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 |  موضوع: كتاب The Mould Design Guide السبت 07 مايو 2022, 7:14 am | |
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The Mould Design Guide
Peter Jones
و المحتوى كما يلي :
Contents
1 Introduction . 1
2 The Injection Moulding Process 5
2.1 Background 5
2.2 Machine Design 6
2.2.1 Machine Base Unit 6
2.2.2 Clamp Unit . 6
2.2.3 Mould Height . 6
2.2.4 Daylight 7
2.2.5 Distance Between Tie Bars . 8
2.2.6 Clamping Mechanisms 9
2.2.7 The Injection Unit . 13
2.3 Theoretical Mould Locking Force 19
2.4 The Moulding Cycle . 20
2.4.1 Mould Closing Phase . 20
2.4.2 Mould Protection Phase 20
2.4.3 Injection (Mould Filling) Phase 20
2.4.4 Holding Time and Pressurising Phase . 20
2.4.5 Cooling and Refill Phase 21
2.4.6 Screw Back Phase 21
2.4.7 Mould Open Phase 21
2.4.8 Ejection Phase . 22Mould Design Guide
3 Plastics Materials 23
3.1 Types of Plastics Materials 23
3.2 Definition of Plastics . 23
3.3 The Nature of Plastics Materials . 24
3.4 Monomers, Polymerisation and Polymers 25
3.5 Classification of Plastics 26
3.5.1 Thermosets and Thermoplastics 26
3.5.2 Homopolymers, Copolymers and Polymer Blends (Alloys) . 27
3.5.3 Amorphous and Semicrystalline Thermoplastics 29
3.6 Melting and Solidification . 30
3.7 Shrinkage . 31
3.8 Engineering and Commodity Plastics . 32
3.8.1 Engineering Plastics . 32
3.8.2 Commodity Plastics 32
3.9 Material Additives 33
3.10 Flow Properties of Thermoplastic Materials . 35
3.11 Variable Molecular Weight . 35
3.12 Melt Flow Index (MFI) . 36
3.13 Reprocessed Material 37
3.14 Polymer Molecules 37
3.15 Material Names and Abbreviations . 37
3.16 Material Applications . 40Contents
iii
3.17 The Behaviour of Thermoplastics
During the Injection Moulding Process 41
3.17.1 Pretreatment of Materials Before Injection Moulding . 41
3.17.2 Reprocessed Materials . 41
3.17.3 Colouring Materials 41
3.17.4 Additives 41
3.17.5 Material Drying 42
3.17.6 Plasticising or Melting . 43
3.17.7 Measurement of Melt Temperature . 44
3.17.8 Degradation of Materials During Plasticising . 44
3.17.9 Selecting the Optimum Melt Temperature 45
3.17.10 The Effect of Screw Rotational Speed and Back Pressure 45
3.17.11 Flow Characteristics of the Melt During the Injection Phase . 46
3.17.12 Selection of Injection Speed . 46
3.18 Initial Cavity Filling Phase . 48
3.19 Cavity Holding Pressure Phase 49
3.20 Gate Freeze-off Phase 49
3.21 Melt Compressibility and Shrinkage 49
3.22 Sinks and Voids 50
3.23 Weld Lines and Meld Lines . 53
3.24 Cooling and Solidification of the Melt . 54
4 Good Design Practice 55
4.1 Predesign Analysis 56
4.2 Reading General Arrangement Diagrams (GA) 56
4.3 Understanding Toolmaking Concepts 57Mould Design Guide
iv
4.4 Observing Mould Tools 58
4.5 Summary of Good Design Practice . 58
5 Design Checklist . 59
5.1 Predesign Checklist . 59
5.2 Original Estimate Details 60
5.3 Component Drawing 60
5.4 Component Geometry . 60
5.5 Component Material . 61
5.6 Quantity Required 61
5.7 Component Function 61
5.8 Component Tolerances . 62
5.9 Number of Impressions . 62
5.10 Gating Method . 62
5.11 Ejection Method . 63
5.12 Component Aesthetics 63
6 Determining the Right Number of Impressions 65
6.1 Quality Versus Quantity . 66
6.2 Appearance . 66
6.3 Part Geometry 67
6.4 Drawing Tolerances 67
6.5 Discussion 67
6.6 More Cavities = Less Control 68
6.7 Summary 70Contents
v
7 Step-by-Step Design 71
7.1 Predesign Requirements 71
7.2 Golden Rules 71
7.3 Step-by-Step Design 72
7.4 Design Example 72
7.4.1 STEP 1: The Split Line . 73
7.4.2 STEP 2: Gating . 75
7.4.3 STEP 3: Ejection 75
7.4.4 STEP 4: Cavity Inserts . 76
7.4.5 STEP 5: Venting 78
7.4.6 STEP 6: Water Cooling 79
7.4.7 STEP 7: Impression Centres . 80
7.4.8 STEP 8: Mould Layout 81
7.4.9 STEP 9: Main Sectional View 82
8 Mouldmaking . 83
8.1 Discussion 83
8.2 General Mould Requirements 83
8.2.1 Mould Materials . 83
8.2.2 Alloy Steels . 84
8.2.3 Mild Steel . 84
8.2.4 Beryllium-Copper 84
8.3 General Construction 85
8.3.1 Cavity Construction 85
8.3.2 Turning 86Mould Design Guide
vi
8.3.3 Milling . 86
8.3.4 Grinding . 87
8.3.5 Fabrication . 88
8.3.6 Standard Electrodischarge Machining (EDM) 89
8.3.7 Wire Electrodischarge Machining 91
8.3.8 Cold Hobbing . 92
8.3.9 Beryllium-Copper 93
8.3.10 Electroforming 93
8.3.11 Cavity Corrosion and Erosion . 95
8.3.12 Gassing and Burning . 95
8.4 Differential Shrinkage . 96
8.5 Maximum Metal Conditions . 97
8.6 Example . 97
