E. Alfredo Campo
The Complete Part Design Handbook
For Injection Molding of Thermoplastics
Dedication
6
Preface
8
Contents
10
1 Polymeric Materials
24
1.1 Introduction to Plastic Materials
24
1.1.1 Beginning of Plastics
24
1.1.2 Polymer Families
26
1.2 Thermoplastic Polymers
27
1.2.1 Classification of Polymers by Performance
27
1.2.2 Molecular Structure of Plastic Materials
29
1.2.3 Acrylonitrile-Butadiene-Styrene (ABS)
29
1.2.4 Acetal (POM, Polyacetal)
32
1.2.5 Polymethyl Metacrylate (Acrylic, PMMA)
35
1.2.6 High Temperature Nylon (HTN)
37
1.2.7 Ionomer Polymers
39
1.2.8 Liquid Crystal Polymer (LCP)
41
1.2.9 Polyamide (PA, Nylon)
43
1.2.10 Polyetherimide (PEI)
46
1.2.11 Polyarylate (PAR)
48
1.2.12 Polyetherether Ketone (PEEK)
50
1.2.13 Polycarbonate (PC)
51
1.2.14 Modified Polyphenylene Oxide (PPO)
54
1.2.15 Polybutylene Terephthalate (PBT)
56
1.2.16 Polyethylene Terephthalate (PET)
57
1.2.17 Polyethylene (PE)
59
1.2.18 Polytetrafluoroethylene (PTFE)
62
1.2.19 Polyphenylene Sulfi de (PPS)
67
1.2.20 Polypropylene (PP)
69
1.2.21 Polystyrene (PS)
71
1.2.22 Polysulfone (PSU)
72
1.2.23 Polyvinyl Chloride (PVC)
74
1.2.24 Styrene Acrylonitrile (SAN)
76
1.3 Thermoplastic Elastomers (TPE)
78
1.3.1 Thermoplastic Elastomer Families
79
1.3.2 Thermoplastic Polyurethane Elastomer (TPU)
80
1.3.3 Styrenic Block Copolymer (SBS)
83
1.3.4 Polyolefin Thermoplastic Elastomer (TPO)
85
1.3.5 Elastomeric Alloy Thermoplastic Vulcanized (TPV).
88
1.3.6 Melt Processible Rubber (MPR)
92
1.3.7 Copolyester Thermoplastic Elastomer
94
1.3.8 Polyamide Thermoplastic Elastomer
98
1.4 Liquid Injection Molding Silicone (LIM®)
100
1.4.1 LIM® Silicone Processing
102
1.5 Thermoset Polymers
105
1.5.1 Polyester Alkyd (PAK)
106
1.5.2 Diallyl Phthalate/Isophthalate (DAP, DAIP)
108
1.5.3 Melamine Formaldehyde (MF)
110
1.5.4 Cellulosic Ester
111
1.5.5 Cyanate
112
1.5.6 Epoxy (EP)
115
1.5.7 Phenol Formaldehyde (Phenolic, PF)
117
1.5.8 Polybutadiene (PB)
120
1.5.9 Bismaleimide (BMI)
120
1.5.10 Unsaturated Polyester (UP)
121
1.5.11 Polyimide (PI)
124
1.5.12 Polyxylene
126
1.5.13 Polyurethane (PUR)
127
1.5.14 Silicone (SI)
130
1.5.15 Urethane Hybrid
132
1.5.16 Vinyl Ester (BPA)
134
2 Engineering Product Design
138
2.1 Understanding the Properties of Materials
138
2.1.1 Plastics Selection Guidelines
140
2.2 Structural Design of Thermoplastic Components
143
2.2.1 Stress-Strain Behavior
144
2.2.2 Tensile Testing of Viscoelastic Materials
145
2.3 Mechanical Properties of Materials
149
2.4 Tension and Compression Curves
152
2.5 Modulus of Elasticity (E)
152
2.6 Stress and Strain Analysis
153
2.7 Thermoplastics Elastic Design Method
154
2.7.1 Working Stress
155
2.7.2 Compressive Stress
156
2.7.3 Flexural Stress
157
2.7.4 Coefficient of Linear Thermal Expansion (?)
158
2.7.5 Poisson’s Ratio (?)
159
2.7.6 Moisture Effects on Nylon
159
2.7.7 Effects of Temperature on the Behavior of Thermoplastics
160
2.8 Stress-Strain Recovery (Hysteresis)
161
2.8.1 Creep Behavior of Thermoplastics
161
2.8.2 Creep and Rupture Under Long-Term Load
162
2.8.3 Creep and Relaxation of Thermoplastics
162
2.9 Flexural Beam Stress Distribution
168
2.10 Viscoelastic Modulus Design Method
170
2.11 Centroid, Section Area, and Moment of Inertia
173
2.12 Radius of Gyration
181
2.13 Stress Analysis of Beams
181
2.13.1 Types of Loads
181
2.13.2 Normal Stresses in Beams
182
2.13.3 Shearing Force
187
2.14 Beam Deflection Analysis
191
2.14.1 Beam Deflection by Double Integration Method
192
2.14.2 Beam Deflection Moment Area Method
201
2.14.3 Applications of Moment Area and Double Integration Methods
202
