Injection Mold Design Handbook

Name: Injection Mold Design Handbook
Brand: Hanser Publications
Price: 279.99 EUR
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Bruce Catoen Herbert Rees(Author)

Hanser Publications (Publisher)

1st Edition

Published on 11. October 2021

820 pages

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978-1-56990-816-7 (ISBN)

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Content

Intro
Preface
Acknowledgments
The Author
Contents
1 Introduction
1.1 Benefits of Injection Molding
1.2 The Injection Mold
1.2.1 The Role of the Injection Mold
1.3 What Is an Injection Mold?
1.3.1 Elements of an Injection Mold
1.4 Classification of Molds
1.5 Continued Innovation in Molds and Hot Runners
1.6 The Injection Molding Machine
2 Overview of Plastics for Mold Design
2.1 What Is Plastic?
2.2 Plastics Terminology
2.3 Polymer Orientation
2.3.1 Shrinkage
2.3.2 Multiple Shrinkages
2.4 Additives
2.5 Mechanical Properties of Plastics
2.6 How Molten Plastics Behave
2.6.1 How Plastics Flow
2.6.2 Plastic Flow in Runners and Cavities
2.7 Degradation
2.8 Selection and Requirements for Plastic Materials
3 Plastic Part Design for Mold Designers
3.1 Plastic Part Drawing
3.2 Product Shape: How Can the Product Best Be Molded?
3.3 Parting Line (P/L)
3.4 Uniform Wall Thickness
3.5 L/t Ratio (Length of Flow Divided by Wall Thickness)
3.6 Drafts
3.7 Corners, Fillets, and Chamfers
3.8 Ribs and Bosses
3.9 Rim Designs
3.10 Stripped Undercuts
3.11 Sidewall Windows in the Part
3.12 Gate Location and Number of Gates
3.12.1 CAE Filling Analysis for Gate Location Optimization
3.12.2 Two or More Gates per Cavity - Large Products
3.12.3 Gate Dimple
3.12.4 Recessed Gate
3.12.5 Deep Undercuts and Mold Design Complexity
3.13 Re-Design of the Product to Avoid the Need for Side Cores
3.13.1 Selecting Other than the Conventional Parting Line
3.14 Shape of Threads and Undercuts
3.15 Need for Multi-Stage Ejection
3.16 Post-Molding Operations versus Mold Complexity
3.17 Plastic Part Tolerances and Effect on Mold Design
3.17.1 General and Specific Plastic Part Tolerances
3.17.2 Are Special Fits with Matching Products Required?
3.17.3 Tolerances for the Filling Volume
3.18 Stacking of Products and Free Dispensing
3.19 Deliberate Mismatches for Easy Mold Design
3.19.1 Mismatch at the Parting Line
3.19.2 Mismatch between Two Matching Pieces, such as Box and Lid
3.20 Surface Finish
3.20.1 Finish of Molding Surfaces
3.20.2 Texturing of Surfaces
3.21 Fitting Surfaces of Mold Parts
3.22 Engravings
3.22.1 Engravings versus Applied Labels
3.22.2 Two-Color and Two-Material Engraving
3.22.3 Depth of Engravings
3.22.4 Font Style and Size of Artwork
3.22.5 Polarity of Engraving
3.22.6 Are the Locations Selected for Engraving Practical?
3.22.7 Engravings in the Walls and Bottoms of Products
3.23 General Appearance of the Product
3.23.1 Flatness
3.23.2 Sinks and Voids
3.23.3 Witness Lines
3.23.4 Weld Lines
3.23.5 Surface Defects (Flow Marks, Splay, Record Grooves, Haze, Jetting, Hooks, and Ripples)
3.24 Identification of the Molded Piece
3.25 Product Strength Requirements
3.25.1 The Role of Gate Location in Increasing Product Strength
3.26 Special Features
3.26.1 Holes and Counter-Bores for Assembly Screws or Rivets
3.26.2 Hinges and Snaps
4 Specifying the Right Machine for the Mold
4.1 Required Clamp Size (Tonnage)