9 Two-Plate Mould Tools 99
9.1 Design Details . 99
9.1.1 Locating or Register Ring .101
9.1.2 Top Plate .101
9.1.3 Split Line .102
9.1.4 Cavity Insert 102
9.1.5 Front Cavity Plate 102
9.1.6 Rear Cavity Plate .102
9.1.7 Cavity Support Plate 103
9.1.8 Ejection System 103
9.1.9 Ejection Gap 104Contents
vii
9.1.10 Support Blocks .104
9.1.11 Guide Pillar 104
9.1.12 Return Pins 104
9.1.13 Fine Tuning the Mould Tool 104
9.1.14 Clearances .106
9.1.15 Bushes .106
9.1.16 Screws .106
9.1.17 Support Pillars .106
9.1.18 Taper Threads .107
9.1.19 Stand-off Buttons .107
9.1.20 Chamfers and Radii .107
9.1.21 Guide Bushes .107
10 Ejection Systems 109
10.1 Requirements .109
10.1.1 Part Geometry 109
10.1.2 Draft Angles 109
10.1.3 Tolerances .110
10.1.4 Material .110
10.1.5 Gating .111
10.1.6 Ejection Balance .112
10.1.7 Machine Specifications .113
10.1.8 Mould Opening Stroke .113
10.1.9 Machine Ejection Features 113
10.1.10 Movement Control Features .114
10.1.11 Component Finish Requirements 114Mould Design Guide
viii
10.2 Ejection Methods .114
10.2.1 Ejector Pins and Blades .114
10.2.2 Sleeve Ejectors 116
10.2.3 Stripper Plate Ejection 117
10.2.4 Valve Ejection 118
10.2.5 Ejection Forces .119
10.3 Ejection Force Calculation .120
10.4 Formulae .120
10.4.1 Example 121
10.5 Ejection Assembly Actuation 122
10.5.1 Mechanical Ejection .122
10.5.2 Hydraulic Ejection .125
10.5.3 Pneumatic Ejection .126
10.5.4 Hybrid Ejection Systems .126
10.5.5 Double Ejection .129
10.6 Unsatisfactory Systems .132
11 Mould Temperature Control 133
11.1 Discussion .133
11.2 Heat Transfer Fluids 134
11.2.1 Water 134
11.2.2 Heat Transfer Oil 134
11.3 Chillers 135
11.4 Temperature Controllers 135
11.5 Cooling Channels 135
11.5.1 Core Cooling .137Contents
ix
11.6 Cavity Cooling .145
11.7 Circuit Efficiency .148
11.7.1 Series Cooling 148
11.7.2 Parallel Cooling .149
11.8 Beryllium-Copper Cores and Cavities .150
11.9 Factors Affecting the Cooling Cycle 150
11.9.1 Part Geometry 151
11.9.2 Wall Sections .151
11.9.3 Moulding Material .151
11.9.4 Influence of the Gate and Runner 152
11.9.5 The Mould Material .152
11.10 Mould Temperature Control 152
11.11 Cooling Efficiency 153
11.11.1 Cavity Material and Construction .153
11.11.2 Channel Geometry .154
11.11.3 Number of Channels Required .154
11.11.4 Rate of Coolant Flow .154
11.12 Coolants 155
11.12.1 Thermal Conductance of Metals .155
11.13 Cooling Calculations 155
11.13.1 Specific Heat 155
11.14 Pulsed Mould Cooling 161
11.14.1 Selective Pulsed Cooling .162
11.15 Mould Cooling Variables .163
11.16 Summary .163Mould Design Guide
x
12 Undercut Injection Mould Tools 165
12.1 Introduction 165
12.1.1 Undercut Components .167
12.1.2 Basic Undercut Mould Designs .168
12.1.3 Loose Inserts 168
12.1.4 Moulding in Splits 170
12.1.5 Straight Angle Dowels 170
12.2 Key Design Features .172
12.2.1 Example 173
12.3 Offset Angle Dowels 175
12.3.1 Key Design Features .177
12.3.2 To Establish Point P .177
12.4 Use of Side Cores .178
12.4.1 Discussion .178
12.5 Angled Lift Splits .179
12.5.1 Discussion .179
12.5.2 Description of Operation 181
12.5.3 Key Design Features .181
12.5.4 Formulae .181
12.6 Form Pins 182
12.6.1 Discussion .182
12.6.2 Straight Action Form Pins .182
12.6.3 Key Design Features .183
12.6.4 Angled Form Pins .184
12.6.5 Angled Action Form Pin .185Contents
xi
12.6.6 Description of Operation 186
12.6.7 Key Design Features .186
12.6.8 Description of Operation 188
12.6.9 Key Design Features .188
12.7 Nonstandard Side Core Designs .188
12.7.1 Undercuts at Angle to Tool Axis .189
12.7.2 Description of Operation 189
12.7.3 Key Design Features .190
12.8 Curved Undercuts 190
12.8.1 Description of Operation 190
12.8.2 Key Design Features .192
12.9 Radial Undercuts .192
12.9.1 Description of Operation 195
12.9.2 Key Design Features .195
12.10 Undercuts on Helical Gears and Pump Impellers .196
12.11 Normal Ejection Techniques 196
12.11.1 Form of Undercut .197
12.11.2 Component Material 198
12.11.3 Satisfactory Materials .198
12.11.4 Unsatisfactory Materials .198
12.12 Special Ejection Designs .199
12.12.1 Splitting the Component .200
12.12.2 Moulding in One Piece .202
12.12.3 Helical Ejection 202Mould Design Guide
xii
13 Automatic Unscrewing Mould Tool Design 205
13.1 Introduction 205
13.2 Injection Moulding Thread Forms 206
13.3 Thread Geometry 207
13.3.1 Parallel Threads .207
13.3.2 Number of Starts 207
13.3.3 Thread Form .208
13.3.4 Taper Threads .213
13.3.5 British Standard Pipe Thread 214