2.14.4 Beam Deflection Superposition Method
206
2.15 Column Structural Analysis
211
2.15.1 Long Slender Column Critical Load (PCr)
211
2.15.2 Column Slenderness Ratio (L / r)
211
2.15.3 Eccentrically Loaded Columns
211
2.16 Flat Circular Plates
217
2.16.1 Classification
218
2.16.2 Stress Analysis Methods
218
2.16.3 Flat Circular Plate Equations
219
2.16.4 Flat Circular Plate Stresses
220
2.16.5 Theory of Flexure Comparison
221
2.16.6 Circular Plates Simply Supported, Concentrated center Load
221
2.16.7 Flat Circular Plate under Concentrated Center Load
222
2.16.8 Flat Circular Plate with Fixed Edge
222
2.16.9 Flat Circular Plate Compensation Factor for Deflection
223
2.16.10 Flat Circular Plate Bending under Edge Boundaries
223
2.17 Torsion Structural Analysis
230
3 Structural Designs for Thermoplastics
234
3.1 Uniform and Symmetrical Wall Thickness
234
3.1.1 Part Geometries Difficult to Mold
235
3.1.2 Wall Draft Angle per Side
236
3.2 Structural Rib Design
236
3.2.1 Rib Strength Analysis Method
238
3.3 Internal Sharp Corners and Notches
245
3.4 Injection Molded Thermoplastic Bosses
245
3.5 Injection Molded Thermoplastic Threads
247
3.6 Collapsible Core for Molding Internal Threads
247
3.7 Preferred Standard Thread Forms for Thermoplastics
248
3.7.1 Thermoplastic Threads Creep Effects
250
3.8 Injection Molded Products with Undercuts
250
3.9 Injection Molded Integral Life Hinges
255
3.9.1 Injection Molded Integral Life Hinge Design
256
3.9.2 Mold Design Considerations for Hinges
258
3.9.3 Proper Gate Design for Life Hinges
259
3.10 Conventional Types of Pin Hinges
260
3.11 Metal Inserts for Thermoplastic Encapsulation
262
3.11.1 Machined Metal Threaded Insert Tolerances
263
3.11.2 Thermoplastic Boss Wall Thickness for Metal Inserts
263
3.11.3 Press/Lock Slotted Metal Insert Installation After Molding
265
3.11.4 Cold Forged Metal Inserts for Encapsulation
266
3.11.5 Threaded Female Metal Inserts
267
3.11.6 Metal Inserts Anchorage for ThermoplasticEncapsulation
269
3.11.7 Metal Insert Encapsulating Process Problems
272
3.11.8 Special Metal Inserts Anchorage for Encapsulation
273
3.11.9 Electrical Lead Inserts for Encapsulation
276
3.11.10 Inserts Preparation for Molding Encapsulation
278
4 Thermoplastic Gearing Design
280
4.1 Classification of Gears
281
4.1.1 Gears Parallel to the Shaft Axis
281
4.1.2 Bevel Gears, Nonparallel and Intersecting Shafts
282
4.1.3 Hypoid Gears, Nonparallel and Nonintersecting Shafts
284
4.1.4 Gears for Straight Linear Motion
285
4.2 Standard Injection Molded Thermoplastic Gears
286
4.2.1 Selection of Thermoplastic Resins for Gears
287
4.2.2 Horsepower Equations for Gears
289
4.2.3 Spur Gear Terminology and Definitions
291
4.3 Properties Required for Injection Molded Thermoplastic Gears
295
4.4 Thermoplastic Spur Gear Design Requirements
296
4.4.1 Gating Effects on Thermoplastic Gear Roundness Dimensions
298
4.4.2 Multifunction Designs with Thermoplastic Gears
300
4.4.3 Mounting Thermoplastic Gears on Metal Shafts
302
4.4.4 Standard Spur Gears, Equations, and Calculations
302
4.4.5 Spur Gear Pitch Backlash
304
4.4.6 Standard Spur Gear Tooth Size Selection
305
4.4.7 Standard Gear Total Composite Tolerances
306
4.5 Tolerances and Mold Shrinkage of Thermoplastic Gears
310
4.6 Standard Helical Gears
312
4.7 Standard Straight Bevel Gears
313
4.8 Standard Worm Gears
315
4.8.1 Standard Worm Gear Analysis
316
4.10 Plastic Gearing Technology Designs
317
4.10.1 Spur and Helical Gears PGT-1 Tooth Design
318
4.10.2 Spur and Helical Gears PGT-2 Tooth Design
320
4.10.3 Spur and Helical Gears PGT-3 Tooth Design
321
