Ch10

Polymer Properties Material AB S ABS (reinforced) Acetals Acetals (reinforced) Acrylics Cellulosics Epoxies Epoxies (reinforced) Fluorocarbons Ny l o n Nylon (reinforced) Phenolics Polycarbonates Polycarbonates (reinforced) Polyesters Polyesters (reinforced) Polyethylenes Polypropylenes Polypropylenes (reinforced) Polystyrenes Polyvinyl chloride

UTS (MPa) 28–55 1 00 55–70 1 35 40–75 10–48 35–140 70–1400 7–48 55–83 70–210 28–70 55–70 11 0 55 110–160 7–4 0 20–35 40–100 14–83 7– 55

(GPa) 1.4–2.8 7. 5 1.4–3.5 10 1.4–3.5 0 .4–1.4 0. 3.5–17 21–52 0. 7–2 1.4–2.8 2–10 2.8–21 2. 5– 3 6 2 8.3–12 0.1–0.14 0.7–1.2 3 . 6–6 1 . 4 –4 0. 01 4– 4

E 

Elongatio Elonga tion n i n 50 m m (%) 75–5 – 75–25 – 5 0–5 100–5 10– 1 4–2 300–100 2 00–6 0 10 –1 2–0 125 –10 6–4 300–5 3–1 1000–15 500–10 50 4–2 6 0–1 450 –40

Poisson’ Poiss on’ss ratio (ν ) – 0 . 35 – 0.35–0.40 – – – – 0.46–0.48 0.32–0.40 – – 0. 38 – 0. 38 – 0. 46 – – 0. 35 –

TABLE 10.1 Approximate range of mechanical properties for various engineering plastics at room temperature. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

H

H

C

C

H

H

Heat, pressure, catalyst

H

H

H

H

H

H

C

C

C

C

C

C

H

H

H

H

H

H

Polyethylene  n

Mer (a)

(b)

Monomer

Polymer repeating unit

H

H

H

H

C

C

C

C

H

H

H

H

H

H

H

H

C

C

C

C

H

CH3

H

CH3

H

H

H

H

C

C

C

C

H

Cl

H

Cl

H

H

H

H

C

C

C

C

H

C6H5

H

C6H5

Fl

Fl

Fl

Fl

C

C

C

C

Fl

Fl

Fl

Fl

Polymer Structure

Polyethylene  n

Polypropylene  n

Polyvinyl chloride  n

Polystyrene  n

Polytetrafluoroethylene (Teflon)  n

(c)

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

FIGURE 10.1 Basic structure of some polymer molecules: (a) ethylene molecule; (b) polyethylene, a linear chain of many ethylene molecules; (c) molecular structure of various polymers. These molecules are examples of  the basic building blocks for plastics.

H

H

C

C

H

H

Heat, pressure, catalyst

H

H

H

H

H

H

C

C

C

C

C

C

H

H

H

H

H

H

Polyethylene  n

Mer (a)

(b)

Monomer

Polymer repeating unit

H

H

H

H

C

C

C

C

H

H

H

H

H

H

H

H

C

C

C

C

H

CH3

H

CH3

H

H

H

H

C

C

C

C

H

Cl

H

Cl

H

H

H

H

C

C

C

C

H

C6H5

H

C6H5

Fl

Fl

Fl

Fl

C

C

C

C

Fl

Fl

Fl

Fl

Polymer Structure

Polyethylene  n

Polypropylene  n

Polyvinyl chloride  n

Polystyrene  n

Polytetrafluoroethylene (Teflon)  n

(c)

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

FIGURE 10.1 Basic structure of some polymer molecules: (a) ethylene molecule; (b) polyethylene, a linear chain of many ethylene molecules; (c) molecular structure of various polymers. These molecules are examples of  the basic building blocks for plastics.

Effect of Molecu Molecular lar Weight Commercial polymers

     y       t      r      e      p      o      r       P

Tensile and impact strength

Viscosity 104 107 Molecular weight, degree of polymerization FIGURE 10.2 Effect of molecular weight and and degree of polymerization on the strength and viscosity of polymers.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Polymer Chains

(a) Linear

(b) Branched

(c) Cross-linked

(d) Network

FIGURE 10.3 Schematic illustration of polymer chains. (a) (a) Linear structure; thermoplastics such as acrylics, acrylics , nylons, polyethylene, and polyvinyl chloride have linear structures. (b) Branched structure, such as polyethylene. (c) Crosslinked structure; many rubbers and elastomers have this structure. Vulcanization of rubber produces this structure. (d) Network structure, which is basically highly cross-linked; examples include thermosetting plastics such as epoxies and phenolics. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Effect Effe ct of Temp empera erature ture Glassy    )   e    l   a   c   s   g   o    l    (   s   u    l   u    d   o   m   c    i    t   s   a    l    E

