模具设计指南(pdf 53页)

Contents
1、General Introduction
1、Design Development ......................................................9
  1.1 Introduction ......................................9
  1.2 Material design factors ................................9
  1.3 Development steps .....................9
  1.3.1 End-use requirements ...9
  1.3.2 Preliminary design ...............................10
  1.3.3 Material selection ...............................10
  1.3.4 Design modification ..10
  1.3.5 CAD/CAE .........10
  1.3.5.1 Flow analysis ..................................................10
  1.3.5.2 Stress analysis .....................11
  1.3.6 Prototyping and testing ..........................................11
  1.3.7 End-use testing .....................11
2、Design for stiffness ........................13
  2.1 Introduction ......................................13
  2.2 How to determine stiffness .............13
  2.2.1 Material .........13
  2.2.2 Geometry & loading ..14
  2.2.3 Other factors influencing stiffness ...................................14
  2.2.4 Calculating the stiffness .............15
  2.2.5 Modal analysis ..................................................15
  2.2.6 Safety factors ....................15
  2.3 Increasing part stiffness ...15
  2.3.1 Ribs .........................................................15
  2.3.2 V-grooves .......................................15
  2.3.3 Corrugation ..........16
  2.4 Optimization of stiffness ...16
  2.4.1 Optimization for part weight .....................................................16
  2.4.1.1 Material Selection ..16
  2.4.1.2 Geometric considerations ..............16
  2.4.2 Optimization for stiffness to cost ratio .......16
3、Design for strength ........................19
  3.1 Introduction ......................................19
  3.2 Material Strength ..................................................19
  3.2.1 Ultimate strength .20
  3.2.2 Yield strength ....................20
  3.2.3 Strain to failure .....................20
  3.2.4 Proportional limit .20
  3.2.5 Material toughness ..20
  3.2.6 Other measures .....................20
  3.3 Effects of various factors on strenght ......20
  3.3.1 Other factors ....................20
  3.4 Part Strength .........21
  3.4.1 Ultimate part strength ...21
  3.4.2 Part yield strength ...............................22
  3.4.3 Part toughness ..................................................22
  3.5 Improving part strength ................................22
  3.5.1 Material choice .....................22
  3.5.2 Geometry optimization ...23
  3.6 Design considerations ..23
4、Design for behaviour over time ..........................................................25
  4.1 Introduction ......................................25
  4.2 Static time dependent phenomena .........................25
  4.2.1 Creep ........25
  4.2.1.1 Creep recovery .....................26
  4.2.1.2 Creep failure modes ................................26
  4.2.1.3 Apparent modulus ..26
  4.2.2 Stress relaxation .27
  4.2.3 Design considerations ...28
  4.3 Dynamic time dependent phenomena ......28
  4.3.1 Fatigue ......................................28
  4.3.1.1 Fatigue and endurance limits ........................28
  4.3.1.2 Factors affecting fatigue ...........................................29
  4.3.2 Wear resistance .....................29
  4.3.2.1 Types of wear ..................................................29
  4.3.2.2 Factors affecting wear ..........................................29
5、Design for impact performance ..........................................................31
  5.1 Introduction ......................................31
  5.2 Common impact testing methods ......................................................31
  5.2.1 Pendulum methods ...............................32
  5.2.2 Falling weight methods ..........................................32
  5.3 Design considerations ..33
6、Design for appearance ...................................35
  6.1 Introduction ......................................35
  6.1.1 General remarks .....................35
  6.2 Surface defects .................................................35
  6.2.1 Sink marks ..........35
  6.2.2 Weld lines ..........35
  6.2.3 Air traps .........35
  6.2.4 Voids ............................36
  6.2.5 Streaks ......................................36
  6.2.6 Delamination ....................36
  6.2.7 Jetting ......................................36
  6.2.8 Gate marks ..........36
  6.2.9 Summary .........37
7、Design for precision ......................................................39
  7.1 Introduction ......................................39
  7.1.1 Mould shrinkage .....................39
  7.1.2 Secondary effects ...............................39
  7.2 Shrinkage phenomena ...............................39
  7.2.1 Cooling ......................................39
  7.2.2 Packing ......................................40
  7.2.3 Orientation ..........40
  7.3 Materials and shrinkage ................................40
  7.3.1 Amourphous materials ...40
  7.3.2 Crystalline materials ................................41
  7.3.3 Reinforced materials ................................41
  7.4 Design related factors ..41
  7.4.1 Part wall thickness ...............................41
  7.4.2 Ribs .........................................................41
  7.5 Mould related factors ...............................41
  7.5.1 Gate location ....................41
  7.5.2 Gate type .......................................42
  7.5.3 Gate size .........42
  7.6 Processing related factors ..........................................42
  7.6.1 Melt temperature .42
  7.6.2 Mould temperature ...............................42
  7.6.3 Injection time ....................42
  7.6.4 Packing pressure .42
  7.7 Secondary effects ..................................................42
  7.7.1 Thermal expansion ...............................42
  7.7.2 Moisture absorption ..42
  7.7.3 Post crystallization ...............................42
  7.7.4 Creep under load .42
  7.8 Simulation techniques ..42
  7.9 Summary ............................43
8、Design for mouldability ......45
  8.1 Introduction ......................................45
  8.2 Material issues .................................................45
  8.2.1 Melt flow length .....................45
  8.2.1.1 Viscosity .......................................45
  8.2.1.2 Thermal properties ..46
  8.2.1.3 Shear properties .46
  8.2.2 Melt temperature .46
  8.3 Shrinkage ............................46
  8.3.1 General remarks .....................46
  8.3.2 Warpage .........47
  8.4 Cooling time .........47
  8.5 Design considerations ..48
  8.5.1 General remarks .....................48
  8.5.2 Nominal wall thickness ..........................................48
  8.5.3 Projections ..........48
  8.5.4 Radii ............................49
  8.5.5 Ribs .........................................................49
  8.5.6 Support ribs .................................................49
  8.5.7 Bosses ......................................50
  8.5.8 Undercuts .......................................50
  8.5.9 Coring ........51
  8.5.10 Draft angles .................................................51
  8.5.11 Textures & lettering ................................51
  8.5.12 Flow leaders ....................52
  8.5.13 Moulded-in-stress ...............................52
  8.5.14 Weld lines ..........52
  8.6 Processing considerations ..........................................52
  8.6.1 Venting ......................................52
  8.6.2 Gating ........53
  8.7 Ejection .........................................................54
9、Design for recyclability ......55
10、Design for automation ......57
11、Appendix .....................59
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