4.10.4 Spur and Helical Gears PGT-4 Tooth Design
322
4.10.5 Plastic Gearing Technology Tooth Form Design Variables
323
4.10.6 Maximum Allowable Outside Diameter DO (Max.)
325
4.10.7 Spur Gear Tooth Form Comparison
326
4.10.8 Mating Spur Gears Tooth Form Comparison
327
4.10.9 PGT Spur Mating Gears Strength Balance
328
4.10.10 PGT Close Mesh Center Distance Between Spur Gears
331
4.10.11 Maximum Close Mesh Center Distance
332
4.11 PGT Helical Thermoplastic Gearing
337
4.11.1 PGT-1 Helical Mating Gears Strength Balance
342
4.11.2 PGT-1 Helical Mating Gears Center Distance
345
4.12 PGT Spur and Helical Gears Horsepower Rating
346
4.12.1 PGT Gear Horsepower Equation Basic Parameters
347
4.13 PGT Spur and Helical Gear Specifications
351
5 Plastic Journal Bearing Design
358
5.1 Introduction
358
5.2 Materials Used for Journal Bearings
358
5.2.1 Babbitt Journal Bearings
359
5.2.2 Bronze Journal Bearings
359
5.2.3 Sintered Porous Metal Journal Bearings
359
5.2.4 Plugged Bronze Journal Bearings
359
5.2.5 Carbon-Graphite Journal Bearings
360
5.2.6 Cast-iron Journal Bearings
360
5.2.7 Wooden Journal Bearings
360
5.2.8 Rubber Journal Bearings
360
5.2.9 Self-Lubricated Thermoplastic Journal Bearings
361
5.3 Hydrodynamics of Lubrication
362
5.4 Journal Bearings Design for Lubrication
365
5.5 Journal Bearing Design Principles
368
5.5.1 Journal Bearing Nomenclature and Equations
368
5.5.2 Thermoplastic Journal Bearing Axial Wall Thickness
370
5.5.3 Mounting Thermoplastic Journal Bearings
370
5.6 Split Bushing Thermoplastic Journal Bearings
371
5.7 Self-Centering Thermoplastic Journal Bearings
371
5.8 Journal Bearing Load Carrying Contact Surface (C)
373
5.9 Load Reaction Across the Length of Thermoplastic Bearing
373
5.10 Injection Molded Journal Bearings Process Defects
374
5.11 Factors Affecting Journal Bearing Performance
375
5.12 Factors Affecting Journal Bearing Dimensions
376
5.12.1 Length-to-Inside Diameter Ratio of Journal Bearings
377
5.12.2 Types of Service and Motion of Journal Bearings
377
5.12.3 Thermoplastic Journal Bearing Annealing Effects
377
5.12.4 Acetal Homopolymer Moisture Absorption Effects
378
5.12.5 TFE and Nylon 6/6 Moisture Absorption Effects
378
5.12.6 Temperature Effects on Thermoplastic Journal Bearings
379
5.12.7 Thermal Effects on Thermoplastic Journal Bearing Clearances
380
5.13 Journal Bearing Pressure-Velocity (PV) Limits
381
5.13.1 Methods to Determine the PV Limits of Plastics
382
5.13.2 Journal Bearing Coefficient of Friction
382
5.13.3 Journal Bearing Failures Due to Small Clearances
383
5.13.4 Definition of Different Types of Wear
384
5.14 Mating Material Hardness and Surface Finishing
385
5.15 Self-Lubricated Thermoplastic Journal Bearings
386
5.15.1 Vespel® Polyimide Bearings
389
5.15.2 Journal Bearing Pressure Equation
390
5.15.3 Vespel® Wear Factor Effects Caused by Temperature
391
5.15.4 Vespel® Wear Transition Temperature
392
5.15.5 Frictional Behavior of Vespel®
392
5.15.6 Vespel® Journal Bearings Length to Inside Diameter Ratio
393
5.15.7 Vespel® Thrust Bearing Ratio Between Diameters
393
5.15.8 Vespel® Journal Bearing Initial Clearance (cI)
393
5.15.9 Vespel® Journal Bearing Inside Diameter (dB)
394
5.16 Teflon® (TFE) Fabric Composite Bearings
396
5.16.1 Bearing Physical Properties
397
5.16.2 Bearing PV Limit Rating
397
5.16.3 Journal Bearing Clearances (c)
398
5.17 Thermoplastic Kevlar® Reinforced Bearings
398
6 Thermoplastic Molded Spring Design
400
6.1 Introduction
400
6.2 Thermoplastic Molded Spring Design Considerations
401
6.3 Thermoplastic Helical Compression Springs
401
