
Runner and Gating Design Handbook
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ISNI: 0000 0001 1452 7717
Content
- Intro
- Preface
- Acknowledgments
- Contents
- 1 Overview of Runners, Gates, and Gate Positioning
- 1.1 Primary Parting Plane Runners
- 1.2 Sub Runners
- 1.2.1 Cold Sub Runners
- 1.2.2 Hot Sub Runners
- 1.3 Hybrid Sub-Runner and Parting Line Runner
- 1.4 Gate Designs
- 2 Rheology and Melt Flow in a Mold of Plastics
- 2.1 Laminar vs. Turbulent Flow
- 2.2 Fountain Flow
- 2.3 Factors Affecting Viscosity
- 2.3.1 Common Viscosity Models
- 2.3.2 Non-Newtonian Fluids
- 2.3.3 Temperature
- 2.3.4 Pressure
- 2.4 Melt Compressibility
- 2.5 Melt Flow Characterization
- 2.5.1 Melt Flow Index
- 2.5.2 Capillary Rheometers
- 2.5.3 Nozzle Rheometers
- 2.6 Melt Flow in a Mold
- 2.6.1 Spiral Flow Molds
- 2.6.2 Injection Molding Simulation
- 2.6.3 Moldometer
- 3 Filling and Packing Effects on Material and Molded Part
- 3.1 Process Effects on Material Flow Characteristics
- 3.1.1 Melt Thermal Balance - Conductive Heat Loss vs. Shear Heating
- 3.1.2 Development of a Frozen Boundary Layer
- 3.2 Factors Affecting Plastic Material Degradation
- 3.2.1 Excessive Shear
- 3.2.2 Excessive Temperature
- 3.3 Effects of Mold Fill Rate on Fill Pressure
- 3.4 Post Filling or Packing Phase
- 3.4.1 Thermal Shrinkage as Plastic Cools
- 3.4.2 Compensation Flow to Offset Volumetric Shrinkage
- 3.4.3 Pressure Distribution During the Post Filling Phase
- 3.4.4 Gate Freeze-Off
- 3.5 Melt Flow Effects on Material and Molded Parts
- 3.5.1 Shrinkage
- 3.5.1.1 Volumetric Shrinkage
- 3.5.1.2 Orientation-Induced Shrinkage
- 3.5.2 Development of Residual Stresses and Warpage
- 3.5.2.1 Warpage and Residual Stress from Side-to-Side Shrinkage Variations
- 3.5.2.2 Warpage and Residual Stress from Global/Regional Shrinkage Variations
- 3.5.2.3 Warpage and Residual Stress from Orientation-Induced Shrinkage Variations
- 3.5.3 Physical Properties as Effected by Orientation
- 3.6 Annealing a Molded Part
- 3.7 Summary
- 4 Gate Positioning and Molding Strategies
- 4.1 Gate Positioning Considerations
- 4.2 Design and Process Strategies for Injection Molding
- 4.2.1 Maintain Uniform Wall Thicknesses in a Part
- 4.2.2 Use Common Design Guidelines for Injection Molded Plastic Parts with Caution
- 4.2.3 Avoid Flowing from Thin to Thick
- 4.2.4 Establish a Simple Strategic Flow Pattern within a Cavity
- 4.2.5 Avoid Picture Framing
- 4.2.6 Integral Hinges
- 4.2.7 Balanced Filling throughout a Mold
- 4.2.7.1 Gating Position(s) within a Cavity
- 4.2.7.2 Multi-Cavity Molds
- 4.2.8 Provide for Uniform Temperatures (Mold and Melt)
- 4.2.9 Eliminate, Strategically Place, or Condition Welds
- 4.2.10 Avoiding Flow Hesitation
- 4.2.11 Managing Frictional Heating of the Melt
- 4.2.12 Minimize Runner Volume in Cold Runners
- 4.2.13 Avoid Excessive Shear Rates
- 4.2.14 Avoid Excessive, and Provide for Uniform Shear Stresses
- 5 The Melt Delivery System
- 5.1 Runner Design Fundamentals
- 5.2 Overview of Runner/Melt Delivery System
