training

Practical Guide to Injection Molding

This Practical Guide to Injection Moulding is based on course material used by ARBURG in training operators of injection moulding machines. It comes from many years of experience in this field and has been edited by an expert injection moulder at Warwick University. It will be of use to experts looking to fill gaps in their knowledge base and to those new to the industry.

The factors involved in injection moulding, from material properties and selection to troubleshooting faults, are all examined in this book. It covers the equipment types in use and machine settings for different types of plastics. Material flow is critical in moulding and there are sections covering rheology and viscosity. High temperature can lead to poor quality mouldings due to material degradation and this is discussed.

There are an exceptional number of figures in this text, with many photographs of machinery and mouldings to illustrate key points. There are also numerous tables listing key properties and processing parameters. Flow charts are included in the chapter on troubleshooting to indicate what can be changed to resolve common problems.

Injection moulding in the Western World is becoming increasingly competitive as the manufacturing base for many plastics materials has moved to the East. Thus Western manufacturers have moved into more technically difficult products and mouldings to provide more added value and maintain market share. Technology is becoming more critical, together with innovation and quality control. There is a chapter on advanced processing in injection moulding covering multi-material and assisted moulding technologies. This Guide will assist progress in developing good technical skills and appropriate processing techniques for the range of plastics and products in the marketplace.

Every injection moulder will find useful information in this text. The text is supported by 71 tables and 215 figures.

About the editor?

ARBURG has been manufacturing injection moulding machines since 1954 and is one of the major global players. The company prides itself on the support offered to clients, which is exemplified in its training courses. This book is based on some of this training material and hence is based on years of experience.

The editor, Dr Vannessa Goodship, is a Senior Research Fellow with 15 years experience in industry and expertise in injection moulding technology. She is based at the Warwick Manufacturing Group in the Advanced Technology Centre at the University of Warwick.

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Report Index:

Preface

1 Introduction
1.1 The Big Picture
1.2 Introduction to Injection Moulding
1.3 The Injection Moulding Process
1.3.1 Piston Injection Unit
1.3.2 Reciprocating Screw Machine
1.3.3 Breaking Down the Injection Moulding Cycle
1.3.3.1 Plastication
1.3.3.2 Filling
1.3.3.3 Packing and Solidification
1.4 Comparison with Other Moulding Methods
1.4.1 Extrusion
1.4.2 Compression Moulding
1.4.3 Transfer Moulding
1.4.4 Blow Moulding
1.4.5 Film Blowing
1.4.6 Intrusion Moulding
1.4.7 Injection-Compression Moulding
1.5 Conclusion
Further Reading

2 Introduction to Plastics
2.1 Introduction
2.2 Structure and Typical Properties of Polymers
2.3 Formation of Macromolecules
2.4 Molecular Weight
2.5 Plastics
2.5.1 Thermoplastics
2.5.2 Thermosets
2.5.3 Elastomers
2.5.3.1 Thermoplastic Elastomers (TPEs)
2.5.4 The Formulation of Plastics
2.5.5 The Binding Structure of Plastics
2.6 The Effects of Processing on Thermoplastics
2.6.1 Rheology
2.6.2 Heat and Heat Transfer
2.6.3 Physical and Chemical Change
2.6.4 Fountain Flow
2.7 Conclusion

3 Injection Moulding Machinery
3.1 Injection Units
3.2 Piston (Plunger) Injection Unit
3.3 Reciprocating Screw Piston Injection Unit
3.3.1 Shot Capacity
3.3.2 Plasticising Capacity
3.3.3 The Feeding Hopper
3.3.4 The Injection Cylinder
3.4 Selection of the Injection Unit
3.5 L/D Ratio
3.5.1 Mixing Screws for Additives and Fast Cycling Machines
3.5.1.1 Mixing Elements
3.5.1.2 Extended Plasticising Cylinder
3.5.2 Non-Return Valve
3.6 General Information on Wear and Tear
3.7 Unit Hardening Treatment
3.8 The Nozzle
3.9 Clamping Units
3.9.1 Differential Piston System
3.9.2 Mould Weights
3.10 Selection of the Clamping Unit
3.11 Mould Clamping Force
3.11.1 Mould Clamping Force Level
3.11.2 Mould Clamping Force and Mould Rigidity
3.11.3 Setting Mould Closing and Clamping Force
3.11.3.1 Mould Closing Force
3.11.3.2 Clamping Force
3.11.3.3 Second Clamping Force
3.12 Data for Mould Closing
3.13 Other Considerations
3.14 International Standard for the Designation of Injection Moulding Machines