6.4 Thermoplastic Molded Cantilever Beam Springs
402
6.5 Cantilever Beam Spring Design Analysis
404
6.5.1 Initial Modulus of Elasticity Cantilever Beam Analysis Method
404
6.5.2 Stress-Strain Curve Cantilever Beam Analysis Method
404
6.5.3 Empirical Data Cantilever Spring Analysis Method
405
6.6 Thermoplastic Cantilever Spring Applications
408
6.7 Thermoplastic Belleville Spring Washers
411
6.7.1 Acetal Homopolymer Belleville Spring Washer Analysis
412
6.7.2 Belleville Spring Washer Loading Rate
415
6.7.3 Belleville Spring Washer Long-Term Loading Characteristics
415
7 Thermoplastic Pressure Vessel Design
416
7.1 Thermoplastic Thin-Walled Pressure Vessels
416
7.2 Thin-Walled Cylinder Basic Principles
417
7.3 Thick-Walled Pressure Vessels
419
7.3.1 Lame’s Equation for Thick-Walled Cylinders
419
7.3.2 Maximum Stresses with Internal and External Pressures
421
7.3.3 Maximum Stresses for Internal Pressure Only
421
7.4 Designing Cylinders for Cost Reduction
423
7.5 Thermoplastic Pressure Vessels Design Guidelines
423
7.5.1 Preliminary Pressure Vessel Design
423
7.6 Testing Prototype Thermoplastic Pressure Vessels
425
7.6.1 Redesign and Retesting the Pressure Vessels
425
7.7 Pressure Vessel Regulations
425
7.7.1 ASME Pressure Vessel Code
426
8 Thermoplastic Assembly Methods
428
8.1 Introduction
428
8.2 Cold Heading Method
428
8.2.1 Cold Heading Procedure and Equipment
429
8.3 Electro Fusion Fitting System
431
8.3.1 The SEF-System
432
8.4 Hot Plate Welding Method
433
8.4.1 Hot Plate Welding Joint Design
435
8.4.2 Flash or Weld Bead
436
8.5 Solvent and Adhesive Bonding Methods
436
8.5.1 Solvents Used to Bond Thermoplastic Polymers
437
8.6 Adhesive Bonding Method
439
8.6.1 Adhesive Families
439
8.6.2 Adhesive Concerns
442
8.6.3 Adhesives Bonding Selection
443
8.6.4 Ultra Violet Curable Adhesives
444
8.6.5 Adhesive Surface Preparation
447
8.6.6 Adhesive Application and Curing Methods
448
8.6.7 Joint Design for Adhesive Bonding
448
8.7 Metal Fasteners Method
450
8.7.1 Thermoplastic Bosses and Self-Tapping Screws
452
8.7.2 Thread Forming and Thread Cutting Screws
453
8.8 Press Fitting Method
460
8.8.1 Press Fitting Interference
462
8.8.2 Circular Press Fitting Assembly Method
464
8.9 Snap Fitting Methods
467
8.9.1 Circular Undercut Snap Fitting Joints
468
8.9.2 Suggestions for Stripping Circular Undercut Snap Fitting
469
8.9.3 Cantilevered Latch Snap Fitting Joint
470
8.9.4 Cantilever Snap Fit Latch Design Guidelines
472
8.9.5 Cantilever Latch Snap Fit Mathematical Model
473
8.9.6 Cantilever Snap Latch Beam Permissible Deflection (?)
475
8.9.7 Cantilever Latch Beam Assembly Force (W)
476
8.9.8 Design and Material Considerations
477
8.9.9 Uniform Cross Section Cantilever Beam
477
8.9.10 Tapered Cross Section Cantilever Beam
478
8.10 Electromagnetic Welding Method
481
8.10.1 Electromagnetic Welding Process
482
8.10.2 Electromagnetic Welding Coil Design
483
8.10.3 Electromagnetic Welding Joint Design
486
8.10.4 Available Welding Gasket Shapes and Forms
487
8.11 Vibration Welding Method
488
8.11.1 High Frequency Vibration Welding
488
8.11.2 Vibration Welding Modes
489
8.11.3 Comparing Vibration Welding to Other Assembly Methods
492
8.11.4 Vibration Welding Equipment
494
8.11.5 Vibration Welding Joint Design
495
8.11.6 Vibration Welding Aligning and Fixturing
496
8.11.7 Vibration Welding Tolerances
497
8.11.8 Vibration Welding Equipment
497
8.12 Spin Welding Method
499
8.12.1 Applications
499
8.12.2 Basic Spin Welding Equipment
499
8.12.3 Spin Welding Variables
500
8.12.4 Types of Spin Welding Processes
500
8.12.5 Spin Welding Joint Designs
503
