIGN CONSIDERATIONS
including stainless steel, mild steel,
cycle time considerably.
The intricacy of detail is limited only
aluminium, copper, brass, n 1 ckel, tin and
by the quality of the photosensitive
silver. Aluminium is the most rapidto
film. Very small details, down to
etch and stainless steel takes the longest.
0.15 mm (0.006 in.) in diameter, can be reproduced. Therefore, it is essential that
Glass, mirror, porcelain and ceramic are also suitable for photo etching,
Labour costs are moderate.
The chemical used to etch the metal is one-third ferric chloride. Caustic soda is used to remove spent protective film. Both of these chemicals are harmful and operators must wear protective clothing. Featured Manufacturer Mercury Engraving www.mengr.corn
TECHNICAL DESCRIPTION
CNC Engraving Process
The cutting speed is determined by the material and engraving tool. Tungsten is the most commonly used material Movement in x. y and z axes
Finishing Technology
CNC Engraving
for cutting tips. It can be re-sharpened and even re-shaped several times. It is not uncommon to cut a fresh
tool for each job, depending on the requirements of the design. Harder
A precise method for engraving 2D and 3D surfaces, CNC engraving is a high quality and repeatable process. Filling
CNC and laser technologies (page 248) are the 2 main methods used for
engravings with different colours and the use of clear materials
engraving.These processes have replaced
are effective ways to enhance design details.
engraving by hand with chisels or a pantograph; both of these methods are
Typical Applications 1 No tooling costs Moderate unit costs
Quality
• Control panels • Toolmaking and diemaking • Trophies, nameplates and signage
Competing Processes Laser cutting Photo etching Screen printing
materials, such as granite, will require
INTRODUCTION
diamond-coated cutting bits. Track and bellows
This is a 3-axis CNC ma'chine, with
Workpiece . Adhesive film .
Engraving tool
ZH
1 Tungsten (or other) cutting tip
all movement controlled by the track and bellows. The operating programme
engraves the design either in straight lines, or following the profile of the
still practised, but the labour costs are
design and creating a centrifugal
too high for them to compete. Another
pattern. The choice of cutting path depends on the shape of the engraving.
Suitability
important factor is that CNC and laser
• One-off to batch production
technology can be used to engrave a
minimum of 3 axes; x,y and z. Machines
speed of cut. Smaller cutting heads,
wi der ran g e of m ateri al s, in cludin g
operating on 3 axes are suitable for
which are often 0.3 mm (0.0012 in.) or
1 mm to 50 mm (0.04-1.97 in.) per
stainless steel andtitanium.
engraving flatworl 2003 Material: Wood Manufacture: Surface decoration created by wood eating insects
different types and new ones emerge all
Images, opposite, above right and below).
the time. Thermoplastics can be melted
The breakthrough was made possible
is an exceptionally strong fibre used in applications ranging from medical
and reprocessed, but their strength will
by the development of microcapsules
devices to bullet-proof armour.
be slightly reduced each time. Even so,
of dicyclopentadlene (DCPD) that acts as a healing agent with a wall thickness
WOOD
No product demonstrates this more
Wood is also made up of polymers: lignin,
cleverly than Table by insects (see image,
plastics do not break down rapidly in
As a natural material, wood is prone to attack by Insects, animals and disease.
landfill and are energy efficient to recycle,
that would rupture when the material
so new products are constantly emerging
began to crack, but not before. The
cellulose and hemicellulose. Lignin is a
above). In this case wood eating Insects
that make use of these properties (see
microcapsules release the healing
polymer composed of repeating and
were let loose on the table after it was
image, above left).Thermosetting
agent, which is catalyzed by chemicals
cross-linked phenylpropane units;
constructed.The patterns formed by
plastics, on the other hand,form polymer
also encapsulated in the material.The
cellulose is made up of repeating glucose
liquid material is drawn Into the crack by
molecules; and hemicellulose is a
the Insects are intriguing and will be different each time a product is made in
capillary action and polymerizes to form
complex branched polymer that forms
the same way.
a strong bond with the parent material.
cross-links between cellulose and lignin.
chains when 2 parts react together, or
(see composite laminating, page 206).
when i part is catalyzed.They differ
The rate of polymerization can be
from thermoplastics because during polymerization they form permanent cross-links, so cannot be heated, melted
andformed;they are shaped in a mold by pouring (see vacuum casting, page 40),
injecting (page 50), or vacuum drawing
adjusted to suit the process and application.This Is critical because the reactions are exothermic, so large wall
Self-healing plastic sample Made by: Beckman Institute, USA Notes: Image of a self-healing fracture specimen after testing. This shows
1 half of the specimen after it has been fractured into 2 pieces.
Wood has anisotropic properties
Up to 75% of material toughness Is
Some biopolymers, such as cellulose and
as aresult of its grain:both tensile
recovered by the self-healing process.
starch (page 446), can be molded and
and compression strength are greater
shaped in similar ways to thermoplastics.
along the grain than across it. Steam
bending (page 198) works by heating and softening the lignin into its plastic
Generally, the properties of families of
thicknesses may buildup too much heat during curing and affect the strength of
materials are similar.There are obviously
Unlike synthetic plastics, they will break
the part.
exceptions to the rule, and among the
down naturally and over a shorter time.
Violin Made by:
Frederick Phelps
Material:
Spruce
Manufacture:
Hand carved from solid wood
Notes:
Knot-free and very high quality spruce is still unsurpassed as a material for making violins.
These materials are relatively high cost compared to the other groups, so nowadays are generally only used when no others are suitable. For example, clear or tinted glass is used in reusable
packaging applications because it is inert and can be cleaned, sterilized, reused or recycled. Refractory ceramics used
for investment casting have very high temperature resistance, but are brittle enough to be broken away afterwards
without damaging the metal part within.
COMPOSITES Composites combine the properties of
different material groups and so blur the boundaries between them. The Glass bottles
and the metal melts varies according to
bulk shapes in arange of metals.The
most readily combined materials are
Made by: Beatson Clark Material: Soda lime glass
its ingredients. Low melting point metals,
hammering or pressing action forces the
plastics with fibre reinforcement.The
such as zinc (42ocC/7880F), become liquid at a temperature that is below the point
metals into shape; as a result the grain
type of plastic determines the method of
follows the contours of the part. Liquid
forming. Fibre reinforcement is selected to suit the performance demands of
Manufacture: Glassblowing (machine blow
and blow) Notes: Clear glass cannot tolerate colour contamination, but brown or green glass can use a high percentage of
mixed cullet (recycled glass).
of degradation of some thermosetting
state forming produces turbulence in the
plastics.They can therefore be shaped
hot metal, and so the resulting part has
the application and has a similar effect
in a plastic mold (page 144), which has
inferior mechanical properties.
to grain in wood, producing materials
obvious financial advantages. Metals
with anisotropic properties. Processes
with a higher melting point can be cast
CERAMICS AND GLASS
such as 3D thermal laminating (page
in molds made from steel. However, steel
Ceramics are made up of non-metallic
they have the potential to replace the conventional materials for any given
violin; maple (page 475) isusedforthe back; and the neck, bridge and tuning
application. Plastics are making the
buttons are carved from rosewood or
biggest impact by replacing metals
is formed into the direction of bend.
cast (page 130) in refractory ceramic
good high temperature properties, but
228),filament winding (page 222) and composite laminating (page 206) take advantage of this property because the fibres can be laid down according to the
The length of the grain also affects the
shells, or formed in their solid or plastic
this also means that a lot of energy is
direction of stress. Even injection molded
in critical applications. However, the
ebony (page 478).The finest violins are produced from wood that was felled
strength of wood. Processes that reduce
state. Unlike polymer chains, the strength
required during production. Ceramics
(page 50) fibre reinforced plastic parts
properties of some materials are
io or more years previously. The tree is felled in the winter months, when it is
state so that the wood can be shaped over aformer.This process utilizes wood's
and refractory metals cannot be cast in
substances and are formed at high
inherent strengths because the grain
this way and so are either investment
temperatures.Therefore, they have
grain length, such as CNC machining
of bond between metallic elements does
are either crystalline or non-crystalline.
have anisotropic properties because the
irreplaceable. High quality acoustic
(page 182), therefore reduce tensile and
not decrease overtime or with repeated
Crystalline ceramics, known simply as
fibres align with the direction of flow.
musical instruments, such as violas,
said to be 'sleeping', so that there is as
recycling.This is of great importance
ceramics, can be shaped by hand (page
little oil and moisture in the wood as
because the process of mining metals
Finite Element Analysis (FEA) software is employed to maximize the efficiency of fibre reinforcement whilst minimizing
violins and cellos, are still hand crafted
by highly skilled makers. Every aspect
possible.These instruments are worth a
of the product from material selection
lot of money, but the harmony that has
molding issues.
to tuning is overseen by the maker
been struck between the materials and
(see image, above), and a signature
manufacturing remains unchallenged by
on the finished piece represents their
modern methods.
compressive strength.
METALS
is more expensive and energy intensive
168), pressing (page 176), slip casting (page 172) or sintering, and are then
Metals are made up of metallic elements,
than the synthesis of plastics.
fired at high temperature in a kiln. Non¬
which are combined in different
When formed in their plastic state,
crystalline ceramics, known as glass,
amounts to form metals with specific
metals have improved grain alignment
are formed in their hot, molten state by
TRADITIONAL AND NEW MATERIALS
properties.The temperature at which the
compared with liquid state formed parts.
hand (page 160), blowing (page 152), press
Composite materials create new
dedication.Traditionally, spruce (page
bonds between the elements break down
Forging (page 114) is used to produce
molding, press bending or kiln forming.
opportunities for designers because
470) is used for the soundboard of a
Materials
Plastics There is an almost unlimited choice of plastics and rubbers; many
TYPES OF PLASTIC
thousands of different types surround us in our everyday lives.
chains of repeating units (monomers) which occur naturally. Synthetic plastics are produced by the petrochemical
Plastics are made up of polymers: long
They offer unique benefits for designers, manufacturers and
industry. Some natural polymers are
users. Certain types can outperform metals in many applications.
refined and molded without the addition of petrochemicals.These are known as
They are produced in large quantities to reduce cost, but we
bioplastics, and they include starch-
Foam swatches
based, cellulose-based and natural
chemicals. The formation of cross-links
still hold onto the values associated with natural materials.
rubber materials.
means that the curing process is i-way;
Material: Various -
they cannot be remolded.
Manufacture: Molded and cut
Therefore, over the years synthetic plastics have been engineered
produce as raw materials and are
Bioplastics require less energy to fully biodegradable at the end of
to look and feel like silk, leather and natural rubber.
Thermoplastics can be remolded
Made by: Beacons Products
Notes: Most plastics can be foamed with open or closed-cell structures. The
many times. Off cuts and scrap (regrind)
density, colour and hardness of
their useful life.There are also grades
can be reprocessed with virgin material
foam can be specified to suit the
of synthetic plastics available that have been modified to break down
without a significant effect on the
requirements of the application.
within a specified time period. This is made possible by the addition of
typically limited to less than 15%, but some materials may contain a much
ability to stretch and return to their
bioactive compounds, which do not
higher percentage.
original shape.Thermoplastic elastomers
affect the physical qualities of the
properties of the material. Regrind is
Thermoplastics are further
Elastomers are characterized by their
(TPE) can be melt processed in exactly the
plastic but enable it to be digested by
categorized by molecular structure and
same way as rigid thermoplastics.They
microorganisms in the ground within
are frequently over-molded and multi-
1 to syears. Products made with this
weight.The structure or crystallinity differs according to the type of material
material include some clear plastic
and method of manufacture. For
bottles, food trays and refuse bags.
example, if polyethylene terephthalate
Synthetic plastics are divided
(PET) is cooled quickly, the polymer
shot injection molded (page 50) onto rigid thermoplastic substrates to harness the qualities of both. Like synthetic plastics, synthetic
into 2 groups: thermoplastics and
chains form a random and amorphous
rubbers are produced by the petro¬
thermosetting plastics (thermosets).
structure. However, if it is allowed to
chemical industry. Natural rubber (NR),
The distinction is not always clear-cut
cool slowly, the polymer chains form an
on the other hand, is produced from a sap
because some materials can be both
orderly crystalline structure. Amorphous
tapped from the Para rubber tree [Hevea
thermoplastic and thermosetting
pi astics ten d to be tran sparent an d h ave
brasiliensis) and is used to make products
depending on their polymeric structure,
greater resistance to impact. In contrast,
such as lorry and aeroplane tyres.
for instance, polyester and polyurethane.
crystalline materials tend to have better
Materials can also be compounded to
resistance to chemicals.
produce composites of both groups.
Polymers are blended together to
Most types ofplastic can be foamed.
This is carried out with a blowing agent. There are many different types of foam,
The defining difference between these
form copolymers and terpolymers
ranging from flexible to rigid, with
2 groups is that thermosetting plastics
such as styrene acrylonitrile (SAN) and acrylonitrile butadiene styrene (ABS).
above). Foams are used for a spectrum of
form permanent cross-links between the polymer chains.This creates a more
All 3 groups ofplastic-bioplastics,
either open or closed cells (see image, applications such as upholstery, safety,
durable molecular structure that is
thermoplastics and thermosets -
model making and as a core material in
generally more resistant to heat and
contain elastomeric (rubber) materials.
composite laminating (page 206).
XI
o o c o
*
Pantone swatches
E-glass fibre reinforcement
Made by: Pantone
Made by: Various
Carbon fibre is manufactured by Material: Woven glass fibre
oxidizing, stretching and heating a
Manufacture: Injection molded
Manufacture: Extruded and woven
polymer, such as polyacrylonitrile
Notes: International reference used to
Notes: E-glass, or electrical grade glass.
Material: Polycarbonate (PC)
select, specify and match colours.
is borosilicate and was first
(PAN),to overi5000C (2732^) in a
made for electrical insulation. The
controlled atmosphere. The process of
type of weave used is determined
carbonization takes places over several
by the application.
stages of heating and so requires a great deal of energy. Eventually, long ribbons of
ADDITIVES, FILLERS AND REINFORCEMENT
plastics include metallic, pearlescent,
almost pure graphite are formed, and the
NOTES ON MANUFACTURING
therefore more suitable for thin wall
thermochromatic, photochromatic and
width of ribbon will affect the strength
Plastics with different molecular
sections and complex features.
Additives and fillers are used to enhance
photoluminescent.
of the carbon fibre.There are different
structures lend themselves to different
grades (strengths) of carbon fibre, which
m ethods of m anufacture. Th ermopl astics
all thermoplastics are compatible. Care
depend on the manufacturer.
are shaped by heating them until they
must be taken when using processes
the properties of plastics. They are used to improve colour, specific mechanical
Fillers to improve mechanical properties include talc, minerals, fibres
Due to their different properties, not
properties, electrical conductivity,mold
and textiles.Thermoplastics can be
Carbon fibre has very high strength to
are soft or liquid enough to be formed, so
such as multi-shot injection molding and
flow and antimicrobial properties and to
injection molded (page 50), extruded
weight and as a result of its own success
they are generally supplied in granulated
plastics welding to ensure a strong inter-
increase the material's resistance to fire,
and compression molded (page 44) with
is becoming more difficult to purchase
form. Processes such as thermoforming
material bond. Material incompatibility
UV light and chemical attack.
all of these fillers. Fibre reinforcement
because production cannot keep up with
(p§ge 30) require sheet materials, which
is sometimes used as an advantage, for
may be less than 1 mm (0.004 i11) 'or|g
demand. It is a relatively expensive
are extruded from granules.This
example, in release agents and lubricants.
Some plastics, such as polycarbonate
Stacking stool Designer: Rob Thqmpson
Date: 2001 Material: Polyester and glass fibre Manufacture: Composite laminating
acetate (CA) andpolylactic acid (PLA) are
(PC), polystyrene (PS) and PET, are water
in thermoplastic molding. Long and
material, but is becoming more
increases the material costs due to the
clear and so take colour very well; they
continuous strand fibre reinforcement
widespread in consumer products such
extra processing that is required.
Some are engineered to cure at room
thermoplastics. For example, Potatopak
can be tinted or opaque.The colours
is incorporated into thermosets by
as sports equipment.This is partly due to
Thermoplastics are also available as
temperature such as polyester, vinyl ester,
are typically made up of a carrier resin
compression molding, composite
the added value that carbon fibre brings
drawn fibres and blown film.
food packaging (see image, page 446 top right) is produced by compression
coated in pigment, which is added to the
laminating and 3D thermal laminating
to an application, but also as a result of
epoxy (EP) andpolyurethane (PUR);these are supplied in liquid form and mixed
Different amounts of crystallinity
Thermosets are cured in the mold.
processed using similar techniques to
molding powdered starch.
(page 228).The types of fibre used
improved manufacturing techniques,
also affect processing. For example,
with a catalyst or hardener. They can be
include glass (see image, above right),
including recent breakthroughs in
amorphous materials do not have a
poured or injected into a mold.
MATERIAL DEVELOPMENTS
reference to either Pantone (see image,
aramid, carbon and more recently hemp
recycling methods.Traditional composite
sharp melting point like crystalline
Alternatively, powdered, liquid or solid
The plastics industry is constantly
above left) or RAL.These are recognized
and jute. Fibre reinforced composite
materials.Therefore, they are more
thermosets are heated in a mold to
evolving. New blends, compounds and
as international standards and ensure
materials have superior strength for
laminating requires a great deal of highly skilled labour and is therefore very
suited to processes like thermoforming,
trigger the formation of cross-links.
additives are being developed to create
raw material during processing.
Colour is generally determined by
th at th e col our th at is specifi ed by th e
their weight, several times greater
expensive. New techniques are now
because the material stays soft and
designer in i country is exactly the same
than metal, and different grades are
being used, such as resin transfer
formable over a wider temperature
as the colour that is injection molded
molding and resin infusion (page 206),
range. In contrast, crystalline materials
by a factory in another country. Other
suitable for everything from boat hulls to lightweight stacking furniture (see
which are more rapid and mechanized
colour effects that can be achieved in
image, opposite).
and so reduce labour costs considerably.
will flow more easily in the mold due to their sharp melting point and are
The production of bioplastics crosses
opportunities, improve performance and
over with both thermoplastics and thermosets; they can be molded with
reduce cost. Many developments will
thermoplastic technology, but the
yeanbelowis abrief outline of some of
process may not be repeatable. Cellulose
the most important.
affect the design industry in the coming
/
Flexible active matrix display Made by: Plastic Logic Material: Plastic display using E Ink® Imaging Film Manufacture: Active-matrix LCD backplane fabricated onto plastic substrate Notes: Displays made from plastic are
more flexible and lighter than those made of glass.
L'Oreal shop, Paris development, and at present there are
Client: L'Oreal
very few commercial applications.
Date: Completed 2004 Material: Bencore Starlight polycarbonate
(PC)
ENVIRONMENTAL IMPACTS
Manufacture: CNC machining
There have been many developments that reduce the environmental impacts of plastics. For example, many disposable products are produced in bioplastics or a
There are many different types of
Bencore Starlight and Lightben
Printed circuitry is used in Plastic
lightweight composite plastic panels.
Made by: Bencore
Logic's flexible active-matrix display
Core materials include aluminium
Material: Polycarbonate [PCI
(see image, opposite above left).
honeycomb, DuPont™ Nomex®
Manufacture: High pressure laminated
honeycomb and corrugated and rigid foam. Bencore, an Italian manufacturer, produce a range of plastic panels used
Notes: Available in polycarbonate (PC), styrene acrylonitrile (SANI, high impact polystyrene 1HIPSI and polyethylene terphthalate modified
with glycol (PETG).
This technology has the potential to
thermoplastic with bioactive additives. Thermoplastics are very efficient to recycle.There is minimal degradation of quality and some products are even
Recycled plastic sheets Made by: Smile Plastics Material: 100% recycled thermoplastic Manufacture: Compression molded Notes: Many thermoplastics can be
revolutionize the way we read books,
made from 100% recycled materials.
preprocessed in this way, including
reports and even the morning paper.
Smile Plastics in the UK manufacture
polyethylene (PE). PET, PVC and polycarbonate (PC).
The rigid glass backpane required for
a range of plastic sheets by made up
in applications such as furniture, trade
conventional amorphous silicon-based
of ioo% recycled plastic material (see
fair stands, shop interiors and exteriors
image, above right).They are produced from packaging, footwear and even old mobile phones. Patagonia, an American
andmelamine contain formaldehyde;
based company, produce a range of
polyurethaneresin (PUR) contains
fleeces from 100% recycled plastics drink bottles (PET).The role of the designer is
diisocyanates; and polyvinyl chloride
(see images, above).The polycarbonate
available include epoxy resin,unfilled
displays has been replaced by a plastic, which means the display can be flexible,
(PC) core, whose commercial name is
nylon, and glass or carbon filled nylon.
thinner and more lightweight.
Birdwing®, is thermoformed into 19 mm
Traditionally these materials have been
(0.75 in.) diameter 3D cells.This core is
engineered to mimic production grade
Light emitting polymers, or polymer light emitting diodes (PLED), are based
laminated between clear or coloured PC
plastics such as acylonitrile butadeine
on the principles of electroluminescence.
sheets (see images, above).These panels
styrene (ABS), polypropylene (PP) and poly methyl methacrylate (PMMA) acrylic.
Sandwiched between 2 electrodes, the
to ensure that plastics can be recycled
are known pollutants and are toxic.
polymer lights up when an electrical
with minimal contamination.Therefore,
Some are referred to as volatile organic
parts shouldbe designed in a single material if possible and with recycling
are also available in styrene acrylonitrile
(SAN),high impact polystyrene (HIPS) or polyethyleneterephthalate modified
Recent developments have made it
current is passed through it. It is now
suitable for direct manufacturing low
with glycol (PETG).
volume parts and one offs as well as pre-
possible to print a matrix of plastics that emit different colours of light to produce
production models.
very thin flat panel displays.
Rapid prototyping (page 232) has revolutionized the design process. Not only are models accurate to within a few microns,but also this process is capable
of producing plastic parts that cannot be made in 1 piece in any other way. Plastics
Conductive polymers combine the
benefits of plastics technology with the
EAPs are similar to electroactive
and disassembly in mind. This book cannot avoid mentioning the negative environmental impacts
ceramics and shape memory metal
of certain plastics. Not only do they
conductivity of metals. Developments
alloys: they respond to electrical
take thousands of years to biodegrade,
include printed circuitry, light emitting plastics and electroactive polymers (EAP).
stimulation with a change in shape or
some are also harmful in production.
size.They are in the very early stages of
For example, polyester and epoxy
contain styrene; phenolic resin, urea
(PVC) contains dioxins.These chemicals
compounds (VOC) and are known carcinogens. During production care must betaken to avoid inhaling them, andsome plastics will continue to off-
gas during their lifetime and so both reduce indoor air quality and pollute the atmosphere.
POLYOLEFINS
Clamshell CD packaging Designer/client: Unknown Date: Unknown
Material: Polypropylene (PP) Manufacture: Injection molding
j^'ces DE CajK
V Polyolefins
POLYOLEFINS
POLYOLEFINS
IKEA Kalas mug
Delices de Cartier
• Polyethylene (PE) • Polypropylene (PP) • Ethylene vinyl acetate (EVA)
Material: Polypropylene |PP)
• lonomer resin
Manufacture: Injection molded
a
Designer/client: Monika Mulder/IKEA Date: 2005
PP and PE are the building blocks of the plastic industry and make up more than half of total global production.