13.3.6 Jointing Threads 214
13.3.7 Longscrew Threads 214
13.3.8 Moulded Thread Forms .216
13.4 Thread Shrinkage Compensation 217
13.4.1 Discussion .217
13.4.2 The Effect of Incorrect Shrinkage on Thread Forms 217
13.4.3 Pitch Inaccuracy .218
13.4.4 Thread Form Inaccuracy 218
13.4.5 Inaccurate Thread Diameters 218
13.5 Application of Shrinkage Allowance on Thread Forms 218
13.5.1 Shrinkage Formulae .219
13.6 Injection Moulding Considerations .220
13.6.1 Moulding-related Problems 220
13.6.2 Injection Pressure .220
13.6.3 Injection Speed .220
13.6.4 Unscrewing Speed 220Contents
xiii
13.6.5 Ejection Speed 220
13.6.6 Operating Window 221
13.6.7 Tool Temperature Control .221
13.7 Basic Screw Thread Mould Designs 222
13.7.1 Split Tooling 222
13.7.2 Thread Jumping .223
13.7.3 Collapsible Coring .224
13.7.4 Operation of Multisegment Cores .227
13.8 Rotary Unscrewing 227
13.8.1 Collapsible Coring Details 228
13.9 Types of Collapsible Core 228
13.9.1 Two-segment Core Details .229
13.9.2 Multisegment Collapsible Cores .230
13.10 Using Silicone Rubber Sleeve Cores 231
13.10.1 Advantages 231
13.10.2 Disadvantages 232
13.11 Core Unscrewing .234
13.11.1 Fixed Core Systems 234
13.11.2 Cavity in Moving Half .234
13.11.3 Cavity in Fixed Half .235
13.11.4 Key Design Features of Figure 13.18 238
13.12 Anti-Rotation Keying .239
13.12.1 Base Key Geometry 239
13.13 Moving Core Systems .240
13.13.1 Key Design Features .241Mould Design Guide
xiv
13.14 Cavity Rotation .242
13.14.1 Key Design Features .244
13.14.2 Guidelines 245
13.15 Two-thread Unscrewing Designs 245
13.15.1 Discussion .245
13.15.2 Key Design Features for Two External Threads .245
13.15.3 Operation 247
13.15.4 Key Design Features .249
13.15.5 Operation 250
13.16 Gearing Geometry .250
13.16.1 Introduction .250
13.16.2 Basic Spur Gear Definitions 252
13.16.3 Basic Spur Gear Formulae 253
13.16.4 Conversion Between ISO and Imperial Systems .253
13.16.5 Example Gear Calculations (ISO) .253
13.16.6 Guidelines for Gear Selection (ISO) .255
13.16.7 Guidelines for Gear Train Design (ISO) 255
13.17 General Mould Design Guide for Threads 256
13.17.1 Observation .256
13.17.2 Stage 1 .256
13.17.3 Stage 2 .257
13.17.4 Stage 3 .258
13.17.5 Stage 4 .259
13.17.6 Stage 5 .259Contents
xv
13.18 Driving Systems .260
13.18.1 Rack-and-Pinion Systems .260
13.18.2 Opening Movement of Mould Tool 260
13.18.3 Actuation by Cylinder 261
13.18.4 Pneumatic Motors 263
13.18.5 Hydraulic Motors 263
13.18.6 Electric Motors 265
13.18.7 Clutches and Rotation Control .265
13.18.8 Using Clutches .266
13.18.9 Using Stepper Motors .267
13.18.10 Using Torque Limiters 268
13.19 Special Designs 269
13.20 Commercial Unscrewing Systems 270
14 Multiplate Tool Systems 271
14.1 Three-Plate Tools 271
14.1.1 Three-Plate Tool Operation .273
14.2 Multiplate Undercut Tools .279
14.2.1 Sequential Opening 281
14.3 Stack Moulds .285
15 Runnerless Moulding .291
15.1 Sprueless Moulding 291
15.1.1 Basic Antechamber Type 291
15.1.2 Heated Hot Sprue Bushes .293
15.1.3 Summary .297Mould Design Guide
xvi
15.2 Insulated Runner Systems .298
15.2.1 Insulated 298
15.2.2 Semi-insulated 299
15.3 Full Hot Runner Systems 300
15.3.1 Advantages Over Cold Runner Moulds .300
15.3.2 Nozzles and Gate Bushes 305
15.3.3 Open Gate Nozzles 305
15.3.4 Spring-Operated Needle Nozzle 307
15.3.5 Hydraulically Operated Needle Valve Nozzle 308
15.3.6 Multipoint Gating 309
15.3.7 Summary .311
15.4 Heating .311
15.4.1 Band Heaters .311
15.4.2 Coil Heaters .312
15.4.3 Cartridge Heaters .312
15.4.4 Tubular Heaters .312
15.4.5 Integral Heating .313
15.4.6 Heat Pipes 313
15.5 Temperature Control in Manifolds .313
15.5.1 Closed-Loop Control .314
15.5.2 Open-Loop Control .314
15.5.3 Other Factors .314
15.6 Gating .315
15.6.1 Pin and Edge Gating .315
15.6.2 Valve Gating 316
15.6.3 Thermal Sealing .316Contents
xvii
15.7 Thermal Expansion 317
15.8 Manifold/Nozzle Interface 318
15.8.1 Nozzle–Mould Interface .318
15.8.2 Heating Capacity Requirements 318
15.8.3 Wattage Density .319
15.8.4 Manifold Heat-Up Time .320
16 Mould Materials 321
16.1 Introduction 321
16.2 Selecting the Material for the Application .322
16.3 Materials Characteristics 323
16.3.1 Steel .323
16.3.2 Plate Steel 324
16.3.3 Cast Steel .326
16.3.4 Nonferrous Materials .329
16.3.5 Aluminium Alloys 330
16.3.6 Zinc Alloys 332
16.3.7 Beryllium–Copper Alloys .332
16.3.8 Bismuth–Tin Alloys .334
16.3.9 Epoxy Resin .335
16.4 Heat Treatment .335