8.12.6 Spin Welding Process Suggestions
503
8.13 Ultrasonic Welding Method
505
8.13.1 Ultrasonic Welding Basic Principles
505
8.13.2 Ultrasonic Welding Basic Components
506
8.13.3 Ultrasonic Welding Equipment
506
8.13.4 Ultrasonic Welding Process Variables
510
8.13.5 Ultrasonic Welding Joint Designs
512
8.13.6 Ultrasonic Welding Energy Director Butt Joint
515
8.13.7 Ultrasonic Welding Method Design Limitations
517
8.13.8 Weldability of Thermoplastic Materials
519
8.13.9 Effects Caused by Thermoplastic Additives on Ultrasonic Welding
520
8.14 Ultrasonic Insertion
523
8.14.1 Applications
523
8.14.2 Ultrasonic Insertion Configurations
524
8.14.3 Ultrasonic Insertion Product Design
525
8.14.4 Ultrasonic Insertion Equipment Requirements
525
8.14.5 Ultrasonic Insertion Process Guidelines
526
8.15 Ultrasonic Stud Staking Method
526
8.15.1 Ultrasonic Stud Staking Joint Design
526
8.16 Ultrasonic Stud Heading Method
529
8.16.1 Thermoplastic Stud Profiles for Ultrasonic Heading
529
8.17 Ultrasonic Spot Welding Method
532
8.17.1 Hand-Held Ultrasonic Spot Welder
533
9 Thermoplastic Effects on Product Design
534
9.1 Polymer Melt Behavior
534
9.1.1 Thermoplastics Glass Transition Temperature
536
9.2 General Characteristics of Polymers
536
9.2.1 Critical Properties of Thermoplastics
537
9.3 Polymer Reinforcements
538
9.3.1 Types of Fiber Reinforcements
539
9.3.2 Isotropic Warpage of Fiber Reinforced Resins
540
9.3.3 Fiber Glass Reinforcement Limitations
540
9.3.4 Injection Molding Process Effects on Fiber Glass Orientation
540
9.3.5 Tensile Stress Effects Caused by Fiber Glass Orientation
541
9.3.6 Flexural Modulus Effects Caused by Fiber Glass Orientation
542
9.4 Chemical and Environmental Resistance
543
9.4.1 Effects of the Environment
544
9.5 Types of Degradations
545
9.5.1 Oxidative Degradation
545
9.5.2 Radiation Degradation
545
9.5.3 Photo Oxidation
545
9.5.4 Mechanical Degradation
545
9.5.5 Microbial Degradation
546
9.6 Moisture Effects on Nylon Molded Parts
546
9.7 Aqueous Potassium Acetate for Moisture Conditioning Nylon
550
9.8 Injection Molding Cycles
551
9.9 Mold Cavity Surface Temperature
552
9.10 Mold Cavity Temperature Control
553
9.10.1 Mold and Post-Mold Shrinkage
554
9.11 Process Condition Effects on Mold Shrinkage
556
9.12 Post-Mold Shrinkage
561
9.13 Weld Lines
564
10 Injection Mold Design
568
10.1 Classification of Injection Molds
568
10.2 Effects of Product Design on the Injection Molding Process
569
10.2.1 Uniform Wall Thickness
570
10.2.2 Balance Geometrical Configuration
570
10.2.3 Smooth Internal Sharp Corners
570
10.2.4 Draft Walls
570
10.2.5 Feather Edges
570
10.2.6 Proportional Boss Geometries
571
10.2.7 Gate Type and Location
571
10.2.8 Molded Product Ejection Surface Area
571
10.2.9 Molded Product Tolerances
571
10.2.10 Surface Finish of Molded Product
572
10.3 Effects of Mold Design on the Injection Molding Process
572
10.3.1 Runner System
572
10.3.2 Mold Cooling System
572
10.3.3 Ejector System
573
10.3.4 Mold Venting
573
10.3.5 Other Mold Devices
573
10.4 Design Considerations for Injection Molds
573
10.4.1 Preliminary Mold Design
574
10.4.2 Detailed Mold Design
575
10.5 Types of Steels Required for Injection Molds
576
10.5.1 Major Steel Families
576
10.6 Steels for Thermoplastic Injection Molds
580
10.6.1 General Steel Selection Procedures
581
10.6.2 Properties and Characteristics of Tool Steels
582
10.6.3 Effects of Alloying Elements on Tool Steel Properties
582
10.6.4 Chemical Composition of Steels Used for Molds
582
10.6.5 Effects of Alloying on Tool Steels
583
10.6.6 Effects of Heat Treatment on Tool Steel Properties
