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Contents
Preface
Nomenclature
1 Introduction
1.1 Overview of the Injection Molding Process
1.2 Mold Functions
1.3 Mold Structures
1.3.1 External View of Mold
1.3.2 View of Mold during Part Ejection
1.3.3 Mold Section and Function
1.4 Other Common Mold Types
1.4.1 Three Plate,Multi-Cavity Family Mold
1.4.2 Hot Runner,Multi-Gated, Single Cavity Mold
1.4.3 Comparison
1.5 The Mold Development Process
1.6 Chapter Review
2 Plastic Part Design
2.1 The Product Development Process
2.1.1 Product Definition
2.1.2 Product Design
2.1.3 Business and Production Development
2.1.4 Scale-Up and Launch
2.1.5 Role of Mold Design
2.2 Design Requirements
2.2.1 Application Engineering Information
2.2.2 Production Data
2.2.3 End Use Requirements
2.2.4 Product Design Methodology
2.2.5 Plastic Material Properties
2.3 Design for Injection Molding
2.3.1 UniformWall Thickness
2.3.2 Rib Design
2.3.3 Boss Design
2.3.4 Corner Design
2.3.5 Surface Finish and Textures
2.3.6 Draft
2.3.7 Undercuts
2.4 Chapter Review
VIII Contents
3 Mold Cost Estimation
3.1 The Mold Quoting Process
3.2 Cost Drivers for Molded Parts
3.2.1 Effect of Production Quantity
3.2.2 Break-Even Analysis
3.3 Mold Cost Estimation
3.3.1 Cavity Cost Estimation
3.3.1.1 Cavity Set Cost
3.3.1.2 Cavity Materials Cost
3.3.1.3 Cavity Machining Cost
3.3.1.4 Cavity Discount Factor
3.3.1.5 Cavity Finishing Cost
3.3.2 Mold Base Cost Estimation
3.3.3 Mold Customization
3.4 Part Cost Estimation
3.4.1 Mold Cost per Part
3.4.2 Material Cost per Part
3.4.3 Processing Cost per Part
3.4.4 Defect Cost per Part
3.5 Chapter Review
4 Mold Layout Design
4.1 Parting Plane Design
4.1.1 Determine Mold Opening Direction
4.1.2 Determine Parting Line
4.1.3 Parting Plane
4.1.4 Shut-Offs
4.2 Cavity and Core Insert Creation
4.2.1 Height Dimension
4.2.2 Length andWidth Dimensions
4.2.3 Adjustments
4.3 Mold Base Selection
4.3.1 Cavity Layouts
4.3.2 Mold Base Sizing
4.3.3 Molding Machine Compatibility
4.3.4 Mold Base Suppliers
4.4 Mold Material Selection
4.4.1 Strength vs. Heat Transfer
4.4.2 Hardness vs.Machinability
4.4.3 Mold-Maker’s Cost vs.Molder’s Cost
4.4.4 Material Summary
4.5 Chapter Review
Contents IX
5 Cavity Filling Analysis and Design
5.1 Overview
5.2 Objectives in Cavity Filling
5.2.1 Complete Filling of Mold Cavities
5.2.2 Avoid Uneven Filling or Over-Packing
5.2.3 Control the Melt Flow
5.3 Viscous Flow
5.3.1 Shear Stress, Shear Rate, and Viscosity
5.3.2 Pressure Drop
5.3.3 Rheological Behavior
5.3.4 Newtonian Model
5.3.5 Power Law Model
5.4 Validation
5.5 Cavity Filling Analyses and Designs
5.5.1 Estimating the Processing Conditions
5.5.2 Estimating the Filling Pressure and MinimumWall Thickness
5.5.3 Estimating Clamp Tonnage
5.5.4 Predicting Filling Patterns
5.5.5 Designing Flow Leaders
5.6 Chapter Review
6 Feed System Design
6.1 Overview
6.2 Objectives in Feed System Design
6.2.1 Conveying the Polymer Melt from Machine to Cavities
6.2.2 Impose Minimal Pressure Drop
6.2.3 Consume Minimal Material
6.2.4 Control Flow Rates