16.4.1 Through-Hardening .336
16.4.2 Pretoughening 338
16.4.3 Carburising or Case Hardening 338
16.4.4 Nitriding 339
16.4.5 Tuftriding 340Mould Design Guide
xviii
16.5 Mould Finishing 340
16.5.1 Polishing 341
16.5.2 Chromium Plating 341
16.5.3 Photochemical Etching .341
16.5.4 EDM Finishes 342
16.5.5 Bead Blasting .342
16.5.6 Vapour Blasting .342
16.6 Mould Maintenance .343
17 Runner and Gate Design 345
17.1 The Feed System 345
17.1.1 The Sprue 346
17.1.2 Cold Slug Well .346
17.1.3 Runner Design .347
17.1.4 Runner System Design Rules 350
17.2 Calculating the Runner Length .352
17.2.1 Example 353
17.3 Gate Design .355
17.3.1 Manually Trimmed Gates 360
17.3.2 Automatically Trimmed Gates 360
17.3.3 Gating Design Rules .362
17.3.4 Computer Simulations of Gate Designs .363
17.3.5 Number and Location of Gates .363
17.3.6 Gate Sizing .365
17.3.7 Example 366Contents
xix
17.3.8 Gate Land Length 367
17.3.9 Gate Diameter 367
17.4 Establishing the Correct Gate Size 369
17.4.1 Computer Analysis .370
17.4.2 Empirical Analysis .370
18 Standard Mould Parts 373
18.1 Standard Parts Available 373
18.1.1 Mould Base Units .374
18.1.2 Mould Plates 374
18.1.3 Location and Alignment Components .374
18.1.4 Ejection Components .374
18.1.5 Feed Systems 374
18.1.6 Cooling Components .375
18.1.7 Unscrewing Components 375
18.1.8 Miscellaneous 375
18.2 Mould Tool Designing Using Standard Parts .375
18.3 Toolmaking Using Standard Parts 376
18.4 Summary .378
19 Deflection and Stress in Mould Components .379
19.1 Discussion .379
19.1.1 Competition .380
19.1.2 Energy Costs 380
19.1.3 Breakages 380
19.1.4 Deflection 381Mould Design Guide
xx
19.2 Force and Stress .381
19.2.1 Definitions of Forces 381
19.2.1.2 Compressive Force .383
19.3 Stress .384
19.4 Strain 384
19.5 Stress–Strain Graph .385
19.5.1 Young’s Modulus of Elasticity 385
19.5.2 Limit of Proportionality .386
19.5.3 The Elastic Limit 386
19.5.4 Yield Stress 386
19.5.5 Tensile Strength .386
19.6 Factor of Safety (FOS) 386
19.6.1 Brittle materials .387
19.6.2 Ductile materials 387
19.7 Poisson’s Ratio 388
19.7.1 Example 389
19.8 Temperature Stresses .390
19.8.1 Example 390
19.9 Beam Theory .390
19.9.1 Beam Models .392
19.10 Bending Moments 393
19.10.1 Neutral Axis 393
19.10.2 Second Moment of Area .394
19.11 Bending Formula .396
19.12 Section Modulus 396Contents
xxi
19.13 Deflection of Beams .397
19.14 Analysing Mould Tools 397
19.14.1 Two-Plate Example 397
19.14.2 Split Tool Example 400
19.14.3 Analysing Core Pins .403
19.15 Summary .405
20 Fatigue 407
20.1 Observations .407
20.2 Facts on Fatigue .408
20.3 Calculating Shut-off Areas .410
20.3.1 Example 412
20.4 Factors Affecting Fatigue Life .414
20.4.1 Stress Concentrations .414
20.4.2 Stress Raisers .416
20.4.3 Machining Marks .418
20.4.4 The Effect of Surface Finish 419
20.4.5 Hardness Factors .420
20.5 Summary .421
21 Limits and Fits .423
21.1 Interchangeability 423
21.2 Tolerance 423
21.2.1 Unilateral .424
21.2.2 Bilateral .424
21.3 Limits 424Mould Design Guide
xxii
21.4 Fits 425
21.4.1 Running Fit 425
21.4.2 Push Fit .426
21.4.3 Drive Fit 426
21.4.4 Force Fit 426
21.5 British Standard Hole and Shaft Fits .426
21.5.1 Clearance Fit 427
21.5.2 Transition Fit .427
21.5.3 Interference Fit .427
21.6 British Standard Clearance Fits .427
21.7 British Standard Clearance Fits – Hole Basis .429
21.7.1 Example 430
21.8 Geometric Tolerancing 431
22 Impression Blanking 437
22.1 Reasons for Impression Blanking 437
22.2 Example 438
22.2.1 Original Estimate .438
22.2.2 Effect of Running on Six Impressions 439
22.2.3 Effect of Running on a 6-imp Basis with an 18-second Cycle 440
22.2.4 Cycle Required to Achieve Original Profit Level 440
22.2.5 Cycle Required to Break Even .441
22.3 Observations .442
22.4 Summary .442Contents
xxii
i
22.5 Methods of Blanking Impressions .442
22.5.1 Glueing 443
22.5.2 Gate Blocking 443
22.5.3 Cavity Rotation .443
22.5.4 Blanking the Branch Runner .445
22.6 Summary .445
23 Summary of Mould Calculations 447
23.1 Production Rates .447
23.2 Cooling Channel Diameters 447
23.3 Runner Length Formulae 448
23.4 Gate Design .449
23.5 Ejection Forces .449
23.6 Stress and Strain .450
23.7 Factors of Safety 450
23.7.1 For Brittle Materials .450
23.7.2 For Ductile Materials .450
23.8 Poisson’s Ratio 450
23.9 Moments of Inertia 451
23.9.1 Rectangular Bar .451
23.9.2 Circular Bar .451
23.10 Temperature Stresses .452
23.11 Bending Formulae 452
23.11.1 Section Modulus 453
23.12 Deflection of Beams .453