585
10.6.7 Prehardened Tool Steels
587
10.6.8 Carburizing Tool Steels
589
10.6.9 Oil and Air Hardening Tool Steels
590
10.6.10 Stainless Steels
591
10.6.11 Steels Used in Thermoplastic Injection Mold Components
592
10.7 Mold Cavity Surface Finishing
594
10.7.1 Mold Surface Finishing Process Procedures
596
10.8 Thermoplastic Injection Mold Bases
601
10.8.1 Standard Mold Base Components
601
10.8.2 Functions of the Mold Base Components
602
10.8.3 Types of Standard Mold Bases
605
10.9 Types of Thermoplastic Injection Molds
606
10.9.1 Two-Plate Molds
607
10.9.2 Round Mate® Interchangeable Insert Molds
608
10.9.3 Master Unit Die Interchangeable Insert Molds
608
10.9.4 Three-Plate Mold Cold Runner System
609
10.9.5 Vertical Insert Mold for Thermoplastic Encapsulations
610
10.9.6 Hot Runner Molding Systems
611
10.9.7 Hot Runner Mold Temperature Control Systems
612
10.9.8 Hot Runner Mold Gates (Drops)
613
10.9.9 Types of Hot Runner Molding Systems
616
10.9.10 Thermoplastic Stack Injection Molds
624
10.9.11 Lost Core Thermoplastic Injection Molds
625
10.10 Number of Mold Cavities
629
10.10.1 Cavity Number Limitations
629
10.10.2 Number of Mold Cavities Equation
629
10.11 Mold Parting Line
630
10.11.1 Flat Mold Parting Line
630
10.11.2 Non-Flat Mold Parting Line
631
10.11.3 Balancing of Mold Parting Line Surfaces
633
10.12 Mold Ejection Systems
633
10.12.1 Ejector Plate Assembly
634
10.12.2 Ejector Plate
634
10.12.3 Retaining Plate
634
10.12.4 Ejector Sleeves
634
10.12.5 Types of Mold Ejection Systems
635
10.13 Injection Mold Cooling
638
10.13.1 Mold Temperature Control
639
10.13.2 Factors Affecting Mold Cooling
640
10.13.3 Effects Caused by Elevated Mold Temperature
640
10.13.4 Effects Caused by Too Low a Mold Temperature
641
10.13.5 Mold Heat Transfer Methods
641
10.13.6 Mold Cavity Insert Cooling
654
10.14 Injection Molding Machine Nozzle
662
10.14.1 Mold Cold Runner System
662
10.14.2 Determining the Injection Pressure Needed
676
10.14.3 Cold Runner Flow Tab
677
10.15 Mold Cavity Gating
678
10.15.1 Types of Mold Cavity Gates
679
10.15.2 Different Types of Hot Runner Gates
686
10.16 Gate Molding Effects
687
10.17 Mold Venting Systems
689
10.17.1 Product Design for Venting
690
10.17.2 Venting Characteristics of Thermoplastic Polymers
692
10.17.3 Mold Deposit Problems
692
10.17.4 How to Avoid Venting Problems
693
10.17.5 Planning Mold Venting
694
10.17.6 Mold Venting Process Problems
695
10.17.7 Mold Venting Design
697
10.17.8 Mold Venting Using Sintered Porous Insert Plugs
713
10.17.9 Logic Seal (Negative Coolant Pressure) Mold Venting
714
10.17.10 Mold Cavity Vacuum Venting System
716
10.18 Mold Cavity Insert Contact Area Strength
721
10.18.1 Cavity Insert Sidewall Strength
722
10.18.2 Methods to Calculate the Strength of Cavity Insert Sidewall
723
10.19 Mold Layout Case Studies
727
10.20 Mold Support Pillars
728
10.21 Tolerances for Thermoplastic Molded Parts
728
10.21.1 Factors Affecting Dimensional Control Tolerances
730
10.22 General Specifications for Mold Construction for Thermoplastic Injection Molding Resins
732
10.22.1 Mold Design Requirements
732
10.22.2 Mold Drawing Standards
732
10.22.3 Required Types of Tool Steels for Mold Construction
734
10.22.4 Mold Construction Requirements
736
10.23 Mold Tryout – Debug – Approvals – “MQ1” Requirements
743
10.23.1 Mold Tryout or Evaluation
743
10.23.2 Mold Debug Procedures
743
10.23.3 Approval of Molded Parts and Pre-Production Molding Process
743
10.23.4 Mold Cavity and Core Surface Temperatures
743
10.23.5 “MQ1” Requirements
744
11 Performance Testing of Thermoplastics