Qualities:These plastics have alow
Made by/client: Alcan Packaging Beauty/Cartier Date:- 2006
Ni
Thin walled bottles
They have superior abrasion resistance
Applications: The whole family of
and tear strength, high levels of
materials are used to make textiles for
transparency and good compatibility and
consumer and industrial applications. PE
adhesion to many metals and polymers.
is used for thin walled plastic packaging.
with very high impact resistance. It was
their resistance to water absorption
developed in the igyos by DSM, who
Various
and attack by many acids and alkalis.
Made by: Material:
manufacture it underthe trade name
Manufacture:
They are non-toxic and are available as
Dyneema®. As a drawn fibre or sheet it is
Notes:
transparent, tinted or opaque. They are
up to 40% stronger than para-aramid
Extrusion blow molding (EBM) Polypropylene (PR), polyethylene (PE). polyethylene terephthalate
generally not suitable for applications
(DuPont™ Kevlar®, see polyamides page
above ioo0C (2i20F).
438) and 15 times stronger than steel. PP has exceptional fatigue resistance,
cap on a glass bottle Manufacture: Cap is injection molded
POLYOLEFINS
U H D P E i s an excepti on al m ateri al
coefficieTit of friction and are notedfor
PE has good resistance to punching
Material: DuPont™ Surlyn® ionomer resin
High density polyethylene (HDPE)
(PET) and polyvinyl chloride (PVC) are all suitable for EBM.
Their exceptional impact resistance
Examples include shopping bags, milk
makes them virtually shatterproof, even
bottles, medical and cosmetic packaging.
at low temperatures. lonomers can be shaped by
and tearing, even at low temperatures,
so is ideal for integral hinges and snap
POLYOLEFINS Plastic cork
It is non-toxic and so is used for toys and chopping boards. UHDPE is used for high performance
As a semi-rigid polymer it has similar
conventional thermal forming processes.
characteristics to LDPE. Increasing
As they cool and solidify the metal ions
applications such as bullet proof garments, ropes and parachute strings.
its properties are partly determined by
fits. It has a waxy feel, due to low surface
Made by:
Various
the vinyl acetate content increases
(sodium or zinc) form cross-links in the
its molecular weight, and it is classified
energy, which means it is difficult to coat
Material:
Ethylene vinyl acetate (EVA)
its flexibility and produces similar
thermoplastic structure, giving them
as high-density (H DPE), ultra high-
with adhesives and paints. Even so, it is
Manufacture:
Co-extrusion
itself to a wide range of applications. It is
easily welded and mechanically joined.
The plastic is tasteless, long lasting
similar characteristics to thermosetting
density (UHDPE),low-density (LDPE), ultra low-density (ULDPE) and linear low-density (LLDPE).
Notes:
characteristics to rubber.
plastics at low temperatures. On heating,
used for food packaging, drinking cups,
EVA can be semi-rigid, or very flexible, depending on the vinyl acetate content.
and can be extracted with a conventional corkscrew.
Atypical ionomeris ethylene
PP is a versatile material that lends
methacrylic acid (E/MAA). lonomers are
the ionic cross-links break down so the
caps and enclosures. Other uses include
thermoplastics with ionic cross-links.
material can be recycled and reprocessed.
furniture,lighting andwaterpipes.
STYRENES
MacBook Pro packaging
VINYLS Kolon Furniture 'Double Chair'
Made by: Unknown
Designer/ownenJan Konings and Jurgen Bey/
Material: Expanded polystyrene (EPS) Manufacture: EPS molding Notes: EPS is lightweight, protective and
Droog Design Date: 1997 Material: Polyvinyl chloride (PVC) covering and used furniture
insulating.
Manufacture: PVC covering stretched over used furniture to create new objects
STYRENES Attila can crusher Designer/client: Julian Brown/Rexite Date: 1996 Material: Glass filled acrylonitrile butadiene styrene (ABS) Manufacture: Injection molding
VINYLS Water soluble pouch
EVA is puncture and tear resistant and is often used for medical packaging such
Made by: Various
as blood transfusion bags. In recent years,
Material: Polyvinyl alcohol (PVOH) Manufacture: Plastic welded film
EVA has seen an explosion in consumer
Notes: The film dissolves in cold water to
and packaging applications such as
deliver a measured dose of
luxurious carrier bags and flexible net
detergent to laundry.
equipment, ear defenders and other safety equipment, children's toys and automotive parts.
SAN has high thermal stability and so
Vinyls • Polyvinyl chloride (PVC) • Polyvinyl alcohol (PVOH) PVC has a glossy appearance and its shore hardness can be adjusted to suit the application.
is often used for transparent kitchen
PVOH is a water soluble barrier film.
appliance mixing bowls, water purifiers
packaging used for glass bottles and
and other products that require a very
fruit. As foam it is used for trainer soles
high surface finish and durability combined with the convenience of
Qualities: PVC is along lasting material
Applications: GPPS is used for disposable
dishwashing. It is also used in the
andmore than half of global production
applications,from blown films and
food packaging, cutlery and drinking
automotive and medical industries.
is for use in the construction industry.
coatings to injection molded and blow
cups, CD 'jewel' cases, lighting diffusers
and imitation cork. lonomers are used in a range of
SBS and SEBS are used extensively
It has a glossy surface finish and is
molded parts. It is possible to mold thick
and model making kits. HIPS is used for
in multishot injection molding (page
available in a range of vivid colours. It is
wall sections without sink marks or voids.
vending cups, product housings and toys.
50) and co-extrusion applications with
either plasticized or not. Unplasticized
It is water-clear and so can feel and look
EPS is used in 3 main ways: either molded
thermoplastics including PE and PP
like glass and is therefore utilized in highinflates them into foam that is 2%
into the desired shape (packaging, .helmets and toys), molded into pellets (loose fill), or as sheet material that
PVC (uPVC) is rigid; where as plasticized PVC is flexible with a shore hardness
polycarbonate, page 435) and PA (see polyamide, page 438). Products include
material and 98% atmosphere.
can be cut (model making, thermal
babies'teats and dummies, ice cube
light, but PVC is not suitable for exposure
insulation and packaging), EPS is the
trays, soft touch grips and children's toys.
to prolonged periods at temperatures
end packaging such as cosmetics. Other
applications Include golf balls covers and
Styrenes
the soles of football boots. Costs; PE, PP and EVA are low cost, lonomers are medium cost.
• Polystyrene (PS) • Acrylonitrile butadiene styrene (ABS) • Styrene acrylonitrile (SAN) • Styrene butadiene styrene (SBS) • Styrene ethylene butylene styrene (SEBS) This is a broad range of thermoplastics that are easy to process and have good visual properties.
ABS has similar properties to HIPS with superior chemical and temperature resistance. It has a high gloss surface (like
GPPS) and is produced in vivid colours. SAN is resistant to impact and
scratching and has excellent light Qualities: PS is categorized as general
purpose (GPPS), expanded (EPS) and high impact (HIPS). GPPS is naturally
transmission qualities (90%). SBS and SEBS are copolymerized with
transparent andbrittle. HIPS is produced
synthetic rubber (page 445) and so have a large range of flexibility, with a shore
by blending PS with polybutadiene; it
hardness range of oA-soD.Theyremain
has improved impact resistance and
flexible even at low temperatures.
toughness. EPS is molded by expanding PS beads with gas and steam, which
These materials are generally limited
to applications below 8o0C (i760F).
(see polyolefins, page 430), ABS, PC (see
retardant and has good resistance to UV
above 6o0C (i400F).
ch eapest polymer foam.
ABS is used for a range of applications
range of 60-95A. It is naturally flame
Costs: Low.
The downside of PVC is that it
including housings for power tools,
contains chlorine and dioxins.This
telephones, computers and medical
has led to many campaigns against its
use, especially in food, medical and toy appli cati on s. H o we ver, th e producti on of PVC is increasing as it replaces more
wood and metal products in the building and construction industries.
Hydrolyzed polyvinyl acetate (PVA) makes PVOH, a water-soluble film. PVA is used in adhesives and coating because it
is not suitable for molding. PVOH is produced as fibres andfilms. It dissolves easily in water and the rate of dissolution
is adjusted by the structure of the polymer (crystallinity) and temperature; PVOH will absorb more water as it warms up. This means that PVOH can be used in water at room temperature without biodegrading; when the water is warmed to its trigger temperature, the polymer chains start breaking down rapidly. Applications: PVC is used to make 'vinyl' records. Now it is more widely used for extruded window frames, doorframes
and guttering. Other applications include identity and credit cards, medical packaging, tubing, hoses, electrical tape and electrically insulating products.
Vinyl is used to coat materials and fabrics to protect them from chemicals, stains and abrasion. Examples include
Acrylic and composites
ACRYLIC AND COMPOSITES Lymm Water Tower kitchen
• Poly methyl methacrylate (PMMA) Acrylic is used for its combination of clarity,
Designer/client: Ellis Williams Architects/
impact resistance, surface hardness and gloss.
Date; Completed 2005 Material: DuPont™ Corian® (acrylic and aluminium trihydratel
coated wallpaper and upholstery fabrics.
PVOH is used in hospital laundry
Russell and Jannette Harris
Manufacture: Thermcformed, CNC machined and
bags, water-soluble packaging,fishing
adhesive bonded
bait rigs and, when mixed with sodium
opposite) is a blend of PMMA and natural
ACRYLIC AND COMPOSITES
Discs showing edge glow
Polycarbonate
mineral (aluminium tri-hydrate).This
Made by: Various
• Polycarbonate (PC)
forms a hard, durable sheet material. It is
PC has excellent clarity and superior mechanical
relatively expensive, but has a luxurious
Material: Poly methyl methacrylate (PMMA) acrylic Manufacture: Cast or extruded
an ideal material for electronic products such as
quality unmatched in thermoplastics.
Notes: Tinted acrylic materials produce
mobile phones and Apple Mac computers.
Sheets are 3680 x 760 mm (145 x 30 in.),
properties. Rich and luminous colours make this
edge glow from ambient light.
6 mm to 12.3 mm (0.024-0.48 in.) thick
tetraborate, children's 'slime'.
Costs: Low.
DuPont™ Corian® (see image,
. and available in a wide range of colours. Qualities: Acrylic sheet materials are
heat the material above 8o°C (i760F),
available as extruded or cast.There are
because it will start to soften. It is an
Applications: Acrylic is used in point of
alternative to glass for certain products
small differences between the 2 that will
ideal material for laser cutting, scoring
sale displays,furniture, signage, light
such as beakers and spectacle lenses.
affect how they are machined and
and engraving (page 248) because the
diffusers, control panels, screens, lenses
It has an amorphous structure, which
formed. Sheets can be up to 60 mm
heat of the laser produces a gloss finish.
and architectural cladding.
contributes to it being the toughest clear
(2.36 in.) thick,but become very
Edge glow (see image, opposite) is caused by light picked up on the surface of the sheet and transmitted out through
Costs: Moderate.
expensive over io mm (0.4 in.). Sheet materials can be thermoformed (page
Qualities: PC is a suitable and safe
plastic. However, this also means that it
is prone to degradation by UV light and certain chemicals.
30), drape formed and machined (page 182). Acrylic can be machined to tight
the edges. Cut edges and scored lines
glow in the right lighting conditions.
such as ABS (see styrenes,page432),to
tolerances because it is a hard material
This effect is exploited in signage and
increase rigidity and impact resistance,
and it can be polished to a high gloss
decorative applications.
finish (especially by diamond polishing,
It is possible to incorporate materials
PC is blended with other polymers,
especially for thin walled parts. Blending and molding materials together
page 376). Sheet materials can be cut
and objects in cast acrylic sheet or blocks.
harnesses the desirable properties of
with conventional wood cutting
Examples included barbed wire, razor
each; PC-ABS is less expensive than PC
equipment, as long as the tool does not
blades, flowers, grass and broken glass.
and improves the properties of ABS, with
POLYCARBONATE Bluetooth Penelope*Phone Designer/clientr Nicolas Roope and Kam Young/
HuLger Ltd Date: 2005 Material: Polycarbonate (PC) Manufacture: Injection molded
THERMOPLASTIC POLYESTERS Sei water bottle Company: Sei Global Date: 2006 Material: Polyethylene terephthalate (PET)
x m 70
o "D > CO
Manufacture: Injection blow molded
i POLYCARBONATE
Miss K table lamp Designer/client: Philippe Starck/Flos Date: 2003 Material: Polycarbonate (PC) internal and external diffuser, and poly methyl
methacrylate (PMMA) acrylic frame Manufacture: Injection molded and vacuum
THERMOPLASTIC POLYURETHANE Feu D'lssey
Thermoplastic polyurethane
Designer/client: Curiosity Inc./Beaute Prestige
Thermoplastic polyesters
International
• Thermoplastic polyurethane (TPU) There is a range of flexibilities from shore hardness 55A to SOD. TPU is resistant to
Material: The red casing is thermoplastic
abrasion, tearing and puncturing.
Manufacture: Injection molded
Date: 2001 polyurethane (TPU1
metalized with aluminium
• Polyethylene terephthalate (PET) • Polyethylene terephthalate modified with
glycol (PETG) • Polybutylene terephthalate (PBT) • Polycyclohexylene dimethylene
this reduces the brittleness and premature ageing of PET. PETG has improved thermoforming properties and
so is ideal for lighting diffusers and medical packaging,for example.
PBT is electrically insulating and flame retardant. It can be glass filled,
terephthalate (PCT)
which improves its heat stability and
• Liquid crystal polymer (LCP) • Thermoplastic polyester elastomer (TPC-ET)
temperature range up to 2000C (3g20F).
better surface finish and processing, for
Qualities: The properties of TPU are
and weatherproof outdoor clothing. It is
There is a range of thermoplastic polyester
example. PC is a relatively compatible
similar to thermoset polyurethane (page
a tactile material and is used to make
engineering materials. All have high dimensional
material, which can be blended,
443).They are tough, durable, resistant
synthetic leather.
stability and are resistant to chemicals.
multishot injection molded (page
to fuels, oils and greases and resistant
50) and coextruded with a number of
to flexural fatigue across a broad
such as conveyor belts, automotive
fl am m abl e, h as excepti on ally 10 w m ol d
different materials.
temperature range,from -450C to 750C
interior linings, instrument panels,
shrinkage and very high dimensional
(-49 -167° F). Th ey exhibit 1 ow 1 e vel s of
wheels and over-molded gear sticks and
stability. LCP has rod-like molecules,
creep and high levels of resilience and so
levers. As well as molded products,TPU is
Applications: Applications include lighting diffusers (indoor, outdoor and automotive), police riot shields and
are suitabl e for 1 oad bearin g appl i cati on s. TPU is available as a resin, sheet, film
It is suitable for abrasive applications
THERMOPLASTIC POLYURETHANE
Golf ball
safety shields, beakers, beer glasses and
and tube. It is naturally opaque but can
Made by:
Various
babies bottles, motorcycle helmets and
be produced in clear.
Material:
Thermoplastic polyurethane (TPU) Injection molded Golf balls are made up of 2 or
Manufacture:
CDs and DVDs.
Notes:
Costs: Moderate.
applied as a coating. Costs: Moderate.
which align during melt processing.They
Qualities: PET is the most widely used
produce superior physical properties
thermoplastic polyester (for thermoset
over a wide temperature range with very
polyesters, see page 442). It can be
little thermal expansion or shrinkage,
amorphous or semi-crystalline
especially in the direction of flow;
depending on how it is processed and
the molecular alignment produces anisotropic properties.
more layersfthe core is typically
cooled (rapid cooling does not allow the
so is usedfor many clothing and
synthetic rubber and the outer
formation of a crystalline structure). It is
layer is TPU.
high temperatures and water absorption. LCP is an aromatic polyester. It is non-
Applications: TPU is breathable and sportswear applications such as shoes
PCT has all the mechanical properties of PET and PBT with greater resistance to
possible to modify PET with glycol (PETG):
TPC-ET is an engineering elastomer, it has excellent fatigue resistance and
ACETAL Flo-Torq® IV propeller hub Designer/client: Mercury Marine
Date: 2006 Material: DuPont™ Delrin® acetal Manufacture: Over-molded by injection molding onto titanium rods
THERMOPLASTIC POLYESTERS
THERMOPLASTIC POLYESTERS
Flexometer® wrist guard
Chevrolet HHR headlamp
POLYAMIDES
Polyamides
5^ Designer/client: Dr Marc-Herve Binet/Skimeter
Designer/client: DuPont™ Automotive/Chevrolet
• Polyamide (PA)
'/] Date: 2003
Date: 2006
• Aromatic polyamide (Kevlar® and Nomex®)
Material: Headlamp bezel and trim ring are
PA. commonly known as nylon, is a versatile
Material: DuPont™ Hytrel® thermoplastic polyester ITPC-ET) Manufacture: Injection molding
DuPont™ Crastin® polybutylene
material used in a wide range of applications.
terephthalate (PBT)
Aromatic polyamides are stronger than steel for
Manufacture: Injection moulded
their weight.
Makita Impact Driver Designer/client: Makita Date: 2006 Material: Polyamide (PA) nylon body and thermoplastic elastomer (TPE) pistol grip Manufacture: Multishot injection molded
as a substitute in garments, apparel and carpets. Following its conception in the
Acetal • Polyoxymethylene (POM)
1930s, nylon rapidly became a material in
POM, known as acetal, is an engineering polymer
its own right. Stockings and tights made
that bridges the gap between plastics and
out of nylon are very successful because
metals.
they are dramatically cheaper than silk versions. Cordura® is the trade name for nylon fabrics from Invista; they are tough, durable and resistant to abrasion.
Qualities: A high level of crystallinity
Qualities: There are many different
430), they are as close as scientists have
high impact strength, tear strength and
security, decoration, to reduce ultraviolet
grades of nylon, which are categorized
come to mimicking spider web.
impact resistance.
light and to preverft glass disintegrating
as follows: nylon 6; nylon 6,6; nylon 6,12;
if it breaks. It is a high performance
amorphous nylon (transparent) and high
their high heat performance, electrical
Applications: PET is used for drinks
material: Northsails jDLandBDr
temperature nylon.These grades can be
insulation andflame resistance.They do
material for ropes and sheets, and
to many chemicals, fuels and oils, and its
bottles because it is transparent in its
technology (page 228) laminates aramid
modified in a number of different ways
not have the same level of resistance to
commonly as fibre reinforcement in
low coefficient of friction reduces wear.
amorphous state, is easily blow molded
and carbon fibres between PET film.
to produce reinforced,flame retardant,
cutting and abrasion as para-aramids
composite materials. Meta-aramids
tough and super-tough versions.
and so they are often reinforced or
are foun d in appl icati on s th at dem an d
with low warpage, and has high fatigue
.laminated into papers.
very high performance such as power
endurance, so is suitable for spring and
its flexibility ranges from 30-80D. It has
used as a coating on glass and plastic for
and can withstand internal gas pressure from carbonated drinks. Post-consumer
PBT and PCT are used for oven handles and knobs, electrical connector blocks,
Nylon is self-lubricating,has alow
PET bottles are reprocessed into new
switches and light bulb housing. LCP is
coefficient of friction, and has good
products such as textiles andfleeces.
used for lighting connectors, computer
resistance to abrasion and chemicals.
PET is used as an industrial film. An
chip carriers, microwave oven parts
There are 2 main types of aromatic
Meta-aramids are used mainly for
Powdered nylon is fused into 3D forms
in rapid prototyping (page 232). Para-aramids are used as a single
means acetal is dimensionally stable at peak temperatures and can operate ¦close to its melting point. It is resistant
It is tough, even at low temperatures,
generation, aircraft, aerospace, racing
snap fits. It is ideally suited to injection
Applications: Nylon is used in bushes
cars and fire fighting. They are often
and bearings, electrical equipment
used as fabrics such as in flame resistant
molding (page 50) and machining (page 182), but can be rotation molded (page
undergarments worn by racing drivers.
36), blown (page 22) and extruded.
example is Madico's Lumisty view control
and cookware, mobile phone parts and
polyamides, including para-aramids
housings,furniture parts (mechanisms
film. The textured surface on the film
aerospace optical components.
known by the DuPont™ trademark name
and feet) and sports equipment.
TPC-ET is used in keypads, tubing,
Kevlar®, and meta-aramids, which are
As a drawn fibre, it exhibits similar
Costs: Nylon is moderate cost and
Applications: Acetal is used if the less
seals, sports goods, medical devices and
also known by the DuPont™ trademark
properties to silk and so is widely used
aromatic polyamides are high cost.
expensive thermoplastic polyester (page
soft touch handles.
name Nomex®.They are only available
refracts light and controls the viewing angle either horizontally or vertically. It is
Costs: Costs vary according to type: PET is
as spun fibre or sheet material because
437), PE (see polyolefins, page 430) and polyamides (opposite) are not suitable. It
there is no other practical way to form
is important in the appliance, hardware
low to moderate cost, TPC-ET is moderate
them. They have superior resistance to
and automotive, industries where it has
cost, PBT and PCT are moderate to high
temperatures up to 5OO0C (9320F) and
replaced metal parts. Uses include
cost and LCP is high cost.
are inherently flame retardant.
speaker grilles, sports goods, seatbelt
Para-aramidfibres have exceptional
systems and automotive fuel systems.
strength to weight, far superior to steel.
Alongside UHDPE (see polyolefms,page
Costs: Moderate to high.
They are non-flammable, resistant to
TPV and ETPV are made up of a thermoplastic matrix embedded with
Polyketone
stress cracking and fatigue, ultraviolet
• Polyetheretherketone (PEEK)
light and virtually all chemicals.They
PEEK is used for its hardness, dimensional
operate effectively at a wide temperature
particles of EPDM (see polyolefins,page 43 o). Th e th erm opl asti c m atri x of TPV
range from -2500Ct0 2500C (-418-482^).
is PP. It is known as ETPV when the PP
stability and wide working temperature range of -20oC to 250oC (-4-A820F|. It is suitable for molding and machining and is available as sheet, plate, rod and tube.
They can be formed by a host of melt processes including injection molding
is replaced by a higher performance thermoplastic.
(page 50), rotation molding (page 36) and extrusion, but they are very expensive
Applications: The range of applications
FORMALDEHYDE CONDENSATION RESINS
Qualities: PEEK is an opaque grey
and so often limited to coatings and
include keypads, soft touch handles and
Aramith billiard balls
material. It is non-flammable, electrically
linings.They can be transparent or
grips, hot water tubing, seals, gaskets,
insulating and hard, with a low friction
opaque, so coatings can appear invisible.
sportswear and goods, medical devices
Date: N/a
and automotive parts.
Material: Phenolic resin
coefficient. Mechanical properties are maintained at temperatures as high as
Applications: These are high cost
2500C (4820F), and it is resistant to many
materials, but they are effective as a thin
acids and chemicals.
PEEK reinforced with carbon fibre
Designer/client: Saluc
Manufacture: Molded, ground and polished
Costs: Moderate to high.
coating. Examples include non-stick cookware and self-cleaning coatings
has dramatically improved mech anical
on fabric and glass. Fluoropolymers are
properties with little increase in weight,
also used for automotive, aerospace and
Formaldehyde
Le Creuset casserole
and is used in the aerospace industry.
laboratory applications.
condensation resins
Designer/client: Le Creuset
Applications: Aerospace, medical
Costs: Very high.
FORMALDEHYDE CONDENSATION RESINS
Date: Unknown
equipment and electronic products.