23.13 Blanking Impressions .454Mould Design Guide
xxiv
24 Integrated Design Examples .455
25 Mathematical and Reference Tables .485
25.1 Logarithms 486
25.2 Anti-logarithms .488
25.3 Natural Sines 490
25.4 Natural Cosines .492
25.5 Natural Tangents .494
25.6 Square Roots .496
25.7 Reciprocals 500
25.8 Powers, Roots and Reciprocals .502
25.9 Thermal Properties of Some Common Mould-making Materials .504
25.10 Typical Thermal and Mechanical Properties
of Steels for Injection Moulds .505
25.11 Thermal Properties of Plastics Materials .506
25.12 I.S.O. Metric Fine Threads in mm 507
25.13 I.S.O. Metric Coarse Threads in mm 508
25.14 B.S.F. Threads (55°) .509
25.15 Whitworth Threads (55°) .509
25.16 British Pipe Thread (B.S.P.) – Basic Sizes in Inches .510
25.17 British Standard Taper Pipe (B.S.T.P.)
Tolerances and Allowances, Turns of Thread .511
25.18 Hardness Comparison Table 512
25.19 Conversion Factors 513Contents
xxv
26 Glossary of Moulding Terminology 515
26.1 Time Elements in a Moulding Cycle .515
26.2 Mould and Processing Terminology .517
Index
Index
A
Acrylics
applications 39
Acrylonitriles
applications 39
Alloys (of polymers) 28–9
Aluminium alloys
characteristics 330–1
Amorphous thermoplastics 29–30
Anisoptropic materials 33
Antioxidants 34
Automatic tool design 205–6
anti-rotation keying
basic key geometry 239–40
application of shrinkage allowance 218
formulae 219
basic designs 222
collapsible coring 224–6
multisegment cores 227
split tooling 222–3
thread jumping 223–4
cavity rotation 242–4
guidelines 245
key design features 244
commercial systems 270
core unscrewing 234
cavity in fixed half 235–8
cavity in moving half 234–5
fixed core 234
key design features 238–9
driving systems 260
actuation by cylinder 261–3
clutches 266
clutches and rotation control 265–6
electric motors 265
hydraulic motors 263–4
pneumatic motors 263
rack-and-pinion systems 260
stepper motors 267
tool opening movement 260–1
torque limiters 268
gearing geometry 250–2
basic spur gear definitions 252–3
example calculations 253–5
gear selection guidelines 255
gear train design guidelines 255–6
ISO/Imperial conversion 253
general mould design for threads 256
observation 256Mould Design Guide
528
stage 1 –
preliminary considerations 256–7
stage 2 – predesign phase 257–8
stage 3 –
integrating design features 258
stage 4 – main design phase 259
stage 5 – design review 259
injection moulding considerations 220
ejection speed 220
injection pressure 220
injection speed 220
operating window 221
tool temperature control 221–2
unscrewing speed 220
moving core systems 240–1
key design features 241
rotary unscrewing 227–8
collapsible coring details 228
collapsible coring types 228
multisegment collapsible cores 230–1
two-segment core details 229–30
silicone rubber sleeve cores 231, 233
advantages 231
disadvantages 232
special designs 269–70
thread forms 206
thread geometry 207
British Standard pipe thread 214
form 208–13
jointing threads 214
longscrew threads 214–15
moulded forms 216
number of starts 207
parallel threads 207
taper 213
thread shrinkage compensation 217
effects of incorrect shrinkage 217
form inaccuracy 218
inaccurate diameters 218
pitch inaccuracy 218
two-thread unscrewing designs 245
key design features 245–7, 249
operation 247–9, 250
B
Back pressure 16
effects 44–5
Bead blasting 342
Beam deflection 397, 453
Beam theory 390–1
models 392
cantilever beams 392
fixed-end beams 393
simply supported beams 392
Bending force 383
Bending formulae 396, 452
Bending moments 393
neutral axis 393–4
second moment of area 394–5
circular bars 396
rectangular bars 395
Beryllium–copper alloys 84, 93
characteristics 332–4
Bismuth–tin alloys
characteristics 334–5Index
529
Blowing agents 34
British Standard
hole and shaft fits 426
clearance fit 427–9
transition fit 427
C
Carburising 338–9
process 339
Cavitation 17
Cavity cooling 145–7
Cellulose plastics
applications 39
Chromium plating 341
Clamping mechanisms 9
combined mechanical–
hydraulic systems 13
direct clamping 12
direct hydraulic clamping 12
double toggle joint clamp 10–12
single toggle joint clamp 9–10
toggle mechanisms 9
Commodity plastics 32
Compressive force 383
Cooling channel diameter
calculations 447–8
Copolymers 27–8
Core cooling 137
angled hole design 139–40
baffle systems 137–8
fountain systems 138–9
heat pipe 143–4
heat rod 142–3
spiral cooling 141–2
stepped hole design 140–1
Customer
definition 3
D
Daylight 7
Decompression 14
