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AM2217.1 A M2217.1 Issue: D
Manual
General Practices of Metallic Parts: Recommended Detailed Design Practices for Compliance to Machining Constraints SUMMA RY:
PURPOSE:
This Manual describes the recommended design practices for metallic mechanical parts. This Manual provides: − typical dimensions of the tools (milling cutter) that are used in machining parts, − standard offset values in all case of machining, − recommended or to be avoided machining methods that impact the design of parts, − specific manufacturing solutions that are (or not) to be designed.
S C O P E :
Design and manufacture of metallic machined parts, for all aircraft programs. This Manual has to be applied for all new design.
Owner's Approval:
Authorization:
Name: MORVAN Stéphane Function: BOS - EDSBI
Name:
SCHWEIM Matthias
Function: Head of EDSBS
© AIRBUS S.A.S. 2009. S.A.S. 2009. ALL RIGHTS RESERVED. RESERVED.CONFIDENTIAL CONFIDENTIAL AND PROPRIETARY DOCUMENT. DOCUMENT.
Manual_FM0400730_v2.0
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General Practices of Metallic Parts: Recommended Detailed Design Practices for Compliance to Machining Constraints
AM2217.1 A M2217.1 Issue: D
TABLE OF CONTENTS 1
About this Document ........................................................... .............................. ........................................................... ................................................ .................. 5 1.1 Background ........................................................... ............................. ........................................................... .............................................................. ................................. 5 1.2 Detailed Scope ........................................................ ........................... ........................................................... ............................................................ .............................. 5 1.3 Organization of the Document.............................................................................................5
2
General Description of the Manual......................................................................................6
3
Explanations About Machining Skills...................................................................................7 3.1 Milling or Lathing Machine Axis Axis System (Extract from ISO 841:2001) ................................ ............................. ... 7 3.2 Different Machined Parts...................................................................................................10
4
Recommended Practices ......................................................... ........................... ........................................................... ......................................... ............ 12 4.1 Background ........................................................... ............................. ........................................................... ............................................................ ............................... 12 4.2 Generalities .......................................................... ............................ ........................................................... ............................................................. ................................ 12 4.2.1 Definitions........... Definitions......................................... ........................................................... ........................................................... .................................................... ...................... 12
4.2.2 Standard Dimensions of Milling Cutter ........................................................ .......................... .................................................... ...................... 13 4.2.3 Standard Values of Wall Corner........................................................................................13 4.3 Stiffener Design............................ Design ......................................................... ........................................................... ........................................................ .......................... 14 4.3.1 Top of Stiffener ......................................................... ............................ ........................................................... ......................................................... ........................... 14 4.3.2 Stiffener Ending........................... Ending ......................................................... ........................................................... ........................................................ ........................... 15 4.3.3 Stiffener Pocket Junction...................................................................................................16 4.3.4 Stiffener Crossing......................... Crossing ....................................................... ........................................................... ....................................................... .......................... 17 4.3.5 Other Rules ........................................................ .......................... ........................................................... ........................................................... .................................. .... 18 4.4 Pocket Machining Design Practices ...................................................... ......................... ......................................................... ............................ 18 4.4.1 Standard Offset ........................................................ .......................... ........................................................... ......................................................... ............................ 18 4.4.2 2 Axis Deep Pockets Design ........................................................... .............................. ........................................................... .................................. .... 19 4.4.3 4 and 5 Axis Machining ........................................................ .......................... ........................................................... ............................................. ................ 21 4.4.4 Special Tools.......................... Tools ....................................................... ........................................................... .............................................................. ................................ 23 4.4.5 Sub-Pockets Design............................ Design ......................................................... ........................................................... ................................................. ................... 23 4.5 Surface Design............................. Design ........................................................... ........................................................... ....................................................... .......................... 26 4.5.1 External Surfaces ....................................................... ......................... ........................................................... ....................................................... .......................... 26 4.5.2 Internal Surfaces ........................................................ .......................... ........................................................... ....................................................... .......................... 29 4.6 Practices.................. Practices................................................ ........................................................... ........................................................... ............................................... ................. 31 4.6.1 Example for External Routing................................ Routing. ............................................................. ............................................................ .............................. 31 4.6.2 Joggles and Chamfers Design .......................................................... ............................ ........................................................... ................................ ... 31 4.6.3 Stringer Hole Design (Mouse hole) ....................................................... .......................... ......................................................... ............................ 32 © AIRBUS S.A.S. 2009. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT.