6.3 Feed SystemTypes
6.3.1 Two-Plate Mold
6.3.2 Three-Plate Mold
6.3.3 Hot Runner Molds
6.4 Feed System Analysis
6.4.1 Determine Type of Feed System
6.4.2 Determine Feed System Layout
6.4.3 Estimate Pressure Drops
6.4.4 Calculate Runner Volume
6.4.5 Optimize Runner Diameters
6.4.6 Balance Flow Rates
6.4.7 Estimate Runner Cooling Times
6.4.8 Estimate Residence Time
6.5 Practical Issues
6.5.1 Runner Cross-Sections
6.5.2 Sucker Pins
X Contents
6.5.3 Runner Shut-Offs
6.5.4 Standard Runner Sizes
6.5.5 Steel Safe Designs
6.6 Chapter Review
7 Gating Design
7.1 Objectives of Gating Design
7.1.1 Connecting the Runner to the Mold Cavity
7.1.2 Provide Automatic De-Gating
7.1.3 Provide Aesthetic De-Gating
7.1.4 Avoid Excessive Shear or Pressure Drop
7.1.5 Control Pack Times
7.2 Common Gate Designs
7.2.1 Sprue Gate
7.2.2 Pin-Point Gate
7.2.3 Edge Gate
7.2.4 Tab Gate
7.2.5 Fan Gate
7.2.6 Flash/Diaphragm Gate
7.2.7 Tunnel/Submarine Gate
7.2.8 Thermal Gate
7.2.9 Valve Gate
7.3 The GatingDesign Process
7.3.1 Determine Type of Gate
7.3.2 Calculate Shear Rates
7.3.3 Calculate Pressure Drop
7.3.4 Calculate Gate Freeze Time
7.3.5 Adjust Dimensions
7.4 Chapter Review
8 Venting
8.1 Venting Design Objectives
8.1.1 Release Compressed Air
8.1.2 Contain Plastic Melt
8.1.3 Minimize Maintenance
8.2 Venting Analysis
8.2.1 Estimate Air Displacement and Rate
8.2.2 Identify Number and Location of Vents
8.2.3 Specify Vent Dimensions
8.3 Venting Designs
8.3.1 Vents on Parting Plane
8.3.2 Vents around Ejector Pins
8.3.3 Vents in Dead Pockets
8.4 Chapter Review
XI
9 Cooling System Design
9.1 Objectives in Cooling System Design
9.1.1 Maximize Heat Transfer Rates
9.1.2 Maintain UniformWall Temperature
9.1.3 Minimize Mold Cost
9.1.4 Minimize Volume and Complexity
9.1.5 Minimize Stress and Corrosion
9.1.6 Facilitate Mold Usage
9.2 The Cooling System Design Process
9.2.1 Calculate the Required Cooling Time
9.2.2 Evaluate Required Heat Transfer Rat |
9.2.3 Assess Coolant Flow Rate
9.2.4 Assess Cooling Line Diameter
9.2.5 Select Cooling Line Depth
9.2.6 Select Cooling Line Pitch
9.2.7 Cooling Line Routing
9.3 Cooling System Designs
9.3.1 Cooling Line Networks
9.3.2 Cooling Inserts
9.3.3 Conformal Cooling
9.3.4 Highly Conductive Inserts
9.3.5 Cooling of Slender Cores
9.3.5.1 Cooling Insert
9.3.5.2 Baffles
9.3.5.3 Bubblers
9.3.5.4 Heat Pipes
9.3.5.5 Conductive Pin
9.3.5.6 Interlocking Core with Air Channel
9.3.6 One-Sided Heat Flow
9.4 Chapter Review
10 Shrinkage andWarpage
10.1 The Shrinkage Analysis Process
10.1.1 Estimate Process Conditions
10.1.2 Model Compressibility Behavior
10.1.3 Assess Volumetric Shrinkage
10.1.4 Evaluate Isotropic Linear Shrinkage
10.1.5 Evaluate Anisotropic Shrinkage
10.1.6 Assess Shrinkage Range
10.1.7 Establishing Final Shrinkage Recommendations
10.2 Shrinkage Analysis and Validation
10.2.1 Numerical Simulation
10.2.2 “Steel Safe”Mold Design
10.2.3 Processing Dependence
Contents
XII
10.2.4 Semi-Crystalline Plastics
10.2.5 Effect of Fillers
10.3 Warpage
10.3.1 Sources of Warpage
10.3.2 Warpage Avoidance Strategies