Deflection 381
Degradation 40, 43–4
Design, good practice 55–6
general arrangement (GA)
diagrams 56–7
observing mould tools 58
predesign analysis 56
summary 58
toolmaking concepts 57
Design, step-by-step approach 72
design requirements 71
example 72–3
1 – split line 73–4
2 – gating 75
3 – ejection 75–6
4 – cavity inserts 76–7
5 – venting 78–9
6 – water cooling 79–80
7 – impression centres 80
8 – mould layout 81
9 – sectional view 82
golden rules 71
Design checklist 59
component aesthetics 63
component drawing 60Mould Design Guide
530
component function 61
component geometry 60
component material 61
component tolerances 62
ejection method 63
gating method 62
number of impressions 62
original estimate details 60
predesign 59
quantity required 61
Distance between tie bars 8
Driving systems 260
actuation by cylinder 261–3
clutches 266
clutches and rotation control 265–6
electric motors 265
hydraulic motors 263–4
pneumatic motors 263
rack-and-pinion systems 260
stepper motors 267
tool opening movement 260–1
torque limiters 268
E
Ejection force
calculations 449
Ejection systems
ejection assembly actuation 122
double ejection 129–31
hybrid systems 126–8
hydraulic 125–6
mechanical 122–5
pneumatic 126
ejection force calculation 120
ejection methods 114
ejection forces 119
ejector pins and blades 114–15
sleeve ejectors 116
stripper plate ejection 117
valve ejection 118–19
formulae 120–1
example 121–2
requirements 109
component finish 114
draft angles 109–10
ejection balance 112
gating 111–12
machine ejection features 113
machine specifications 113
material 110–11
mould opening stroke 113
movement control features 114
part geometry 109
tolerances 110
unsatisfactory systems 132
Elastic limit 386
Electrodischarge machining (EDM)
mould finishing 342
standard 89–90
wire 91–2
Engineering plastics 32
Epoxides
applications 39
Epoxy resin
characteristics 335
Ethylene-vinyl acetate
applications 39Index
531
F
Factor of safety (FOS) 386
brittle materials 387
calculations 450
ductile materials 387
Fatigue
background 408–10
calculating shut-off areas 410–12
example 412–14
factors affecting fatigue life 414
effects of surface finish 419–20
hardness factors 420
matching marks 418
stress concentrations 414–16
stress raisers 416–17
observations 407
summary 421
Feed system design 345
cold slug well 346–7
sprue 346
Feed throat 15
Fibrous reinforcement 33
Fillers 34
Fits 425
drive fit 426
force fit 426
push fit 426
running fit 425
Flame retardants 34
Flow promoters 33
Fluorinated polymers
applications 39
Fungicides 34
G
Gate design 355–60
automatically trimmed gates 360–2
calculations 449
computer simulations 363
diameter 367
effect of time 369
shearing 367–9
establishing correct size 369
computer analysis 370
empirical analysis 370–1
land length 367
manually trimmed gates 360
number and location of gates 363–4
rules 362–3
sizing 365
example 366–7
Gearing geometry 250–2
basic spur gear definitions 252–3
example calculations 253–5
gear selection guidelines 255
gear train design guidelines 255–6
ISO/Imperial conversion 253
General arrangement (GA) diagrams 56–7
Geometric tolerancing 431–5
Granular masterbatch 40
H
Hold-on pressure 17
Homopolymers 27Mould Design Guide
532
I
Impression blanking
calculations 454
example
cycle required to achieve original
profit level 440–1
cycle required to break even 441
effect of running six impressions 439
effect of running six impressions with
18-second cycle 440
observations 442
original estimate 438–9
summary 442
methods 442
blanking the branch runner 445
cavity rotation 443–4
gate blocking 443
glueing 443
rationale 437–8
summary 445–6
Impressions, number of 62, 65–6, 67–8
appearance 66–7
cavities versus control 68–9
checklist 70
drawing tolerances 67
part geometry 67
quality versus quantity 66
summary 70
Injection moulding 1–3
Injection unit 13–14
hold-on pressure 17
injection speeds and pressures 16–17
reciprocating screw design 14–16
screw forward 16
screw rotation 16
screw speed 18
screw stroke 18–19
Integrated design examples 455
common gate designs 457
mould opening sequence 483
nozzle location on sprue 456
rotating cavity 482
stack tool 459
sub gates 458
two-impression coil platform 464
two-impression family mould 462–3
two-impression forceps mould 470–1
details 472–81
two-impression hot runner mould 461
two-impression spacer mould 466–7
details 468–9
two-impression split tool 460
interchangeability 423
L
Limit of proportionality 386
Limits 424–5