• Phenol formaldehyde resin (PF) • Urea formaldehyde (UF) • Melamine formaldehyde (MF)
Material: Phenolic resin handle Manufacture: Compression molded
These thermosetting materials have a hard and glossy finish that is resistant to scratching.
Costs: Very high.
They are resistant to most chemicals, have good dielectric properties and operate across a wide
Fluropolymers • Polytetrafluoroethylene (PTFE) • Ethylene tetrafluoroethylene (ETFE) • Fluorinated ethylene propylene (FEP) Commonly known by the DuPont™ trademark
Thermoplastic
temperature range.
and are also resistant to burning.
rubber compounds
name Teflon®, fluoropolymers are well suited to
• Melt-processible rubber (MPRI • Thermoplastic vulcanizate (TPVl • Engineering thermoplastic vulcanizate (ETPV!
use in extreme environments: they are inert and
These combine the performance of rubberwith
stable across a wide temperature range.
the processing advantages of thermoplastics.
suitable for food and drink applications, PF is suitable for operating temperatures up to i2o0C (248^). MF forms more cross-links than the other 2, and so has superior mechanical and chemical resistance properties. Applications: Examples include electrical
FORMALDEHYDE CONDENSATION RESINS
Qualities: These are classified as a family
Qualities: These materials contain
Qualities: PF, under the trade name
housing, plugs and sockets, kitchen
together with UF and Formica is a
containing fluorine atoms, which give
elements of rubber but do no"t cross-link
Bakelite, revolutionized the plastics and
equipment, tableware, ashtrays, knife
laminate of paper or cotton and MF.
them superior resistance to virtually all
during shaping, so can be recycled many
design industry. It was invented around
and oven handles, light fittings and
chemicals and an extremely low friction
times.They have similar mechanical and
1900 and became the first commercially
snooker, pool,bowling andcroquet
Costs: PF and UF are low cost. MF is more
coeffi ci ent. Th e low fricti on coeffi ci ent
physical properties to rubber but can be
molded synthetic polymer in the 1920s.
balls. Demand has recently increased
expensive.
acts like a lubricant and stops other
molded on conventional thermoplastic
PF is naturally dark brown or black and so
for under-the-bonnet applications
equipment.This means much more rapid
does not colour easily.
materials sticking to them.
processing times.They typically range from shore hardness 20 to 90A. These materials are resistant to
UF and MF are sub-categorized as
in battery-powered cars because
these materials provide the electrical
amino resins.They are naturally white
insulation and stability that is required
or clear and so are available in a range of
at a reasonable price. They are used in adhesives for
abrasion, chemicals, fuels and oils.They
vivid colours. In the 1930s, they began to
have high impact strength, are flexible
replace PF for use in domestic products
laminating plywood and they are
even at low temperatures and resistance
like tableware.
impregnated into papers andfibres.
toflexural fatigue. MPR can withstand
Formaldehyde resins are resistant
constant use at 1250C (2570F) and ETPV up
to moisture absorption and so do not
toi500C (3020F).
stain easily.They are tasteless and so are
For example, DuPont™ Nomex® (see
polyamides, page 438) is impregnated with PF, laminated wood is bonded
Mebel clam ashtray Designer/client; Alan Fletcher/Mebel Date: 1970 Material: Melamine Manufacture: Compression molded
Vinyl esters
EPOXIES AND COMPOSITES
Lux table
and composites • Vinyl ester
Vinyl esters bridge the gap between polyester and epoxy resins.
Qualities: These materials are similar to polyesters.They are also catalyzed with
methyl ethyl ketone peroxide (MEKP). However, the reaction does not produce as much heat, so thicker sections can be cured. This leads to faster cycle times. They are tougher and more resilient than polyesters, and they are less prone
Polyesters and composites
POLYESTERS
to water absorption and more resistant
Material memories
to chemicals.
Designer; Rob Thompson
Date: 2002 • Polyester
Material: Polyester resin and natural fibres
Polyesters are the least expensive composite
Manufacture: Composite laminating
As with polyesters, styrene is offgassed by the material. Applications: Vinyl esters have become
laminating resins.
popular laminating materials because they are less expensive than epoxy, but have superior properties to polyester.
Qualities: These differ from thermoplastic polyesters (page 437) because they are unsaturated, with double bonds between molecules.
visible texture on the surface. Gel coats are used to minimize print through. They are naturally translucent and can
Styrene is added to assist
Costs: Low to moderate. Applications: A range of composite
more liquid, so it can be cast or laminated
applications such as automotive body
at room temperature. Polymerization
panels, lorry cabs, cherry picker cradles
is catalyzed with methyl ethyl ketone
and boat hulls.They are prone to water
peroxide (MEKP). MEKP is not part of the
absorption, so have to be covered with a
polymerization process; it activates it and
gel coat or vinyl ester for increased lifespan in outdoor and marine settings.
Polyesters exhibit high levels of shrinkage, in the region of 5-10%.This
cars, aeroplane fuselage, wings and interiors.
be coloured to form an opaque material.
polymerization. It makes the material
causes a rapid exothermic reaction.
They are used in mold making, racing
Costs: Low.These are the least expensive
causes fibre reinforcement and other
of the 3 main laminating resins:
fillers to'print through'and create a
polyesters, vinyl esters and epoxies.
EPOXIES AND COMPOSITES Carbon chair Designer/ Bertjan Pot and Marcel Wanders/ made by: Moooi Date: 2004 Material: Carbon fibre reinforced epoxy
Epoxies are suitable for outdoor and marine applications because they are not prone to water absorption. Costs: Moderate.
resin (EP) Manufacture: Carbon fibre saturated in EP is hand-coiled over a mold.
Epoxies and composites • Polyepoxide resin (BP)
little during polymerization, typically
POLYURETHANES Maverick Television awards
less than 0.5%. Epoxies are electrically
Epoxies are high performance resins. They form
insulating and have high resistance
very strong bonds with other materials and so
to chemicals.They are suitable for
are applied as coatings and adhesives as well as
high temperature applications, up to
laminated and molded products.
Polyurethanes • Polyurethane resin (PUR)
Designer/client: Maverick Television/Channel h,
PUR is a versatile material available in a range of densities and hardnesses, used as a solid cast
Date: 2005 Material: Polyurethane resin (PUR)
material, foam, adhesive and liquid coating.
Manufacture: Vacuum casting
200°C (392°F), and also have very good resistance to fatigue. Qualities: Epoxies are naturally clear and
Applications: Epoxies are used in many
Qualities: PUR is naturally tan or clear,
injection molded (page 50) materials
rigid. They can be pigmented and filled with metallic flake. It is also possible to fill them with objects and materials
different formats such as liquid for
and available in an almost unlimited
like PR (see polyolefins, page 430), ABS
casting and laminating, paint, coating
colour range (see image, above right).
and encapsulation, structural adhesives
(see styrenes, page 432) and nylon (see polyamides, page 438). Snap fits, live
during casting. ,
and impregnated in carbon fibre weaves.
Thermoplastic polyurethanes (see page 436) are used in molding and coating
hinges and other details otherwise
Laminated products include furniture,
applications such as trainer soles, sports
limited to injection molding can be
is facilitated by a hardener, which makes
boat hulls, canoes, automotive panels
wear and golf balls. PUR prototyping
made by vacuum casting (page 40) and
up 1 half of the resin,They shrink very
and interiors.
materials are designed to mimic
reaction injection molding (page 64).
Epoxies are not catalyzed.The reaction
SILICONES Flexible ice cube tray Designer/client: Unknown Date: Unknown Material: Silicone Manufacture: Compression molded
POLYURETHANES Open-cell foam balls Made by: Various
Material: Foamed polyurethane resin (PUR] Manufacture: Reaction injection molded Notes: Most plastic can be foamed with open or closed-cell structures.
PUR is used for prototyping and low volume production. Examples include car bumpers, dashboards and interiors, toys, sports equipment and housings for
SILICONES
SILICONES
Animal rubber bands
Skin Light
Designer/client: D-Bros/H Concept
Designer; PD Design Studio Date: 2006
Date: 2003 Material: Silicone
Material: Silicone
Synthetic rubbers »Isoprene rubber [IRl • Chloroprene rubber ICR) • Ethylene propylene rubbers [EPM and EPDM] • Butyl rubber (lIRl • Butadiene rubber IBRl • Acrylonitrile butadiene rubber (ABRl • Styrene butadiene rubber ISBR)
Manufacture: Extruded and cut
Manufacture: Cast
and have low levels of volatile organic
Typical uses include O-rings, gaskets,
There are several different types of
weather strips, seals, medical and
synthetic rubber.They are used in place
surgical equipment, and food processing
of natural rubbers. They have shape
(for example, molds for chocolate).
memory and so will return to their
consumer electronics.
PUR drawn fibre is resistant to cutting and abrasion and is used in textiles, shoe uppers and sports equipment. PUR materials are resilient and
As an adhesive and coating PUR is
durable, and resistant to flexural fatigue,
used to protect and bond wood with
abrasion and tearing.They operate at
other materials. It is quick drying and
compounds (VOCs), which makes them suitable for food preparation and
temperatures up to i2o0C (2480F), but
forms a watertight and rigid seal.
packaging and medical applications.
tbey are affected by ultraviolet light and will become hard and brittle with
Silicones have a wide operating Costs: Low to moderate.
prolonged exposure.
Applications: More than half of all PUR is foamed.There are 3 main types: spray
Silicones
Spray foam is used for filling holes, as insulation or adhesive and to fill cavities in products to make them more rigid.
• Silicone resins
These are low strength but highly versatile materials. They are used as adhesives, gels, rubbers and rigid plastics. They have excellent are chemically inert.
melamine resin
uncertain whether silicone causes tissue
abrasion, have good low temperature
modified with a carbon additive to make
disease and so it is not recommended for
properties, good resistance to chemicals
them conductive.
more than 25 days in the body. As a liquid it is used as a lubricant and
and are typically electrically insulating. IR is the synthetic version of natural
fuel, and SBR is the cheapest and most
release agent in RIM (page 64), composite
rubber (page 447) and consequently has
common form of synthetic rubber.
laminating (page 206) and compression
similar characteristics and applications.
SBR is a widely used low cost rubber
CR was the first synthetic rubber,
with properties similarto natural rubber.
(page 50), compression molding (page 44), casting (page 40) and extrusion. They are used by model makers because
molding (page 44).
Manufacture:
Compression molding and
injection molding
ABRhas superior resistance to oil and
invented by DuPont™ in the 1930s, and is
certain grades cure at room temperature.
also known by their trademark name of
Applications: Synthetic rubbers are used
vulcanizing (RTV) rubbers. They can
Neoprene®. it has very good resistance to
in place of natural rubbers in a range of
be coloured with a range of plain,
oils and atmospheric corrosion, making it
applications.Typical products include
a suitable substitute for natural rubber.
fuel hoses, gaskets, washers, O-rings,
polymers are derivedfrom the element
pearlescent, metallic, thermochromatic
linings in clothes and bags.
silicon (14 in the periodic table), but their
and fluorescent pigments.
Costs: High cost.
EPM and EPDM have good resistance to atmospheric corrosion and heat.They
properties should not be confused.
Silicone resins are typically resistant
original shape after deformation.
electrically insulating, but can be
car interiors, packaging, shoe soles and
liner in fridges and freezers, in sports
1973 Synthetic rubber, acrylonitirile butadiene styrene [ABS] and
Qualities:They are resilient, resistant to
underlining, most upholstered foam
Rigid foam is used as an insulating
Date,; Material;
and medical implants. However, it is
cushioning in gym mats, carpet
Qualities: This family of synthetic
Designer/client: Mario Bellini/Olivetti SPA
3i50C (-t66- 5990F).They are naturally
These are known as room temperature
furniture, other seating, mattresses,
SYNTHETIC RUBBERS Divisuma 18 portable calculator
for children's toys, baby bottle teats
electrical resistance and high heat stability, and
Flexible foams are used to provide
CO
temperature range from -no0C to
They are shaped by injection molding
foam, flexible foam and rigid foam.
Certain grades are considered safe
O
Applications: These are relatively
range from 30A to 95A shore hardness.
diaphragms, tank linings and seals. Neoprene® is well known for use in wetsuits, footwear and other sportswear.
IIR is impermeable to gas and
and protective equipment and as a
to water, chemicals and heat. They have
expensive materials, but their high
core material in composite lamination
good insulating and lubricating
performance properties mean they
resistant to atmospheric corrosion. It
(page 206).
properties.These materials are non-toxic
are suitable for a range of applications.
is utilized in tyre inner tubes.
Costs: Low to high cost.
STARCH-BASED
Potatopak plate Made by: Potatopak Material: Potato starch Manufacture: Compression molded
Notes: 100% biodegradable plates and packaging.
NATURAL RUBBER
CELLULOSE-BASED
Cellulose-based • Cellulose acetate (CA) • Cellulose acetate propionate (CAP) These are thermoplastic self-shining materials that maintain a glossy finish. They are used in products that have a lot of user contact because they feel 'natural.
Irwin Marples chisels Made by: Irwin Industrial Tools Date: The first acetate chisel handles in the 1950s, still in production today Material: Cellulose acetate propionate (CAP) handle and tool steel blade) Manufacture: Cast handle with forged and tempered blade
NATURAL RUBBER James the bookend
to be chemically refined into dextrose,
Latex coated gloves
which is fermented into lactic acid and
Made by: Unknown
Designer: Black+Blum
Material: Natural rubber (NR) latex Manufacture: Dip coated (dip molding)
Date: 2002 Material: Natural rubber (NR)
Notes: Rubber makes a flexible, protective
Manufacture: Compression molded
then distilled to form polymerized PLA. Roughly 2.5 kg (5.51 lb) of maize are required to produce 1 kg (0.22 lb) of PLA.
and non-slip coating.
These materials require about 50% less energy to produce than conventional thermoplastics.They can
Qualities: Cellulose-based polymers are
mixing together cellulose, pigments and
partly made up of cellulose, which is a
various chemicals, which are rolled into
naturally occurring polymer and can
flat sheets and left to dry.This produces
be derived from wood pulp or cotton.
colour patterns that cannot be achieved
It is similar to starch, which is also a
with injection molding (page 50) such as
polysaccharide (glucose polymer).The
marbling andtortoiseshell.
difference is that cellulose is structural
CAP is available in transparent grades
STARCH-BASED
be thermoformed (page 30), injection molded (page 50) and extruded.
Envirofill Made by:
Pro-Pac Packaging
Material:
Potato or wheat starch
Manufacture:
Extrusion
Notes:
A reusable alternative to
Potato and corn starch materials are not so chemically refined as PLA; instead,
in truck and aeroplane tyres. It is
occurring sap that is drained from trees.
into a mold and baked. It is possible to
gloves, condoms, clothes and medical
extrude and compression mold (page
equipment. Gloves are coated with latex to improve grip, puncture, tear and
than CA. It is the more expensive of the 2.
plastics typically contain 70% or more
abrasion resistance.
Starch-based
starch. The higher the starch content, th e
Qualities: NR is stabilized by vulcanizing
more rapidly the plastic will break down; high starch content plastics will dissolve
it using sulphur. It is used in almost pure
• Polylactic acid (PLA)
form (dip) or mixed with other materials.
in water within 15 minutes.
It has excellent flex, tear and abrasion
resistant and transparent, and certain
Applications: Cellulose-based polymers
grades are biodegradable.The raw
are available as sheet material, drawn
• Rice, potato and corn starch
material has to be processed heavily
fibre or molded product. Sheet materials
Starch is made up of carbon dioxide, water and
and chemically modified to produce a
are used in the production of spectacle and watch straps, for example.
Also known as latex, NR is derived from naturally
biodegradable in water.
form of storage.
Sheets of cellulose are produced by
materials.The majority of NR is used
polystyrene (PS) and 100%
44) starch-based plastics. Starch-based
frames, hairclips, cutlery handles, toys
resistance and is more elastic than most
other elements. Thermoplastic starch plastics will breakdown into those elements readily when exposed to microorganisms or water.
Applications: PLA is used in the production ofcompost bags, disposable
Cellulose is also used to make
synthetic rubbers (page 445). The majority of N R production is
cutlery, food and beverage packaging,
carried out in Malaysia, Indonesia and
photographic film and is drawn into
Qualities: PLA has similar characteristics
women's hygiene products and
Thailand. It is drained from trees in a
fibres for textiles. Edible films are made
to LDPE (see polyolefins, page 430).
pharmaceutical intermediates.
process known as tapping.The trees
with cellulose; they can be flavoured and are used for packaging food. Costs: Moderate.
as liqui d coatin g s, foam s an d soli d
• Natural rubber (NR)
dip molded (page 68) to produce
and is stiffer and more impact resistant
commercially viable and stable material.
Applications: Natural rubber is used
starch rich mulch or powder is placed
(found in cell walls), while starch is a These polymers are tough, impact
Natural rubber
It is transparent and is available as a
Rice, potato and corn starch are used
produce latex for up to 30 years, after which time they are replaced, so NR is
blown film, fibre or foam. The starch
in food serving and packaging (plates,
used in the production of PLAs can be
trays, bowls and punnets), electronics
available from renewable sources. In a
packaging and loose fill packaging.
factory the latex is coagulated and rolled
derived from agricultural by-products
into sheets ranging from 0.2 mm to
of barley, maize and sugar beet crops, all of which are annually renewable. It has
Costs: Low to moderate.
3 mm (0.0079- 0-118111-) thick.
Costs: Moderate.
MS
/ Metals Metals are elements, many essential for sustaining life on earth. In the correct quantities they play a vital role in our diets and the existence of plants and animals. They are even useful in the fight
Metals are extracted from their mineral ore, refined and processed to form combinations of metallic and other elements suitable for use in products. This is an energy intensive process, and
against diseases: certain metals are known to have natural antimicrobial properties. However, these same properties mean that certain metals are toxic and polluting in sufficient quantities. Metals are used for structural and aesthetic applications from packaging to bridges. A range of finishes can be produced, some
so metals are typically more expensive
than plastics that have equivalent strength characteristics. In recent years plastics have replaced con sum pti on. Th ere i s a 1 arg e n umber of
ease with which they can be produced and their physical and mechanical
different iron alloys.
properties modified for specific
of which are self healing and so dramatically increase longevity.
Arcos chef's knife
metals in many applications, due to the
Most, but not all, ferrous metals are magnetic, due to their iron content.
applications. Even so, metals are still
Non-magnetic ferrous metals include
widely used in engineering, medical,
austenitic stainless steels. Non-ferrous
large-scale, performance and high
metals are nearly always non-magnetic,
perceived value applications.
but cobalt and nickel are exceptions
As a group of materials they are
typically heavy and have high melting points. There are many different types
to the rule. Even so, iron is by far the strongest naturally magnetic element.
Alloys are hybrids of different
Made by.- Arcos Material: Molybdenum vanadium stainless steel Manufacture: Forged and polished
CORROSION, PATINA AND PROTECTIVE OXIDE FILMS Certain ferrous metals are prone to
of metal suitable for an unlimited range
metallic elements combined to enhance
surface corrosion. In the presence of
of applications. Some are non-toxic and
properties and reduce cost.They can be
oxygen and water the iron reacts to form
sufficiently inert to implant into the
made up with properties suitable for
alayer of iron oxide, commonly known as
human body; examples include titanium
the demands of specific applications.
rust.This is a degradation process that
joint replacements and gold teeth.
For example, Arcos knives (see image,
gradually consumes metal that contains
Others are poisonous, prone to corrosion
above) use a specially developed
iron from the outside inwards. Protective
or explosive.
stainless steel.The alloying elements are
coatings, such as galvanizing (page 368),
chromium, molybdenum and vanadium.
painting (page 350) and powder coating
TYPES OF METAL
The proportions and combination of
(page 356) are used to prevent corrosion.
Metals are divided into 2 main groups:
properties produce an exceptionally
Stainless steels are produced by alloying
ferrous and non-ferrous. The defining
sharp and long lasting cutting edge that
steel with chromium and other metallic
feature is that ferrous metals contain
can be maintained by sharpening.
elements. Chromium forms a protective
iron. Ferrous metals are produced
Molybdenum is part of a class of
oxide on the surface of steel and reduces
and used in larger quantities than
materials known as refractory metals.
subsequent corrosion of the base metal.
non-ferrous.This is mainly due to
Surprisingly, pure iron is more resistant
the versatility of steel; it is used in
This group of metals has extremely high melting points: while steels melt at
to atmospheric corrosion than steel.This
products, from domestic appliances
approximately i3500C (2462^), refractory
is due to its lower carbon content.
to the automotive, construction and
metals have a melting point above
shipbuilding industries,for example.
Cor-ten is high-strength low alloy
i75O0C (3i82cF).This makes them very
steel. It is distinguished by a protective
Even though ferrous metals are
difficult and expensive to manufacture.
patina that develops on its surface in
limited to those containing iron, they
To utilize their superior properties, they
the atmosphere.This reduces the need
make up more than half of all metal
are alloyed to form hybrid materials.
for painting or other protective coatings.
Black-Light Designer:
Charlie Davidson
Date:
2005
Material:
Aluminium foil
Manufacture:
Handmade
Aluminium extrusions Made by: Various
Material; Aluminium alloy Manufacture: Extrusion Notes: Most non-ferrous metals can be extruded into profiles with internal features.
BeoSound and BeoLab
(see image, above) or pre-weathered
NOTES ON MANUFACTURING
Designer/client: David Lewis/Bang & Olufsen Date: 2003 Material: Aluminium alloy
copper (see image, page 460).These
There are 3 categories of forming process:
products such as foil (see image, above),
has superior resistance to stress and
self-protecting metals are virtually
liquid, plastic and solid state forming.
sheet, strip, rod, tube, angle and other
fatigue. Products used in construction
maintenance-free and so are often used
As the names suggest, the processes are
extruded profiles (see image, above
and high performance applications are
Manufacture: Anodized
in building facades,roofs and cladding.
categorized by the relative temperature
right). These can be further processed
typically formed in their plastic state by
into coloured, perforated, woven,
rolling orforging.
dissimilar metals are electrically connected and submerged in water
plastic state forming the metal is heated
textured materials.