4.2 Required Opening Stroke and Shut-Height
4.3 Platen Mounting Pattern and Ejector Positions
4.4 Locating Ring Size and Machine Nozzle Size
4.5 Extruder Sizing and Specification
4.5.1 Extruder Shot Size Calculation
4.5.2 Requirements for Machine Plasticizing Capacity
4.5.3 Screw Selection
4.6 Machine Nozzle Selection
4.6.1 Open Nozzles
4.6.2 Shut-off Nozzles
4.7 Injection Unit Selection
4.7.1 Reciprocating Screw versus Two-Stage Injection Units
4.7.2 Injection Speed and Pressure Requirements
5 Factors Affecting the Design of an Injection Mold
5.1 Total Equipment Productivity (TEP) Objectives
5.2 Cycle Time
5.3 Projected Annual Requirements
5.4 Purpose of the Mold
5.4.1 Prototype Mold
5.4.2 Experimental Mold
5.4.3 Combination of Prototype and Experimental Mold
5.4.4 Production Mold
5.4.5 New Products
5.4.6 Existing Product, Large Quantities
5.4.7 Limited Quantities, Limited Product Lifecycle
5.4.8 Short Runs, Small Production Requirements
5.5 The Injection Molding Machine
5.6 The Plant Environment
5.6.1 Condition of Ambient (Shop) Air
5.7 Coolant Supply
5.7.1 Is the Cooling Water Clean?
5.7.2 Chiller Sizing Guidelines
5.8 Power Supply
6 Cycle Time Estimation
6.1 Factors Impacting Cycle Time
6.1.1 Type of Plastic
6.1.2 Wall Thickness of Product
6.1.3 Mold Materials
6.1.4 Efficiency of Cooling
6.1.5 Venting
6.1.6 Ejection
6.1.7 Molding Machine
6.1.8 Impact of Cold Runners versus Hot Runners on Cycle Time
6.2 Estimating Cycle Time
7 Product Cost Estimation
7.1 Machine Hour Cost per Unit Molded
7.2 Mold Cost per Unit Molded
7.3 Labor Costs
7.4 Estimating Product Cost
8 Mold Layout, Drawings, and Inspection
8.1 Steps to Designing the Mold
8.2 Information and Documentation
8.2.1 Machine Specifications
8.2.2 Productivity Features
8.2.3 Additional Requirements
8.3 Determining the Mold Cavitation
8.3.1 Minimum Number of Cavities
8.3.2 Preferred (Practical) Number of Cavities
8.4 Assembly and Detail Drawings
8.4.1 Drawings and Views
8.4.2 Arrangement of Views
8.4.3 Notes on Drawings
8.4.4 Additional Information on the Drawings
8.5 Mold Layout and Assembly Drawings
8.5.1 Machine Platen Layout
8.5.2 Symmetry of Layout, Balancing of Clamp
8.5.3 The Views
8.5.4 Completing the Assembly Drawing
8.5.5 Bill of Materials (BOM) and "Ballooning"
8.5.6 Finishing Touches
8.6 Inspection Features on Drawings
8.6.1 Rollers or Roller Balls
8.6.2 How to Inspect Tapers
8.7 Chamfers and Radii
8.7.1 General Information
8.7.2 Specifying Chamfers
8.7.3 Radii in Corners
9 Mold Shoe Design
9.1 Mold Plates
9.2 Mold Hardware
9.3 Location of Fittings, Hoses, and Cables
9.4 Forces Affecting Mold Shoes
9.4.1 Deflection of Mold Plates
9.4.2 Calculation of Plate Deflection and Stress
9.5 Selection of Materials for Mold Plates
9.6 Guiding of Moving Plates
9.6.1 Gibs
9.7 Mounting Holes and Clamp Slots
9.8 Locating Rings
9.9 Mold Handling - Lift Holes, Lift Bars, and Latches
9.9.1 Lift Bars
9.9.2 Latches
9.10 Mold Identification Nameplates
10 Cavity and Core Design Overview
10.1 Mold Cavity Space
10.2 Plastic versus Steel Part Drawing
10.3 The Preliminary Stack Layout
10.3.1 Where Should the Parting Line Be Located?
10.3.2 Will the Product Pull out of the Cavity and Stay on the Core?
10.3.3 Will the Product Eject Easily from the Core?
10.3.4 Is the Cavity Balanced?
10.4 Determining the Method of Cavity Construction