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4.6.4 Stiffener Flange Thickness................................................................................................33 4.6.5 High Thin Web Design .......................................................... ............................. ........................................................... ............................................ .............. 34 4.6.6 Thickness of Suspended Web...........................................................................................34 4.7 Axis System Definition............................................... Definition................. ............................................................ ........................................................ .......................... 35 5
Reference Documents.......................................................................................................36
6
Glossary ......................................................... ............................ ........................................................... ........................................................... ..................................... ........ 36
Contributors......................... Contributors ....................................................... ............................................................ ........................................................... ................................................ ................... 37 Record of Revisions .......................................................... ............................. ........................................................... .............................................................. ................................ 38
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LIST OF FIGURES Figure 1 - Example Example of machine motion.......... motion........................................ ........................................................... ...................................................... ......................... 7 Figure 2 - Parallel lathe (engine lathe) ..................................................... ......................... ........................................................ ......................................... ............. 7 Figure 3 ........................................................ ........................... ........................................................... ........................................................... ....................................................... .......................... 8 Figure 4 ........................................................ ........................... ........................................................... ........................................................... ....................................................... .......................... 8 Figure 5 - Profile and contour milling machine machine with tilting head ..................................................... ........................ ................................ ... 9 Figure 6 - Ruled Surface ....................................................... .......................... ........................................................... .......................................................... ............................ 27
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AM2217.1 A M2217.1 Issue: D
1
About this Document The document is dedicated to engineering people who have to design metallic mechanical parts. The purpose is to guide the designer in his choices and to give the methods and rules to ensure the manufacturing easy feasibility. All aircraft programs are concerned by this document. For each program, refer also to the Reference Structure Design Principles document, which gives general design recommendations and rules to be satisfied for optimum definition of structural parts.
1.1 Background The design process for metallic (AP2247) must be applied. The implementation domain is the same than the aircraft programs cited above. For the CATIA V5 method, see the AM5018.
1.2 Detailed Scope The information inside this Airbus Method is linking the design principles and detailed CAD model of the Geometrical Reference Mock-up in the frame of the design manufacturing. These rules are to be considered as advises or recommendations from manufacturing to designers in order to design part which are the easiest to manufacture. These recommendations deal with general cases only. In case of special need of design or manufacturing, the solutions have to be discussed in integrated program teams between design, stress and manufacturing in order to make a common decision that satisfies all conditions.
1.3 Organization of the Document This document is composed of: − − − −
Index AM2217.1: General Practices AM2217.2: Panels AM2217.3: Profiles
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General Description of the Manual The Manual aims at presenting all the practices and standard values used to design mechanical parts in Airbus. They are organized in two main chapters in this method: −
−
Firstly some explanations about machining skills that are used by manufacturing and that designer needs to know. The second chapter deals with general practices that are used to design a simple shaped part. The practices for complex parts are to be discussed between manufacturing and design office.
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Explanations About Machining Skills This chapter aims at presenting the machining skills used in Airbus and that the designer has to know in order to design part that can be machined the more easily and the less costly as possible.
3.1 Milling or Lathing Machine Axis Sy System stem (Extract from ISO 841:2001) Note: We use the "normative right-hand coordinate coordinate system".
Figure 1 - Example of machine motion a) Parallel Lathe: this 2 axis machine can manufacture cylindrical parts (axis X and Z).
Figure 2 - Parallel lathe (engine lathe) There are other machines with 2 axis: flame cutting machine, turning and boring lathe, horizontal or vertical filament winding machines, drafting machine.