(electrolyte).The electrolyte may
Date: Material:
Richard Serra Completed 1987 Cor-ten high strength low
alloy steel Manufacture:
N/a
expanded, corrugated, embossed and
Grain structure can be further improved with heat treatment.This is
It is used in architecture and outdoor
be seawater or even a thin film
up to below its melting point and in liquid state forming it is heated to above
cast or wrought. Wrought metal is cast
cooling. The rate of cooling affects grain
sculpture. Over time the surface develops
of condensation. The reaction is
its melting point. Plastic and solid state
into bars and then rolled (see forging,
structure and produces either hard and
arust-like appearance, as in the case of
similar to electrolytic processes such
forming can be used to shape most
page 114) into profiles, sheets, strips and
brittle or ductile and tough structures.
the sculpture Fulcrum (see image, left).
as electroplating (page 364) and electropolishing (page 384):! of the
metals. Casting processes are liquid state
other profiles. The difference between
forming, and most use steel molds, so the
the products is the grain structure. Cast
Some non-ferrous metals, such as
Designer:
linear grain alignment. This alignment
of forming: solid state forming is carried out with no additional heat, while in
Galvanic corrosion occurs when
Detail of Fulcrum, London, UK
Primarily, there are many standard
Many metals are available as either
the process of controlled heating and
MATERIAL DEVELOPMENTS
gold and platinum, are practically inert.
metals becomes the anode and the other
metal being cast must have a melting
products have a random grain structure,
Metal foam is produced by a similar
Others react with the atmosphere and
the cathode.The metal that becomes
temperature below that of steel. Steel is
while forged and rolled metals have a
technique to polymerfoam; afoaming
produce a surface oxide layer that forms
the anode will erode more quickly than
cast in ceramic molds such as those used
a protective barrier against further
normal. Metals will only corrode each
for investment casting (page 130),
corrosion.The oxide layer is also very
other in this way if there is sufficient
durable, such as anodized (page 360)
potential difference between them, and
Certain metals are reactive and even explosive in certain conditions.
aluminium. The layer of oxide that is
the rate of corrosion is determined by the
For example, titanium is reactive with
produced by anodizing is among the
strength of the potential difference. For
oxygen in its molten state.Therefore,
hardest materials known.The patina
example, aluminium and steel must be
liquid forming is carried out in a vacuum
can be used for decorative effect such
insulated in application, otherwise the
or inert atmosphere. This increases the
as coloured anodized aluminium
steel may corrode the aluminium.
cost of production.
porosity.This is removed by soaking the part in molten nickel (or other suitable metal), which solidifies to fill the voids. In contrast, direct metal laser sintering
(rapid prototyping, page 232) produces parts that are 98% metal.The metal is
sufficiently dense to make tooling for injection molding (page 50). Powder metallurgy makes it possible to form materials that it is not practical to liquid state form such as refractory metals. It is also used to combine the properties of dissimilar materials. For example,flexible magnets are made up of iron powder in a polymer matrix. Metal composites, also known as metal matrix composites, are made up of non-ferrous metal reinforced with particles of high performance ceramic 33
o D
such as silicon carbide or alumina
(page 490) or carbon fibres.They exhibit higher levels of wear resistance,
O z
temperature resistance and stiffness. Typical carbon reinforced aluminium
panels are lighter than aluminium with the stiffness of steel. Foamed metal Made by: Various
(more than 1000%) when heated up to 450°C to 5000C (840- 9320F) for
materials that exhibit molecular
Material: Aluminium alloy
aluminium or up to 8500C to 9000C
rearrangement at specific temperatures.
Manufacture: Foamed (open-cell)
(1562-1652 0F) for titanium.They are
In other words, they can be deformed
superformed (page 92), which is a
and then, when triggered at a specific
similar process to thermoforming
temperature, they will return to their
plastics (page 30). Superforming
original shape.The temperature that
requires less pressure than conventional
triggers the rearrangement can be
techniques and can form deep profiles
engineered to suit specific applications
with tight radii from a single sheet.
andean range from approximately-25[,C
Notes: Aluminium and copper are the most common metal foams.
agent is mixed with the metal and is
Shape memory alloys are novel
that is constantly springing back to its
Scrap metal
metals into new metal products.The
original shape.The original shape is
Made by:
N/a
econ om i c val ue of m etal an d effi ci en cy of
formed and set by heat-treating the raw
Material:
Steel wire
recycling means that nearly all industrial
material in the desired shape.
Amorphous metals combine the
Manufacture:
N/a
Notes:
All types of metals are cost effective to recycle.
physical properties of metals with the
metal scrap is recycled (see image, above). Consumer waste has to be collected and separated, which increases the costs
processing advantages of plastics (see
slightly. But it is still up to 90% more
image, above left).This is made possible
energy efficient to recycle than mine raw
•by the random arrangement of the
material. Unlike plastics, metals retain
atomic structure, which is similar to
is energy intensive and produces a lot
their strength when they are recycled.
glass; the atoms are aligned randomly,
of waste and hazardous by-products.
Therefore, they can be shaped and
as opposed to the typical crystalline
Metals are extracted from their ores
recycledmany times without anyloss of
structure of metal. Casting conventional
in a reduction process. Electrolysis or
strength. Endless recycling reduces the
metals produces inferior grain structure,
a chemical reducing agent (carbon or
environmental impact of the mining and
but cast amorphous metals have
hydrogen) removes the oxygen atoms
extraction of the material.
exceptional properties such as high
from the metal atoms.The concentration
impact strength, strength to weight (twice that of titanium), hardness and
of metal in the ore varies, and low
aeross, or very 1 arg e an d gi ving a foam that is up to 95% air. Metal foam can be
resistance to corrosion and wear.
triggered at a specific temperature in
Metal powders compressed into
to ioo0C (-13°- 2i20F). An example is
Nitinol, which is a nickel titanium alloy.
the mold to produce an open or closed
3D bulk parts are porous.There are
cell structure (see image).There is a
different processes used to shape metal
wide range of alloys, densities, porosities
powders and each produces a different
superelasticity when the temperature for
and shapes.They are lightweight, rigid,
level of porosity. For example, pressing
rearrangement is set lower than room
conductive and impact absorbing.The
and sintering produces a high level of
temperature.The result is a material
cells can be less than i mm (0.04 in.)
This property is referred to as
used as a core material, either skinned or
concentrations will produce more waste as a result. Inert metals do not always need to be extracted from ore because
foamed inside a hollow metal profile to
ENVIRONMENTAL IMPACTS
they do not react with oxygen in the first
produce li ghtwei ght pan el s an d tubes.
Metal products are typically long lasting and have higher perceived value than
place. For example, gold can be found in
Superplastic alloys include certain grades of aluminium and titanium. They
plastic equivalents. However, mining
exhibit extremely high levels of elasticity
and extracting metals from their ores
its raw metallic state. Much less energy is required to recycle post-consumer and industrial waste
STEEL
VW Beetle Designer/client: Ferdinand Porsche/Volkswagen
Date: 1960s model Material: Low carbon steel Manufacture: Cold metal pressing [stamping and
deep drawing), welding and painting
STEEL
Bird Kettle Designer/client: Michael Graves/Alessi Date: 1985 Material: Stainless steel Manufacture: Deep drawing, welding and
polishing
Steel • Carbon steel • Low alloy steel • Stainless steel • Tool steel These are the most common metals and can be found in many industrial and domestic
applications. The specific properties of each type are determined by the carbon content and alloys.
Iron • Wrought iron • Cast iron Iron is a low cost structural material whose use predates steel by many hundreds of years.
It is soft, ductile and has been replaced by carbon steel for most applications due to its inferior strength. Cast iron is made up of iron, carbon
IRON
Qualities: Carbon steels have a low,
York railway station roof, UK Architect: William Peachey and Thomas Prosser
Date: Completed 1876
and small amounts of silicon.There
Material: Wrought iron I-beams
are different types, including grey,
Manufacture: Hot and cold rolled
medium or high carbon content, ranging from approximately 0.2-2%. Higher carbon content produces a harder, less ductile and more brittle material.
Mild steel (plain carbon steel) is a term
white, ductile and malleable.They are
that covers a range of carbon steels
differentiated by the formation of carbon
up to 0.25% carbon content. They are
in the iron matrix and alloying elements.
distinguished by ease of solid state
Qualities: Iron ore is an abundant
Generally, cast iron has gopd dampening
forming and welding. Carbon steels are
material in the earth's crust and it is
properties and machinability is resistant to fatigue and corrosion and is difficult to
prone to oxidization and corrosion, so are
believed to make up a large percentage of the mantle and core, it is a heavy
weld due to the high carbon content.
protected with a coating in some form. Low carbon steels are relatively ductile, malleable and easy to shape. In
and soft material that is relatively easy to form hot or cold. It is classified as
Applications: Wrought iron has been
contrast, high carbon steels are hard and
wrought or cast. Wrought iron contains less than 0.2% carbon and cast iron
largely replaced by steel.Traditional applications include architectural
to abrasion and more brittle. Medium
contains between 2-4% carbon. Iron
metalwork and fencing. It remains a
IRON
carbon steels have levels of carbon and
the steel such as resistance to corrosion,
other alloys. The high levels of chromium
with a carbon content between 0.2-2% is
useful material in the construction
Le Creuset giant grill and griddle
alloys that are ideal for hardening by
formability and toughness. Certain
result in very good resistance to
classified as steel.
industry, for manufacturing tools,
Made by: Le Creuset
heat treatment.
grades of these materials are also
corrosion.There are 4 main types, which
automotive crankshafts and suspension
Material: Cast iron
referred to as high strength low alloy steels (HSLA).
precipitation hardening. Austenitic
Wrought iron has a very low carbon
as a consequence they are both resistant
Manufacture: Cast and enamelled
Low alloy steels are made up of iron, carbon and up to approximately io% of
are austenitic, ferritic, martensitic and
content and very few contaminants.
arms, and also for cooking equipment,
It can have a visible grain, produced by
due to its high thermal conductivity.
other metals, such as nickel (page 462) and chromium. The additional alloys are
steels that contain iron, less than 1%
magnetic; ferritic grades are less strong,
Costs: Low to moderate.
used to improve certain properties of
carbon, 10% chromium or more and
magnetic and generally used for indoor
forging or rolling (page 114) the iron and slag together in the production process.
Stainless steels are a group of alloy
grades are ductile, strong and non¬
ALUMINIUM ALLOYS
Lightweight composite panel Made by: Cellbond Composites Material: Aluminium alloy honeycomb Manufacture: N/a Notes: Wood, metal, glass reinforced
plastic and polycarbonate (PC) are all used as surface materials.
STEEL
ALUMINIUM ALLOYS
Leatherman Wave
Fluted tart tins
Made by: Leatherman Tool Group
Made by: Various
Date: 20(U
Material: Aluminium alloy
Material: Stainless steel
Manufacture: Pressed
Manufacture: Punching, grinding, polishing and heat treating
_ STEEL
ALUMINIUM ALLOYS
Coloured stainless steel
Coca-Cola Pocket Dr.
Made by: Rimex Metals
Made by: Coca-Cola
Material: Stainless steel
Material: Aluminium alloy
Manufacture: Chemical colouring process
Manufacture: Various
Notes: The range of colours includes red, green, blue, gold, bronze and black.
an d decorative appli cati on s; m arten siti c
then heated up to 2oo0C (3920F) for an
coatings.The material develops a
are the hardest but least resistant to
hour before cooling, which allows the
protective oxidized layer that prevents
corrosion; and precipitation hardening
carbon particles to diffuse and develop
further corrosion of the metal.
grades are high strength and have
the steel's toughness and ductility.
Stainless steels are used in a range of
Aluminium alloys • Aluminium alloys This is a lightweight and conductive metal that is non-toxic and does not affect the taste of food
decorative andfunctional applications.
or drink. It is used in a range of decorative and
Applications: More than three-quarters
They are expensive and so are only used
functional applications.
areusedforcuttingtoolsanddies.The
of all steel production is carbon steel.
if necessary, usually for decorative appeal.
carbon and alloy content make them
Low carbon steel is used a great deal in
Examples include sinks, worktops,food
hard, tough and resistant to abrasion
construction, automotive metalwork and
preparation and cooking equipment,
even at high temperatures. Specific
mill products such as sheet, strip, beams
cutlery, architectural metalwork,
examples include high-speed steel (HSS)
and sections. Medium carbon steel is
furniture, lighting and jewelry.
and mold steels.
used for crankshafts, chassis, axles,
moderate resistance to corrosion. Tool steels are so called because they
Tool steels are typically used in tools
roughly half the weight of aluminium as
Applications: It is used in a wide range
aluminium is extracted, is an abundant
of steel (page 455). It is also a very good
of applications including packaging,
material in the earth's crust. But
electrical and thermal conductor.
drinks cans and cooking equipment.
Qualities: Bauxite ore, from which
springs, forgings and pressure vessels.
such as screwdrivers,hammers, cutting
extracting the aluminium is an energy
approximately 0.3-0.7% are suitable
High carbon steel isusedforsprings,high
tips and saw blades. They are also used
intensive process; it takes roughly 3 kg
reacts to form a protective layer, which
electronics and appliances are made in
for hardening by heat treatment. This
strength wire and low cost cutting tools.
to make dies for melt processing plastics
(6.6 lb) of bauxite to produce 0.5 kg (1.1 lb)
makes it almost maintenance free.The
aluminium, and automotive applications
and some metals.
of aluminium. This is why it is so efficient
protective layer is enhanced and can
include engine parts, bodywork and
to recycle aluminium rather than extract
be coloured with the anodizing process
chassis. Aeroplanes, trains and ships
if from new bauxite.
(page 360). The surface of aluminium
use a great deal of aluminium. In the construction industry uses include
Steels with a carbon content between
is the process of heating up the steel
Low alloy steels are also used in
In the presence of oxygen the surface
and cooling it at different rates to form
construction. Interesting examples in the
different microstructures. Normalized
U K are Richard Serra's sculpture Fulcrum,
Costs: Like all metals, the price of steel
steel is heated to between 8oo0Cand
in London (see image, page 450), Antony
fluctuates according to fuel prices and
Pure aluminium is quite soft and
900dC (1472-1652^) and then slowly
Gormley's sculpture The Angel of the
global demand. Prices ranges according
ductile. It is alloyed with small amounts
can also be polished (page 376) to a bright and high quality surface finish.
cooled, which allows the microstructure
North, at Gateshead and Heatherwick
to the type of steel: carbon steels are the
of copper (page 460), manganese, silicon,
Aluminium is a highly reflective metal,
to develop into a strong formation.
Studio's sculpture B of the Bang, in
least expensive, but still generally more
Quenched steel is cooled very rapidly in
Manchester, all made in Cor-ten steel.The
expensive than iron, followed by low alloy
coldwaterandsoisveryhardandvery
alloys in this particular grade of steel
steels and stainless steels.Tool steels are
magnesium (page 458) and zinc (page 459) to improve hardness and durability. It has good strength to weight; the
metalizing (page 372), which is the process of applying a very thin film of
brittle.Tempered steel is quenched and
eliminate the need for protective
the most expensive.
same strength can be achieved with
aluminium onto a high gloss surface.
and this quality is exploited by vacuum
Housings and frameworks for consumer
windowframes, trims anddoors. Costs: Moderate to high.
Metal uses only make up a small percentage of the total use of titanium. It is more commonly found as titanium
dioxide, a white pigment used in the production of paints and paper. Costs: High.
TITANIUM ALLOYS
Joint Strike Fighter blisk
Zinc alloys
Made by:
Rolls-Royce pic
• Zinc alloys
Date:
2006
Zinc alloys exhibit high resistance to corrosion
Material:
Titanium alloy Blades linear friction welded onto central disk A blisk is a 1-piece bladed disk
and so a great deal of zinc production is for
Manufacture: Notes:
galvanizing steel.
rotor design.
TITANIUM ALLOYS
Magnesium alloys • Magnesium alloys
These have better strength to weight than aluminium, but are more expensive.
S9 Matta Titanium bicycle frame
forms on its surface. Anodizing (page
Qualities: Zinc has low viscosity
Made by: Bianchi Date: 2006 Material: Titanium alloy
360) thickens the layer and increases
and a relatively low melting point,
protection.The oxide is porous and can
approximately 4200C (7880F).These qualities make it particularly suited to
Manufacture: Extruded tube cut to length, welded
and polished
be dyed with a range of vivid colours. Titanium is reactive with oxygen
casting. Itis suitable for forming small,
and so high temperature processing is
bulk, sheet, complex and intricate shapes.
typically carried out in a vacuum or inert
Zinc castings are often electroplated
atmosphere. Low temperature processes, Qualities: Magnesium is extracted by a
Other examples include casings for
such as spinning (page 78), stamping
(page 364) with another metal to combine the casting opportunities of
very energy intensive electrolytic or oxide
electronics products such as mobile
(page 82) and superforming (page 92),
zinc with the aesthetic properties of
reduction process, which makes it more
phones, MP3 players, camcorders and
can be carried out in normal atmospheric
other metals, such as nickel (page 462),
expensive than aluminium (page 457). it is often alloyed with aluminium, silicon
laptops, as well as sports equipment
conditions, so titanium can be processed
such as bicycle frames and tennis rackets.
with similar ease to aluminium.
Costs: Moderate to high.
its susceptibility to stress cracking.
It is suitable for many aluminium forming and finishing processes such
Titanium alloys • Titanium alloys
(page 92) and anodizing (page 360). It
Titanium alloys are an expensive alternative to
is less reflective and conductive than
aluminium and magnesium, so are limited to
(especially in salt water).
applications that demand high strength to weight
Qualities:Titanium is more energy intensive to produce than aluminium
that forms on the surface of the zinc
Frank Gehry and completed in 1997.
and protects it from further corrosion.
many industries. Examples include door handles, bathroom furniture, automotive
for medical implants such as bone and
Galvanized (page 368) parts are very bright at first. Without treatment, the
joint replacement and strengthening
surface will become less bright over time.
In construction zincis usedfor gutters,
or dental implants, for piercings and for
Building products are often treated in
drain pipes,roofs, wall cladding and
a process known as pre-weathering to
facades. Sheets of zinc are also used as
it has also been used for casing for
avoi d col our vari ation.
worktops in kitchens and bars. Although
As abuilding material itis
it is less common now, worktops in
It is particularly suitable for springs, due to its low density and low modulus
maintenance free and in normal
hospitals and laboratories were once
ZINC ALLOYS
conditions will last for 80-100 years
covered with zinc.
Heavy-Weight tape dispenser
before it needs to be replaced.
of elasticity. Springs in titanium can
are similar to aluminium; magnesium is
be less than half the size and weight
used when greater strength to weight
to corrosion, especially to salt water and certain chemicals.
of steel (page 455) equivalents, and it is therefore used for this type of application
Applications: Most zinc is used in
is required. In the automotive industry
in performance motorbikes, cars and
produce brass (page 460). Zinc alloys
aerospace applications.
(other than brass) are used for castings in
by naturally occurring oxide that
parts and jewelry.
jewelry. Like aluminium and magnesium,
(page 457) and magnesium and so is
and bodywork of performance cars.
pre-weathered blue-grey and pre-weathered slate-grey.
Museum in Bilbao, Spain, designed by
more expensive. It has excellent resistant
Like aluminium, titanium is protected
Manufacture: Notes:
Rheinzink Zinc alloy Cast and rolled The 3 finishes are bright,
patina on its surface.This is a visible layer
Applications: Many of the applications
it is used for the chassis, engine parts
Material:
tarnishes very quickly and develops a rich
mobile phones, cameras and laptops.
powdered form. It has a bright flame and is used for pyrotechnics and flares.
Made by:
Applications: A famous application is
and superior corrosion resistance.
Magnesium is explosive, especially in
Zinc sheet
the metal cladding on the Guggenheim
Titanium is non-toxic and so is used
as die casting (page 124), superforming
aluminium, and more prone to corrosion
It is resistant to atmospheric corrosion and many acids and alkalis. However, it
and zinc to improve its performance in
specific forming applications and reduce
chrome or precious metals (page 462).
ZINC ALLOYS
Designer: EUack+Blum
Costs: Moderate.
galvanizing oris alloyed with copper to
Date: 2004 Material: Zinc alloy Manufacture: Die cast
3D XI
O
Copper alloys • Copper • Brass • Bronze
The rate of colour change depends on the oxygen, sulphur dioxide and moisture content of the atmosphere.
COPPER ALLOYS Villa ArenA, Amsterdam Architect:
Virgile & Stone Associates Ltd. and Benthem Crouwel Architecten
Indoors, copper will change very slowly,
Leebo bouwsystemen
Copper alloys are ductile, have a low melting
whereas next to the sea, or an industrial
Date:
point and are easy to form. Copper develops a
area, copper will develop a green
Material:
Completed 2001 Tecu® Patina copper alloy
Manufacture:
The process pre-weathers metal
protective and decorative patina on its surface, which changes colour over time.
sulphate layer in as little as 5 years.
by mimicking natural oxidization
Alloyed with zinc (page 459) or tin (page 462), it has a lower viscosity and Qualities: Copper is an efficient
so is suitable for casting complex and
heating elements, and conductive bases
thermal and electrical conductor. It is
intricate shapes.
for pots and pans.
considered to be a hygienic material with
Brass is an alloy of copper and 5-45%
It is also used for roofs and cladding
antimicrobial properties. Many types of
zinc. A greenish brown patina develops
(see images, above and opposite above),
bacteria are neutralized when they come
on its surface and becomes a dark brown
typically pre-weathered for decorative or
into contact with it, which is one reason
overtime.There are many different types
restoration purposes, Other outdoor
it is used in hospital door handles.
of brass, which are categorized by the
applications include decorative
quantity of zinc. Higherlevels of zinc
metal work and sculptures: the Statue
produce harder and more brittle brasses.
of Liberty in New York is made from
Copper is a bright reddish pink when first produced.This does not last long.
The surface quickly develops a layer of oxide, which is dark brown in colour. This will gradually become greenish in colour
Bronze is an alloy of copper and up to 40% tin.The patina develops much more slowly and is a brownish colour.
(verdigris) as it develops. With prolonged
copper and shows the green patina that develops with prolonged exposure. Instruments, including trumpets, saxophones,bells and symbols, are
exposure, the film becomes very durable
Applications: Many uses for copper are
and protective.This means the copper is
associated with its conductive properties.
maintenance free andlong lasting.
Examples include electrical cables,
produced in brass and bronze. Costs: Low to moderate.
COPPER ALLOYS
COPPER ALLOYS
Copper coffee pot
Brass darts
Designer: Unknown
Designer: Unknown
Date: Unknown
Date: Unknown
Material: Copper alloy and tin
Material: Brass
Manufacture: Metal spinning and pressing
Manufacture: Turned on a lathe
Pewter is an alloy of tin with small
Nickel alloys
amounts of copper (page 460) andlead. It is so soft it can be carved by hand.
• Nickel alloys Nickel is used mainly for electroforming, electroplating and as an alloy in stainless steel.
Applications: So-called'white metals' are used in many casting applications such as jewelry, architectural models and scale models.They are often plated with another metal or painted.
Qualities: Nickel is a bright metal and
Lead is still used in construction and
has very good resistance to oxidization
as radiation shielding. It is also useful
and corrosion.The properties are used in
as a weight, for example, in the keel of
low alloy and stainless steels (page 455). It has a rapid rate of deposition in electrolytic solution and so is an efficient
sailing boats.
and plating other metals.Tin plated
and useful material for electroplating
products include steel packaging, toys,
Tin is used a great deal for alloying
(page 364) and electroforming (page 140). Skin contact can result in the user's sweat dissolving nickel salts, which may result in allergic reaction, or more specifically, allergic contact dermatitis.
cooking utensils and furniture. NICKEL ALLOYS Costs: Low.
silver (alloy of nickel, copper and
zinc) sheet
Manufacture: Die cast body, electroplated with
Material: Lead alloy nose cone and nickel-
18 ct gold
Manufacture: Centrifugal cast nose cone and
and can operate at over 6oo0C (iii20F).
Bedside Gun light Designer/client: Philippe Starck/Flos Date: 2005 Material: Gold and aluminium body
Made by: Aero Base
Nickel is the base alloy element in so-called'superalloys'that are stable
PRECIOUS METALS
Scale model part
photochemical machined'sheet
They also have very high resistance to corrosion and oxidization.These
materials are typically shaped by investment casting (page 130). Applications: Very large electroformed
Lead and tin alloys
Precious metals
• Lead alloys
• Silver
• Tin alloys
• Gold
• Pewter
• Platinum
parts can be produced in nickel. It is used
These are soft metals that are suitable for
These are rare and therefore expensive metals.
to make molds for the aerospace, marine
casting. They are sometimes referred to as 'white metals'.
Most have exceptional resistance to corrosion.
and performance automotive industries.