100% cr y  ys   t alline

Leathery

Increasing crystallinity

Rubbery

A   

m  

o  

r     p  h  o  u   s  

Viscous

   )   e    l   a   c   s   g   o    l    (   s   u    l   u    d   o   m   c    i    t   s   a    l    E

Leathery

Rubbery N   

o  

c   

r    o  s   s 

Viscous T  g

Increasing cross-linking

Glassy

- l   l  i  n k  k i   in      g   

T  m

T  m

Temperature

Temperature

(a)

(b)

FIGURE 10.4 Behavior of polymers polymers as a function of temperature and (a) degree degree of crystallinity and (b) crosslinking. The combined elastic el astic and viscous behavior of polymers is known as viscoelasticity.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Crystallinity Amorphous region

Crystalline region

FIGURE 10.5 Amorphous and crystalline regions in a polymer. Note that the crystalline region (crystallite) has an orderly arrangement of molecules. The higher the crystallinity, the harder, stiffer, and less ductile is the polymer.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Glass-Transition Temperature

  e   m   u    l   o   v   c    i    f    i   c   e   p    S

Amorphous polymers Partly crystalline polymers

 g:  C o o l  in  r a p i d  s l o w

T   g

T   m

Material Nylon 6,6 Polycarbonate Polyester Polyethylene High density Low density Polymethylmethacrylate Polypropylene Polystyrene Polytetrafluoroethylene (Teflon) Polyvinyl chloride Rubber

( C) 57 150 73

T g

◦

-90 -110 105 -14 100 -90 87 -73

( C) 265 265 265

T m

◦

137 115 – 176 239 327 212 –

Temperature

FIGURE 10.6 Specific volume of polymers as a function of temperature. Amorphous polymers, such as acrylic and polycarbonate, have a glass-transition temperature, T   g , but do not have a specific melting point, T m. Partly crystalline polymers, such as polyethylene and nylons, contract sharply at their melting points during cooling. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

TABLE 10.2 Glass-Transition Temperatures of Selected Polymers

and

Melting

Deformation of Polymers      n       i      a      r       t        S

     n       i      a      r       t        S

Increasing viscosity t 0

t 1

t 0

Time

Rigid and brittle (melamine, phenolic)

t 1

Time

(a)

(b)      s      s      e      r       t

Tough and ductile (ABS, nylon)

       S

     n       i      a      r       t        S

Recovered strain

t 0

t 1

Time (c)

Soft and flexible (polyethylene, PTFE)

     n       i      a      r       t        S

Recovered strain t 0

0 Strain

t 1

Time (d)

FIGURE 10.7 Various deformation modes for polymers.: (a) elastic; (b) viscous; (c) viscoelastic (Maxwell model); and (d) viscoelastic (Voigt or Kelvin model). In all cases, an instantaneously applied load occurs at time to, resulting in the strain paths shown. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

FIGURE 10.8 General terminology describing the behavior of three types of plastics. PTFE is polytetrafluoroethylene (Teflon, a trade name). Source: After R.L.E. Brown.

Temperature Effects °C 218

225°C

10    )    0    1   x    i   s   p    (   s   s   e   r    t    S

   3

70

0°

Low-density polyethylene

32 High-impact polypropylene

60

8

50 6

25°

40 30 50° 65° 20 80° 10

4 2 0

0

0

5

10

15 20 Strain (%)

25

30

0

FIGURE 10.9 Effect of temperature on the stressstrain curve for cellulose acetate, a thermoplastic. Note the large drop in strength and increase in ductility with a relatively small increase in temperature. Source: After T.S. Carswell and H.K. Nason.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

  a    P    M

   h    t   g   n   e   r    t   s    t   c   a   p   m    I

Polyvinyl chloride

Polymethylmethacrylate 0

32 90 Temperature (°F)

FIGURE 10.10 impact strength small changes significant effect Powell.

Effect of temperature on the of various plastics. Note that in temperature can have a on impact strength. Source: P.C.

Viscosity of Melted Polymers v

Viscous behavior:

t

y

 τ

=

η

  dv dy

=

ηγ ˙

t

FIGURE 10.11 Parameters used to describe viscosity; see Eq. (10.3). 104 !

   )

   2

FIGURE 10.12 Viscosity of some thermoplastics as a function of (a) temperature and (b) shear rate. Source: After D.H. Morton-Jones.