10.4 Chapter Review
11 Ejection System Design
11.1 Objectives in Ejection System Design
11.1.1 Allow Mold to Open
11.1.2 Transmit Ejection Forces to Moldings
11.1.3 Minimize Distortion of Moldings
11.1.4 Actuate Quickly and Reliably
11.1.5 Minimize Cooling Interference
11.1.6 Minimize Impact on Part Surfaces
11.1.7 Minimize Complexity and Cost
11.2 The Ejector System Design Process
11.2.1 Identify Mold Parting Surfaces
11.2.2 Estimate Ejection Forces
11.2.3 Determine Ejector Push Area and Perimeter
11.2.4 Specify Type, Number, and Size of Ejectors
11.2.5 Layout Ejectors
11.2.6 Detail Ejectors and Related Components
11.3 Ejector System Analyses and Designs
11.3.1 Ejector Pins
11.3.2 Ejector Blades
11.3.3 Ejector Sleeves
11.3.4 Stripper Plates
11.3.5 Elastic Deformation around Undercuts
11.3.6 Core Pulls
11.3.7 Slides
11.3.8 Early Ejector Return Systems
11.3.9 Advanced Ejection Systems
11.4 Chapter Review
12 Structural System Design
12.1 Objectives in Structural System Design
12.1.1 Minimize Stress
12.1.2 Minimize Mold Deflection
12.1.3 Minimize Mold Size
12.2 Analysis and Design of Plates
12.2.1 Plate Compression
12.2.2 Plate Bending
12.2.3 Support Pillars
Contents
XIII
12.2.4 Shear Stress in SideWalls
12.2.5 Interlocks
12.2.6 Stress Concentrations
12.3 Analysis and Design of Cores
12.3.1 Axial Compression
12.3.2 Compressive Hoop Stresses
12.3.3 Core Deflection
12.4 Fasteners
12.4.1 Fits
12.4.2 Socket Head Cap Screws
12.4.3 Dowels
12.5 Review
13 Mold Technologies
13.1 Introduction
13.2 Coinjection Molds
13.2.1 Coinjection Process
13.2.2 Coinjection Mold Design
13.2.3 Gas Assist/Water Assist Molding
13.3 Insert Molds
13.3.1 Low Pressure Compression Molding
13.3.2 Insert Mold withWall Temperature Control
13.3.3 Lost Core Molding
13.4 Injection Blow Molds
13.4.1 Injection Blow Molding
13.4.2 Multilayer Injection Blow Molding
13.5 Multi-Shot Molds
13.5.1 Overmolding
13.5.2 Core-Back Molding
13.5.3 Multi-Station Mold
13.6 Feed Systems
13.6.1 Insulated Runner
13.6.2 Stack Molds
13.6.3 Branched Runners
13.6.4 Dynamic Melt Control
13.7 MoldWall Temperature Control
13.7.1 Pulsed Cooling
13.7.2 Conduction Heating
13.7.3 Induction Heating
13.7.4 Managed Heat Transfer
13.8 In-Mold Labeling
13.8.1 Statically Charged Film
13.8.2 Indexed Film
13.9 Ejection
Contents
XIV
13.9.1 Split Cavity Molds
13.9.2 Collapsible Cores
13.9.3 Rotating Cores
13.9.4 Reverse Ejection
13.10 Review
Appendix
Appendix A: Plastic Material Properties
Appendix B:Mold Material Properties
B.1 Non-Ferrous Metals
B.2 Common Mold Steels
B.3 Other Mold Steels
B.4 Notes
Appendix C: Properties of Coolants
Appendix D: Statistical Labor Data
D.1 United States Labor Rates
D.2 International Labor Rates
D.3 Trends in International Manufacturing Costs
Appendix E: Unit Conversions
E.1 Length Conversions
E.2 Mass/Force Conversions
E.3 Pressure Conversions
E.4 Flow Rate Conversions
E.5 Viscosity Conversions
E.6 Energy Conversions
Appendix F: Advanced Derivations
Bibliography
Subject Index | 
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