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b) Milling Machines: To machine a cubic part, the cutting tools have to move in different directions relative to the work piece. There could be 5 degrees of freedom: 3 translations (axis X, Y and Z) and 2 rotations (ex. axis A and B).
3 axes gantry-type milling machine
Figure 3
5 axis milling machine with vertical spindle
Figure 4
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The half axis refers to a fixed axis during machining. −
−
−
−
2.5 axis: The cutter can only move during the machining on a plane perpendicular to its rotation axis. 3 axis: The cutter can move following the three simultaneous directions during the machining. Tool axis orientation is fixed. 5 axis: The cutter is able to move following the three directions and to rotate around two axes during a pass. N axis: Special machines can have more than 5 axis (principal and secondary): portal-type milling machines, gantry-type milling machines, profile and contour milling machines with movable or tilting table, robot.
Figure 5 - Profile and contour milling machine with tilting head For further information, see RSDP (Reference Structure Design Principles), Volume 3 Metallic Design Principles, Chapter 2.
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3.2 Different Machined Parts 2,5 Axis part:
3 Axis part:
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5 Axis part:
Note: 5 Axis part can be machined on a 3 Axis NC machine with special tool path. Definitions Axis: principal direction in which a part of a machine can move in a linear or rotary mode NC machines: Numerical Control Machines DNC: Direct Numerical Control HSM: High Speed Machining If needed see ISO 2806. 2806.
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Recommended Practices
4.1 Background This chapter contains the recommended practices for the design of simple mechanical parts. Firstly the standards values that are to be used are detailed, then some recommendations for each type of need of design are related: stiffener, surface, pocket and others. Reminder: The drawing of machined parts has to be done by respecting the dedicated Reminder: standard drawing.
4.2 Generalities 4.2.1 Definitions
Faced Milling Cutter diameter
CH: Cutting height End Milling Cutter fillet radius
A milling cutter is characterized by its maximum cutting height recommended by manufacturing to limit costs. It determines the maximum depth of a pocket that can be machined. This value depends on the cutter diameter: Maximum cutting height: CH = A x Diameter 2 < A < 4 (The choice of the value is to discuss with the Manufacturing) Manufacturing) 4.4.2 A A pocket less or equal than A pocket deeper than C H is called "deep pocket" see § 4.4.2 CH is called "standard pocket". © AIRBUS S.A.S. 2009. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT.
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4.2.2 Standard Dimensions of Milling Cutter The actual with cutter usage will be dependant on the material properties being cut and should be discussed manufacturing. M i lli ng c u t t e r 8 di a m eter
10
12
16
20
25
32
40
50
Cutter f fii lle t r ad i i 2 2 .5 4
X X
5 6 8
X X X X
X X X X
X X
X X X
X X X X X X
X X X X X X
X X X X X X
X X X X X X
X X X X X X
All DIAMETERS and RADII values are in millimeter (mm). RADII. Typical milling cutter size is 16 DIA 4 RADII. Note: −
− −
Stress requirements (fatigue, materials, hard materials) may dictate the minimum cutter fillet radius (5, 6 or 8). This radius value will be decreased if design requirements requirements demand for it (2 or 2.5). For optimized machining, the choice of cutting tool is to be agreed with Manufacturing.
4.2.3 Standard Values of Wall Corner It is necessary to have between wall corners a radius a bit higher than the milling cutter radius to avoid an engagement of the tool in the part corner. The risk in case of engagement is to stamp the part and produce a non-quality part. Schema: R
Milling cutter radius
R = (Milling cutter radius) + 1 mm mm
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4.3 Stiffener Design 4.3.1 Top of Stiffener
Design offset value: Typical value X = 0,3 mm (mini) Note: For optimized machining, the choice of cutting tool is to be agreed with Manufacturing. Manufacturing. Top of stiffener should be flat designed to avoid generation of complex surfaces in case of double curvature. CAD MODEL:
Note: It should be modelized with respect to cutter diameters referenced in section § 4.2.2. 4.2.2. Ø
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4.3.2 Stiffener Ending 4.3.2.1 Outside a Pocket An distance between the end of the stiffener and the corner is required: X = 0.5 mm is a minimum Recommended
X
To avoid
4.3.2.2 Inside a Pocket See RSDP (Reference Structure Design Principles), Volume 3 Metallic Design Principles, Chapter 2.