103

  m    /   s    N    (   y    t    i   s   o   c   s 2    i    V10

R    i     g    i    d    P    V     C   

=

1000 s-1

A  c   r    y  l    i    c  

   )

   2

N   y l on   

P ol  y pr    o p yl  e n  e  Lo w d  en    si t y    p ol   y et h    yl e    ne   

10 140 160 180 200 220 240 260 280 300 320 Temperature (°C) (a)

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Poly c ar bona t e

104

  m    /   s    N    (   y    t    i 103   s   o   c   s    i   v    t   n   e   r 2   a10   p   p    A

10

Ac r y   

l ic    (  

LD P E 

2 4 0  °  C   ) 

R    i     g   i    d    P    V   

( 17 0°    C )   

C    (    1   9   

0    °    C     )   

Nylon ( 2 85° C  )

Polypropylene (230°C) 1

10

102 103 Shear rate, ! (s-1) (b)

104

Polymer Behavior in Tension mm 0

25

16

75

100

125

Molecules are being oriented

14

100

50

12    )   a    P    M    (   s   s   e   r    t    S

80    ) 10    0    1

   3

60

40

      x

   i   s   p    (

8 6         d       a       o         L

4 20 2 0

0

0

1

2 3 Elongation (in.)

4

(a)

  i n g  a d   o   l   U n

Elongation

5 (b)

FIGURE 10.13 (a) Load-elongation curve for polycarbonate, a thermoplastic. Source: After R.P. Kambour and R.E. Robertson. (b) High-density polyethylene tension-test specimen, showing uniform elongation (the long, narrow region in the specimen).

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

  i  n g  a d  o   L

FIGURE 10.14 Typical loadelongation curve for elastomers. The area within the clockwise loop, indicating loading and unloading paths, is the hysteresis loss. Hysteresis gives rubbers the capacity to dissipate energy, damp vibration, and absorb shock  loading, as in automobile tires and vibration dampeners for

Applications for Plastics Design Requirement Mechanical strength

Typical Applications

Plastics

Gears, cams, rollers, valves, fan blades, impellers, pistons.

Wear resistance

Gears, wear strips and liners, bearings, bushings, roller-skate wheels.

Acetals, nylon, phenolics, polycarbonates, polyesters, polypropylenes, epoxies, polyimides. Acetals, nylon, phenolics, polyimides, polyurethane, ultrahigh-molecular-weight polyethylene.

Frictional properties High Low Electrical resistance Chemical resistance

Heat resistance Functional and decorative features Functional and transparent features Housings and hollow shapes

Tires, nonskid surfa ces, fo otware, flooring. Sliding surfaces, artificial joints. All types of electrical components and equipment, appliances, electrical fixtures. Containers for chemicals, laboratory equipment, components for chemical industry, food and beverage containers. Appliances, cookware, electrical components. Handles, knobs, camera and battery cases, trim moldings, pipe fittings.

Elastomers, rubbers. Fluorocarbons, polyesters, polyethylene, polyimides. Polymethylmethacrylate, ABS, fluorocarbons, nylon, polycarbonate, polyester, polypropylenes, ureas, phenolics, silicones, rubbers. Acetals, ABS, epoxies, p olymethylmethacrylate, fluorocarbons, nylon, polycarbonate, polyester, polypropylene, ureas, silicones.

Lenses, goggles, safety glazing, signs, food-processing equipment

Fluorocarbons, polyimides, silicones, acetals, polysulfones, phenolics, epoxies. ABS, acrylics, cellulosics, phenolics, polyethylenes, polpropylenes, polystyrenes, polyvinyl chloride. Acrylics, polycarbonates, polystyrenes, polysulfones. laboratory hardware.

Power tools, housings, sport helmets, telephone cases.

ABS, cellulosics, phenolics, polycarbonates, polyethylenes, polypropylene, polystyrenes.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

TA B L E 1 0 . 3 recommendations products.

Gen er al for plastic

Reinforced Polymers Laminate

Foam

Particles (a)

Honeycomb

Short or long fibers, or flakes

Continuous fibers

(b)

(c)

(d)

FIGURE 10.15 Schematic illustration of types of reinforcing plastics. (a) Matrix with particles; (b) matrix with short or long fibers or flakes; (c) continuous fibers; and (d) and (e) laminate or sandwich composite structures using a foam or honeycomb core (see also Fig. 7.48 on making of honeycombs).

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Properties of Reinforcing Fibers 40 Thornel P-100    ) 30    0    1   x   m    (   y    t    i   s 20   n   e    d    /    h    t   g   n   e   r    t    S 10

Spectra 2000

   4

Kevlar 29 Kevlar 129

Kevlar 49 Spectra 900

Celion 3000

High-tensile graphite

S-glass

Boron

E-glass

Thornel P-55

High-modulus graphite

Titanium Steel 0

0

Aluminum 5

10 Stiffness/density (m

15 x

20

Tensile Elastic Density Relative Typ e Strength (MPa) M odulus (GPa) ( kg/m3 ) Cost Boron 3500 380 2600 Highest Carbon High strength 3000 275 1900 Low High modulus 2000 415 1900 Low Glass E type 3500 73 2480 Lowest S type 4600 85 2540 Lowest Kevlar 29 2800 62 1440 High 49 2800 117 1440 High 129 3200 85 1440 High Nextel 312 1630 135 2700 High 610 2770 328 3960 High Spectra 900 2270 64 970 High 1000 2670 90 970 High Note: These properties vary significantly, depending on the material and method of preparation. Strain to failure for these fibers is typically in the range of 1.5% to 5.5%.