They are very efficient thermal and electrical conductors, and are also non-toxic.
It is used to electroplate trophies and
content. Red or pink gold contains
Decorative uses include jewelry, cutlery
copper (page 460); white gold contains
and tableware. Silver ions are used in
platinum, silver or zinc (page 459);
paints, powder coats and varnish to
purple gold contains a precise measure
inhibit the growth of bacteria or fungi.
of aluminium (page 457); blue and black are also possible. Alloying gold with other metallic elements will alter the
tableware and medals. Its non-toxic
mechanical properties as well as colour.
qualities are used in tooth repairs and
The purity of gold is measured in carat
plaques because it produces a bright and long lasting finish, but is generally not
Qualities: These alloys have low melting
used on products that have prolonged
Gold has a rich and lustrous appearance that is useful in jewelry,
PRECIOUS METALS Memento Globe necklace Designer: Rachel Galley Date: 2006 Material: Silver globe and 9 ct gold ball Manufacture: Centrifugal cast, soldered
and polished
capping. It is even used in food and drink
Qualities: Silver is bright and highly
(ct): 24 ct is pure gold; 18 ct is 75% gold;
such as gold flake in Goldschlager. It is
reflective, but the surface oxidizes quite
14 ct is 58.3% gold; andio ct is 41.1% gold
plated onto cables for high quality sound
of platinum is to damage the DNA in
and intimate contact with the user's
points: tin is below 2500C (4820F),lead is below 3500C (6620F), and alloys of these
readily and so has to be frequently
by weight. Unlike many gold standards,
systems and telecommunications due
cancerous cells to inhibit cell division.
skin. Short-term contact, such as with
metals can be as low as 200°C (3920F).
polished or'coloured over'to keep its
the U l< allows no negative tolerance.
to its high conductivity and tarnish free
nickel plated coins and keypads, is not
They have low viscosity when they are
brightness. Like the other precious
usually problematic.
molten and so are efficient materials to
metals, it is a very efficient conductor.
precious of these 3 metals and so the
cast. Low pressure casting techniques
Silver ions have antimicrobial properties.
most expensive. It is hard, durable and
medical applications because it is does
can produce high definition of detail.
Electroforming (page 140) and
ductile and is resistant to corrosion by
not corrode or tarnish and is non-toxic.
electroplating (page 364) can produce
abrasion, oxygen and many chemicals.
It is also a very effective catalyst and
Austenitic grades of stainless steel contain nickel. They have superior resistance to corrosion and oxidization
Lead is toxic and a heavy metal, and
and so are commonly found in outdoor
its use in many applications is now being
and construction applications.
phased out due to its link with blood and
The properties of nickel-based
brain disorders.
superalloys are exploited in jet engine
Tin is non-toxic and has excellent
parts and other extreme applications.
resistance to corrosion. It is alloyed with other metals to reduce their melting
Costs: Moderate to high.
point and increase corrosion resistance.
Platinum is the most rare and
surface finish.
Platinum isusedin jewelry and
Platinum is a very good conductor and
this quality is employed by catalytic
Gold is a very soft, malleable and
catalyst. It is a member of a group of
converters: platinum catalyzes the
ductile material. It can be beaten into
precious metals including rhodium,
conversion of polluting exhaust fumes
very thin sheets, known as gold leaf. It has
palladium and iridium among others.
products in almost pure silver.
Pure gold is yellow. Different colours
are produced by varying the alloy
into water, carbon dioxide and other less harmful substances. It plays an
a shiny and tarnish free surface finish.
Applications: Silver is used for both
important role in fighting cancer
industrial and decorative applications.
because it is an active ingredient in
certain chemotherapy drugs.The role
Costs: High to very high. Silver is the least expensive, and platinum is considerably more expensive than gold.
Machine stress-rated pine Made by: Various
Material: Pine [EW) or spruce (ER) Manufacture: Sawn timber Notes: This is a construction softwood
Materials
categorized as EW/ER (European
Wood and natural fibres
whitewood/European redwood),
which has been kiln dried (KD) to less than 20% moisture content.
Wood is a natural composite material made up of xylem tissue,
The qualities of wood are the result of
which is a fibrous material consisting mostly of elongated, rigid
natural growth and the influence of the
walled cells that provides trees and shrubs with an upwards flow
timber with particular strengths,
elements. Each species of tree produces
O O o >
of water and mechanical support. Its strength and lightness have
weaknesses and visual characteristics.
been exploited for millennia. Fibrous woody materials include
are slow growing with interlocking
Some growfast.tall and straight; others grain. Over the years certain woods have
bamboo, reed, rush and vines such as rattan. These grow fast
become essential and irreplaceable in th e con structi on of buildi n g s, musi cal
and when treated are suitable for similar applications to wood.
instruments, tools andfurniture.
Demand for bamboo is increasing because it is proving to be an
Wood is a sensual material that is warm to the touch. Some species are
economic, environmental alternative to wood in many projects.
more aromatic than others, such as cedar
(page 470), which has been traditionally used in coat hangers to deter moths, as shoetrees to counteract foot odour,
and light but is classified as a hardwood,
Rotary cut (peeled) veneer
taste andis resistant to splintering. As
while certain softwoods are dense and
Made by: Various
a natural, edible and biodegradable
hardwearing like some hardwoods.
Material: Birch
and in pencils because it has a pleasant
' 4W mm,
material, woodis prone to disease, insect
Lumber is sawn timber. It comes in
Manufacture: Rotary cut Notes: The grain stretches and
attack and decay. A famous example
a range of profiles and sizes from only
compresses on either side of the
is Dutch elm disease, which wiped out
a few millimetres (under 0.25 in.) up
veneer as it is bent. It will bend
much of Europe and North America's
to 75 mm x 250 mm (3 x 10 in.). Larger
more easily in the direction that it was peeled from the log.
elm population. Many species of tree
sections are produced as laminated
take several decades to mature ready
engineering timber. Softwood is
for timber production. Elm was once a
typically graded as either structural or
(0.04-0.2 in.) thick, from logs.They are
popular timber but may never recover
aesthetic. Stress grading is carried out
either peeled continuously around the
from the impacts of the disease, which is
either visually or by non-destructive
circumference of the log (rotary cut) or
still active.
testing in machine stress rating (MSR).
cut across the width of the log. Veneers
MSR is carried out by non-destructive
are used in the construction of laminates
TYPES OF WOOD
bending, or ultrasound.There are many
and for surfacing other materials.
Wood is used as logs, lumber, veneer,
different grades such as truss rafter
Panel products (see image, page 466
panel products, engineering timber,
(TR) and construction (C) grades.The
top left) are made up of wood veneers,
pulp and paper. It is classified as either
stress rating is indicated on a numerical
particles or core materials that are
softwood or hardwood.
scale.This grading is used by engineers
bonded together with strong adhesives
Softwoods are coniferous and typically
to specify the correct bearing strength
and high pressure.They are an efficient
evergreen trees, and include pine, spruce,
and elasticity of timber in architectural
use of materials and include plywood,
fir and cedar. Hardwoods are typically
projects (see image, top).
particleboard, oriented strand board
Veneers (see image, above) are
(OSB) and composite constructions.
terms softwood and hardwood are
produced by cutting very thin strips
misleading. For example, balsa is very soft
of wood, between 1 mm and 5 mm
Engineering timbers utilize the strength and stability of laminated
deciduous and broad leaved trees. The
to leave knotholes. All knots produce sap and so have to be sealed with shellac or 'knotting'prior to painting. Other defects, such as warping,
twisting, bowing, checking and splitting, are caused by drying the wood. Reducing the moisture content of wood (up to
Growing tree
a certain point) is important for many reasons. Drier wood is stronger, stiffer,
lighter and less prone to decay than 'green' wood.Traditionally, wood was seasoned in a process known as airdrying at a rate of i year per 25.4 mm (1 in.) to give afinal moisture content of Quartersawn
18-20%. Nowadays,modern kiln-drying techniques can reduce the moisture content of 25.4mm (1 in.) thick lumber to under 20% in 10 days. However, kiln-
Panel products
Structural timber beam
Laguiole knife handle
Made by: Various
Made by: Trus Joist
Material: Various
Material: Parallam® parallel strand lumber
Made by; Laguiole Material: Hardwood burl
are preferred for good quality timber
Manufacture: High pressure laminated
Manufacture: Laminated with adhesive
Manufacture: N/a
even though this is more expensive.
Notes: From the top down: veneered MDF
Notes: PSL is made up of strips of veneer
by Tin Tab; DuPont™ Nomex®
up to 2 m (6.6 ft) long, which are
Decore™; birch core with ash faces
pressed with an adhesive to form
by Tin Tab; beech ply by Tin Tab;
billets up to 20 m (66 ft) long.
drying procedures of 3 months or more
Notes: Other types of figured grain include Plainsawn
The moisture content of wood
bird's-eye, curly and flame.
continues to change even in application. Cross-section of tree grain, with rings
This is inevitable, and so a combination
and rays, and sawing techniques
and cork rubber by Tin Tab.
of joinery, sealants and design is
employed to reduce the effects of wood and include laminated strand
Wood grain is produced by growth
lumber (LSL), parallel strand lumber (PSL)
rings and rays.These are made up of
durability of wood. The surface of aplank is typically flat grain; in other words the
(see image, top right) and I-beams.The
cell structures that transport water
plank is cut lengthways from the tree.
including burl (see image, above right),
across the grain. Quartersawn timber is
construction industry is the largest user
and nutrients around the tree. Annual
Planing with the grain will produce a
bird's-eye, curly andflame. Bird's-eye is
cut in a pattern radiating from the centre
of these products.
growth rings develop as a consequence
smooth finish, whereas planing against
rare, but it occurs more frequently in
of the log and so has more even grain
of seasonal change and can be used
or across the grain may cause 'tear out'.
sugar maple than any other tree. It is
pattern, it is therefore less liable to twist
of paper andpulp. Xylem contains both
to tell the age of the tree. Early in the
and warp as it dries and shrinks.
growing season tree growth is rapid and
End grain is produced by cutting across the width of the tree and is therefore at
unclear what causes this distortion of
cellulose fibres and lignin. The fibres are
the annual growth rings.
structural and are bonded with lignin.
the wood is typically lighter in colour.
Paper and board can be embossed
Darker rings indicate slower growth,
effectively with heat and pressure
usually from later in the growing season.
Wood pulp is used in the production
Embossed coasters Designer: Shunsuke Ishikawa
because the lignin softens when heated,
Rings are intersected with rays, which
Date: 2006 Material: White board
to allow the structure to be formed (see
are structures radiating from the centre
Manufacture: Blind embossing
image, right). Recycling paper and pulp reduces the length of the fibres and so
of the tree to transport food and waste
Notes: A metal tool forms an impression
laterally.The combination of rings and
reduces their strength; it is therefore not
rays produces patterns and flecks of
an infinitely repeatable process.
colour on the surface of sawn timber. As a tree matures the centre darkens,
on 1 side of the board with heat and pressure.
theendof sawn lumber. Fasteners such
expensive and so are often only available as veneers. There are many types
Knots are the most common defect
shrinkage and expansion. Wood is prone to greater shrinkage
NOTES ON MANUFACTURING
as nails and screws will easily pull out of
found in timber.They occur where
Wood is available for manufacturing as a
end grain. Joint designs in joinery (page 324) have evolved to maximize the
branches and trunks come together and
sheet material, solid lumber, and as chips,
affect the surrounding grain pattern.
particles and shavings.
contact of flat-grain at an end grain
They affect the aesthetics and structural
junction. For example, dowel, biscuit and
integrity of wood and so are often used
finger joints maximize flat grain contact
as an indicator of its quality. They are
and lightweight.They are also typically
and thus improve joint strength.
classified as either dead or alive. Alive
more stable than solid lumber because
Sheet materials include veneers and panel products.They are versatile, strong
However, end grain does have its benefits;
knots are where branches were attached
they are made up of thin plies bonded
image, opposite left),Tangential sawing,
it is frequently used in chopping boards
to the trunk when the tree was felled.
with strong adhesives.Thin sheet
WOOD GRAIN, STRUCTURE AND APPEARANCE
and this is known as heartwood; the
known as plainsawn, is the most efficient
and butcher's blocks because it does not
They can be sound and tight and typically
materials can be shaped by sawing, laser
lighter wood near the bark is sapwood.
and economic method for cutting a log.
splinter like flat grain and causes less
have little effect on strength. Dead knots
The strength and appearance of lumber
The depth of sapwood and colour
Radial cutting,known as quartersawn,
wear on the knife.
are the result of branches and twigs
are determined by many important
contrast depend on the species of tree.
produces a more wear resistant surface
factors. These include the type of tree,
Grain pattern is further influenced by
defects, the method of drying andhow it
the angle of sawing. Afterfelling, trees
was sawn.
are sawn tangentially or radially (see
finish with an even grain pattern.
The direction of grain affects the strength, working properties and
material. Defects and figured grain
earlier in its life; the tree continued to
cutting (page 248),laminating (page 190),bending (page 198) and machining (page 182).Thick sheet materials are typically used flat and profiled by sawing
patterns are not always predictable.
grow and so encapsulated the knot.
or machining. Slight bends maybe
Figured grain patterns are rare and
These knots can come loose and fall out
achieved with kerfing (page 190).
Wood is a natural and variable
that became detached from the trunk
Treeplast® golf tee Made by: PE Design and Engineering Material: Treeplast® biocomposite of wood. corn and natural resins Manufacture: Injection molded
Bendywood®
Environ® panels
molded into products. Other uses include
The panels are conventional sizes,
furniture and sculpture,The maximum
sourced timber such as origin and chain
Made by: Phenix Biocomposites
wood shavings as a protective packaging
1220 mm x 2440 mm (4x8 ft), and
size of the raw material is currently
of custody certification. These systems
Made by: Candidus Prugger
material and bedding for animals,
between 12,7 mm and 21,4 mm (0,5-1 in,)
100 mm X120 mm x 2200 mm (3-94 in-x
verify the flow of wood from forest to
Material: Hardwood
Material: Soy based or thermosetting resin
thick. They can be machined with
4.72 in. x 7,22 ft). It is possible to bend
factory and end use, and ensure that the
conventional woodworking equipment,
thin sections by hand; thicker sections
timber comes from renewable sources,
reinforced with natural fibre Manufacture: High pressure laminated Notes: Panels are used for construction, .interiors and furniture.
Most timber can be purchased as solid
MATERIAL DEVELOPMENTS Much of the development in wood has
Treeplast® is made of wood (50-70%),
are bent on a ring roller (see page 98) or other suitable bending equipment,
Manufacture: Formed by hand around a mandrel Notes: This treated hardwood can be bent in its cold and dry state.
Woodhas relatively low'embodied energy';harvesting, sawing, drying and
been in producing stronger, lighter
crushed corn and natural resins (see
and more reliable products such as
image, above right). It can be processed
engineering timbers.
with conventional injection molding
ENVIRONMENTAL IMPACTS
of energy,The cost and environmental
(page 50) equipment. Shape is unlimited,
Wood is an environmentally
impact of drying timber is often reduced
However, they also tend to be difficult to
Another interesting area of
transporting it does not take a great deal
lumber. Limiting factors are price and
development is biocomposites.These
except for a minimum 3 mm (0,118 in,)
beneficial material. It is non-polluting,
by air-drying the first stage so that it
bond with adhesives, impregnate with
availability such as in the case of bird's-
are moldable materials made up
wall thickness and 30 draft angle,The
biodegradable, can be recycled and
requires less kiln-drying to reduce the
preservative or coat finish.
eye maple. Planks more than 150 mm
of natural fibres (commonly wood) bonded together with either natural
basic material will biodegrade very
should be from renewable sources.
moisture content to 18-20%,
(5.91 in.) wide are typically stabilized by cutting the wood into strips and bonding
rapidly in water and within 4-6 weeks
Deforestation is a problem in many
Oily woods that are self-protective
or thermosetting adhesives. In some
in soil. Another grade is available that is
developing countries. Systems are in
and virtually maintenance-free outdoors
them back together alternating opposing
cases they crossover with bio-fibre
water resi stant an d 1 on g er 1 astin g,
place to minimize the use of illegally
include cedar,larch, teak and iroko.
directions of growth. This means that as
reinforced plastics andbioplastics (see
it shrinks and expands the wood works
page 425).Two examples are Environ®
material development (see image,
against itself and is less likely to buckle,
and Treeplast®. Phenix Biocomposites
opposite). It is made by steaming and
bow or twist. Solid lumber is typically
produce a range of panel products made
compressing hardwoods along their
shaped by sawing, machining, steam
up of natural fibres bonded with soy
length, and its advantage is that it can
bending or carving. Large radii bends can
based or synthetic resins (see image,
then be bent in a cold and dry state. Bend
be achieved by kerfing and laminating: Chips, particles and shaving are
typically bonded into sheet materials or
Bendywood® is an exciting new
above left).Types of fibre reinforcement
radius is approximately 10 times greater
include agricultural by-products such as
than the thickness of the material. So
wheat straw, and recycled newspapers.
far it has been used to make handrails.
The dust produced by machining and sanding certain woods is irritating to the lungs and eyes. Examples include teak, wenge, iroko and walnut.
SOFTWOODS Colouring pencils
SOFTWOODS
Violin table (work in progress)
Douglas fir is mainly used in structural applications, such as timber
Made by: Various
Made by: Frederick Phelps
Material: Cedar
Material: Spruce
frame construction (page 344), andthe
Manufacture: N/a
Manufacture: Hand carved from solid wood
framework for light aircraft.
Notes: Cedar is straight grained, aromatic
Notes: Knot-free and very high quality
and is resistant to splintering.
spruce is radially cut and air dried
Cedar is the most resistant to decay
for 10 years or more, before carving
of all the softwoods and so is used in
into a violin or cello table (front).
outdoor decking,furniture,fencing, roof shingles, wall cladding, saunas (indoors
Softwoods
and suitable for different applications. Common properties are a coarse and
SOFTWOODS
Larch [Larix species) is a deciduous
Inn the Park, London
softwood grown in Europe, Asia and
If left untreated, it will gradually turn from light golden brown to grey.
and outdoors) and baths. Its distinctive smell and insect repelling qualities are used in the construction of wardrobes,
straight grain, off-white to dark brown
Designer: Hopkins Architects
America. Like other coniferous woods, its
colouring and a distinctive odour
Date: Completed 2004 Material: Larch
strength depends on the climate.Trees
Applications: These woods are available
clothes hangers and shoetrees. It is
that is produced by the resin. Unless
also used to make pencils because it is
Notes: Inn the Park was shortlisted in the
grow more slowly in cold climates and
as sawn timber and plywood.
Softwoods have moderate strength, straight grain and a distinctive odour. They are predominantly
impregnated with preservative, these
• Pine • Spruce •Douglas fir •Cedar • Larch
evergreen, fast growing and useful in the DIY, construction, pulp and paper industries.
so are more dense andhardwearing.
Pine is widely used in furniture,
woods are generally not suitable for
Larch differentiates itself because the
fl oorin g, con struct'on, kitchen uten sils
exterior applications. Their colour will
core turns into heartwood more rapidly
and wall panelling.
darken overtime.
than other softwoods.The benefit of
Qualities: These coniferous softwoods
Spruce {Picea species) has a long,
are grown all over the world, but some
straight grain and is an even,yellowish
2004 Wood Awards, UK.
Spruce's light colour and long fibres
andpiles. A well-known use of larch is in
and taller than inland varieties.The
more resistant to decay, so larch is
paper. It is also used for pallets, crates,
the construction of Venice, the support
more resistant to salt water, fungus,
flooring and structural applications,
structure of which has been submerged
temperature change, denting and
and the framework of small boats and
in water for hundreds of years.
and altitudes. The rate of growth
Norway spruce and Sitka spruce. Sitka
tones. It has good strength to weight and
determines the strength and economic
spruce trees are some of the tallest in
dimensional stability. It is stiff and so is
abrasion. Natural oils producedby the
light aircraft. Its acoustic properties are
value of the wood. Slower grown trees
the world and are commonly 40 m to
used mainly in structural applications.
sawn timber protect it from the elements
utilized in musical instruments including
have fewer knots and more tightly
50 m (130-165 ft) or more high.The wood
Cedar {Cedrus species) can be off-
and so it can be used untreated outdoors.
guitars, violins and pianos.
packed grain, and so they are harder and
has a uniform, knot-free appearance
pine (also known as European redwood), pine.There are over too different species.
construction, fences, walkways, bridges
make it ideal for producing pulp and
timber is off-white with yellow and red
jack pine, red pine and eastern white
Larch is used in flooring, house
this is that heartwood is naturally
white colour.There are 2 main types, the
Pine (Pirus species) includes Scots
the most expensive of the softwoods.
the coast: coastal Douglas firs grow faster
species are limited to certain latitudes
more expensive.
resistant to splintering. It also tends to be
white, light yellow orlight reddish brown.
and is stable after drying.This produces
It is relatively soft and light, and so prone
superior acoustic properties, utilized in
to scratching, abrasion and indentation.
soundboards in musical instruments.
When cut, it produces oils that repel
Douglas fir [Pseudotsuga species) is
insects and protect it against decay.
grown across North America.The trees
Of these woods it is the most resistant
Even though many of the trees cannot
are very tall andean reach heights of
to decay and can be used untreated
be easily differentiated, the properties
100 m (328 ft).The height and properties
outdoors and submerged in water. Over
of the sawn timber are slightly different
of the tree are affected by distance from
time the surface will become silvery grey.
Costs: Low to moderate.
POPLAR
BIRCH
Wooden packaging
Die cut plywood Tyrannosaurus
Applications: Solid birch and veneers are used to make disposable cutlery,
Made by: Various
Made by: Unknown
Material: Poplar
Material: Aspen
Made by: Muji Material: Birch plywood
Manufacture: Stapled or glued
Manufacture: Turned on a lathe
Manufacture: Die cut
Notes: Poplar is relatively fast growing.
Notes: Other readily available woods
Notes: Plywood up to 15 mm (0.59 in.) thick is suitable for die cutting.
inexpensive and can be formed into
suitable for turning include lime,
tight bends without splitting.
birch and alder.
toothpicks, toys and wooden puzzles. Birch is commonly used as plywood in furniture and interior doors.
BIRCH
BEECH
Disposable wooden cutlery
Wooden spheres
Made by: Various
Made by: Unknown
Material: Birch veneer
Material: Beech
Manufacture: Pressed and cut
Manufacture: Turned on a lathe
Notes: This cutlery is an alternative to
Notes: Beech is hard and uniform density,
disposable plastic cutlery with
so a good finish can be achieved
a lower environmental impact.
with machining.
Costs: Low to moderate.
Poplar
(page 470), including pine, Douglas fir and spruce.
• Poplar • Aspen
This is a lightweight and relatively soft hardwood. It is a fast growing commodity timber used in
It can be stained to take on the appearance of other woods such as
cherry (page 478) or maple (page 475).
Birch
Beech
• Birch
• Beech
Birch is relatively durable and strong. It has a
This is popular material used as both sawn
light colourwith a uniform texture.
tirpber and veneer. The sapwood is off-white and the heartwood is a reddish brown.
pulp, paper, packaging and engineering timbers.