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4.3.3 Stiffener Pocket Junction The machining of a stiffener pocket junction with needs twofrom passes: first the pocket base is machined and secondly the stiffener is finished a pass the bottom to top. Schema of the second pass:
X
X
Detail: cutter path during stiffener machining
Typical value X = 0.3 mm (mini) Note: For optimized machining, the choice of cutting tool is to be agreed with Manufacturing. Manufacturing. CAD MODEL (Traditional MODEL (Traditional milling):
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4.3.4 Stiffener Crossing General case: The stiffener crossing is flat designed because the cross is machined in one tool path only. CA D Model desig n
Specific case with one ramped stiffener: The stiffener crossing is flat designed. CA D Model desig n
Ramped stiffener
Cutted Radius
Cross flat designed
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4.3.5 Other Rules The flange top edge can be designed with two methods: C hea pes t s o luti luti o n
Mo re ex pens i v e s o luti luti o n B etter fo r da da m a agg e to llera era nc e rea s o ns M an da t or y fo r e x t r ud e d p r of i le s
Flange top profile α >
≤ 10°
10°
Flange
Web Parallel profiles
4.4 Pocket Machining Design Practices 4.4.1 Standard Offset For traditional machining means, an offset is used in case of rework machining on already machined surfaces. In the CAD Model, the value of the offset is X = 0.3 mm (mini). Note: For optimized machining, the choice of cutting tool is to be agreed with Manufacturing. Cad model design example:
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4.4.2 2 Axis Deep Pocke Pockets ts Design In case thethe depth of the pocket with at a large milling cutter that can be this larger than corner radius: the constrains corner hasto tomachine be reworked the requested dimension in a second phase with a smaller milling cutter. First rule: Schema of the milling tool paths: Typical value X = 0.3 mm (mini)
Side view
X
Note: For optimized machining, the choice of cutting tool is to be agreed with Manufacturing.
X
First machining tool path Second machining tool path
X
Two tool paths are required: Tool path 1: Machining of the base face and lateral face with a big diameter of tool to decrease the milling time. Tool path 2: Rework and finish of radii radii with finish radius milling cutter − −
with X mm as over thickness on bottom and flank, with flank radius milling cutter.
This first solution allows reducing the distance between the corner and the first fastener and is always applied except in case of some contraindications as: − − −
Stress requirement, Flank highness or thickness, The rework geometry is in a fastener zone, … CAD Model Design Tool path 1
Tool path 2 2
Note: Each rework machining requires an offset X. © AIRBUS S.A.S. 2009. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT.
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Second rule: Two tool paths are also required: − −
Tool path 1: Machining of the base with blank radius milling cutter Tool path 2: Rework and finish the lateral face with finish radius milling cutter
Schema of the milling tool paths: Typical value X = 0.3 mm (mini)
Side view
Note: For optimized machining, machining, the choice of cutting tool is to be agreed with Manufacturing.
X
X
First machining tool path Top view Second machining tool path
X
CAD Model Design
Tool path 1
Tool path 2 2
Note: Each rework machining requires an offset X.