106)

FIGURE 10.16 Specific tensile strength (ratio of tensile strength-to-density) and specific tensile modulus (ratio of  modulus of elasticity-to-density) for various fibers used in reinforced plastics. Note the wide range of specific strength and stiffness available.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

TABLE 10.4 Typical properties of reinforcing fibers.

Metal and Ceramic Matrix Composites Material FIBER Glass Graphite Boron Aramids (Kevlar) Other

MATRIX Thermosets Thermoplastics Metals Ceramics

Characteristics High strength, low stiff ness, high density; E (calcium aluminoborosilicate) and S (magnesiaaluminosilicate) types are commonly used; lowest cost. Available typically as high modulus or high strength; less dense than glass; low cost. High strength and stiff ness; has tungsten filament at its center (coaxial); highest density; highest cost. Highest strength-to-weight ratio of all fibers; high cost. Nylon, silicon carbide, silicon nitride, aluminum oxide, boron carbide, boron nitride, tantalum carbide, steel, tungsten, and molybdenum; see Chapters 3, 8, 9, and 10. Epoxy and polyester, with the former most commonly used; others are phenolics, fluorocarbons, polyethersulfone, silicon, and polyimides. Polyetheretherketone; tougher than thermosets, but lower resistance to temperature. Aluminum, aluminumlithium alloy, magnesium, and titanium; fibers used are graphite, aluminum oxide, silicon carbide, and boron. Silicon carbide, silicon nitride, aluminum oxide, and mullite; fibers used are various ceramics.

TABLE 10.4 Types and General Characteristics of Reinforced Plastics and Metal-Matrix and Ceramic-Matrix Composites

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Fiber Spinning Polymer chips Feed hopper

Spinneret

Cold air Melter/extruder Melt spinning

Bobbin

Stretching Twisting and winding

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

FIGURE 10.1 The melt spinning process for producing polymer fibers. The fibers are used in a variety of applications, including fabrics and as reinforcements for composite materials.

Composite Material Microstructure Matrix

Tungsten diameter 0.012 mm

Kevlar fibers

Boron diameter 0.1 mm

Graphite fibers

Matrix (a)

(b)

FIGURE 10.18 (a) Cross-section of a tennis racket, showing graphite and aramid (Kevlar) reinforcing fibers. Source: After J. Dvorak and F. Garrett. (b) Cross-section of boron-fiber-reinforced composite material.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Effect of Fibers 60

6

400

   )    0    1 50   x    i   s 40   p    (    h    t   g 30   n   e   r    t   s 20   e    l    i   s 10   n   e    T

   3

300

Carbon fibers

 f i  s s

 g l a   n g

 s

 r   b e

200

  a    P    M

  L  o

 e r s  s s f  ib   a  l  g  t  S h o r

0

0

10 20 30 Reinforcement (%)

100

   )  .   n    i    /    b    l      t    f    (   y   g   r   e   n   e    t   c   a   p   m    I

0 40

2

 s  e  r   f  i  b  s   l a s  g g   n   L o  s  f  ib e r  l a s s  g   t  r  S h o

1

Carbon fibers

5 4 3

0 0

(a)

   )    0    1   x    i   s   p    (   s   u    l   u    d   o   m    l   a   r   u   x   e    l    F

   6

40

   )    0    1

2 1 0 0

  m    /    J

100

0 40

 h o r t  a n d s  L o n g  f  ib e r s  g l a s s 10 20 30 Reinforcement (%)

10 0 40

(c)

400

 r s

50

  b e

 f i   n  r s   b o  i  e  r  f  b  a  s  s   C  g l a  s  n g   ib e r  L o  s s f

      x

   i   s   p    (

30  r s   b e   i   f  n 20   b o  r  C a

60

   3

5

3

200

(b)

6

4

10 20 30 Reinforcement (%)

300

  a    P    G

   h    t   g   n   e   r    t   s    l   a   r   u   x   e    l    F

40

 l a  r t g  S h o

30

300   a

200    P    M

20 100

10 0 0

10 20 30 Reinforcement (%)

0 40

(d)

FIGURE 10.19 Effect of the percentage of reinforcing fibers and fiber length on the mechanical properties of  reinforced nylon. Note the significant improvement with increasing percentage of fiber reinforcement. Source: Courtesy of Wilson Fiberfill International. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Strength and Fracture of Composites 2.0    )    5    0    1   x 1.5    i   s   p    (    h    t   g 1.0   n   e   r    t   s   e    l    i 0.5   s   n   e    T

0

(a)

Unidirectional 1000 Orthogonal

  a    P    M

Random 500

20 40 60 80 Glass content (% by weight)

0

(b)

FIGURE 10.20 (a) Fracture surface of glass-fiberreinforced epoxy composite. The fibers are 10 µm (400 µin.) in diameter and have random orientation. (b) Fracture surface of a graphite-fiber-reinforced epoxy composite. The fibers are 9-11 µm in diameter. Note that the fibers are in bundles and are all aligned in the same direction. Source: Courtesy of L.J. Broutman.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

FIGURE 10.21 Tensile strength of glass-reinforced polyester as a function of fiber content and fiber direction in the matrix. Source: After R.M. Ogorkiewicz.