Applications: Poplar is available as a sawn and engineering timber. As an alternative to softwoods it is used Qualities: Poplar (Populus species, some
as plywood core, laminated strand
Qualities: There are many different
Qualities: Beeches {Fagus species) are
commonly called aspens) has a light
lumber (LSI, see page 466), furniture
types of birch {Betula species), which
hardwoods suited to northern temperate
yellowish green colour. It is a soft timber
construction, pallets and boxes. Due to
grow across North America, Asia and
regions, which can grow to over 30 m
and so machines very easily. However,
its high level of flexibility and relative low
Europe. Birch is a relatively fast growing
this also means that it dents and wears
cost it is the most widely used wood for
deciduous tree that can reach heights of
rapidly. It is low density, lightweight and has good flexibility. It is porous and
matchsticks and packaging soft cheese.
30 m (98 ft) or so.
(98 ft),The grain is short and tightly packed, resulting in a hard material that is resistant to denting and is relatively
resistant to splitting, so thin sheets can
Costs: Low to moderate.
species are quite hard, while others are
It is quite heavy and strong. Certain
easy to work, Th e wood h as an even density and so wears in a slow and
be bent into moderately tight curves,
soft and flexible, which makes them easy
BEECH
but it is not suitable for steam bending
to machine and work. Birch is suitable for
Flight 1-Seat
because it has relatively short fibres and
steam bending, but is prone to warping
Designer: Artur Moustafa and Jonas
these are prone to warping as they dry.
as it dries and so has to be clamped in
It is used a great deal as a core and composite material in engineering
place for the duration of the drying cycle. Unless it has been coated or
timbers, in this application, poplar is
impregnated with preservative, it is not
used in much the same way as softwoods
suitable for outdoor use.
Nordgren for Vujj Date: 2006 Material: Beech Manufacture: CNC machined
uniform manner. Beech is relatively porous and so prone
to shrinking and expanding rapidly with changes in moisture content. Unless it has been impregnated with preservative, it is not suitable for outdoor use. Due to its short grain, beech is liable to split under tension and is not very elastic.
m >
O o o D CO
BEECH Wooden utensils Made by: Various Material: Beech Manufacture: CNC machined Notes: Beech is non-toxic and safe for food use, but cannot be left in water for prolonged periods.
ASH Therefore, it is not generally used for structural applications. It is suitable for
steam bending (page 198),laminating (page 190) and machining (page 182).
ELM
MAPLE
Windsor hall table
Violin backs
Made by: Vic Firth Material: Hickory
Made by: Ercol Date: 2005
Made by: Frederick Phelps
• Pecan
Material: Hard maple or European sycamore
> o o
These are North American trees used in the
Manufacture: Turned on a lathe
Material: Elm
Manufacture: Hand carved from solid wood
CD
production of tool and axe handles. They are
Notes: A dense wood is ideal, with little
Manufacture: CNC machining
Notes: The figured grain (flame) is
Hickory
Designer: Johannes Herbertsson and Karl
• Hickory
Henrik Rennstam forVujj Date: 2006 Material: Ash shelves and MDF (particle board) wall mount
Applications: Beech is i of the most
HICKORY Drumsticks
Alog shelving system
essential for the acoustic
fleck for more pronounced
tough, hard and strong.
properties of the violin because the
acoustic properties.
Manufacture: CNC machined
m
grain is interrupted.
widely used woods. It is available as sawn timber, plywood and veneer.Typical uses include woodworking tools, furniture,
Unless impregnated with preservative,
Qualities: These trees [Carya species) are
cooking utensils, doors,floors,beds, toys,
it is not suitable for outdoor use.
native to North America.The properties
disposable cutlery and clothes pegs. Costs: Moderate.
Ash has a long straight grain and long
curly, are rare and high cost hard maples,
and barge hulls, furniture and beds.
typically only available as veneers.The
Costs: Low to high.
maple, often with interlocking grain.
Elm is a light brown timber with an interlocking
Eufbpean sycamore is a type of hard
strength to weight.The sawn timber
light brown streaks, and the heartwood
is hard, durable and elastic with good
is reddish brown; in some trees they
This reduces splitting and produces
resistance to shock. It is ideal for steam
contrast with dramatic effect.
interesting patterns on sawn timber.
grain. It is ideal for steam bending.
Hickory is considered to be among the
Soft maple has similar characteristics to hard maple and is a less expensive
(page 324). Machining (page 182) and polishing (page 376) will produce a high
strongest and most durable hardwoods.
It is tough and flexible and so is ideal
Qualities: There are many species of elm
surface finish.
for tool and axe handles. It is dense and
{Ulmus). Deciduous hardwoods, they
Maple
alternative in painted applications. But as th e n ame suggests, it is a little softer.
• Maple
so can be difficult to work by hand.The
grow across much of the northern
Applications: Ash is typically available
hardness produces a fine finish that is
hemisphere, but were almost completely
These are deciduous hardwoods that have similar
Applications: These woods are available
as sawn timber. It has traditionally
durable to abrasion and denting.
wiped out in Europe and parts of North
strength characteristics. They are off-white
as sawn timber and veneer; some grades
• Black ash
degree of shock resistance.
sawn timber. Applications include boat
Generally,the sapwood is off-white with
• White ash
has been used for tool handles that require a high
• Elm
Figured maples, such as bird's-eye and
fibres. It is tough, resilient and has good
bending (page 198), turning and joinery
Ash is hard, elastic and resilient. Traditionally it
vary according to the particular species.
Applications: Limited availability as
• Sycamore or field maple
and darken gradually with age. They have no
America by Dutch elm disease in the
been used for tool handles and sports equipments such as baseball bats,
Applications: it is available as sawn
latter half of the 20th century. This has
hockey sticks, snooker cues and oars.
timber and occasionally as a veneer.
made elm much harder to purchase.
Qualities: There are many trees in
Wooden car chassis were commonly
Typical applications include walking
It is a medium brown timber that
the ash {Fraximus) family.The 2 main
made from ash. It is also commonly used
sticks, tool handles, axe handles, drum
commercial timber producing types and
in furniture, toys andflooring.
has a similar appearance to oak, with
distinctive taste or smell.
are suitable for steam bending.Typical applications include frameworks for upholstered furniture, cutting surfaces,
Qualities: There are many different
chopping boards and butcher's blocks
species of maple {Acer), which are
(particularly hard maple and sycamore), flooring, handles, buttons and knobs.
sticks, sports equipment, cabinets,
an interlocking grain that is resistant to
categorized as either hard or soft.The
the white ash (American) and black ash
furniture andflooring. In Europe it is
splitting, it is supple when wet and so is
timber has a uniform off-white colour
Unless coated or treated, they are limited
(European).These are deciduous trees
largely replaced by ash, which is more
very good for steam bending (page 198).
with light brown heartwood. Hard
to indoor use. In North America, the sap
that can reach 30 m (98 ft) in height. The timber is off-white to light brown
readily available and so is less expensive.
Certain species are resistant to decay
maple is a heavy and strong timber with
of hard maple is refined into maple syrup.
outdoors, especially when constantly
tightly packed grain; it is very hard and
(tan). It has no distinctive odour or taste.
Costs: Moderate to high.
submerged in water.
so is resistant to denting and abrasion.
Costs: Moderate.
Costs: Moderate.
o o
ilk
OAK
OAK
Oak side table
Architectural cladding
Made by: Unknown Material: Oak Manufacture: CNC machined
Notes: Oak is widely used in furniture because it is dense and hardwearing.
yiiii-
Made by: Various
Material: Oak Manufacture: Sawn Notes; Oak gradually becomes silvery grey when used untreated outdoors. It is
long lasting and durable against the elements.
Oak • European oak • American oak
reddish brown; and Asian oak is typically
WALNUT
a lighter off-white colour.
Wing sideboard
Oak is hard, strong and stiff.The
• Asian oak
surface is resistant to denting and
Oak is particularly hard, dense and resistant to
abrasion and so is particularly difficult
denting. It is a heavy timber used in furniture construction, house building and floorboards.
splinter easily. Designer/client: Michael Sodeau/isokon Plus Date: 1999 Material: Walnut veneer Manufacture: Wood veneer laminating
veneer. It has rich dark brown heartwood
slightly different physical and aesthetic characteristics. They are categorized by their country of origin, and each country
Oak is suitable for machining (page 182), joinery (page 324) and certain types can be steam bent (page 198). It can be
may produce several different types such
used outdoors untreated, where over
as the USA whose principle commercial
time it will gradually turn grey. Indoors, it
oaks are known as white oak and red oak. straight grain, and are very durable. European and Asian oaks are slow growing.This produces a heavy and
dense material with a tightly packed grain. Colour varies according to origin:
timber. For its weight it is strong, resilient and
Material: Balsawood
shock absorbing.
Manufacture: Die cut and inkjet printed
• Walnut
Certain species of walnut are prized as highly decorative timbers. They are also very hard and resistant to shock.
is commonly figured with burls and curls.
Qualities: Balsa [Ochroma pyramidale)
being pumped full of water; more than
Timber with such details is considerably
trees are fast growing and low density.
half of the living tree is made up of water.
more expensive.
They grow in humid environments such
The grain is coarse and open, so it is
as central and southern America. Kiln
difficult to achieve a smooth surface
in contact with the soil.
drying reduces the water content to
finish. It is easily carved by hand and
produce alow density andlightweight
machine. Balsa is a light and uniform
Applications: Walnut is available as sawn
timber.The density varies from tree to
yellowish brown colour.
timber and veneer.Typical applications
tree; lower density balsa is less common
It can be used untreated outdoors and
Qualities: Walnut {Juglans species)
include floors, furniture, car interiors,
and so is more expensive, even though
Applications: It is available as a sawn
Applications: Oak is available as sawn
is a deciduous hardwood that grows
tableware, knife handles, ornaments,
heavier balsa is stronger.
timber and veneer. Typical applications
timber and veneer. It is widely used in
across America, Europe and Asia. Certain
musical instruments and gunstocks.
house building, boat building, furniture,
species, including the black or American
doors, windows and floors. Wines and
walnut and the Persian walnut, have
spirits are stored in oak casks or barrels.
European oak is light brown to light grey; American oak is light brown to dark
Designer/client: Walt Mooney/Peck-Polymers Date:--' N/a
richness slightly.The grain is straight, but
Walnut
will slowly become darker over time.
These are relatively fast growing with a
• Balsa Balsa wood is the lightest commercial grade
more uniform plank, but will dull the
tannin.This is a preservative that has leather tanning industries for centuries.
BALSA Andreason BA4-B aeroplane model
sapwood. Steaming the wood makes a
Oak has a particularly high level of
deciduous hardwoods and each type has
Balsa
that contrasts with the lighter coloured
prone to chipping and splitting.
been exploited by the winemaking and
Due to its popularity as a decorative
timber, it is mostly only available as a
to work by hand. Its hardness makes it
Qualities: Oaks [Quercus species) are
(page 190), because it does not split or
Costs: Moderate to high.
Balsa contains less lignin than
include architectural models, radio
most other woods, contributing to its
controlled aeroplanes, rockets and
softness, and the cells are large and
toys. It is also used as a core material in
hard and dense wood with a tight and
open, contributing towards its relative
surfboards andboatbuilding.
densely packed grain. Walnut can be
lightness.This means the tree is less rigid
steam bent (page 198) and laminated
than most, and its stability depends on it
Costs: Moderate to high.
Costs: Low to moderate.
Apple (Malus species) is a slow growing and not very tall tree. This
means that it is difficult to obtain large planks of it. The timber has a tightly packed grain and is heavy and hard. Like other fruitwoods, apple shrinks a great deal as it is dried, and this can cause warping and cracking. Pear trees (Pyrus species) are similar to apple trees.- they are slow growing and
not very tall. The timber varies from light pinkish brown to yellowish brown. It has a tight grain and smooth, hard surface. Applications: These woods are available as sawn timber and veneer. They are used FRUITWOOD
for turning, machining (page 782) and as
Bread board
decorative veneers. Cherry is used in
IROKO
furniture, cabinets, floors and doors, Made by: Unknown • Material: cherry
Apple and pear are used for ornaments,
Manufacture: Hand carved
tableware, wooden instruments and
Iroko work surface Designer: Date:
Notes: Cherry is a hard, dense and decorative wood.
furniture. They have fragrant smoke, so
Material:
are used to flavour food and tobacco.
Manufacture:
Retrouvius
Completed 2006 Reclaimed iroko Machining
Costs: High,
Fruitwood
Iroko
Applications: Sawn timber and veneer
EXOTIC HARDWOODS
• Apple
• Iroko
are used for flooring, decking, outdoor
Reclaimed teak stool
• Pear
Iroko is an African hardwood that is naturally
furniture, worktops and general joinery.
This range of deciduous hardwood fruiting
resistant to chemicals and decay. It has similar
Date: 2006
trees are used for their decorative appearance
properties to teak and so is often-used as a cheaper alternative.
It has been used in laboratories due to its resistance to chemicals and water decay.
Material: Reclaimed teak
• Cherry
combined with moderate strength. Cherry is the most well known.
Designer: Mandala
Manufacture: Hand carved
Costs: Moderate.
Qualities: Cherry {Prums species) has distinctive and desirable heartwood of a rich reddish brown colour that gradually darkens with age. Sometimes
it is speckled with darker patches. It is moderately slow growing and reaches
heights of 30 m (98 ft) or so. There are many different species including
American cherry (black cherry), wild cherry and Brazilian cherry. Once dried it 15 Stab,e' moderately dense and strong.'
It has a straight and uniform grain that can be polished to a high finish. The heartwood is resistant to decay. However, it is a high cost timber and so is often us6d as a. veneer.
Qualities: Iroko [Chlorophora species) is an African hardwood. It is endangered
Exotic hardwoods
and protected in some countries, but
• Mahogany . Teak
brown and mahogany (Khaya species) is
there is sufficient production from other
•Ziricote -Ebony
a rich brown that darkens with age.
sources for it to be competitively priced.
• Keruing . Weng. • Rosewood
It has light yellow sapwood and brown heartwood. It is used for decorative appeal as well as durability and strength.
Outdoors it gradually turns silvery grey Its interlocking grain produces good mechanical properties, but can cause
tearing during machining (page 182). Hard calcium carbonate deposits in the wood fibres can blunt cutting tools.
These materials, especially ebony and
This is a group of highly decorative timbers with
wenge, are very hard and resistant to
lustrous colours. Certain species are very hard
denting.Teak (Tectona species), keruing
and durable. Some are endangered.
Iroko contains natural oils that protect it from water decay and chemicals
rosewood {Dalbergia species) is a veined
Qualities: These woods are highly priced and hard to come by, due to their places of origin, desirability and rate of growth They are prized for their lustrous colours;
ebony [Diospyros ebenum) is black or very dark red, ziricote [Cordia dodecandm) has a deep, contrasting swirling grain, wenge
(Millettia laurentii] is a dark chocolate,
[Dipterocarpus species) and mahogany contain natural oils that protect them against decay, so are popularfor outdoor
Applications: Limited availability as
EXOTIC HARDWOODS
furniture, decking and boat building.
sawn timber and veneers. They are used
Bluetooth ziricote Pip*Phone
in flooring,furniture, ornaments,musical
Designer/client: Nicolas Roope and Kam Young/
Care must be taken when specifying or purchasing exotic hardwoods. Certain
instruments and for decorative inlay.
endangered species (such as Swietenia,
the original mahogany) are protected by international legislation, and permits are requi re d for tradi n g.
Costs: High to very high.
Hulger Date: 2005 Material: Ziricote Manufacture: CNC machined
Wicker lights
Made by: Various
Designer: Mandala
Material: Cork
Date: 2006
Manufacture: Compression molded
Material: Rattan
Notes: Sheets and blocks are made up of
Manufacture: Hand woven
scrap produced in the manufacture
o o o >
> CD XI
RATTAN, REED AND RUSH
CORK Cork sheet
of cork stoppers.
Cork
CORK to bind joints in the furniture. Once dry,
Cork low table
the inner core has a similar hardness to • Cork
Designer/client: Jasper Morrison/Moooi
Cork is light, buoyant and up to 85% air by
Date: 2002 Material: Cork
many species of softwood (page 470). It is lightweight and flexible and so can be
Manufacture: Turned from agglomerate cork
formed around tight bends. Once formed
volume. It is naturally resistant to decay.
it holds its shape. Unlike bamboo, these materials have a solid core.The choice of
material depends upon local availability. Qualities: Cork is harvested from the
Reed and rush are grasslike plants that
Bamboo
grow in wetlands and are used in seating
which grows across the Mediterranean.
• Bamboo
and musical instruments. The flexible
On ce a tree i s ol d en ough, th e bark i s
This is a fast growing grass that is harvested and
shoots of a willow, known as switches, are
bark of the cork oak [Quercus suber),
used as a hardwood-like material.
also suitable for weaving.
peeled from the tree every io years or so. Production is sustainable because
peeling the bark does not damage these
Applications: Available as lengths of
trees permanently; most other trees will
fibrous material, which are typically used
die if their bark is cut around the trunk.
Cork is naturally light tan, but can be
Qualities: There are many different
coloured. Suberin, a waxy substance, is
species and genera of bamboo, which
naturally present in the cork and protects
have different rates of growth. Certain
it from water penetration and microbial
attack. It is resistant to decay and difficult
species grow up to i m (3.3 ft) per day and reach heights of 30 m (98 ft) or
to burn, which makes it useful as an
more. China is the largest producer of
insulating material in construction.
bamboo and has utilized its properties
in the production of wicker baskets,
Bamboo flooring
BAMBOO Bamboo resin stool
Rattan, reed and rush
Made by: Various
Designer: Mandala
• Rattan
Material: Bamboo
Date: 2005
• Reed
Manufacture: Laminated and CNC machined
Material: Bamboo in black resin
• Rush
Notes: Bamboo is fast growing,
Manufacture: Molded and machined
Collectively known as wicker (which also includes
BAMBOO
bamboo and willow), these materials are used in
hardwearing and lightweight.
making baskets, tableware and furniture.
in construction and furniture for many Applications: Cork is available as compressed blocks and sheets mounted onto a backing material. Applications
thousands ofyears. Once harvested, bamboo continues to send out shoots. Its popularity is growing
include fishing floats, bottle stoppers,
beyond the countries of production due
seals, insulation, pin boards, furniture
to its rapid growth, sustainability and
andflooring. Costs: Low to moderate.
Bamboo has similar characteristics
to hardwoods (pages 472-9). It is harder and lighter than many hardwoods and
relatively low cost. It can be harvested
suitable for turning, machining (page 182) and working by hand. The stems are hollow with ringed joints, which
every 4 years, compared with several
produces decorative patterns when cut
decades for many hardwoods.
or split into planks and bonded together.
Applications: Bamboo is available round
Qualities: Rattan is a diverse group of
and cut to length, split into strands
climbing palms that produce vines up to
(wicker and cane) and compressed into
200 m (656 ft) long and 70 mm (2.75 in.)
planks.Typical applications include
in diameter.The largest producer is
buildings, scaffolding, furniture,
Indonesia, but they grow across Asia.The
tableware, countertops andflooring.
outer bark is removed and the core is dried to form material suitable for wicker
Costs: Low to moderate.
furniture. The outer bark is often used
tableware and furniture. Costs: Low to moderate.
CD 33
Random Light Designer/
Bertjan Pot/ Moooi
made by; Date:
2001
Material:
Glass fibre reinforced epoxy
Materials
resin lEPl Manufacture:
Ceramics and Glass Ceramics and glass are classified as non-metallic materials that are made by firing. They are hard and brittle materials that
Chair #1
TYPES OF CERAMIC There are 2 main groups of ceramics,
Designer: Ansel Thompson
Date: 2001
which are clay-based and high
have been used for millennia in the production of decorative and functional objects. In recent years the boundary between
reinforced epoxy resin (EP) Manufacture: Composite laminating
pottery and include earthenware, stoneware and porcelain.They are fine-grained materials made up of clay
| of high performance materials including glass ceramic. This
minerals (aluminium silicate), quartz and rock fragments. Historically, the
CD
quality of ingredients differed according
£ crystallized structure following heat treatment.
to location. Nowadays, clay is purchased
cn
honeycomb and glass fibre
ceramics are those associated with
o ceramics and glass has been blurred with the development
g material is formed like glass, but develops a ceramic-like
Material: Fibre optics, aluminium
performance ceramics. Clay-based
> CD
Resin soaked yarn is draped around an inflatable mold
from manufacturers that produce raw materials in accordance with guidelines. High performance ceramics have fewer impurities than clay-based ceramics and superior properties.They are resistant to high temperatures, most chemicals and corrosion, and outperform metals in many demanding applications. However, like clay-based ceramics they are hard and brittle, and their porous structure has high compression strength
butlowtensile strength, which typically falls between metal and plastic.
TYPES OF GLASS
tops (see image, page 493) as well as
short asi mm (o.o4in.).Thesematerials
There are several different glasses and
industrial applications.
have greater toughness, strength and
the exact ingredients differ slightly
Glass fibres are used to produce
resilience, and are used in the production
according to location, processing plant
textiles, insulation, structural
of powertools, furniture and automotive
and application.The most common glass,
reinforcement and fibre optics.The type
parts,for example. Continuous and long
soda-lime glass, is widely used in design,
of glass depends on the application,
strand fibre reinforcement produces
architecture and jewelry. Other glasses
for example, textiles are generally a
maximum strength to weight properties.
are more expensive and so tend to be
borosilicate or similar glass, whereas
Processes used to mold continuous
used only when necessary. For example,
insulation (glass wool) is filaments of
andlong strandfibre reinforcement
borosilicate glass is more resistant to
soda-lime glass. Glass fibres and textiles
include composite laminating (page
high temperatures and thermal shock
are used for structural reinforcement
than soda-lime glass and so is used in kitchenware and laboratory products.
in GRP (glass reinforced plastic).The length of fibre used is determined by
206), compression molding (page 44), filament winding (page 222) and 3D thermal laminating (page 228).Typical
Glass ceramic is even more resistant
the application and manufacturing
products include racing cars, monocoque
to chemicals, high temperature and
process. Glass fibre used to reinforce
boat hulls, canoes, furniture (see image,
thermal shock, and is used in glass cooker
injection molded thermoplastic can be as
above) and light shades (see image, top).
> llac Centre, Dublin Designer/client: Christopher Tipping and Fusion Glass/British Land Ltd and Chartered Land Ltd Date: Completed 2006
I
Material:
Soda-lime glass
Manufacture:
Sand blasting, deep carving, gilding
Stella Polare Pure Magic Candlestick
Kaipo light
Designer/client: Georg Baldele/Swarovski Crystal Palace Project Date: 2002-2005
Designer: Antonio Arevalo, Fusion Design
Designer/
Date: 2005
made by:
Edward van Vliet/Moooi
Material: Crystal glass
Date:
2001
Material: Strass® Swarovski® crystal
Manufacture: Sub-surface laser engraving,
Material:
Silvered crystal glass
Manufacture: Diamond ground, polished, rouged
CNC machining and polishing
Manufacture: Glassblowing and silvering
and buffed
and colour rub
Fibre optics carry light along their length as a result of internal reflection.
Modulated light is used to transfer information across vast distances in the communication industries via cables
Prada Store, Tokyo Architect/Client; Herzog & de Meuron/Prada Date: Completed 2003 Material: Laminated soda-lime glass Manufacture: Kiln formed
and water jet cut (page 272).Tungsten carbide Is sufficiently conductive to be cut and shaped using die sink EDM and wire EDM (page 254).
made up of bundles of fine glass fibres.