746
11.1 Property Data Sheet for Thermoplastics
747
11.2 Tensile Testing (ASTM D-638)
748
11.2.1 Tensile Testing Equipment
748
11.2.2 Tensile Test Specimen
749
11.2.3 Specimen Conditioning
749
11.2.4 Tensile Strength Test Procedures
749
11.2.5 Tensile Modulus and Elongation
750
11.2.6 Molecular Orientation Effects
751
11.2.7 Crosshead Speed Effects
752
11.2.8 Temperature Effects
752
11.2.9 Moisture Absorption Effects
752
11.2.10 Stress-Strain Effects Caused by Creep
753
11.3 Flexural Testing (ASTM D-790)
753
11.3.1 Apparatus
754
11.3.2 Test Procedures and Equations
755
11.3.3 Modulus of Elasticity
756
11.4 Compressive Strength Testing (ASTM D-695)
756
11.4.1 Compressive Testing Apparatus
757
11.4.2 Test Specimens and Conditioning
757
11.4.3 Test Procedures
757
11.4.4 Stress-Strain Tension and Compression Curves
758
11.5 Shear Strength Testing (ASTM D-732)
758
11.5.1 Test Specimen and Apparatus
758
11.5.2 Test Procedures
759
11.5.3 Significance and Limitations
759
11.6 Surface Hardness Testing
759
11.6.1 Rockwell Hardness Testing (ASTM D-785-60T)
760
11.6.2 Barcol Hardness Testing (ASTM D-2583)
762
11.6.3 Factors Affecting the Test Results
763
11.7 Abrasion Resistance Testing (ASTM D-1044)
763
11.7.1 Taber Abrasion Testing
764
11.7.2 Theoretical Analysis of Wear
764
11.8 Coefficient of Friction (ASTM D-1894)
765
11.8.1 Coefficient of Friction of Thermoplastic Materials
766
11.8.3 Effects of Lubricants
767
11.9 Mold Shrinkage Test (ASTM D-955)
767
11.9.1 Purpose of the Mold Shrinkage Test
767
11.9.2 Factors Affecting Mold Shrinkage
768
11.9.3 Injection Molding Effects on Shrinkage
768
11.9.4 Requirements for Sampling
768
11.9.5 Test Procedures
769
11.10 Specific Gravity Testing (ASTM D-792)
771
11.10.1 Test Procedures
772
11.11 Density Gradient Testing (ASTM D-1505)
773
11.12 Water Absorption Testing (ASTM D-570)
773
11.12.1 Test Specimen
774
11.12.2 Test Procedure
774
11.13 Impact Resistance Testing
774
11.13.1 Pendulum Impact Tests
776
11.13.2 Charpy Impact Testing (ASTM D-256)
778
11.13.3 Chip Impact Testing
778
11.13.4 Tensile Impact Testing (ASTM D-1822)
778
11.13.5 Drop Weight Impact Testing (ASTM D-3029)
779
11.13.6 Falling Weight Impact Testing
780
11.13.7 Instrumented Impact Testing
781
11.14 Creep, Rupture, Relaxation, and Fatigue
784
11.14.1 Tensile Creep Testing
784
11.14.2 Flexural Creep Testing
785
11.14.3 Procedure for Applying Creep Modulus
787
11.15 Melting Point Test (ASTM D-795)
790
11.16 Vicat Softening Point (ASTM D-1525)
790
11.16.1 Melting Point, Glass Transition Temperature
791
11.17 Brittleness Temperature (ASTM D-746)
791
11.17.1 Test Apparatus and Procedures
791
11.18 UL – Temperature Index
793
11.18.1 Relative Thermal Indices
793
11.18.2 Long Term Thermal Aging Index
795
11.18.3 Creep Modulus/Creep Rupture Tests
796
11.19 Heat Deflection Temperature (ASTM D-648)
797
11.19.1 Apparatus and Test Specimens
797
11.19.2 Test Procedure
798
11.19.3 Test Variables and Limitations
798
11.20 Soldering Heat Resistance
798
11.21 Coefficient of Linear Thermal Expansion Testing
799
11.21.1 Test Procedure
800
11.22 Thermal Conductivity Testing (ASTM C-177)
800
11.23 Melt Flow Testing
802
11.23.1 Moisture Content
803
11.24 Melt Index Testing (ASTM D-1238)
803
11.24.1 Melt Flow Rate
804
11.25 Capillary Rheometer Melt Viscosity Testing (ASTM D-1703)
805
11.25.1 Melt Viscosity vs. Shear Rate Curves
806
11.26 Electrical Properties Testing
807
11.26.1 Underwriter’s Laboratories (UL) Yellow Cards
808
11.26.2 How to Read and Interpret the “UL Yellow Card”
809
11.26.3 “UL Insulation Systems Recognition”