Plastics Processes Process Extrusion Injection molding Structural foam molding Blow molding Rotational molding Thermoforming Compression molding Transfer molding Casting Processing of  reinforced plastics

Characteristics Long, uniform, solid or hollow, simple or complex cross-sections; wide range of dimensional tolerances; high production rates; low tooling cost. Complex shapes of various sizes and with fine detail; good dimensional accuracy; high production rates; high tooling cost. Large parts with high sti ff ness-to-weight ratio; low production rates; less expensive tooling than in injection molding. Hollow thin-walled parts of various sizes; high production rates and low cost for making beverage and food containers. Large hollow shapes of relatively simple design; low production rates; low tooling cost. Shallow or deep cavities; medium production rates; low tooling costs. Parts similar to impression-die forging; medium production rates; relatively inexpensive tooling. More complex parts than in compression molding, and higher production rates; some scrap loss; medium tooling cost. Simple or intricate shapes, made with flexible molds; low production rates. Long cycle times; dimensional tolerances and tooling costs depend on the specific process.

TABLE 10.6 Characteristics of processing plastics and reinforced plastics.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Extrusion Barrel liner

Barrel heater/cooler

Hopper

Wire filter screen

Melt thermocouple

Thermocouples

Throat Breaker plate

Barrel Thrust bearing Throat-cooling channel Gear reducer box

Adapter Die Feed section

Melt section

Melt-pumping section

Motor

FIGURE 10.22 Schematic illustration of a typical extruder.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Screw

Pitch Barrel H

Flight

Extrusion Mechanics

!

W 

D

Drag flow:

w

2

Qd 

Barrel

FIGURE 10.23 Geometry of the pumping section of an extruder screw.

   5   -

   0    1   x 2    )       q   s    /  ,   3   e    t   m   a   r   ( 1   w   o    l    F

0

=

2

Pressure flow: Q p =

3

2

π  HD  N sin θ cos θ

W H 3 p 12η (l / sin θ)

=

pπ DH 3 sin2 θ 12ηl

Extruder characteristic

Die characteristic

Operating point

Qdie

=

Kp

Die characteristic 0

5 10 Pressure (MPa)

15

FIGURE 10.1 Extruder and die characteristics for Example 10.5. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

K for circular cross-sections: 4

K 

π Dd  =

128ηld 

Blown-Film Manufacture Pinch rolls

Wind-up

Guide rolls

Blown tube

Mandrel

Extruder

Die

Air (a) (a)

(b)

FIGURE 10.25 (a) Schematic illustration of production of thin film and plastic bags from a tube produced by an extruder, and then blown by air. (b) A blown-film operation. Source: Courtesy of Windmoeller & Hoelscher Corp.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Tube Extrusion Spider die Breaker plate Polymer melt

Extruder barrel

A

Section A–A B

Screen pack

Section B–B Spider legs (3)

Melt flow direction

v

B Spider legs (3) Mandrel

A

Air channel Air in (a)

Co-extrusion blow molding Extruder 1

Plastic melt: two or more layers

Parison

Mandrel Extruder 2 (b)

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

FIGURE 10.26 Extrusion of plastic tubes. (a) Extrusion using a spider die (see also Fig.6.59) and pressurized air; (b) coextrusion of tube for producing a bottle.

Injection Molding Powder, Pellets

Hopper Heating zones Nozzle Mold Vent

Piston (ram) Cooling zone

Cylinder (barrel) Injection chamber

Torpedo (spreader) Sprue Molded part

Press Ejector pins (clamp) force

Vent

(a)

Rotating and reciprocating screw (b)

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

FIGURE 10.27 Injection molding with (a) a plunger and (b) a reciprocating rotating screw. Telephone receivers, plumbing fittings, tool handles, and housings are examples of parts made by injection molding.

Mold Features Gate

Cavity

Sprue Main runner Part Gate

Branch runner

Cold slug well

Cavity

Main Sprue Guide runner pin

Branch runner

(a)

Guide pin (b)

FIGURE 10.28 Illustration of mold features for injection molding. (a) Two-plate mold, with important features identified; (b) injection molding of four parts, showing details and the volume of material involved. Source: Courtesy of Tooling Molds West, Inc.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Mold Types Plate

Gate

Plate

Stripper plate

Plate

Plate

Part Sprue bushing

Sprue

Ejector pins

Sprue bushing

Ejector pins

Part Parts Runner (a)

(b)

Hot plate; Runner stays molten

Plate

Plate Sprue bushing

Ejector pins

Parts (c)

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

FIGURE 10.29 Types of molds used in injection molding. (a) Two-plate mold, (b) three-plate mold, and (c) hot-runner mold.