- 5.2.1 Machine Nozzle
- 5.2.1.1 Nozzle Filter
- 5.2.1.2 Static Mixers
- 5.2.2 Sprue
- 5.2.3 Runner
- 5.2.4 Gate
- 5.3 Melt Flow through the Melt Delivery System
- 5.3.1 Melt Preparation - The Injection Molding Machine
- 5.3.1.1 Pressure Development from a Molding Machine
- 5.3.1.2 Flow Through a Runner Channel
- 5.3.2 Effect of Temperature on Flow
- 5.3.2.1 Melt Temperature
- 5.3.2.2 Mold Temperature
- 5.3.3 Cold vs. Hot Runners
- 5.3.4 Pressure Drop through the Melt Delivery System (Nozzle vs. Sprue vs. Runner vs. Gate vs. Part Forming Cavity)
- 5.4 Use of Mold Filling Analysis
- 5.5 Runner Cross-Sectional Size and Shape
- 5.5.1 The Efficient Flow Channel
- 5.5.2 Pressure Development in the Runner
- 5.5.2.1 Flow through a Hot Runner vs. a Cold Runner
- 5.5.3 Runner Effect on Cycle Time
- 5.5.3.1 Cold Runner and Sprue Cooling Time
- 5.5.3.2 Hot Runner
- 5.5.4 Constant Diameter vs. Graduated Diameter Runners
- 5.6 Designing Runners for Shear- and Thermally-Sensitive Materials
- 5.7 Runner Layouts
- 5.7.1 Geometrical Balanced Runners
- 5.7.2 Non-Geometrically Balanced Runners
- 5.7.3 Fishbone Runners vs. Geometrically Balanced Runners
- 5.7.3.1 Flow Balance Ratio
- 5.7.3.2 Melt Variation in Unbalanced Molds
- 5.7.3.3 Artificial Balancing of Runners
- 5.7.3.4 Do the Artificially Balanced Runners Reduce Runner Volume?
- 5.7.4 Family Molds
- 6 Filling, Melt, and Product Variations Developed in Multi-Cavity Molds
- 6.1 Sources of Product Variation in Multi-Cavity Molds of Mold Filling Imbalances
- 6.1.1 Product Variations Resulting from the Runner Design
- 6.1.2 Product Variations Resulting from Non-Runner Layout Issues
- 6.2 Imbalance Effects on Process, Product, and Productivity
- 6.2.1 Artificial Balancing of Runners
- 6.3 Shear-Induced Melt/Molding Variations from Geometrically Balanced Runners
- 6.3.1 Development and Stratification of Melt Variations Across a Runner Channel
- 6.3.2 Laminate Separation in Branching Runners Causing Cavity-to-Cavity Product Variations
- 6.3.3 Shear-Induced Melt Imbalances in Stack Molds
- 6.3.4 Development of Intra-Cavity Variations and Influence on Residual Stresses and Warpage
- 6.3.4.1 Warpage
- 6.3.4.2 Core Deflection
- 6.3.4.3 Effect on Concentric Parts (Gears, Fans, and Others)
- 6.3.5 Alternative Theories of the Cause of Mold Filling Imbalances
- 6.3.5.1 Cooling Variations
- 6.3.5.2 Plate Deflection
- 6.3.5.3 Corner Effect of Branching Runners
- 6.3.5.4 Melt Pressure as the Cause of Filling Imbalance
- 6.4 Runner Layouts
- 6.4.1 Identification of Various Flow Groups in Common Geometrically Balanced Runners
- 6.4.2 Apparent Geometrically Balanced Runner Layouts
- 6.5 Effect of Shear-Induced Melt Variations on Two-Stage Injection Processes
- 6.5.1 Gas Assist Injection Molding
- 6.5.2 Co-Injection Molding
- 6.5.3 Structural and Microcellular Foam Molding
- 6.6 The Cost of Melt Imbalances
- 7 Managing Shear-Induced Melt Variations for Successful Molding
- 7.1 Static Mixers
- 7.2 Artificial Balancing
