Runner and Gating Design Handbook

Runner and Gating Design Handbook
اسم المؤلف
John P. Beaumont
23 سبتمبر 2019
(لا توجد تقييمات)

Runner and Gating Design Handbook
Tools for Successful Injection Molding
John P. Beaumont
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 Rheologyof 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
3 Filling and Packing Effects on Material and Molded Part
3.1 Process Effects on Material Viscosity
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 Volumetric Shrinkage Orientation-Induced Shrinkage
3.5.2 Development of Residual Stresses and Warpage Warpage and Residual Stress from Side-to-Side Shrinkage Variations . . 31 Warpage and Residual Stress from Global/Regional Shrinkage Variations 31 Warpage and Residual Stress from Orientation-Induced Shrinkage
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 Gating Position(s) Within a Cavity 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 NozzleFilter 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 Pressure Development from a Molding Machine Flow Through a Runner Channel
5.3.2 Effect of Temperature on Flow Melt Temperature 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)
Use of Mold Filling Analysis
Runner Cross Sectional Size and Shape
5.5.1 The Efficient Flow Channel
5.5.2 Pressure Development in the Runner Flow through a Hot Runner vs. a Cold Runner
5.5.3 Runner Effect on Cycle Time Cold Runner and Sprue Cooling Time Hot Runner
5.5.4 Constant Diameter vs. Varying Diameter Runners
Designing Runners for Shear- and Thermally-Sensitive Materials
Runner Layouts
5.7.1 Geometrical Balanced Runners
5.7.2 Non-Geometrically Balanced Runners
5.7.3 Family Molds
6 Filling and Melt Imbalances Developed in Multi-Cavity Molds
6.1 Source of Mold Filling Imbalances
6.1.1 Imbalances Developed from the Runner
6.1.2 Imbalance Caused by Non-Runner Layout Issues
6.2 Imbalance Effects on Process, Product, and Productivity
6.3 Shear-Induced Melt/Molding Imbalances in Geometrically Balanced Runners
6.3.1 Development and Stratification of Melt Variations Across a Runner Channel . . . 94
6.3.2 Laminate Separation in Branching Runners Causing
Cavity-to-Cavity Filling Imbalances
6.3.3 Shear Induced Melt Imbalances in Stack Molds
6.3.4 Development of Intra-Cavity Variations Warpage Core Deflection Effect on Concentric Parts (Gears, Fans, and Others)
6.3.5 Alternative Theories of the Cause of Mold Filling Imbalances Cooling Variations Plate Deflection Corner Effect Melt Pressure as the Cause of Filling Imbalance 102
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 Miocrocellular Foam Molding
6.6 The Cost of Melt Imbalances
7 Managing Shear-Induced Melt Variations for Successful Molding
7.1 Static Mixers
7.2 Artificially 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
7.4 Melt Rotation for Controlling Two Stage Injection Processes
8 Cold Runner Molds 127
8.1 Sprue 128
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 Sprue Puller Secondary Sprue/Cold Drop Runner
8.2.5 Cold Slug Wells
8.3 Runners for Three-Plate Cold Runner Molds
8.4 Gate Designs
8.4.1 SprueGate
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 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 TabGate
9 Hot Runner Molds
9.1 Overview
9.1.1 Advantages and Disadvantage of Hot Runner Systems Advantages of Hot Runners Disadvantages of Hot Runners 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
10.4 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 Mechanical Valve Gates Sequential Valve Gates
11.3.5 Thermal Shut-Off Gates
11.3.6 Hot Edge Gates
11.3.7 Multi Tip Nozzles
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 204
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 Orientation Volumetric Shrinkage (Regional) Unbalanced Filling
14.2.3 Structural Issues Gate Stress 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) 212
14.10 Color Changes
14.11 Material Change
14.12 Regrind of Runners
14.13 Part Thickness
14.13.1Thin 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 The 5 Step Process
15.1.1 Shear-Induced Flow Imbalance Developed in a Geometrically Balanced Runner . . 217
15.1.2 Steel Variations in the Mold
15.1.3 Cooling Affects
15.1.4 Hot Runner Systems
15.1.5 Summary of Test Data
15.1.6 The 5 Step Process: Method of Application
15.2 Injection Molding Troubleshooting Guidelines for Scientific Injection Molding
15.3 Two Stage Molding Set-Up
15.4 Intensification Ratio (Ri)
15.5 Characterizing Flow Behavior in an Injection Mold
15.6 List of Amorphous and Semi-Crystalline Resins
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