Injection Molding Machines

Friedrich Johannaber Injection Molding Machines A User's Guide 3rd Edition Hanser Publishers, Munich Vienna New York Hanser/Gardner Publications, I...
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Friedrich Johannaber

Injection Molding Machines A User's Guide

3rd Edition

Hanser Publishers, Munich Vienna New York Hanser/Gardner Publications, Inc., Cincinnati

Contents Foreword Preface to the Third Edition Preface to the First Edition Notes

V VI VII VIII

The Economic Significance of Injection Molding

1

1 General Design and Function

4

2 Characterization of the Injection Molding Process

2.1 Pressure 2.1.1 Hydraulic Pressure on the Injection Side 2.1.2 Cavity Pressure 2.1.2.1 Switch-over from Injection to Holding Pressure 2.1.3 Holding Pressure 2.2 Temperature 2.2.1 Temperature of the Hydraulic Oil 2.2.2 Melt Temperature 2.2.3 Mold Temperature 2.3 Velocity 2.4 Effect of Molding Technique on Properties 2.4.1 Dimensional Stability 2.4.2 Mechanical and Physical Properties 2.4.2.1 Molecular Orientation 2.4.2.2 Residual Stresses 2.4.3 Crystallinity and Structure 3 The Injection Unit

3.1 Injection Pressure 3.2 Carriage Guide for the Injection Unit 3.3 Rotatory Screw Drive Systems 3.3.1 Electromotive Screw Drive 3.3.2 Hydraulic Screw Drive 3.3.3 Torque 3.3.4 Screw Speed 3.4 Screws 3.4.1 Standard Screws for Thermoplastics 3.4.2 Special Screws for Thermoplastics 3.4.3 Barrier Screws

12

12 12 17 19 22 23 23 24 24 25 27 27 29 30 35 36 38

39 42 44 45 46 48 49 51 52 57 57

X

Contents

3.4.4 Screws for Rigid PVC 3.4.5 Screws for Vented Barrels 3.4.6 Screws for Thermosets 3.4.7 Screws for Elastomers 3.4.8 Screws for Processing Silicones 3.4.9 Other Types of Screws 3.4.10 Wear and Wear Protection 3.4.11 Screw Tips 3.4.12 Nonreturn Valves 3.5 The Barrel 3.6 The Nozzle 3.6.1 Open Nozzles 3.6.2 Shut-off Nozzles 3.6.3 Nozzles with Material Filters 3.6.4 Internally Heated Nozzles 3.7 Accessories for the Injection Unit 4 The Clamping Unit

4.1 Mechanical Clamping Systems 4.1.1 Clamping Sequence 4.1.2 Clamping Force of Toggle Machines 4.1.3 Opening Force 4.2 Hydraulic Clamping Systems 4.3 Combined Clamping Systems 4.4 Accessories for the Clamping Unit 5 The Drive Unit

5.1 The Electric Drive 5.1.1 Methods of Operation and Torque 5.1.2 Environmental Conditions 5.1.3 Electric Motors 5.1.3.1 Polyphase Induction Motors 5.1.3.2 Speed Control of Polyphase Motors 5.2 The Electromechanical Drive 5.3 The Electrohydraulic Drive 5.3.1 Hydraulic Motors 5.3.2 Hydraulic Pumps 5.4 The Hydraulic System 5.4.1 Fixed-Displacement Pumps 5.4.2 Variable-Displacement Pumps 5.4.3 Accumulators

58 59 61 64 65 65 65 71 72 75 77 77 78 85 87 89 92

93 97 100 102 103 Ill 112 115

115 115 116 116 116 117 119 121 122 128 134 142 144 145

Contents XI

5.5 Hydraulic Controls 147 5.5.1 Flow-Control Valves 150 5.5.2 Pressure-Control Valves 154 5.5.3 Digital Control Elements 154 5.6 Monitoring Devices in the Hydraulic System 160 5.7 Noise Supression in the Hydraulic System 161 5.8 Efficiency and Energy Consumption 162 5.8.1 Efficiency and Energy Consumption of the Hydraulic Drive . . 162 5.8.2 Efficiency and Energy Consumption of the Electromechanical Drive 170 6 The Control System