10.4.1 Cavity and/or Core Are Cut Right into the Mold Plate
10.4.2 Individual Cavities and Cores
10.5 Stack Sizing and Total Area of the Stack
10.6 Forces on the Cores and Cavities
10.6.1 Checking for Sufficient Steel Shut-off Area in Stack
10.6.2 Checking for Stack Compression due to Clamp Tonnage
10.6.3 Checking for Acceptable Hoop Stress in the Cavity
10.7 Core and Cavity Material Selection
10.8 Determining the Stack Construction
10.9 Venting
10.9.1 Parting Line (P/L) Venting
10.9.2 Vent Grooves and Channels
10.9.3 Vent Pins
10.9.4 Venting of Ribs
10.9.5 Venting the Bottom of a Cavity
10.9.6 Core Cap and Core Sidewall Venting
11 Ejection
11.1 Manual or Semi-Automatic Ejection
11.2 Automatic Ejection
11.3 Basic Requirements for Ejection
11.3.1 Machine Opening Stroke for Ejection
11.3.2 Venting for Ease of Ejection
11.3.3 Surface Finish Forces on Ejection
11.4 Force Required for Ejection
11.5 Where to Eject the Product
11.5.1 Ejection of Deep Cup-Shaped Parts
11.5.2 Ejection of Parts with Deep Ribs
11.5.3 Ejection of Bosses
11.5.4 Ejection of Shallow Parts
11.5.5 Ejection of Rim Shapes
11.5.6 Ejection of Cold Runners
11.6 Ejector Pins, Blade Ejectors, and Sleeves
11.6.1 Ejector Pin Clearance (Fit) and Length of Land
11.6.2 Blade Ejectors
11.6.3 Number, Size, and Location of Ejector Pins
11.6.4 Finish of Ejector Pins and Bores
11.6.5 Preventing Ejector Pins from Turning
11.7 Ejector and Ejector Retainer Plates
11.7.1 Ejection Forces
11.7.2 Injection Forces
11.7.3 Number and Location of Machine Ejectors to Be Used
11.7.4 Calculation of Ejector Plate Deflection
11.7.5 Ejector Pin Retainer Plate
11.7.6 Ejector Return Pins
11.7.7 Ejector Box
11.7.8 Returning the Ejector Plate
11.8 Stripper Ejection
11.8.1 General Rules for Stripper Ejection
11.8.2 Guiding the Stripper Plate
11.8.3 Stripper Rings
11.8.4 Stripper Bars
11.8.5 Stripper Ring Ejection of Lids
11.8.6 Stripping from the Injection (Cavity) Side
11.9 Air Ejection
11.9.1 Requirements and Timing for Air Ejection
11.9.2 Poppet Air Ejection
11.9.3 Core Air
11.9.4 Blow-off Jets
11.9.5 Blow-down Jets
11.9.6 Air Ejection from the Cavity Side
11.10 Ejection of Significant Undercuts
11.10.1 Cam Ejection (Internal and External) Using Neck Rings
11.10.2 Core Pull Ejection
11.10.3 Collapsible Cores
11.10.4 Lifter Ejection
11.10.5 Sliders
11.10.6 Unscrewing Ejection
11.10.7 Cam and Harmonic Linkage Ejection
11.11 Multiple Ejection Strokes
11.12 Multi-Stage Ejection
11.12.1 Why and When to Use Multi-Stage Ejection
11.12.2 Typical Two-Stage Ejection Actuations
11.12.3 Moving-Cavity Ejection Assist
12 Mold Cooling
12.1 Injection and Mold Temperatures for Common Plastics
12.2 Coolant Requirements for a Mold
12.3 What Affects Mold Cooling Performance?
12.3.1 Temperature of the Cooling Medium
12.3.2 Achieving Steady-State Temperature in the Mold
12.4 Principles of Heat Transfer and Thermodynamics
12.4.1 Heat Transfer Basics
12.4.2 Melting and Cooling Behavior of Plastics
12.4.3 Conduction and Thermal Conductivity
12.4.4 Convective Heat Transfer
12.5 Calculation of Cooling Requirements for a Mold
12.5.1 Heat Input Required to Condition the Plastic for Injection
12.5.2 Cooling Required to Remove the Inputted Heat
12.5.3 Temperature of Cooling Water
12.5.4 Quantity of Cooling Water Required
12.5.5 Efficiency of Cooling on Required Water Flow