M
Meld lines 52
Melt flow index (MFI) 36
Moments of inertia
circular bars 451
rectangular bars 451
Monomers 25–6Index
533
Mould design 2–3, 379
breakages 380
competition 380
energy costs 380
factor of safety (FOS) 386
brittle materials 387
ductile materials 387
summary 405
Mould finishing 340
bead blasting 342
chromium plating 341
EDM finishing 342
photochemical etching 341–2
polishing 341
vapour blasting 342–3
Mould height 6
Mould maintenance 343
Mould materials 321
heat treatment 335–6
carburising or case hardening 338–9
nitriding 339
pretoughening 338
through-hardening 336–7
tuftriding 340
material characteristics 323
aluminium alloys 330–1
beryllium–copper alloys 332–4
bismuth–tin alloys 334–5
cast steel 326–9
epoxy resin 335
plate steel 324–6
steel 323
zinc alloys 332
material selection 322–3
Mould tool analysis 397
core pins 403
supported cores 404
unsupported cores 403–4
split tool example 400–2
two-plate 397–400
Mould tool
definition 3
Moulder
definition 3
Moulding process 5
machine design
base unit 6
clamp unit 6
clamping mechanisms 9–13
daylight 7
distance between tie bars 8
injection unit 13–16
mould height 6
moulding cycle
closing phase 20
cooling and refill phase 21
ejection phase 22
holding time and
pressurising phase 20–1
injection phase 20
open phase 21
protection phase 20
screw back phase 21
summary 22
theoretical mould locking force 19–20
Mouldmaking 83
differential shrinkage 96–7
example 97–8Mould Design Guide
534
general construction 85
beryllium–copper 93
cavity construction 85
cavity corrosion and erosion 95
cold hobbing 92
electrodischarge machining (EDM),
standard 89–90
electrodischarge machining (EDM),
wire 91–2
electroforming 93–4
fabrication 88
gassing and burning 95
grinding 87–8
milling 86
turning 86
general requirements
alloy steels 84
beryllium–copper 84
materials 83
mild steel 84
maximum metal conditions 97
Multiplate tool systems
stack moulds 285–90
three-plate systems 271–2
operation 273–8
undercut tools 279–80
sequential opening 281–4
N
Nucleating agents 33
P
Photochemical etching 341–2
Plastics materials
additives 33–4
applications 39
cavity filling phase 47
cavity holding pressure phase 48
classification
amorphous and semicrystalline
thermoplastics 29–30
homopolymers, copolymers and
polymer blends 27–9
thermosets and thermoplastics 26–7
commodity plastics 32
cooling and solidification 53
definition 23
engineering plastics 32
flow properties 35
gate freeze-off phase 48
melt compressibility and shrinkage 48
melt flow index (MFI) 36
melting and solidification 30
monomers, polymerisation
and polymers 25–6
moulding behaviour of thermoplastics
additives 40–1
colouring materials 40
degradation 43–4
drying 41–2
effect of screw rotational speed and
back pressure 44
flow characteristics 45
injection speed 45–7Index
535
melt temperature 43
melt temperature,
selecting optimal 44
melting 42–3
pretreatment 40
reprocessed materials 40
names and abbreviations 37–9
nature 24–5
polymer molecules 37
reprocessed material 37
shrinkage 31
sinks and voids 49–51
types 23
variable molecular weight 35
weld lines and meld lines 52
Poisson's ratio 388–9, 450
Polishing 341
Polymer blends 28–9
Polymerisation 25–6
Polymers 25–6
Production rate
calculations 447
R
Reaction pressure 16
Runner design 347
calculating runner length 352–3
example 353–4
cross-section and layout 347–50
length formulae 448–9
rules 350–2
Runnerless moulding 291
full hot runner systems
advantages over
cold runner moulds 300–4
hydraulically operated
needle nozzle 308
multipoint gating 309–10
nozzles and gate bushes 305
open gate nozzles 305–6
spring-operated needle nozzle 307
summary 311
gating 315
pin and edge gating 315
thermal sealing 316
valve gating 316
heating 311
band heating 311
cartridge heaters 312
coil heaters 312
heat pipes 313
integral heating 313
tubular heaters 312
insulated runner systems 298
fully insulated 298–9
semi-insulated 299–300
manifold temperature control 313
closed-loop control 314
open-loop control 314
other factors 314–15
manifold/nozzle interface 318
heating capacity requirements 318
manifold heat-up time 320
nozzle–mould interface 318Mould Design Guide
536
wattage density 319–20
sprueless moulding 291
basic antechamber type 291–3
heated hot sprue brushes 293–6
summary 297
thermal expansion 317
S
Screw back 15, 21
Screw rotation 16
effects 44–5
Section modulus 396, 453
Self-annealing 46
Semicrystalline thermoplastics 29–30
Shear force 383–4
Shear heat 16