814
11.27 Electrical Insulation Properties
815
11.28 Electrical Resistance Properties
815
11.28.1 Volume Resistivity Testing (ASTM D-257)
816
11.28.2 Surface Resistivity Testing (ASTM D-257)
817
11.28.3 Dielectric Strength Testing (ASTM D-149)
818
11.28.4 Dielectric Constant Testing (ASTM D-150)
820
11.28.5 Dissipation Factor Testing (ASTM D-150)
823
11.28.6 Arc Resistance Testing (ASTM D-495)
824
11.28.7 High Voltage Arc Tracking Rate (UL-746 A)
826
11.28.8 Comparative Track Index Testing (ASTM D-3638/UL 746 A).
827
11.29 Self and Flash Ignition Temperature Testing (ASTM D-1929)
828
11.29.1 Test Description
828
11.29.2 High Current Arc Ignition Testing (UL 746A)
829
11.29.3 Hot Wire Coil Ignition Testing (UL 746A/ASTM D-3874)
830
11.29.4 Hot Mandrel Testing
830
11.29.5 Glow Wire Testing
830
11.30 Flammability Characteristics of Polymers
832
11.30.1 Inherently Flame Retardant Polymers
833
11.30.2 Less Flame Retardant Polymers
833
11.30.3 Flammable Polymers
833
11.31 UL 94 Flammability Testing
834
11.31.1 Horizontal Burning Testing, UL 94HB
834
11.31.2 Vertical Burning Testing, UL 94-V0, UL 94-V1, UL 94-V2
835
11.31.3 Vertical Burning Testing, UL 94-5V, UL 94-5VA, UL 94-5VB
836
11.31.4 Factors Affecting UL 94 Flammability Testing
838
11.32 Limited Oxygen Index Testing (ASTM D-2863)
838
11.32.1 Test Procedures
839
11.32.2 Factors Affecting the Test Results
839
11.33 Smoke Generation Testing
840
11.33.1 Smoke Density Testing (ASTM D-2843)
840
11.34 Weathering Tests for Thermoplastic Materials
841
11.34.1 Weathering Creep Factors (Degradation)
841
11.34.2 Ultraviolet (UV) Radiation
842
11.34.3 Temperature
842
11.34.4 Moisture
843
11.34.5 Oxidation
22
11.34.6 Micro-Organisms
843
11.35 Accelerated Weathering Testing (ASTM G 23)
844
11.35.1 Exposure to Fluorescent UV Lamp, Condensation (ASTM G 53)
844
11.35.2 Accelerated Weather Testing, Weather-Ometer®
845
11.35.3 Exposure to Carbon Arc Light and Water Testing (ASTM D-1499)
846
11.35.4 Exposure to Xenon Arc Light and Water Testing (ASTM D-2565)
848
11.35.5 Outdoor Weathering Testing of Thermoplastics (ASTM D-1435)
850
11.36 Fungi Resistance Testing of Thermoplastics (ASTM G 21)
851
11.37 Bacteria Resistance Testing of Thermoplastics (ASTM G 22)
852
11.38 Fungi and Bacteria Outdoor Exposure Resistance Limitations
852
12 Thermoplastic Product Cost Analysis
854
12.1 Injection Molding Process
855
12.2 Molding Cycle Time
855
12.3 Material Handling (Regrinds)
856
12.4 Capital Equipment
856
12.5 Injection Molding Machine Size
856
12.6 Injection Molding Machine Cost
859
12.7 Machine Installation and Safety Considerations
860
12.8 Auxiliary Equipment and Automation
860
12.9 Mold Cost
861
12.10 Molded Products Cost Analysis
864
12.10.1 Cost Analysis Basic Method
864
12.10.2 Cost Analysis Graph Method
865
12.10.3 Advanced Cost Analysis Method
866
12.11 Secondary Molding Operations
871
12.12 Additional Manufacturing Costs
871
Appendix
872
Acronyms for Polymeric Materials
872
Common Acronyms
873
Process Acronyms
874
Reinforcement and Filler Acronyms
874
Nomenclature
875
English and Metric Units Conversion Guide
876
Subject Index
878
About the Author
892
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