- 7.2.1 Varying Sizes of Branching Runners or Gates to Achieve a Filling Balance
- 7.2.2 Varying Temperatures to Control Filling Balance
- 7.3 Melt Rotation Technology
- 7.3.1 Melt Rotation Technology in Hot Runner Molds
- 7.3.2 Melt Rotation Technology in Cold Runner Molds
- 7.3.3 Melt Rotation for Intra-Cavity Imbalances
- 7.3.4 Multi-Axis Melt Symmetry
- 7.3.5 In-Mold Adjustable Rheological Control (iMARCT)
- 7.3.5.1 3D Molding
- 7.4 Melt Rotation for Controlling Two Stage Injection Processes
- 7.5 Controlling Warpage through Melt Rotation Technology
- 7.5.1 Development of Warpage Potential
- 7.5.2 Controlled Warpage through Melt Rotation Technology
- 7.5.3 New Application for 3D Molding
- 7.6 MeltFlipper® Melt Rotation Technologies
- 7.6.1 Important MeltFlipper Patent Issues
- 7.6.2 Melt Rotation in Cold Runner Molds
- 7.6.3 Melt Rotation Technology in Hot Runner Molds
- 7.6.4 Multi-Axis Melt Symmetry
- 7.6.5 In-Mold Adjustable Rheological Control (iMARCT)
- 8 Cold Runner Molds
- 8.1 Sprue
- 8.1.1 Cold Sprue
- 8.1.2 Hot Sprue
- 8.2 The Cold Runner
- 8.2.1 Important Machining Considerations
- 8.2.2 Sizing of Runners
- 8.2.3 Venting
- 8.2.4 Runner Ejection
- 8.2.4.1 Sprue Puller
- 8.2.4.2 Secondary Sprue/Cold Drop
- 8.2.4.3 Runner
- 8.2.5 Cold Slug Wells
- 8.3 Runners for Three-Plate Cold Runner Molds
- 8.4 Gate Designs
- 8.4.1 Sprue Gate
- 8.4.2 Common Edge Gate
- 8.4.3 Fan Gate
- 8.4.4 Film Gate or Flash Gate
- 8.4.5 Ring Gate
- 8.4.6 Diaphragm (Disk) Gate
- 8.4.7 Tunnel Gate
- 8.4.8 Cashew or Banana Gate
- 8.4.9 Jump Gate
- 8.4.10 Pin Point Gate
- 8.4.11 Chisel Gate
- 8.4.12 Overflow Gate
- 8.5 Effects of Gate Diameter in Multi-Cavity Molds
- 8.5.1 Study 1
- 8.5.2 Study 2
- 8.5.3 Measuring Tolerances
- 9 Hot Runner Molds
- 9.1 Overview
- 9.1.1 Advantages and Disadvantages of Hot Runner Systems
- 9.1.1.1 Advantages of Hot Runners
- 9.1.1.2 Disadvantages of Hot Runners
- 9.1.1.3 Summary of Attributes of Different Runner Systems
- 9.2 Overview of Multi-Cavity Hot Runner Systems (Contrasting Systems)
- 9.2.1 Externally Heated Manifold and Drops/Nozzles
- 9.2.2 Externally Heated Manifold with Internally Heated Drops
- 9.2.3 Internally Heated Manifold and Internally Heated Drops
- 9.2.4 Insulated Manifold and Drops
- 9.3 Stack Molds
- 10 Hot Runner Flow Channel Design
- 10.1 Layout for Balanced Molding
- 10.2 Cross-Sectional Shape
- 10.3 Corners
- 10.3.1 Drilled Runner Channels
- 10.3.2 Machined Laminate Plate Runner Channels
- 10.4 Effect of Diameter
- 10.4.1 Pressure
- 10.4.2 Shot Control
- 10.4.3 Color Change
- 10.4.4 Material Change
- 11 Hot Runner Drops, Nozzles, and Gates
- 11.1 Hot Drops
- 11.1.1 Externally Heated Hot Drops (Nozzles)
- 11.1.2 Internally Heated Hot Drops
- 11.1.3 Heat Conducting Nozzles
- 11.2 Restrictive/Pin Point Gates
- 11.3 Gate Design Considerations
- 11.3.1 Gate Freeze-Off
- 11.3.2 Stringing/Drooling
- 11.3.3 Packing
- 11.3.4 Nozzle Tips for Hot Runner Thermal Gates
- 11.3.4.1 Ported Tips
- 11.3.4.2 Torpedo-Style Tips
- 11.3.5 Mechanical Valve Gates