Insert Molding

(a)

(b)

FIGURE 10.30 Products made by insert injection molding. Metallic components are embedded in these parts during molding. Source: (a) Courtesy of Plainfield Molding, Inc., and (b) Courtesy of Rayco Mold and Mfg. LLC.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Reaction-Injection Molding Heat exchanger Stirrer Heat exchanger

Displacement cylinders Monomer 2 Pump Recirculation loop

Stirrer

Mixing head

Monomer 1 Pump Mold Recirculation loop

FIGURE 10.31 Schematic illustration of the reaction-injection-molding process.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Heating passages

Extruder Extruded parison

Tail

Knife Bottle mold

Blown bottle

Mold closed and bottle blown

Blow pin

Blow Molding

(a)

Blow pin removed Blow pin Injection-molding machine

Parison Blown bottle

Cooling passages Parison transferred to blow mold

Parison mold

(b)

2 Blown-mold station Core-pin opening (Blown air passage)

Blow-mold bottom plug

Blow mold

Blown bottle

Parison 1 Preform mold station

Blow-mold neck ring

Indexing direction

Transfer head Reciprocating-screw extruder 3 Stripper station Stripper plate Bottle

Preform Preform neck ring mold (c)

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

FIGURE 10.32 Schematic illustrations of (a) the blowmolding process for making plastic beverage bottles and (b) a three-station injection-blow-molding machine.

Rotational Molding Inlet Outlet vent Primary axis

Pressurizing fluid

Mold Spindle

Secondary axis

FIGURE 10.33 The rotational molding (rotomolding or rotocasting) process. Trash cans, buckets, carousel horses and plastic footballs can be made by this process.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Thermoforming Heater Vacuum line

Clamp

Ram

Plastic sheet

Mold

Plastic sheet

Mold Vacuum line (a) Straight vacuum forming

Clamp

(b) Drape vacuum forming

(c) Force above sheet

(d) Plug and ring forming

FIGURE 10.35 Various thermoforming processes for thermoplastic sheet. These processes are commonly used in making advertising signs, cookie and candy trays, panels for shower stalls, and packaging.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Ring

Compression Molding Heating elements

Punch

Open

Charge Mold Knockout (ejector pin) Land

Overlap Closed

Flash Molded part (a)

(b)

(c)

Part

Plug

(d)

FIGURE 10.35 Types of compression molding, a process similar to forging: (a) positive, (b) semipositive, and (c) flash. The flash in part (c) is trimmed off. (d) Die design for making a compression-molded part with undercuts. Such designs also are used in other molding and shaping operations. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Transfer Molding Sprue Transfer plunger Transfer pot and molding powder

Punch Molded parts

Knockout (ejector) pin

1. Insert polymer in mold

2. Mold closed and cavities filled

3. Mold open and molded parts ejected

FIGURE 10.36 Sequence of operations in transfer molding of thermosetting plastics. This process is particularly suitable for making intricate parts with varying wall thicknesses.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Casting, Potting, Encapsulation & Calendering Mold

Liquid plastic

Mold

Electrical coil

Mold

1.

Coil

Housing or case 2.

3.

FIGURE 10.37 Schematic illustration of (a) casting, (b) potting, and (c) encapsulation of plastics.

Rubber feed Calender rolls Finished film

FIGURE 10.38 Schematic illustration of calendering. Sheets produced by this process are subsequently used in processes such as thermoforming.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Takeoff or stripper roll

Reinforced Plastic Components

FIGURE 10.39 Reinforced-plastic components for a Honda motorcycle. The parts shown are front and rear forks, a rear swing arm, a wheel, and brake disks.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Manufacture of Prepregs Continuous strands

FIGURE 10.40 (a) Manufacturing process for polymer-matrix composite. Source: After T.-W. Chou, R.L. McCullough, and R.B. Pipes. (b) Boronepoxy prepreg tape. Source: Textron Systems.