4 Injection Mould Tooling Basics
4.1 Types of Moulds
4.1.1 Two-Plate Mould
4.1.2 Stripper Mould
4.1.3 Slide Mould
4.1.4 Three-Plate Mould
4.2 The Feed System
4.2.1 Introduction
4.2.2 Runner System
4.2.3 Runner Shape
4.2.4 Runner Layout
4.2.4.1 Standard Runner
4.2.4.2 Cold Runner
4.2.4.3 Hot Runner
4.3 Gate Design
4.3.1 Sprue Gate
4.3.2 Restricted Gate
4.3.3 Side or Edge Gate
4.3.4 Flash Gate
4.3.5 Fan Gate
4.3.6 Tab Gate
4.3.7 Diaphragm Gate
4.3.8 Spider Gate
4.3.9 Ring Gate
4.3.10 HOT TIP Gating
4.4 Mould Temperature Control
4.5 Ejection Systems
4.6 Venting
4.7 Conclusion
Further Reading

5 Process Control Systems
5.1 Introduction
5.2 Explanation of the Different Concepts in Control and Regulation Technology
5.2.1 Pump
5.2.2 Motor
5.2.3 Cylinder
5.2.4 Directional Valves
5.2.5 Pressure Valves
5.2.6 Flow-Regulator Valves
5.2.7 Location and Setting of Proportional Valves
5.2.7.1 Valve Bodies
5.2.7.2 Function of the Volume Proportional Valve
5.2.7.3 Function of the Pressure Proportional Valve
5.2.8 Check Valves
5.2.9 Receivers
5.3General Information Concerning Control Units, Regulators, Position Regulation and Injection Process Regulation
5.3.1 Control Unit
5.3.2 Regulator
5.3.3 Screw with Position Regulator
5.3.4 Injection Process Regulation
5.4 The User Interface
5.4.1 Multitronica Control Unit ? Standard Equipment
5.4.2 Dialogica Control Unit ? Standard Equipment
5.4.3 Selogica Control Unit ? Standard Equipment

6 Processing Amorphous and Semi-Crystalline Thermoplastics
6.1 Introduction
6.2 Amorphous Plastics
6.2.1 Overview and Common Properties
6.2.2 Standard Polystyrene (PS) Homopolymer
6.2.3 Styrene Copolymers
6.2.4 Modified Polyphenylene Oxide (PPO mod.)
6.2.5 Polyvinyl Chloride (PVC)
6.2.6 Cellulose Materials
6.2.7 Polymethyl Methacrylate (PMMA)
6.2.8 Polycarbonate (PC)
6.2.9 Polyacrylates (PAR, PAE, APE, PEC)
6.2.10 Polysulfones
6.2.11 Polyetherimide (PEI)
6.2.12 Polyamide Imide (PAl)
6.3 Semi-Crystalline Plastics
6.3.1 Overview and Common Properties
6.3.2 Polyethylene (PE)
6.3.3 Polypropylene (PP)
6.3.4 Polyamide (PA)
6.3.5 Polyacetals (POM)
6.3.6 Polyterephthalates (Linear Polyesters)
6.3.7 Polyphenylene sulfide (PPS)
6.3.8 Polyfluoroolefins
6.3.9 Polyacrylic Acid (PAA)
6.3.10 Polyphthalamide (PPA)
6.3.11 Polyaryl Ether Ketones (PAEK)
6.3.12 Liquid-Crystalline-Polymers (LCP)
6.4 Conclusion