6.1 Process Control Methods 6.1.1 Open-Loop Control 6.1.2 Closed-Loop Control 6.2 Temperature Control 6.2.1 Temperature Measurements 6.2.1.1 Wall Temperatures 6.2.1.2 Melt Temperatures 6.2.2 Temperature Control 6.2.2.1 Introduction 6.2.2.2 Control Algorithms and Parameters 6.2.2.3 Power Elements 6.2.2.4 Load 6.2.2.5 Design and Setup of Heaters and Controllers 6.2.2.6 Special Means of Controlling the Barrel Temperature 6.2.2.7 Homogenizing the Melt Temperature 6.3 Pressure Measurements 6.3.1 Pressure in Front of the Screw Tip 6.3.2 The Hydraulic Pressure 6.3.3 Cavity Pressure During Injection Molding 6.4 The Control Unit 6.4.1 Objects of Process Control 6.4.2 Components of the Control Unit 6.4.3 Disturbances 6.4.4 Methods of Process Control 6.4.4.1 Cycle Control with Electric or Electronic Timers and Manuel Control of Pressure-, Flow-Control, and Directional Valves 6.4.4.2 Control with Central Control Setting 6.4.4.3 Control System with Central Control Setting and Digital Flow- and Pressure-Control Valves

172

173 174 175 176 177 177 179 181 181 183 185 186 186 . 187 187 187 187 189 190 193 193 195 196 197 198 198 198

XII

Contents

6.4.4.4 Control of Injection and Holding-Pressure Stages . . . 6.4.4.5 Optimizing the Holding-Pressure Stage with the P-V-T Diagram 6.4.4.6 The P-m-T Control 6.4.4.7 Row-Number Control 6.4.4.8 Integrated Control of Injection and Holding-Pressure Stages 6.4.5 Microprocessor Control Units 6.4.5.1 Design of a Microprocessor 6.4.6 Electronic Data Processing in Injection Molding 6.4.7 Computer-Controlled Automatic Injection Molding Installation 7 Types of Injection Molding Machines

7.1 Machines for Off-Center Molding 7.2 Multi-Component Injection Molding Techniques 7.2.1 Machines in Horizontal Design 7.2.2 Machines in Vertical Design 7.2.3 Coinjection Molding Machines 7.2.4 Fi-Fo Molding Machines 7.3 Gas-Assiste,d Injection Molding 7.4 Injection Molding with Pulsating Melt 7.5 Fusible-Core Technique 7.6 Low-Pressure Injection Molding for Injection Stamping and In-Mold Decorating 7.6.1 Injection Stamping 7.6.2 In-Mold Decorating 7.7 Machines for Intrusion 7.8 Injection Molding of Polyester Resins 7.9 Machines and Equipment for Processing Liquid Silicones 7.10 Tandem Injection Molding Machines 7.11 Plunger-Type Injection Molding Machines 7.12 Two-Stage Injection Molding Machines with Screw Plastication and Plunger Injection 7.13 Multi-Station Machines 7.14 Special Types without Commercial Significance 8 Machine Sizes and Performance Data

8.1 Sizes 8.2 Performance Data 8.2.1 Performance Data of the Injection Unit 8.2.2 Performance Data of the Clamping Unit 8.2.3 General Performance Date

199 200 203 203 204 204 204 208 210 214

214 215 217 218 219 226 227 223 236 237 238 239 242 243 245 246 248 249 255 259 260

260 260 262 272 281

Contents

XIII

9 Safety

287

10 Plastic Materials for Injection Molding

288

11 Accessories

294

11.1 Injection Molds 11.2 Auxiliary Equipment for Automation 11.3 Heat Exchangers

294 299 300

References

303

Index

317