Surface treatment

Resin

Spools

(a)

Backing paper

(b)

Chopper

FIGURE 10.41 Manufacturing process for producing reinforced-plastic sheets. The sheet is still viscous at this stage and can later be shaped into various products. Source: After T.-W. Chou, R. L. McCullough, and R. B. Pipes.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Resin paste

Carrier film Compaction belt

Continuous strands

Resin paste

Carrier film

Vacuum and Pressure Molding Clamping bar

Vacuum trap

Atmospheric pressure

Flexible bag

Air pressure 345 kPa (50 psi)

Clamp Gasket Vacuum trap

Flexible bag

Steam or hot water

Mold Mold Gel release coat

Resin and glass

Metal or plastic mold

Mold release

Gel Resin and coat glass

Room-temperature or oven cure Hand or spray lay-up

Hand or spray lay-up

(a)

(b)

FIGURE 10.42 (a) Vacuum-bag forming. (b) Pressure-bag forming. Source: After T. H. Meister.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Open Mold Processing Roving Roller

Resin

Brush

Lay-up of resin and reinforcement

Chopped glass roving Spray

Mold Mold (a)

(b)

Mold

Gantry crane

Boat hull Mold

(c) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

FIGURE 10.43 Manual methods of processing reinforced plastics: (a) hand lay-up and (b) spray-up. These methods are also called open-mold processing . (c) A boat hull made by these processes. Source: Courtesy of Genmar Holdings, Inc.

Filament Winding Continuous roving

Traversing resin bath

Rotating mandrel (a)

(b)

FIGURE 10.44 (a) Schematic illustration of the filament-winding process. (b) Fiberglass being wound over aluminum liners for slide-raft inflation vessels for the Boeing 767 aircraft. Source: Advanced Technical Products Group, Inc., Lincoln Composites.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Pultrusion

Preforming die

Saw

Heated die Pultrusion cut to length Prepreg feed system Infiltration tank Puller

Cured pultrusion (a)

(b)

FIGURE 10.45 (a) Schematic illustration of the pultrusion process. (b) Examples of parts made by pultrusion. Source: Courtesy of Strongwell Corporation.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Processing of RP Parts

(a)

(b)

Side view Model

Model

Support

FIGURE 10.46 The computational steps involved in producing a stereolithography file. (a) Three-dimensional description of the part. (b) The part is divided into slices. (Only 1 in 10 is shown.) (c) Support material is planned. (d) A set of tool directions is determined for manufacturing each slice. Shown is the extruder path at section A-A from (c), for a fused-deposition modeling operation.

A Support A

(c)

(d)

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Rapid Prototyping Processes Supply Phase Liquid

Process Stereolithography

Polyjet

Powder

Selective laser sintering

Fused-deposition modeling Three-dimensional printing

Layer of powder

Layer Creation Technique Liquid-layer curing

Phase-Change Type Photopolymerization

Liquid-layer curing Extrusion of  melted plastic Binder-droplet deposition onto powder layer Laser-driven

Photopolymerization Solidification by cooling No phase change

Sintering or melting

Materials Photopolymers (acrylates, epoxies, colorable resins, and filled resins) Photopolymers Thermoplastics (ABS, polycarbonate, and polysulfone) Polymer, ceramic and metal powder with binder

Polymers, metals with binder, metals, ceramics, and sand with binder

TABLE 10.7 Characteristics of rapid-prototyping processes.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Process Stereolithography

Material Somos 7120a

Tensile Strength (MPa) 63

Elastic Modulus (GPa) 2.59

Elongation in 50 mm (%) 2.3-4.1

Somos 9120a

32

1.14-1.55

15-25

47.1-53.6

2.65-2.88

3.3-3.5

Prototool 20Lb

72-79

10.1-11.2

1.2-1.3

FC 700

42.3

2.0

15-25

FC800

49.9-55.1

2.5-2.7

15-25

FC900

2.0-4.6

–

47

Polycarbonate

52

2.0

3

ABS

22

1.63

6

34.8

1.83

4.3

Duraform PA

44

1.6

9

Duraform GF

38.1

5.9

2

SOMOS 201

17.3

14

130

ST-100c

305

137

10

WaterShed 11120

Polyjet

Fuseddeposition modeling

PC-ABS Selective laser sintering

Notes Transparent amber; good general purpose material for rapid prototyping. Transparent amber; good chemical resistance; good fatigue properties; used for producing patterns in rubber molding. Optically clear with a slight green tinge; similar mechanical properties as ABS; used for rapid tooling. Opaque beige; higher strength polymer suitable for automotive components, housings, and injection molds. Transparent amber; good impact strength, good paint absorption and machinability. White, blue or black; good humidity resistance; suitable for general purpose applications. Gray or black; very flexible material, simulates the feel of rubber or silicone. White; high-strength polymer suitable for rapid prototyping and general use. Available in multiple colors, most commonly white; a strong and durable material suitable for general use. Black; good combination of mechanical properties and heat resistance. White; produces durable heat- and chemical-resistant parts; suitable for snap-fit assemblies and sandcasting or silicone tooling. White; glass-filled form of Duraform PA, has increased stiff n ess and is suitable for higher temperature applications. Multiple colors available; mimics rubber mechanical properties Bronze-infiltrated steel powder.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

RP Materials

TABLE 10.8 Mechanical properties of  selected materials for rapid prototyping.

Stereolithography and FDM UV light source

UV curable liquid c  b  a

FIGURE 10.47 Schematic illustration of the stereolithography process. Source: Courtesy of 3D Systems.