12.6 General Cooling Design Rules
12.7 Cooling Channels in Plates
12.7.1 Series and Parallel Plate Cooling
12.7.2 Distance of Waterlines from Holes and Surfaces
12.7.3 Plugging of Cooling Channels
12.7.4 Plugs and Baffles in Plates
12.7.5 Cooling of Hot Runner Plates
12.8 Layout of Cooling Channels in Inserts
12.8.1 Shrinkage of Plastic and Cooling Layout
12.8.2 Preventing Water Leakage in the Mold
12.8.3 Cooling Channel Distances in Inserts
12.8.4 Distance to Pipe Threads and Fittings
12.8.5 Cooling Channels Split between Inserts
12.8.6 Design of Insert Cooling for Flat Products
12.8.7 Cooling Design for Cup-Shaped Products
12.8.8 Use of CAE Molding Simulation for Cooling Design and Warpage Analysis
12.9 Supplying Water to the Mold
12.10 Thermal Expansion
13 Mold and Stack Alignment
13.1 Leader Pin and Bushing Alignment
13.2 Taper or Straight Interlock Alignment between Plates
13.3 Taper Lock between Each Cavity and Core
13.3.1 Backing up a Taper
13.3.2 Core Lock and Cavity Lock Alignment
13.4 Preloads
13.4.1 Restoring Preload by Grinding of the Tapers
13.4.2 Preload Stresses
13.4.3 Mounting of Stacks to Mold Plates
13.5 Over-Constrained Alignment
14 Melt Distribution and Gate Design
14.1 Cold Runners
14.1.1 Cold Runner, Single-Cavity Molds
14.1.2 Cold Runner, Two-Plate Molds
14.1.3 Cold Runner, Three-Plate Molds
14.1.4 Cold Runner Gate Types and Configurations
14.1.5 Layout and Balancing of Cold Runner Melt Channels
14.1.6 Cold Runner Ejection
14.2 Insulated Runners
14.3 Hot Runners
14.3.1 Considerations for Specifying a Hot Runner
14.3.2 Overview of Hot Runner Design
14.3.3 Layout and Balancing of Hot Runner Melt Channels
14.3.4 Melt Channel Sizing
14.3.5 The Hot Runner Manifold
14.3.6 Heating of the Hot Runner
14.3.7 Hot Runner Nozzles
14.3.8 Nozzle Tips and Gating in Hot Runners
14.3.9 Hot Runner Temperature Controls
14.3.10 Hot Runner Gate Location
14.3.11 Hot Runner Gate Sizing
14.3.12 Gate Inserts (Gate Pads)
14.4 Hot and Cold Runner Molds in Combination
14.5 Selection of Hot Runner or Cold Runner System
15 Selection of Mold Materials
15.1 Forces on the Mold Affect Material Choices
15.1.1 Characteristics of Steels and Other Mold Materials
15.2 Steel Properties
15.2.1 Types of Steels
15.3 Quality of Materials
15.4 Manufacturing Considerations for Choosing Materials
15.4.1 EDM
15.4.2 Welding
15.5 Heat Treatment
15.6 Overview of Surface Treatments
15.7 Hardness of Mating Parts
16 Fasteners
16.1 How Screws Work
16.2 Rolled versus Cut Threads
16.3 Holding Action and Preload of Screws
16.4 Influence of Temperature on Screws
16.5 Effect of Cyclical Loads on Screws
16.6 Screw Standards and Properties
16.7 Length of Thread Engagement
16.8 Additional Recommendations Regarding Screws
16.8.1 Always Use Standard Available Screw Sizes and Lengths
16.8.2 Increase the Depth of the Counter-Bore
16.9 Use of Set Screws
16.10 Holding Screws in Place (if Needed)
16.10.1 Lock Washers
16.10.2 Screw-Securing Compounds
16.10.3 Screws Secured by Plastic Inserts (NylokT, etc.)
17 Dimensioning and Tolerancing
17.1 Conventional versus Geometric Tolerancing
17.2 Limitations of Conventional Dimensions and Tolerances
17.2.1 Origins of Measurement
17.2.2 Non-Repeatable Sizes and Centers
17.2.3 Orientation and Angles
17.2.4 Tolerance Accumulation
17.3 Geometric Dimensioning and Tolerancing
17.3.1 Three Core Steps for Applying or Inspecting GD&T