NOTES ON MANUFACTURING GLASS
Fractures and imperfections will cause
Glass is shaped in a hot and molten
light to escape along the length of the
state.The process begins in afurnace,
fibre. In recent years this quality has been
where the raw materials are all crushed
used by designers to illuminate interiors
(2192—2372^); and porcelain is fired at
into uniform sized particles and mixed
and products such as furniture (see
0ven3oooC (23720F).
together.The raw materials are mixed
image, below, page 483) in novel ways.
NOTES ON MANUFACTURING CERAMICS Ceramics and glass are processed in different ways. Clay-based ceramics are plastic andformable in their wet state.
High performance ceramics are
typically formed in a powdered state.
with cullet (crushed recycled glass) at 15000C (27320F) and fuse together to
Processes used to shape them include
form a homogenous, molten mass. At
powder injection molding (see metal
this stage they are either coloured with
injection molding, page 136), ceramic injection molding (CIM) and press molding followed by sintering.The
additives, or a decolourant is added to make clear glass.The material is conditioned for 8-12 hours, which is
Processes used to shape them include
particles are sintered or fired at around
long enough for all the bubbles to rise
throwing (page 168), slip casting (page 172) and press molding (page 176). They are fired to fuse the ingredients and
2500°C (45320F), which makes them
to the surface and dissipate, and cooled
much more expensive to fabricate than
to ii500C (2io20F).The glass is now
clay-based ceramics.
ready to be formed by blowing (page
lock the shape in place. Earthenware is
High performance ceramics can be
fired at iooo0C to 12500C (1832- 2282CF),
machined (page 182), although this can
152), pressing (page 152) or molding. Lampworking (page 160) is the process
stoneware is fired at i2oo0C to i3oo0C
be a lengthy process, laser cut (page 248)
of local heating andforming of glass.
so it does not require the same level of
months. In such cases the temperature
and crystal glass are relatively soft and
conditioning beforehand.
may be reduced by i0C to 20C (2.7-3.4^)
so can be cut more easily. Cutting facets
Sheet materials (see image, opposite) can be shaped by kiln forming, which
each day to minimize potential stress.
into these glasses enhances their sparkle
is also known as slumping and
for safety, security and decorative effect.
decorative tableware are commonly
sag bending, or press bending. Car
Laminated safety glass is produced by bonding together sheets of glass with a
made in this way. Machining can produce
windshields are formed by precision press bending.Textured and glass sheet
polyvinyl butyral (PVB) film.The process
(0.00059 In.). Hard glasses, such as
is produced by rolling hot glass between
uses heat and pressure to remove any
borosilicate, take much longerto cut and
profiled rollers; wire reinforced glass is
air bubbles, so the sheet looks solid.This
polish and so are less commonly worked
produced in a similar continuous process.
product is primarily used in automotive
in this way. Layering coloured and clear
and construction applications. It is also
glass can enhance the effects of cutting.
Once formed, glass is annealed by
Glass sheets are laminated tog ether
and lustre. Chandeliers, ornaments and
shapes accurate to within 15 microns
heating and slow cooling to remove
possible to laminate decorative wire
internal stresses in the molecular
mesh, fabric, wood veneer, and coloured
process of creating 2D and 3D designs
structure. Borosilicate glass is heated
and printed PVB into glass sheets.
within glass objects (see image, above
up to around 5700C (1058^),'soaked'
Glass can bemodifiedbymachining,
Sub-surface laser engraving is the
centre). It is possible to engrave either
at this temperature, and then very
abrasive blasting (page 388), deep
a 2D illustration or a 3D CAD file or
gradually cooled down. Each type of glass is annealed at a different
carving, laser engraving (page 248)
scan below the surface of glass. Careful
and water jet cutting (page 272). Deep
consideration should be given to 3D
temperature.Thicker sections take longer
carving is an abrasive blasting process.
designs because the engraving is
to anneal because the temperature
Instead of simply frosting the surface,
see-through and it can easily become
throughout the glass structure has to
a skilled operator can use the high-
cluttered and overcrowded. Lead alkali
be equalized.Therefore, some pieces,
pressure jet of abrasive particles to 'carve'
glass (crystal glass) is the ideal medium
particularly artwork and sculpture, have
3D shapes and patterns into the surface
for this process because it has excellent
to be annealed for several days, or even
of the glass (see image, opposite). Lead
optical properties.
Aerogel and Peter Tsou, JPL scientist Made by: JPL (Jet Propulsion Laboratory] Material: Aerogel (NASA/JPL) Manufacture: N/a
jsql* VvA
Notes: Silica with a porous, dendriticlike structure
gg.8% atmosphere, so it is extremely
lightweight. Like ordinary glass, it is fragile and brittle, but it is a much more efficient insulator because the internal structure has avast surface area. It is considerably more expensive than ordinary glass and is not yet available in transparent grades.There are not many commercial applications outside
Sponge and sponge vase
aerospace. However, in 2007 Dunlop Designer/
Marcel Wanders/Moooi
Sports released a range of tennis
made by: Date:
1997
rackets with an aerogel core. Its extreme
Material:
Porcelain
lightness is used to produce a racket with
Manufacture:
To make this form a natural
high strength to weight and stiffness.
sponge (top) is dipped in liquid
Avast range of coatings have been
ceramic slip and fired (above).
developed to improve the characteristics of glass. These include dichroic, antimachined. When it breaks, the fragments
are very thin and make up approximately
developed a similar technique for the
reflective, thermally insulating, sound
tend to be small and blunt as a result of
4% of the material, so they do not affect
production of domestic ceramics (see
reflecting, self-cleaning and view control.
the modified structure, so it is used in
its structural integrity.
images, opposite).
safety applications such as door glazing,
Glass mirrors are produced by coating
by copper (or other metal) and a
Made by: Litracon Bt, Hungary
Material: Glass fibres (4%) in a fine concrete matrix
foaming agent to the raw material.
produced by coating flat glass with a very
Bubbles form in the molten glass and are
thin, transparent layer of titanium oxide.
el evated tem peratures an d so i s m ore
structural materials. Ceramic foams are
locked in place as it cools. Each bubble is
This produces a surface that is both
difficult and expensive to fabricate.
typically formed by saturating polymer
sealed into the glass (closed cell), so it
hydrophilic and photocatalytic. In
fo^m (or similar porous material) with
remains watertight and gastight. Foams
combination, these qualities help to
MATERIAL DEVELOPMENTS
ceramic slurry.The firing process hardens
can be formed from crushed (recycled)
maintain a surface that is free of dirt and
Developments in ceramics and glass
the ceramic and simultaneously burns
glass by mixing the ingredients in a
watermarks: UV radiation helps to break
have been concentrated in the high
out the foam. A range of ceramics can
mold. As the crushed glass is heated the
down surface dirt, which is subsequently washed away by rain.
performance materials and coatings.
be formed in this way.Two applications
gassing agent produces bubbles that are
glass (see image, page 485,right) can be
Materials are being combined in
include high temperature filtration and
encapsulated in the molten structure.
silvered on the inside and sealed without
different ways to produce new composite
thermal insulation. In a project for Droog
the need for a protective layer. Protecting
materials such as light transmitting
Design and Rosenthal, Marcel Wanders
protective 1 acquer. Twin-walled bl own
Manufacture: Cast
or sealing is essential because otherwise
concrete and lightweight foamed panels.
silver will tarnish and corrode.The blown
approximately 6500C (i2O20F) and then
glass technique has both decorative and
quenched in blasts of cool air. This forces
Pilkington developed self-cleaning glass in 2001. Pilkington Activ™ is
materials in the form of lightweight
High performance glass is made at
glass with a fine layer of silver, followed
Glass foams are formed by adding a
high temperature properties of these
car windscreens anddinnerware.
Litracon® light transmitting concrete
Ceramic and glass foams harness the
Litracon® (see image, above left) is
Ceramic fibres and textiles can
ENVIRONMENTAL IMPACTS
withstand temperatures up to 14500C
Glass production is a hot and energy
(2642°F).The material determines the
intensive process. Gullet mixed with the
temperature resistance. They are used for
raw ingredients reduces the amount
a light transmitting concrete invented
insulation (as mineral wool),fire
of energy required in production. Glass
protection and other high temperature
can be recycled indefinitely without any
functional uses. Silver prevents radiation
the surface of the glass to cool more
by Hungarian architect Aron Losonczi
of heat, a quality used in the production
rapidly than the core andthus forms a
in 2001. It is made up of glass fibres
applications. Products include textiles,
degradation to its structure. However,
of glass vacuum (thermos) flasks.
structure under compression. As a result,
embedded in a fine concrete matrix.The
non-wovens,foil and rope.
the use of cull et may have an impact
Aerogel (see image) is made up of
on the colour of the glass. Clear glass
tempered glass is several times stronger
glass fibres are in parallel alignment and
or toughened glass, is produced by heat
than annealed glass. However, once
so transmit light through the concrete
an open cell silica structure. It is very
cannot tolerate impurities and colour
treatment. Soda-lime glass is heated to
tempered, it cannot be modified or
without distorting the image.The fibres
low density and can be as much as
contamination, whereas brown and
Tempered glass, also known as safety
Blue Carpet
Pottery ceramics
Designer/client: Heatherwick Studio/Newcastle City Council
Date: Completed 2002 Material: Crushed glass in white resin Manufacture: Cast
• Earthenware • Stoneware • Porcelain
Clay combined with other minerals is plastic and can be formed by hand. When fired at high temperatures it becomes hard, brittle and in some cases vitreous.
crack in freezing conditions due to moisture absorption. Stoneware is fired at i2000C to 13000C (2192- 23720F). This produces a vitreous or semi-vitreous ceramic that is less
POTTERY CERAMICS
Is That Plastic? butter dish Designer: Helen Johannessen
Date: 2004 Material: Earthenware Manufacture: Slip cast and glazed
porous and stronger than earthenware. Even though it is less porous, it is not
completely watertight unless it has been glazed.The Ingredients are not as refined green glass may contain a higher
Qualities: Earthenware is clay that has
as those of porcelain, so the raw material
13000C (23720F) these minerals combine
percentage of mixed cullet.
been fired at iooo0C to i25o"0C {1832-
Is often visibly speckled.
to form a vitreous and translucent
2048 0F). Clay Is made up of aluminium
ceramic. It is dense and watertight, but is
crushed state. Applications Include glass
silicate, quartz and other fine rock
Porcelain is made up of a specific type of clay, kaolin (china clay), mixed with
foam for insulation and aggregate in
particles, and the ingredients will vary
petuntse, quartz and other minerals. It is
concrete. Heatherwick Studio found a
slightly according to the geographical
typically more refined than earthenware
new and interesting use for Bristol
location.The type of clay determines the
and stoneware. When fired at over
Cream bottles In Newcastle upon Tyne,
quality of the earthenware.Terracotta,
floor tiles, toilets, sinks, garden pots
U K. Crushed blue glass is mixed with
for example, is a type of clay used in the
and tableware. Stoneware is used for
Costs: Pottery ceramics are moderately
POTTERY CERAMICS
white resin to form hardwearing and
production of earthenware. When fired, it
these applications as well as cookware.
expensive materials: earthenware is
Ramekin
decorative paving slabs, benches and
is a characteristic reddish brown colour.
Porcelain is more expensive, so typical
the least expensive and porcelain is the
kerbs (see image, above). Glass is non¬
Earthenware tends to be porous and
applications are more likely to Include
most expensive.
Alternatively, cullet can be used in its
often glazed for decorative purposes.
Applications: Earthenware is typically used in the production of wall and
Material: Stoneware Manufacture: Press molded Made by: Unknown
toxic and safe to dispose of, although this
brittle, and will chip more easily than
dinnerware, vases, cups and saucers.
is not desirable for such a valuable
stoneware or porcelain. It has to be
Porcelain is also used for dental implants
earthenware and can be used
reusable material. It is long lasting and
glazed to be made watertight. Unglazed
and certain industrial applications.
as cookware.
can be sterilized and refilled many times.
pots that are left outdoors frequently
Notes: Stoneware is more durable than
non-toxic, do not absorb odours and are safe for food contact, but not all.
Applications: Applications include medical and dental implants, armour, cutting tools and blades and wear resistant nozzles, such as for water jet
cutting (page 272). Due to their high cost and brittle nature they are often applied as high performance coatings, to provide protection against corrosion, chemicals and wear, without needing lubrication. They are used by the aerospace and high performance automotive industries. Costs: Very high.
POTTERY CERAMICS
Soda-lime glass
Egg vase
SODA-LIME GLASS
LEAD ALKALI GLASS
Condiment jar
Glitterbox
Designer/
• Soda-lime glass
Made by:
Various
made by:
Also known as 'commercial glass', this is
Material:
Soda-lime glass
Designer/client: Georg Baldele/Swarovski® Crystal Palace Project
Date: 1997
the least expensive and most common glass.
Manufacture:
Machine press and blow
Date:
2006
Material: Porcelain
Applications range from blown glass packaging
Material:
Swarovski® crystal
Manufacture: Slip cast
to windowpanes.
Manufacture:
Diamond ground, polished, rouged
and buffed
HIGH PERFORMANCE CERAMICS
High performance ceramics • Alumina • Zirconia
• Silicon nitride • Silicon carbide • Tungsten carbide • Boron carbide A wide range of almost pure non-metallic
Jamie Oliver Flavour Shaker Designer: Jamie Oliver and William Levene Date: 2006 Material: Alumina ceramic ball in a
plastic flask Manufacture: Pressed, sintered, ground and polished ceramic
materials for demanding or extreme applications.
Qualities: These are the most common of
finish that can be achieved with zirconia
the high performance ceramics.They are
is utilized in cutting blades; unlike metal,
hard and durable and have very good
it requires no lubrication. Silicon carbide
resistance to temperatures up to over
ceramic has a very high melting point,
2000°C (36320F), wear and corrosion.
above 2500oC (4532^). Boron carbide is
However, they tend to be brittle and have
1 ofthe hardest materials known and is
poor resistance to impact and shock.
used in nuclear applications and armour.
Alumina (aluminium oxide) ceramic
has high chemical stability. Silicon nitride ceramic is very hard and has good resistance to shock and heat.Tungsten carbide is exceptionally hard, so is used in cutting tools and as an abrasive powder
for blasting (page 388), grinding and polishing (page 376).The hardness, abrasion resistance and fine surface
Some high performance ceramics are
Qualities: Soda-lime glass is made up
Lead alkali glass
of silica sand (up to 75%), soda ash, lime
Cutting enhances the sparkle ofthe glass and as such is used in the production
(calcium oxide) and other additives.
• Lead glass
of decorative tableware, lighting (see
The exact ingredients depend on the
• Crystal glass
image), ornaments and jewelry.
Due to the lead content these glasses have
processing and application.
a higher refractive index than other types.
It is a'soft'glass that is relatively easy to mold and fabricate. It softens at
Lead content makes it suitable for
Increased refraction produces a clearer and more
certain radiation shielding applications.
lustrous glass.
Such glasses typically have more than
around 4000C to 500°C (752- 9320F) and
50% lead content and are used in
so is economical for mass production.
hospitals, airports and laboratories. Like soda-lime glass, lead alkali glass is
However, this also means that soda-
packaging liquids,food andmany
Qualities: Like soda-lime glass, lead
lime glass is prone to shatter at high
chemicals. However, borosilicate glass
alkali glass is silica based, but the lime is
not suitable for use in high temperature
(page 492) is more resistant to many
replaced by lead and the soda replaced
applications or those that will experience rapid temperature change.
temperatures or in response to sudden changes in temperature. Soda-lime glass finishes with a smooth and non-porous surface. It is
acids and alkalis and so is more suitable
with potash. If it has less than 25% lead
for packaging and storing certain
it is known as crystal glass and when
products.
there is more than 25% lead it is known
Applications: Typical applications
as lead glass. Over prolonged periods the
include cut glass, packaging, tableware,
Applications: Applications are
lead content can leach, so this glass is not
vases, candlesticks and ornaments. For
widespread and include windowpanes
suitable for storing liquids and foods.
their superior optical properties, lead and
inert and tasteless and suitable for
(float glass, page 494), automotive
The lead oxide acts as a flux to reduce
crystal glass are used in jewelry, awards,
windows, mirrors, tableware, dinnerware,
the softening temperature ofthe glass.
trophies, pri sm s an d lenses for telescopes
light bulbs,light shades, packaging,
As a consequence it is even 'softer'than
and cameras.They are also used as
storage jars and laboratory glassware.
soda-lime glass. It is relatively easy to
clear radiation shielding in hospitals,
form by glass blowing (page 152), press molding, cutting, CNC machining (page 182) andfinish by polishing (page 376).
laboratories and airports.
Costs: Low.
Costs: Moderate to high.
BOROSILICATE GLASS
ground airtight seal, produced by honing
Glass profile
(page 376), to preserve the contents.
Made by: Dixon Glass, UK
Extruded glass profiles are typically
Material: Borosilicate glass
borosilicate glass, because soda-lime is
Manufacture: N/a
'softer' and prone to breaking during
Notes: Range of profiles includes rod. tube, ribbed and triangular.
V 1
processing.There is a range of diameters in each profile: tube can be up to 415 mm (16.34 i1"1-) ar|(i complex profiles can be up to 120 mm (4.72 in.),but certain profiles
BOROSILICATE GLASS GlassGlass Designer/client: Paolo Rizzatto/Luceplan Date: 1998 Material: Borosilicate glass Manufacture: Pressed
(such as triangles) are limited to only 20 mm (0.79 in.).
Applications:Typical applications include ovenware, glass tea and coffee pots, kettles, scientific glassware (test
tubes and distillation equipment) and pharmaceutical products. As well as industrial and performance applications,
Borosilicate glass
borosilicate has superior lampworking (page 160) characteristics, so is used in
• Borosilicate glass This is also known under the trade names Duran,
the production of jewelry, beads,
Simax and Pyrex (although the Pyrex consumer
paperweights, sculpture and ornaments.
brand no longer uses borosilicate glass in North America). It is used primarily for its resistance to high temperatures and thermal shock.
Qualities: Borosilicate glass is so called because it contains up to 15% boric oxide and small amounts of other alkalis. It Is
Costs: Moderate to high.
High performance glasses
high temperatures and thermal shock. It can operate at temperatures of up to
75o0C (i3820F). Quartz glass, also known as fused
'harder'an dm ore durablethan soda-
• Glass ceramic • Aluminosilicate glass
lime and lead alkali glass (pages 491).
• Quartz glass
quartz and silica glass, is made up of
These glasses have high working temperatures;
almost pure silica (silicon dioxide). It is
Borosilicate glass is more likely to survive
being dropped or hit. It has 1 ow 1 evels
they are relatively difficult to fabricate, but have superior resistance to heat and thermal shock.
manufactured by heating up quartz to together. It has exceptional resistance to
to thermal shock, so it is useful for
laboratory equipment that is repeatedly
Qualities: These are high performance
high temperatures, thermal shock and
heated and cooled.
andhigh cost materials. Class ceramics
most chemicals. It can be heated up to
are so calledbecause they are shaped like
over iooo0C (i8320F) and rapidly cooled
at 8oo0C to 8500C (i472-i562°F).This
glass in a molten state but heat-treated
without any structural degradation.
makes it more difficult to mold and
to give a high level of crystallinity, similar
fabricate,but means that it can be used
to ceramics.The resulting material is
Applications: Glass ceramics are used
for high temperature applications and
harder, more durable and resistant to
in stove and fireplace doors, light
can tolerate up to 5000C (9320F) for
rapid temperature change. It has very
covers, cooker tops, oven windows,
short periods.
low levels of thermal expansion andean
and ovenware that can be placed in a
operate at temperatures ranging from
preheated oven straight from the freezer.
-2000C to 7OO0C (-328-i2g20F).
Other high performance glasses are
Its softening point is relatively high
It is more resistant to acids than sodalime glass and has moderate resistance to alkalis. As a result, it is used to store
Aluminosilicate glass contains
used in light covers mainly for industrial
chemicals and is suitable for long periods
higherlevels of aluminium oxide
applications, but also halogen bulbs,
of storage. Museums use borosilicate
than other lower cost glasses. It is
cookware and even jewelry.
storage jars for their precious collections
similar to borosilicate glass, but has
of specimens.They have a precision
improved resistance to chemicals.
Glass ceramic cooker top Made by: Kuppersbusch Material: Glass ceramic Manufacture: Formed as glass and then
2000°C (36320F), which causes it to fuse
of thermal expansion, and is resistant
HIGH PERFORMANCE GLASSES
Costs: High to very high.
crystallized with heat treatment Notes: Glass ceramic can withstand thermal shock, is very durable and can withstand moderate impacts.
Case Study
-> Pilkington float glass Float glass is soda-1ime glass with slightly
soda are mixed with cullet (recycled glass)
modified ingredients to make it suitable
in a furnace (image i).The mix is heated by
applied during production for specific
for mass production. Alastair Pilkington
burning a combination of natural gas and
functional improvements. Examples include
developed the process, which was unveiled
pre-heated air at i6oo0C (29i20F) (image 2),
self-cleaning Pilkington Activ™ produced by
to the public in 1959 and has since become
The hot molten glass leaves the furnace at
a very thin coating of titanium oxide; low
the standard method for mass producing
approximately iooo0C (i8320F) and is floated
emissivity Pilkington K Glass™ that reflects
flat glass. It is now widely used in the
on a bath of molten tin in a controlled
heat back into buildings and so reduces heat
construction and automotive industries.
atmosphere of hydrogen and nitrogen which
loss; and Pilkington Optifloat™, which is ideal
Flat glass sheets are available in a range of
Modifications, such as coatings, are
prevents the tin from oxidizing (image 3).
for facades and furniture due to a higher
thicknesses from 0.4 mm to 25 mm (0.016-
The glass is annealed and cooled (image 4).
level of clarity than 'clear'glass. This material
0.98 in.). It is produced in a 4 stage process.
Finally, the sheet is scored and snapped into
is utilized in the Mall of Millennia, Florida,
First of all silica sand, lime, dolomite and
pre-determined sizes.
designed byJPRAArchitects (image 5).
Glossary and Abbreviations
CNC
DMLS
Engineering Timber
Machining equipment that is operated
Direct metal laser sintering (page 232).
These high-strength and dimensionally
by a computer is known as computer
stable lumbers typically for architectural
numeric control (CNC).This includes
Durometer Hardness
applications are produced by laminating
milling machines,lathes and routers
Another name for Shore hardness (see
wood with strong adhesives. Examples
used to manufacture all types of
page 500).
include laminated strand lumber (LSI) and parallel strand lumber (PSL) (see wood and natural fibres, page 466).
materials.The number of operational
3DL
Acrylic
Biopolymers
Three-dimensional thermal laminating
Common name for poly methyl
Another name for bioplastics.
(page 228).
methacrylate (PMMA) (page 434).
axes determines the types of geometries
Dyneema®
that can be achieved: 2-axis, 3-axis and
DSM trade name for ultra high-density
5-axis (page 183) are the most common.
polyethylene (UHDPE) (see polyolefins,
EP
page 430).
Epoxy resin.
COE BR
Coefficient of expansion.
Butadiene rubber.
EBM
EPDM
Extrusion blow molding (page 22).
Ethyl en e propyl en e di en e m on om er.
3Dr
Air-dried Timber
Three-dimensi on al rotary 1 amin ating
Lumber seasoned without the use of
(page 228).
a kiln to 20% or less moisture content
CA
A common name for the least expensive
EBW
EPM
(see also kiln-dried timber, page 498,
Cellulose acetate.
thermoplastics that make up the
Electron beam welding (page 288).