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4.4.3 4 and 5 Axis Machining 4.4.3.1 Inclined St Stiffener, iffener, Open Angle Like in three axis, the machining of the base and lateral face are done in two separate operations: first the base and then the lateral face. Schema of the milling tool passes:
Machining pass 1
Machining pass 2
X mm X mm
(mini) Typical value X = 0.3 mm (mini) Note: For optimized machining, the choice of cutting tool is to be agreed with Manufacturing. Manufacturing. CA D Model desig n
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4.4.3.2 Inclined Stif Stiffener, fener, Clos Closed ed Angle The machining is done in two operations: a tool offset between the two passes is used. Between the cutting tool path and the top of the higher flange of the main pocket, it must be designed an offset of X mm to ensure there is no clash with the pocket upper edge. + 1 mm
Y mm
Typical values:
X = 0.3 mm (mini) Y = 0.3 mm (mini) (mini)
Note: For optimized machining, the choice of cutting tool is to be agreed with Manufacturing. Manufacturing. designed in This offset is designed in the 3D model. CA D Model desig n
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4.4.3.3 Perpendicular Angle See RSDP Chapter 2. (Reference Structure Design Principles), Volume 3 Metallic Design Principles,
4.4.4 Special Tools Some solutions require special cutters. For further information, see RSDP (Reference Structure Design Principles), Machined Component chapter, Cost awareness (Cutter shape) subchapter.
4.4.5 Sub-Pockets Design This is a pocket machined inside a larger pocket for stress and weight constraints. All pockets skill rules apply to a sub-pocket.
4.4.5.1 Cliff Edge
If the fillet radius r is is greater than the pocket depth, the designer has to take into account this difference and to add a correction to respect the real edge:
ToolOffset = r − r 2 − ( r + Pot − Pat )2
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4.4.5.2 Step Machining The solution on the and rightfor is stress to be reasons. avoided for manufacturing constraints, weight decreasing, fastener positioning, C A D Mo del: del:
As in the manufactured part, the 0.3 mm offset (mini) is (mini) is designed Do uble uble F l ang ang e R educ ti o n Preferred
Non P referred
A X
X
Note: For optimized machining, the choice of cutting tool is to be agreed with Manufacturing. For A minimal value, please see RSDP (Reference Structure Design Principles), Volume 3 Metallic Design Principles, Chapter 2. (mini) Typical value: X = 0.3 mm (mini)
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S i m ple pl e F lang la ng e R e du c t i on P referred
No n P referred
Note: For Thickness values a and b please see RSDP (Reference Structure Design Principles), Volume 3 Metallic Design Principles, Chapter 2.
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4.5 Surface Design 4.5.1 External Surfaces 4.5.1.1 True Surface Offset SECTION A-A
A
A
IML (Inner Mold Line) Line) Surface Machined with Multiple Scanning Paths
non-preferred option, Design the surface directly from an offset of the Master Geometry is a non-preferred option, because of manufacturing cost, but it can be used in case of design constraints.
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4.5.1.2 Approximation by a Single Facet Faceted ed Ruled Surface Surface If possible, is less costlytotobemachine surface has itconsequently ruled. the surface with the flank of the cutter. The designed A ruled surface for manufacturing is a surface generated with two curves that are parallel, iso-parametric and have the same curvilinear length. mm.. For each surface there is an allowable chord height error tolerance value of X = 0.2 mm
Surface Machined with the Flank Of Cutter B
SECTION B-B
B
X
X
IML (Inner Mold Line)
X X
X
X X
Ruled surface Surface Machined with the Flank Of Cutter
Figure 6 - Ruled Surface IML: the Inner Mold Line is a section generated from the Aircraft Skin. Note: For optimized machining, the choice of cutting tool is to be agreed with Manufacturing. Manufacturing. © AIRBUS S.A.S. 2009. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT.
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4.5.1.3 Approximation by a Multiple Facet Faceted ed Ruled Surface Surface When height error is overtaken with a single ruled surface, is possible to replacechord the surface by a double faceted ruled one infaceted order to achieve the it allowable chord mm on height error of X = 0.2 mm on each surface machined with the flank of the cutter.
Surface Machined with the Flank Of Cutter C
C
SECTION C-C X
IML (Inner Mold Line)
C
X
C
X
Surface Machined with the Flank Of Cutter
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The preferred solution is to design a surface as less faceted as possible Picture:
See Figure 6 page 6 page 27 27.. Note: For optimized machining, the choice of cutting tool is to be agreed with Manufacturing. Manufacturing.