17.3.2 Geometric Tolerancing Benefits versus Conventional Tolerancing
17.4 Implementation of Geometric Tolerancing
17.4.1 Implementation of GD&T-Lite (not Recommended)
17.4.2 Implementation of GD&T Integration
17.4.3 Implementation of Model-Based Definition
17.5 Considerations for Tolerancing
17.5.1 CAD Modelling Practices
17.5.2 Materials, Manufacturing, and Inspection
17.5.3 Thermal Expansion and Tolerancing
17.6 Application of GD&T to Mold Components
17.6.1 GD&T Applied to an Injection Mold Core
17.6.2 GD&T Applied to an Injection Mold Lock Ring
17.6.3 GD&T Applied to an Injection Mold Core Plate
17.6.4 GD&T and Mold Engineering
18 Mold Design References
18.1 Plastic Housing (Using Shut-offs)
18.2 Facemask
18.3 Plastic Cutlery
18.4 Vial
18.5 Open-Ended Floss Spool Tube
18.6 Overcap Lid (Using Stripper Ring Ejection)
18.7 Plug Lid
18.8 Urine Tub Cap (Using Stripper Ring Ejection)
18.9 Deli or Yellow Fats Container (Using Air Ejection and with Cavity Lock Alignment)
18.10 Stadium Cup (Using Core Lock Alignment)
18.11 Polystyrene Tumbler (Using Stripper Ring Ejection)
18.12 False-Bottom Cup (Using Moving Cavity and Air Ejection)
18.13 Round Closure (Using Stripper Ring (Bump-off) Ejection)
18.14 Paint Pail with Handle Inserts
18.15 Rectangular Container with Tamper-Evident Skirt
18.16 Power Tool Housing
18.17 Rear Hatch Door
18.18 Crinkle Bag
18.19 Preform (Using Neck Ring Ejection)
18.20 Living Hinge Cap
18.21 Rectangular Box with Undercuts (Using Split-Cavity Mold)
18.22 Detergent Cap (Using Unscrewing Ejection)
18.23 Folding Crate
18.24 Automotive Panel Cover
18.25 Pallet
18.26 Automotive Covers
18.27 Double-Walled Threaded Cap (Using Collapsible-Core Mold)
18.28 Automotive Cover
18.29 Externally Threaded Cap Mold
18.30 Oxygen Mask (with Side Core Retraction)
18.31 Living-Hinge Case
18.32 Iron Housing (Using Split-Cavity Mold)
18.33 Oral Care Product (Using Split-Cavity Mold)
18.34 Actuator (Using Split Cavity with Multi-Stage Ejection)
19 Mold Testing, Approval, and Troubleshooting
19.1 Information to Be Supplied to the Mold Tester
19.2 Dry-Cycle Testing before Injecting Plastic
19.2.1 Bluing to Ensure Proper Shut-off, Venting, and Taper Fit
19.2.2 Procedure for Aligning Mold Halves in the Injection Molding Machine
19.2.3 Lead Test Procedure to Check Wall Thicknesses and Alignment
19.3 Initial Mold Start-up and First Shots
19.3.1 Mold Start-up Procedure
19.4 Changing Materials or Colors
19.4.1 General Color Change Procedure
19.5 Mold Test Information and Data to Be Collected
19.5.1 Core Shift Mapping
19.6 APQP and PPAP
19.7 Mold Test Troubleshooting Guide
20 Appendix
Appendix 1: Mold Material Properties
Appendix 2: Frequently Used Conversion Factors
Appendix 3: Plastics and their Abbreviations
Appendix 4: Mold Design Review Checklist
Appendix 5: Contents of a Mold Manual
Appendix 6: Mold Setup Guide Template
Appendix 7: Order Confirmation Template
Appendix 8: General Properties of Plastics
Appendix 9: Thermal Properties of Plastics
Appendix 10: Mechanical Properties of Plastics
Appendix 11: Thermal and Processing Properties of Plastics
Appendix 12: Mold Preventative Maintenance Checklist
Appendix 13: Surface Finishes
Index

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Injection Mold Design Handbook

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