Shear heating 42
Shrinkage 48
differential 96–7
Silicone rubber sleeve cores 231, 233
advantages 231
disadvantages 232
Sinks 49–51
Specific heat calculations 155
amorphous materials 156
crystalline materials 156–7
enthalpy curves 157–9
example 159–60
Sprue 346
Sprueless moulding 291
basic antechamber type 291–3
heated hot sprue brushes 293
externally heated 295–6
internally heated 294
summary 297
Stack moulds 285–90
Standard mould parts 373
availability 373
base units 374
cooling components 375
ejection components 374
feed systems 374
location and alignment
components 374
plates 374
unscrewing components 375
designing with 375
summary 378
toolmaking 376–7
Steel
characteristics 323
Steel, cast
characteristics 326–9
Steel, plate
characteristics 324–6
Stepped control 16
Strain 384
calculations 450
Stress 384
calculations 450Index
537
forces 381–2
bending force 383
compressive force 383
shear force 383–4
tensile force 383
temperature stresses 390
Stress–strain graphs 385
elastic limit 386
limit of proportionality 386
tensile strength 386
yield stress 386
Young's modulus of elasticity 385
Suck back 14
T
Temperature control 133–4
beryllium–copper cores and cavities 150
chillers 135
controllers 135
coolants 155
thermal conductance of metals 155
cooling 135–7
cavity cooling 145–7
core cooling 137–44
cooling calculations 155
specific heat 155–60
cooling efficiency 148, 153
cavity material and
construction 153–4
channel geometry 154
channel number required 154
coolant flow rate 154
parallel cooling 149
series cooling 148
factors affecting cooling cycle 150
gate and runner 152
mould material 152
moulding material 151
part geometry 151
wall sections 151
heat transfer fluids
oil 134
water 134
mould cooling variables 163
moulds 152–3
pulsed mould cooling 161–2
selective 162
summary 163
Temperature stresses 390, 452
Tensile force 383
Tensile strength 386
Thermoplastics 26–7
amorphous and semicrystalline 29–30
flow properties 35
moulding behaviour
degradation 43–4
drying 41–2
effect of screw rotational speed
and back pressure 44
flow characteristics 45
injection speed 45–7
melt temperature 43
melt temperature,
selecting optimal 44
melting 42–3
Thermosets 26–7
ThreadsMould Design Guide
538
application of shrinkage allowance 218
formulae 219
forms 206
geometry 207
British Standard pipe thread 214
form 208–13
jointing threads 214
longscrew threads 214–15
moulded forms 216
parallel threads 207
taper 213
shrinkage compensation 217
effects of incorrect shrinkage 217
form inaccuracy 218
inaccurate diameters 218
pitch inaccuracy 218
Through-hardening 336–7
process 337
Tolerance 423
bilateral 424
geometric tolerancing 431–5
unilateral 424
Toolmaker
definition 3
Tuftriding 340
Two-plate mould tools
design 99–100
bushes 106
cavity insert 102
cavity plate, front 102
cavity plate, rear 102
cavity support plate 103
chamfers and radii 107
clearances 106
ejection gap 104
ejection system 103
fine tuning mould tune 104–6
guide bushes 107
guide pillar 104
locating or register ring 101
return pins 104
screws 106
split line 102
stand-off buttons 107
support blocks 104
support pillars 106
taper threads 107
top plate 101–2
U
Undercut injection mould tools 165–6
angled action form pins
key design features 186–7, 188
operation 186, 188
angled lift splits 179–80
formulae 181
key design features 181
operation 180–1
basic designs 168
components 167
curved undercuts 190
key design features 192
operation 190–1
form pins 182
angled action form pins 185Index
539
angled form pins 184–5
key design features 183–4
straight action 182–3
helical gears and pump impellers 196
key design features 172–3
example 173–5
loose inserts 168–70
multiplate systems 279–80
sequential opening 281–4
nonstandard side core designs 188
key design features 190
operation 189–90
undercuts at angle to tool axis 189
normal ejection techniques 196
component material 198
form of undercut 197
satisfactory materials 198
unsatisfactory materials 198–9
offset angle dowels 175–6
establishing point P 177–8
key design features 177
radial undercuts 192–4
key design features 195–6
side cores 178–9
special ejection designs 199
component splitting 200–1
helical ejection 202–3
one-piece moulding 202
splits 170
straight angle dowels 170–1
V
Vapour blasting 342–3
Virgin materials 40
Voids 49–51
W
Weld lines 52
Y
Yield stress 386
Young's modulus of elasticity 385
Z
Zinc alloys
characteristics 332
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