Ethylene propylene monomer.
ABR
Commodity Thermoplastic
and seasoned timber, page 500).
majority of total plastic production-,
CAD
Acrylonitrile butadiene rubber.
for example, polypropylene (PP) and certain grades of polyethylenes (PE) (see
EDM
EPS
Electrical discharge machining (page
Expanded polystyrene.
polyolefins, page 430).
254)-
Amorphous
Computer-aided design is a general term
ABS
Unorganized and non-crystalline
used to cover computer programmes
Acrylonitrile butadiene styrene.
molecular structure materials, which
that assist with engineering, product
melt across a wider temperature range
design, graphic design and architecture.
Copolymer
EL
than crystalline materials.
Some of the most popular 3D packages
A polymer made up of long chains of
Electroluminescent.
A-class Finish The automotive industry uses this term
ETFE
include Alias, Auto CAD, Maya,
2 repeating monomers:for example,
Ethylene tetrafluoroethylene.
EVA
to describe a high gloss surface finish.
Biocomposite
Professional Engineer (commonly
styrene acrylonitrile (SAN) (see styrenes,
Elastomer
Processes such as composite laminating
Natural materials, such as woodfibres
known as Pro E), Rhino and Solid Works.
page 432).
A natural or synthetic material that
(page 206), metal stamping (page 82),
or wheat straw, molded and bonded
Many products are now designed and
exhibits elastic properties, and has the
FEA
panel beating (page 72), polishing (page
together with a natural or synthetic
engineered in this way. Some notable
CR
ability to deform under load and return
Finite element analysis is a computer
376), spray painting (page 350) and superforming (page 92), are all capable of
resin. Examples include Environ® and
examples include aluminium forging
Chloroprene rubber.
to its original shape once the load is
simulation technique that uses FEM
Treeplast® (see wood, page 468).They
removed. Examples include rubber (page
producing parts with an A-class finish.
sometimes crossover with biofibre
(page457),Chair#! (page483),the Eye chair (page 342) and Pedalite (page 53).
(page 16) to analyse designs, improve molding efficiency and predict part
CRP Carbon reinforced plastic.
reinforced plastics.
CAE
A-side
425), thermoplastic elastomers (page 425) and thermoplastic polyurethane (page
FEM
Biofibre Reinforced Plastics
Computer-aided engineering is a general
Crystalline
have an A- side and a B-side.The A-side
These are plastics reinforced with natural
term used to cover the use of computer
Highly organized molecular structure
EMI
does not come into contact with the
fibres such as cotton, hemp and jute;
programmes in the design, simulation,
that has a sharper melting point than
Electromagnetic interference.
tool and so has a higher surface finish
they are similar to biocomposites (page
an alysi s, production an d optim i zati on
comparable amorphous materials.
than the B-side. Processes that use a
468). Developments are concentrated
of products and assemblies. Examples
single-sided mold include composite
in composite laminating (page 206) for
include FEA and Moldflow (page 56).
laminating (page 206), superforming
automotive applications.
30).
Computer aided manufacturing.
Natural polymers that are made without
Finite element method is a numerical system that assists with engineering
calculations by dividing an object in Engineering Thermoplastic
smaller parts, known as finite elements.
DfS
High -perform an ce therm opl astics
The properties of these parts are
Design for sustainability.
materials for demanding applications.
mathematically formulated to obtain the
These tend to be more expensive and
properties of the entire object.
CAM Bioplastic
performance post-molding.
436).
Parts produced over a single-sided mold
(page 92) andthermoforming (page
Ethylene vinyl acetate.
Direct Manufacturing
less widely applied than commodity
Manufacturing products directly from
thermoplastics (page 435), and include
FEP
Acetal
petrochemicals:for example, cellulose-
CAP
CAD data: for example, rapid prototyping
thermoplastics such as acetal (page 439),
Fluorinated ethylene propylene.
Common name for polyoxymethylene
based (page 446), starch-based (page 446) and natural rubber materials (page
Cellulose acetate propionate.
(page 232).
polyamides (page 438), polycarbonate (PC) (page 428) and thermoplastic
Ferrous
447). Some are completely biodegradable
DMC
(POM) (page 439). Acetate
and require less energy to produce than
Checks Splits that form in the end of a length of
Alternative name for cellulose acetate
synthetic polymers.
timber as it is seasoned or kiln dried.
(CA) (see cellulose-based, page 446).
Dough molding compound (page 218).
polyesters (page 437).
Metals that contain iron: for example, steel (page 455) (see also non-ferrous,
page 499).
Figured Grain
HAZ
Kevlar®
surface finish. Fire retardant MDF grades
Nylon
PE
Wood grain with a distinctive pattern
Heat-affected zone.
DuPont™ trade name for aramid fibre
are typically red, and moisture resistant
Common name for polyamide (PA) (page
Polyethylene.
(see polyamides, page 438).
grades are green.
438). Nylon is an acronym of New York
such as bird's-eye,fiddleback, flame and curly (see wood and natural fibres, page
HOPE
475)-
High-density polyethylene.
Kiln-dried Timber
MF
Lumber dried in a kiln.The moisture
Melamine formaldehyde.
and London, where it is believed to have
Pearlescent
been discovered simultaneously.
A lustrous translucence with a
shimmering quality affected by the
OFW
FRP
Heartwood
content of small cross-section lumber can
Fibre reinforced plastic is molded plastic
The central section of amaturetree
be reduced to 12%. The moisture content
MIG
reinforced with lengths of fibre, which
trunk, which is usually darker in colour.
has to be less than 14% for impregnated
Metal inert gas.
can be carbon, aramid, glass or natural
It is often harder and denser than the
preservative to be effective (see also
material such as cotton, hemp or jute.
surrounding sapwood (page 473) and
air-dried timber, page 467, and seasoned
MIM
They are formed by a range of processes
no longer transports water, because it
timber, page 500).
Metal injection molding (page 136).
including composite laminating (page 206), DMC and SMC molding (page 218)
becomes saturated with resin (page 500)
Overmolding
Polyethylene terephthalate modified
LBW
MMA
All molding and casting processes can
with glycol.
Laser beam welding (page 288).
Manual metal arc welding (page 282).
be used to overmold. It is the process of
LCA
Monomer
Life cycle analysis.
A small, simple compound with low
LCP Liquid crystal polymer.
long chains,known as polymers.Two
and tannin.
and injection molding (page 50) (see also biofibre reinforced plastics, page 496, and
HIPS
GRP, page 498).
High impact polystyrene.
FSW
HSLA
Friction stir welding (page 294).
High strength low alloy steel.
GPPS General-purpose polystyrene (same as
IBM Injection blow molding (page 22).
PS).
Low-density polyethylene.
IIR Green Timber
Polyisobutylene; but is commonly known
LFW
as butyl rubber, because it is very similar
Linear friction welding (page 294).
fibre saturation point, which is typically
in composition to natural rubber.
LLDPE
the structure of the wood will not be
IR
affected, because the water being
Isoprene rubber.
removed is from the cells cavities as opposed to the cell walls. Green timber is
Iridescent
used for steam bending (page 198).
Abright colourthat changes according to the viewing angle.
GRP Glass reinforced plastic is molded plastic
ISBM
reinforced with lengths of glass fibre.
Injection stretch blow molding (page 22)
Polyethylene terephthalate.
Orientated strand board.
PETG
molding over an insert, which becomes
PF
integral to the part on cooling.
Phenol formaldehyde resin.
molecular weight, which can be joined
PA
Photochromic
with other identical compounds to form
Polyamide.
A compound that changes colour with light intensity: for example, glasses that
PAP
become sunglasses in bright light. It is
long chain is known as a copolymer, and
Paper (abbreviation usedfor recycling
added to materials as a dye.
3 similar monomers makes a terpolymen
purposes).
PIM
for example, acrylonitirile butadiene
Lumber with a moisture content above around 25%. Up to this percentage
PET OSB
similar monomers joined together in a
LDPE
viewing angle.
Orbital friction welding.
styrene (ABS) (see styrenes, page 432).
Patina
Powder injection molding.
A surface layerthat develops over time
NA
(such as verdigris copper, page 460) or
PLA
Natural rubber.
a surface pattern that develops with
Polylacticacid.
Linear low-density polyethylene.
frequent use (such as a smooth-worn
NdrYAG
wooden handle).
Plastic State
LSL
Neodymium:yttrium aluminum garnet
Laminated strand lumber.
(Nd:YAG) is a crystal used in solid state
Pattern
becomes viscous and can be molded or
lasers.This is one of the most common
An original design or prototype that is
formed.
reproduced to form a mold: for example,
The point at which a heated material
Lumber
types of laser and is used for laser beam
Sawn wood for use in building and
welding (page 288), laser cutting (page
in composite laminating (page 206).This
PMB
furniture making,for example.
248) and drilling a range of materials.
mold can then be used to produce many
PI asti c m edi a bl asti n g.
identical parts.
Machining
Neoprene®
short fibre length up to 3 mm (o.n8 in.),
JIT
Removing precise amounts of material
The DuPont™ tradename for chloroprene
PBT
whereas composite laminating (page
Just in time is a strategy employed by
with acutting action:for example,by
rubber (CR).
Polybutylene terephthalate.
206) and DMC and SMC molding (page
businesses to reduce stock and thus
electrical discharge machinery (page
218) have long or continuous lengths of
improve efficiency. Many factories are
254), laser cutting (page 248) or milling.
Nomex®
PC
glass fibre reinforcement (see also FRP,
now set up to supply J IT, which is the
DuPont™ trade name for aramid sheet
Polycarbonate.
page 498).
process of supplying products in low
MDF
volumes as and when they are needed.
Medium-density fibreboard is made
Hardwood
Some manufacturing techniques are not
up of particles of softwood bonded
Non-ferrous
Wood from deciduous and broad-leaved
suited to short production runs and so
together with UF adhesive.The mix of
Metals that do not contain iron: for
trees such as ash (page 474), beech (page
stock has to be kept somewhere in the
wood particles and adhesive are formed
435). (See also copolymer, page 497, and
supply chain, which is usually with the
into panels by heating and pressing in
example, aluminium alloys (page 457) and copper alloys (page 460) (see also
PCT
473), birch (page 472) and oak (page 476).
Polycycl oh exyl en e di m ethyl en e
terpolymer, page 501).
manufacturer.
steel molds, which produces a smooth
ferrous, page 497).
terephthalate.
Injection molded (page 50) GRP has very
PMMA Poly methyl methacrylate. Polymer
(see polyamides, page 438).
A natural or synthetic compound made up of long chains of repeating identical monomers. Examples include
PCB
cellulose (page 446), starch (page 446),
Printed circuit board.
polypropylene (page 430), polystyrene (page 432) and polycarbonate (page
Resin
electrical resistance, resistance to
SMC
(see polyolefins, page 430) (see also
uPVC
A natural or synthetic, semi-solid or solid
decay and adhesive bond strength. The
Sheet molding compound (page 218).
commodity thermoplastic, page 497, and
Unplasticized polyvinyl chloride.
substance, produced by polymerization
required level of moisture depends on
PP
or extraction from plants, and used in
the application (see also air-dried timber,
Softwood
Polypropylene.
plastics, varnishes and paints.
page 496, and kiln-dried timber, page
Wood from coniferous and typical
Thermoplastic Elastomer
498).
evergreen trees, such as cedar,fir, pine
A general name used to describe
and spruce (see softwoods, page 470).
thermoplastic materials that exhibit
POM Polyoxymethylene.
PS
RF
Polystyrene.
Radio frequency.
SEBS Styrene ethylene butylene styrene.
PSL
RFW
Parallel strand lumber.
Rotary friction welding (page 294).
engineering thermoplastic, page 497).
similar elastic properties to rubber.
SRIM Structural reaction injection molding.
Semi-crystalline A molecular structure that contains both
UV Ultraviolet.
Verdigris Another name for the green patina that forms on the surface of copper (page
Thermosetting Plastic
460). It comes from the French vert de
A material formed by heating,
Grice.
Sub-surface Laser Engraving
catalyzing or mixing 2 parts to trigger a
PTFE
RIM
crystalline (page 425) and amorphous
The process of laser-marking clear
i-way polymeric reaction. Unlike most
Vulcanize
Polytetrafl uoro ethyl en e.
Reaction injection molding (page 64).
(page 425) patterns: for example, polyethylene terephthalate (PET) (see
materials below the surface: 2D and 3D
thermoplastics, therm osetting pi astics
The process of curing natural rubber
designs are reproduced as point clouds,
form cross-links between the polymer
with sulphur, heat and pressure in a
PU
RRIM
thermoplastic polyesters, page 437).
which are sets of closely packed laser
chains, which cannot be undone, and
i-way reaction to form a thermosetting
Polyurethane [thermoplastic, almost
Reinforced reaction injection molding.
markings that outline the shape. Sub¬
so this material cannot be reshaped or
material (see thermoset, page 445).
surface laser engraving is also known as
remolded once cured. Thermosetting
RTM
Shape Memory The ability of a material to be heavily
Resin transfer molding.
manipulated andthen return to its
exclusively injection molding].
PUR Polyurethane resin [thermosetting, resin,
vitrography.
original shape, sometimes with the
Tampo Printing
ie most occurences],
RTV
application of heat. Materials with shape
Another name for pad printing (page
Room temperature vulcanizing,
memory include synthetic rubbers (page
404).
PVA
occurs when certain rubbers, such as
445) and certain metal alloys (page 452).
Polyvinyl acetate.
silicone, are chemically cured at room temperature, as opposed to heat curing.
PVC Polyvinyl chloride.
Xylem The fibrous material that makes up the
thermoplastic (page 435).
TIG
rigid walled cells and provides trees and
Tungsten inert gas.
shrubs with an upward flow of water and
page 498, and sapwood, page 500).
Teflon®
mechanical support (see also heartwood,
Shore Hardness
DuPont™ trade name for
TPC-ET
Thehardness of aplastic, rubber or
polytetrafluoroethylene (PTFE) and ethylene tetrafluoroethylene (ETFE) (see
Thermoplastic polyester elastomer.
elastomer is measured by the depth of
Styrene acrylonitrile.
indentation by a shaped metal foot on
fluropolymers, page 440).
TPE
a measuring instrument known as a
Sapwood
urometer. The depth of indentation is
Thermoplastic elastomer.
Terpolymer
Young and light-coloured wood that
measured on a scale of o to 100; higher
A polymer made up of long chains
TPU
PW
forms between the bark and heartwood
numbers indicate harder materials.
of 3 repeating monomers, such as
Thermoplastic polyurethane.
Plasma welding (page 282).
(page 471) of a tree.
These tests are generally used to
acrylonitirile butadiene styrene (ABS)
denote the flexibility of a material. The
(see styrenes, page 432).
RAL
SAW
2 most popular are Shore A and Shore D.
Reichsausschuss fiir Lieferbedingungen
Submerged arc welding (page 282).
Indenterfeet with different profiles are
Thermochromatic
used in each case, and so each method is
UF Urea form aldehyde.
A compound that changes colour
UHDPE
mainly in paint and pigment colour
SBR
suitable for different material harnesses.
as its temperature goes up or down.
Ultra high-density polyethylene.
specification.
Styrene butadiene rubber.
For example, soft materials are measured
Thermochromatic pigments are available
on the Shore A scale, and hard materials
for inks, plastics and coatings.
Rays
SBS
are measured on the Shore D scale.There
Vessels radiating from the centre of a
Styrene butadiene styrene.
is not a strong correlation between different scales. Shore hardness is also
A polymer that becomes soft and pliable
food and waste laterally.They are
Seasoned Timber
known as durometer hardness.
when heated. In its plastic state it can
responsible for the characteristic flecks of
Traditionally used to describe air-dried
colour in hardwoods (page 472) such as
timber with a moisture content of less
SLA
of molding processes, such as blow
beech and oak.
than 20%. Compared to green timber
Stereolithography (page 232).
molding (page 22) and injection molding (page 50). Examples include polyamide
dimensional stability,toughness,
SLS
(PA) nylon (page 438), polycarbonate
bending stiffness, impact resistance,
Selective laser sintering (page 232).
(PC) (page 428) and polypropylene (PP)
is a German colour chart system used
tree's stem andbranchesfortransporting
be shaped and re-shaped by a range
(page 467), dried timber has improved
ULDPE Ultra low-density polyethylene.
Thermoplastic
stem and branches of trees and shrubs. It consists mostly of a series of elongated,
SAN
PVOH Polyvinyl alcohol.
plastics tend to have superior resistance
to fatigue and chemical attack than
Cullen Packaging
Featured Companies
10 Dawsholm Avenue
Heywood Metal Finishers Field Mills
Madleaze Industrail Estate
Dawsholm Industrial Estate
Red Doles Lane, Leeds Road
Bristol Road
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Huddersfield, HD21YG United Kingdom
Gloucester GLi 5SG United Kingdom
www.cullen.co.uk
www.hmfltd.co.uk
www.kayplast.com
Processes: Die cutting; Paper pulp molding
Processes: anodizing
Processes: Thermoforming
Deangroup International Brinell Drive
Hydrographies Unit 4 Brockett Industrial Estate
systems; pallets
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Kaysersberg Plastics
Products: packaging materials; packaging
MANUFACTURERS
Branson Ultrasonics (UK)
Beatson Clark
686 Stirling Road, Slough Trading Estate
The GlassWorks Greasbrough Road
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YorkY023 2PT United Kingdom
Kaysersberg Plastics
Coventry
Manchester M44 5BL United Kingdon
www.hydro-graphics.co.uk
68240 Kaysersberg
West Midlands CV3 4LB
www.deangroup-int.com
Processes: Hydro transfer printing; Spray
France
Processes: Investment casting
painting
www.kayplast.com
Seven Stars Industrial Estate
BP No. 27
Rotherham S6o iTZ
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United Kingdom
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www.covproto.com
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Processes: Friction welding; Fiot plate
Processes: Arc welding; Grinding, sanding
Dixon Glass
Hymid Multi-Shot
Processes: Machine blow and blow
welding; Laser beam welding; Staking; Vibration welding; Ultrasonic welding
and polishing; Panel beating
127-129 Avenue Road
Unit 10-12 Brixham Enterprise Estate
Beckenham
Rea Barn Road
Lola Cars International
Products: see Processes
CRDM
Kent BR3 4RX United Kingdom
Brixham
Glebe Road, St Peters Road
Huntington
glassblowing
Processes: as above Products: as above
High Wycombe Buckinghamshire HP11 2JZ
www.dixonglass.co.uk
Perivale Greenford
Chiltern Casting Company Unit F
Devon TQs gDF United Kingdom
Processes: Lampworking
www.hymid.co.uk
Cambridgeshire PE29 7DS United Kingdom
Middlesex UB67PP
11 Cradock Road
United Kingdom
Products: extruded glass profiles;
Processes: CNC machining; Electrical
www.l ol acars .com
laboratory glassware
discharge machining; Injection molding
Processes: Composite laminating
BJS Company 65 Bideford Avenue
Queen Alexandra Road
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Luton LU40JF
www.crdm.co.uk
www.bjsco.com
United Kingdom
Processes: CNC machining; Electrical
Processes: Electroforming; Electroplating
www.chilterncastingcompany.co.uk
discharge machining; Rapid prototyping;
Elmill Group
Impressions Foil Blocking
Marlows Timber Engineering Ltd
Vacuum casting
31 Shannon Way
Howarth House, Hollow Road
Sand casting
139A Engineer Road West Wilts Trading Estate
Thames Industrial Estate
Bury St Edmunds
Crompton Technology Group
Canvey Island
Suffolk IP327QW
Brunei Drive, Newark
CMA Moldform
Thorpe Park,Thorpe Way
Westbury, Wiltshire BA13 4JW United Kingdom
Essex SS8 oPD
United Kingdom
Nottinghamshire NG242EG United Kingdom
Unit B6 The Seedbed Centre
Banbury
www.elmill.co.uk
United Kingdom
www.marlows.com
100 Avenue Road
Oxfordshire OX16 4SU
Processes: Swaging
www.impressionsfoiling.co.uk
Processes: Timber frame structures
United Kingdom
Processes: Arc welding; Laser cutting; Press
Birmingham B74NT United Kingdom
www.ctgltd.co.uk
braking; Roll forming
www.cmamoldform.co.uk
Processes: Composite laminating;
Units 6-8,VictoriaTrading Estate,
Instrument Glasses
Processes: Centrifugal casting; Reaction
Kiln Road, Portsmouth
236-258 Alma Road
Hampshire PO3 5 LP United Kingdom
Enfield EN37BB
www.enl.co.uk
United Kingdom
Processes: Abrasive blasting; Arc welding;
Blagg & Johnson Newark Business Park
w ww.bl ag g s.co.uk
Branson Ultrasonics Corporation
injection molding; Vacuum casting
Filament winding; CNC machining Products: propshafts and driveline
Corporate Headquarters
Products:scale models
products
41 Eagle Road, PO Box 1961
Processes: Foil blocking and embossing
EN,L
Ponders End
Danbury.CT 06813-1961
Cove Industries
Cromwell Plastics
Processes: Injection molding; CNC
www.instrument-glasses.co.uk
USA
Industries House
53-54 New Street, Quarry Bank
machining
Processes: Class scoring; Grinding, sanding
www.branson-plasticsjoin.com
18 Invincible Road
Processes:Friction welding;Hotplate
Farnborough
Dudley West Midlands DY5 2AZ
Firma-Chrome
and polishing; Screen printing; Water jet cutting
welding; Laser beam welding; Staking; Vibration welding; Ultrasonic welding
Hampshire G U14 7OU United Kingdom
Products: see Processes
www.cove-industries.co.uk
Processes: Compression molding; DMC
United Kingdom
Processes: Arc welding; Dip molding; Press
and SMC molding
www.firma-chrome.co.uk
braking; Punching and blanking
United Kingdom
Soho Works, Saxon Road
www.cromwell-plastics.co.uk
Sheffield S8 oXZ
Processes: Electroplating; Electropolishing
MATERIALS AND FINISHES
Distrupol 119 Guildford Street
Riverside, CA 92517-5375
B&M Finishers
Chertsey
USA
201 South 31st Street
Kenilworth, NJ 07033
Surrey KT16 9AL United Kingdom
USA
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www.bmfinishers.com
Products: engineering thermoplastics
Radcor
Superform USA 6825 Jurupa Avenue
Castle Road
Pipecraft Units 6-7 Wayside
Eurolink Industrial Centre
Commerce Way
Sittingbourne KentMEiojRN United Kingdom
Lancing
Hingham Road Industrial Estate Great Ellingham Norfolk NR17 iJE
West Sussex BNi5 8SW
United Kingdom
www.superformusa.com
United Kingdom
www.radcor.co.uk
Processes: as above
www.medgalv.co.uk
www.pipecraft.co.uk
Processes: Composite laminating
Medway Galvanising
Processes: Galvanizing; Powder coating
RS Bookbinders
W. H. Tildesley Clifford Works
61-63 Cudworth Street
Bow Street, Willenhall
Processes: Swaging; Tube and section
bending Mercury Engraving
Products: coloured and pattern embossed stainless steel
Dixon Glass 127-129 Avenue Road
Unit A5 Bounds Green Industrial Estate
Polimoon
London Ei 5OU
West Midlands WV13 2AN
Beacons Products
Beckenham
Ring way
Rusel0kkveien 6
United Kingdom
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Unit 10 EEI Industrial Estate
London Nn 2UD
PO 60x1943 vil
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