4.5.1.4 Concave Surface Avoidance For further information, see RSDP (Reference Structure Design Principles), Volume 3 Metallic Design Principles, Chapter 2.
4.5.2 Internal Surfaces
Inside surface Faceted IML or planar surface
parallelsurface to the Outside
If the external surface is not planar and can not be ruled, the internal surface must ruled for machined details being produced on 5 axis machines.
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AM2217.1 A M2217.1 Issue: D
IML (Inner Mold Line) Surface Machined with the Flank Of Cutter X
X = 0.2 mm (maxi) (maxi) Note: For optimized machining, the choice of cutting tool is to be agreed with Manufacturing. Picture: See
Figure 6 page 27.. 6 page 27
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General Practices of Metallic Parts: Recommended Detailed Design Practices for Compliance to Machining Constraints
AM2217.1 A M2217.1 Issue: D
4.6 Practices 4.6.1 Example for External Routing The milling of the external contour is operated in two paths: − −
the first path to machine the two faces at 4 mm and the flange contour, the second path to machine the face at 4.3 mm and the flange upper face.
PRINCIPLE DETAIL
Typical value X = 0,3 mm (mini) (mini) Note: For optimized machining, the choice of cutting tool is to be agreed with Manufacturing. Manufacturing.
4.6.2 Joggles and Chamfers Design See RSDP (Reference Structure Design Principles), Volume 3 Metallic Design Principles, chapter 2.2.6 Joggles and 2.2.7 Chamfers.
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General Practices of Metallic Parts: Recommended Detailed Design Practices for Compliance to Machining Constraints
AM2217.1 A M2217.1 Issue: D
4.6.3 Stringer Hole Design (Mouse hole) DETAIL
(mini)
CAD MODEL DESIGN
X
(mini) Typical value X = 0,3 mm (mini) Note: For optimized machining, the choice of cutting tool is to be agreed with Manufacturing.
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AM2217.1 A M2217.1 Issue: D
4.6.4 Stiffener Flange Thickness This practice concerns High Speed Milling and traditional machining. But by using the most up to date machining facilities, adopting High Speed Milling with improved cutter technology and advanced cutter-holding systems, it is possible to machine bases and flanges thinner and thinner. The following tables present the minimum ratio to define the flange thickness
Flange thick
Ratio = Flange thickness/Flange height Flange height
Ratio for hard material and aluminum alloy: M i n . R at i o R = T/ T/H H
X
Fea ture T y pe D efi ni ti o n
Flange thickness
1/20 < X < 1/10 Note: For optimized machining, the choice of cutting tool is to be agreed with Manufacturing.
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AM2217.1 A M2217.1 Issue: D
4.6.5 High Thin Web Design Traditional machining: The definition of a high thin web is as H > 10 x e, with H the total high of the web, and e the thickness of the base. The designer has to respect: − −
an offset of 0.3 mm for each step, Hi < 1.5 x Ø milling tool.
Remark: If H ≤ 4 Ø the High Speed Milling don’t require a step. For optimized machining, value is to be agreed with Manufacturing.
4.6.6 Thickness of Suspended Web To prevent vibrations on pockets and delete anti-vibrating tools, respect if possible the following rule: − −
T:
web thickness and 2: pocket length and width 1
If L1 < L2, use L = L1 to calculate the minimum thickness value T. = L2 to calculate the minimum thickness value T If L2 < L1, use L =
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AM2217.1 A M2217.1 Issue: D
Web ty pe
W E B d i me me n s i o n s
M i n i m um um t h i c k n e s s A lu lum m i nu m alloy
Supported WEB Unsupported WEB
≤ 100
mm > 100 mm ≤ 100 mm > 100 mm
Ha rd material
1,6% x L 1,8% x L 2,5% x L 2,7% x L
1,8% x L 2% x L 2,8% x L 3% x L
1
T
2
If value
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