Liquid surface Formed part Vat

Thermoplastic or wax filament

Platform  z   y 

 x 

FIGURE 10.48 (a) Schematic illustration of  the fused-deposition modeling process. (b) The FDM Vantage X rapid prototyping machine. Source: Courtesy of Stratasys, Inc.

Plastic model created in minutes

Heated FDM head moves in  x  – y  plane

Table moves in  z -direction

Fixtureless foundation

Filament supply (a)

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

(b)

Support Structures

 a

Gussets (a)

Island

Ceiling within an arch

Ceiling

(b)

FIGURE 10.49 (a) A part with a protruding section that requires support material. (b) Common support structures used in rapid-prototyping machines. Source: After P.F. Jacobs.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Selective Laser Sintering Galvanometers

Laser

Optics Environmentalcontrol unit

Process chamber Roller mechanism

Powderfeed cylinder

Process-control computer

Motor

Part-build cylinder

Motor

FIGURE 10.50 Schematic illustration of the selective-laser-sintering process. Source: After C. Deckard and P.F. McClure.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Three-Dimensional Printing Powder

1. Spread powder

Binder

2. Print layer

3. Piston movement

FIGURE 10.51 Schematic illustration of the threedimensional-printing process. Source : After E. Sachs and M. Cima.

4. Intermediate stage

5. Last layer printed

6. Finished part

FIGURE 10.52 (a) Examples of parts produced through three-dimensional printing. Full color parts also are possible, and the colors can be blended throughout the volume. Source: Courtesy ZCorp, Inc. (a)

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

(b)

3D Printing of Metal Parts Infiltrating metal, permeates into P/M part

Binder deposition

Microstructure detail

Unfused powder Binder Metal powder

Particles are loosely sintered Binder is burned off

Infiltrated by lower-melting-point metal

(b)

(c)

(a)

FIGURE 10.53 The three-dimensional printing process: (a) part build; (b) sintering, and (c) infiltration steps to produce metal parts. Source: Courtesy of the ProMetal Division of Ex One Corporation.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Rapid Manufacturing: Investment Casting

1. Pattern creation

2. Tree assembly

3. Insert into flask

4. Fill with investment

7. Cool

8. Finish

Crucible Molten metal

Heat

5. Wax meltout/burnout

6. Fill mold with metal

FIGURE 10.54 Manufacturing steps for investment casting that uses rapid-prototyped wax parts as patterns. This approach uses a flask for the investment, but a shell method can also be used. Source: 3D Systems, Inc. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Sprayed Metal Tooling Process Aluminum-filled epoxy

Metal spray

Flask

Alignment tabs Pattern

Coating

Base plate (a)

(b)

(c)

Finished mold half

Molded part Pattern

Base plate (d)

Second mold half (e)

FIGURE 10.55 Production of tooling for injection molding by the sprayed-metal tooling process. (a) A pattern and base plate are prepared through a rapid-prototyping operation; (b) a zinc-aluminum alloy is sprayed onto the pattern (See Section 4.5.1); (c) the coated base plate and pattern assembly is placed in a flask and back-filled with aluminum-impregnated epoxy; (d) after curing, the base plate is removed from the finished mold; and (e) a second mold half suitable for injection molding is prepared. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Example: RP Injection Manifold

FIGURE 10.56 Rapid prototyped model of an injection-manifold design, produced through stereolithography. Source: 3D Systems.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Design of Polymer Parts Original design

Modified design

Distortion

(a) Thick

Die shape

Pull-in (sink mark)

Thin Extruded product (b)

(c)

(d)

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

FIGURE 10.57 Examples of design modifications to eliminate or minimize distortion of plastic parts. (a) Suggested design changes to minimize distortion. Source: After F. Strasser. (b) Die design (exaggerated) for extrusion of square sections. Without this design modification, product cross-sections would not have the desired shape because of the recovery of the material, known as die swell. (c) Design change in a rib to minimize pull-in caused by shrinkage during cooling. (d) Stiffening of the bottom of thin plastic containers by doming, similar to the process used to make the bottoms of aluminum beverage cans and similar containers.

Costs and Production Volumes Equipment Capital Cost Med High High High Med Low Med Low Low High High

Production Rate Med Med Med High High Low Med Low Very low Low Med

Tooling Cost Low High High High Low Low Med Low Low Med Med

Typical Production Volume, Number of Parts 2 10 103 104 105 106 107

Process 10 Machining Compression molding Transfer molding Injection molding Extrusion * Rotational molding Blow molding Thermoforming Casting Forging Foam molding *Continuous process. c 1980 by John Wiley Source: After R. L. E. Brown, Design and Manufacture of Plastic Parts. Copyright  & Sons, Inc. Reprinted by permission of John Wiley & Sons, Inc.

TABLE 10.9 Comparative costs and production volumes for processing of plastics.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education