7 Processing Thermoset, LSR and Ceramic Materials
7.1 Thermosets
7.1.1 Overview and Common Properties
7.1.2 Materials for Screw Injection Moulding Machines
7.1.3 Processing Procedures for Thermoset Plastics
7.1.3.1 Compression Moulding
7.1.3.2 Injection Moulding
7.1.4 Screw Injection Machine for Thermosets
7.1.5 Mould
7.1.6 Guide Values for Cylinder and Mould Temperature Settings
7.1.7 The Injection Unit for Granulated Thermosets
7.1.8 The Injection Unit for Processing Moist Polyester
7.1.9 Nozzle Temperature (if nozzle heating is applied)
7.1.10 Common Thermoset Materials: Properties and Applications
7.1.10.1 Phenol-Formaldehyde Compounds (PF)
7.1.10.2 Urea-Formaldehyde Compounds (UF)
7.1.10.3 Melamine-Formaldehyde Compounds (MF, MP)
7.1.10.4 Unsaturated Polyester (UP, DAP)
7.1.10.5 Epoxy Compounds (EP)
7.2 Elastomer Injection Moulding Compounds
7.2.1 Processing Procedures for Elastomeric Materials
7.2.1.1 Compression Moulding
7.2.1.2 Injection Moulding
7.2.1.3 Injection Moulding Machines for Rubber Compounds
7.2.1.4 Peripheral Device
7.2.1.5 Mould
7.2.2 Silicone Elastomers - Liquid Silicone Rubber (LSR) Systems
7.2.2.1 Classification
7.2.2.2 Crosslinking
7.2.2.3 Processing of Two-Component LSR
7.2.2.4 Advantages of Processing LSR Materials
7.2.2.5 Injection Process
7.2.2.6 Configuration of Injection Moulding Machines and Processing Data
7.2.2.7 Specific Properties
7.2.2.8 Crosslinking Reaction
7.2.2.9 Structural Viscosity
7.2.2.10 Vulcanisation
7.2.2.11 Internal Mould Pressure
7.2.2.12 Shrinkage
7.2.2.13 Tempering
7.2.2.14 Preparation of LSR
7.2.3 Processing Components for LIM
7.2.3.1 Dosing Equipment for LSR
7.2.3.2 Machine Technology
7.2.3.3 Injection Unit
7.2.3.4 Cylinder Module
7.2.3.5 Non-Return Valve
7.2.3.6 Auxiliary Heating Control Circuits
7.2.3.7 Interface for Brush and Cleaner Units
7.2.3.8 Handling Interface
7.2.3.9 User-Programmable Inputs/Outputs
7.2.3.10 Air Blast Equipment with Pressure Reducer
7.2.3.11 Control Unit for Vacuum Pump
7.2.3.12 Hydraulic/Pneumatic Cold Runner Control
7.2.3.13 Protective Screens Made of PC
7.2.3.14 Simple Cold Runner Nozzle
7.2.3.15 Cold Runner Head
7.2.3.16 Mould Technology
7.2.4 Application of LSR Parts in Food Production
7.2.5 Summary
7.3 Processing of Ceramic and Metal Powder Materials
7.3.1 Introduction
7.3.2 Binder
7.3.3 Processing
7.3.3.1 Compression Moulding
7.3.3.2 Injection Moulding
7.3.4 Configuration of Injection Moulding Machines
7.3.5 The Process Requirements
7.3.5.1 Debinding and Sintering
7.4 A Growing Market for Moulders

8 Guide Values and Processing Instructions for the Most Important Thermoplastic Injection Moulding Compounds
8.1 Pre-Drying Material
8.2 Examples of Moulding Parameters of Selected Materials
8.3 Injection Moulding Process Parameters and Quality of Moulded Parts
8.4 Injection and Mould Cavity Pressure
8.5 Injection Pressure and Injection Time
8.6 General Information on Filling Speed
8.6.1 Initial Injection Speed
8.7 Filling Speed and Orientations
8.8 Effects of Too High Filling Speed
8.9 Setting the Initial Injection Speed
8.10 Plasticising
8.10.1 Compound Temperature
8.10.2 Cylinder Temperatures
8.10.3 Nozzle Temperature
8.10.4 Temperature Profile Guideline for Plasticising Cylinder
8.10.5 Recommended Temperatures for Cylinder and Mould
8.10.6 Measuring the Compound Temperature
8.10.7 Screw Speed
8.10.8 Back Pressure
8.11 The Injection Stage
8.11.1 Filling to Packing
8.11.2 The Mould
8.11.2.1 Mould Temperature: General Information
8.11.2.2 Level of Mould Temperature
8.11.2.3 Uniformity of Mould Temperatures
8.11.2.4 Mould Temperature Patterns
8.11.2.5 Temperature Control Devices
8.11.2.6 Matching Temperature Control Units and Mould Maintenance
8.11.2.7 Measuring the Mould Temperature - Checking the Uniformity of the Mould Temperature Control
8.12 Recommended Values for Holding Pressure Time and Remaining Cooling Time
8.13 Cycle Time
8.14 Setting the Injection Moulding Machine