- 11.3.5.1 Consideration of Valve Pin Flow Restrictions
- 11.3.5.2 Sequential Valve Gates
- 11.3.5.3 Valve Pin Movement Control for Sequential Gating
- 11.3.6 Thermal Shut-Off Gates
- 11.3.7 Hot Edge Gates
- 11.3.8 Multi-Tip Nozzles
- 11.4 Special Nozzle Arrangement
- 12 Thermal Issues of Hot Runner Systems
- 12.1 Heating
- 12.1.1 Coil (Cable) Heaters
- 12.1.2 Band Heaters
- 12.1.3 Tubular Heaters
- 12.1.4 Cartridge Heaters
- 12.1.5 Heat Pipe Technology
- 12.2 Heater Temperature Control
- 12.2.1 Thermocouples
- 12.2.2 Temperature Controllers
- 12.3 Power Requirements
- 12.4 Thermal Isolation of the Hot Runner
- 12.5 Gate Temperature Control
- 12.5.1 Gate Heating
- 12.5.2 Gate Cooling
- 13 The Mechanics and Operation of Hot Runners
- 13.1 Assembly and Leakage Issues
- 13.1.1 System Design
- 13.1.2 Hot Runner System Machining and Assembly
- 13.2 Mold and Machine Distortions
- 13.3 Startup Procedures
- 13.4 Color and Material Changes
- 13.5 Gates
- 13.5.1 Vestige
- 13.5.2 Clog
- 13.5.3 Wear
- 13.6 Maintenance
- 14 Process of Designing and Selecting a Runner System (Gate and Runner) - A Summary
- 14.1 Number of Gates
- 14.2 Gating Position on a Part
- 14.2.1 Cosmetic
- 14.2.2 Effect on Shrinkage, Warp, and Residual Stress
- 14.2.2.1 Orientation
- 14.2.2.2 Volumetric Shrinkage (Regional)
- 14.2.2.3 Unbalanced Filling
- 14.2.3 Structural Issues
- 14.2.3.1 Gate Stress
- 14.2.3.2 Flow Orientation
- 14.2.4 Gating into Restricted, or otherwise Difficult to Reach Locations
- 14.3 Cavity Positioning
- 14.4 Material
- 14.5 Jetting
- 14.6 Thick vs. Thin Regions of the Part
- 14.6.1 Volumetric Shrinkage
- 14.6.2 Hesitation
- 14.7 Number of Cavities
- 14.8 Production Volume
- 14.9 Precision Molding (Precision Size, Shape, Weight, Mechanical Properties, and Consistency)
- 14.10 Color Changes
- 14.11 Material Change
- 14.12 Regrind of Runners
- 14.13 Part Thickness
- 14.13.1 Thin Part
- 14.13.2 Thick Part
- 14.14 Part Size
- 14.15 Labor Skill Level
- 14.16 Post Mold Handling
- 14.17 Part/Gate Stress Issues
- 14.18 Hot and Cold Runner Combinations
- 14.19 Two-Phase Injection Processes
- 15 Troubleshooting
- 15.1 Flow Grouping Mold Diagnostics
- 15.1.1 Shear-Induced Flow Imbalance Developed in a Geometrically Balanced Runner
- 15.1.2 Steel Variations in the Mold
- 15.1.3 Cooling Effects
- 15.1.4 Hot Runner Systems
- 15.1.5 Summary of Test Data
- 15.1.6 Flow Grouping: Method of Application
- 15.2 Injection Molding Troubleshooting Guidelines for Scientific Injection Molding
- 15.3 Injection Molding Process Development
- 15.3.1 The Molding Process
- 15.3.1.1 Mold Cooling
- 15.3.1.2 Clamp Unit - Initial Settings
- 15.3.1.3 Injection Unit - Initial Settings
- 15.3.1.4 Fill Time Scan - Evaluating First Stage Flow Rate
- 15.3.1.5 Pack Scans - Evaluating Second Stage Pack Pressure and Pack Time
- 15.3.1.6 Evaluate Cushion, Cooling Time, and Cycle Time
- 15.3.2 Process Monitoring and Process Documentation
- 15.4 List of Amorphous and Semi-Crystalline Resins
- Index
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