9 Troubleshooting
9.1 Introduction
9.2 Troubleshooting Guide
9.2.1 Detection and Classification of Defects
9.2.2 Flow Charts for Troubleshooting
9.2.3 Sink Marks
9.2.4 Streaks
9.2.4.1 Burnt Streaks (Brown or Silver)
9.2.4.2 Moisture Streaks
9.2.4.3 Colour Streaks
9.2.4.4 Air Streaks/Air Hooks
9.2.4.5 Glass Fibre Streaks
9.2.5 Gloss/Gloss Differences
9.2.6 Weld Line (Visible Notch or Colour Change)
9.2.7 Jetting
9.2.8 Diesel Effect (Burns)
9.2.9 Record Grooves Effect
9.2.10 Stress Whitening/Stress Cracks
9.2.11 Incompletely Filled Parts
9.2.12 Oversprayed Parts (Flashes)
9.2.13 Visible Ejector Marks
9.2.14 Deformation During Demoulding
9.2.15 Flaking of the Surface Layer
9.2.16 Cold Slugs/Cold Flow Lines
9.2.17 Entrapped Air (Blister Formation)
9.2.18 Dark Spots
9.2.19 Dull Spots Near the Sprue
9.3 Data Acquisition Record
9.3.1 Using the Data Acquisition Record
9.3.2 Data Acquisition Record for Optimising Moulded Parts
9.3.2.1 Moulded Part Data
9.3.2.2 Machine Settings and Defect Evaluation
9.4 Case Studies of Injection Moulded Components
9.4.1 Threaded Connecting Sleeves for Ink Drafting Apparatus
9.4.2 Meter Cases
9.4.3 Wristwatch Glass
9.4.4 Alarm Clock Glass
9.4.5 Glass Cover for Digital Gauge
9.4.6 Plug Boards with Insert Pins
9.4.7 Hair Slides
9.4.8 Toothbrush Components
9.4.9 Screw Cap with Conical Nipple
9.4.10 Switch Housing
9.4.11 Battery Housing

10 Advanced Processing Techniques
10.1 Introduction
10.2 Multi-Component Moulding
10.2.1 Co-Injection Moulding
10.2.2 Bi-Injection Moulding
10.2.3 Interval Injection Moulding
10.3 Assisted Moulding
10.4 Multi-Shot Moulding
10.5 Over-Moulding
10.6 Business Trends
10.7 Material Selection
10.8 Process Technology
10.8.1 Multi-Component Injection Moulding
10.8.2 Co-Injection Moulding
10.8.2.1 Material Selection for Co-Injection Moulding
10.8.2.2 Process Sequence
10.8.2.3 Co-Injection Moulding: Different Techniques
10.8.2.4 Part Design and Tooling Requirements for Co-Injection Moulding
10.8.2.5 Rheology and Mould Filling: Why and How Co-Injection Moulding Works
10.8.2.6 Immiscible Materials Research in Co-Injection Moulding
10.8.2.7 Setting Optimum Parameters
10.8.2.8 Co-Injection Moulding Application Case Studies
10.8.2.9 Recycling and Legislation
10.8.2.10 Discussion and Conclusions
10.8.3 Bi-Injection
10.8.4 Interval Injection Moulding
10.9 Assisted Moulding
10.9.1 Gas Injection Moulding Technology (GIT)
10.9.1.1 Process Technology
10.9.1.2 Patent Situation
10.9.1.3 Advantages and Disadvantages of GIT
10.9.1.4 Process Variations in the Application of Gas Injection Moulding Technology
10.9.1.5 Systems Technology for the Implementation of Gas Injection Technology
10.9.1.6 Configuration Guidelines for GIT Moulding
10.9.1.7 KoolGas?
10.9.2 Water Assisted Injection Moulding (WAIM)
10.10 Multi-Shot Moulding
10.10.1 Machine Technology
10.10.1.1 Injection Unit Configurations
10.10.2 Core Back Moulding
10.10.3 Rotating Tool
10.10.4 Transfer Moulding
10.10.5 Multi-Shot with a Single Injection Unit
10.10.6 Materials for Muti-Shot Moulding
10.10.6.1 Material Selection for Multi-Shot Moulding
10.10.6.2 Material Process Order
10.10.6.3 Using Thermoset Materials
10.10.6.4 Liquid Silicone Rubber (LSR)
10.10.6.5 Thermoplastic Elastomers (TPEs)
10.10.7 Multi-Shot Application Case Studies
10.10.7.1 Trio Knob
10.10.7.2 Stanley Screwdriver
10.10.8 Limitations to Multi-Shot
10.11 Over-Moulding
10.11.1 Insert Moulding
10.11.2 Lost Core Moulding
10.12 The Future?
References
Further Reading

Appendix 1 Abbreviations and Acronyms
Appendix 2 Trade Names, Specific Weight and Suppliers of Some Plastic Materials

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Report Data Summary:
ARBURG Practical Guide to Injection Moulding
Date Published: 7/7/2004
Number of Pages: 258
Category: Plastics
URL: www.researchandmarkets.com/reports/c11302

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