Practical Injection Molding

Practical Injection Molding
اسم المؤلف
Bernie A. Olmsted , Martin E. Dauis
التاريخ
22 سبتمبر 2019
المشاهدات
35
التقييم
(لا توجد تقييمات)
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Practical Injection Molding
Bernie A. Olmsted
Consultant
Springfield, Massachusetts
Martin E. Dauis
Consultant
Prescott, Arizona
Contents
1 Introduction . 1
1.1 Elements of the Injection Molding Process 1
1.2 Summarizing the Elements . 6
2.1 Thermoplastics 8
2.3 Crystalline vs. Amorphous Materials 10
2.4 How Plastics Affect the Molding Process . 11
2.4.1 Melting Characteristics 11
2.4.2 Thermal Conductivity 12
2.4.3 Shear Sensitivity 13
2.4.4 Viscosity (Melt Index) . 14
3 Additives . 16
3.1 Fillers and Reinforcements . 16
3.2 Plasticizers 17
3.3 Stabilizers 17
3.4 Flame Retardants 18
3.5 Colorants . 18
3.6 Adding the Additives 18
4 Loaders and Dryers . 21
4.1 Hopper Loaders and Conveying Systems . 21
4.2 Dryers 22
2 Plastics 8
2.2 Thermosets 9
4.2.1 Hot Air Dryers . 22
4.2.2 Dessicant Dryers 23
5 hjection Unit 26
5.1 The Barrel . 29
5.3 Heater Bands . 33
5.4 Non-Return Valve . 34
5.5 Screw . 38
5.5. I Length-to-Diameter Ratio 39
5.2 End Cap and Nozzle 30
1xX
5.5.2 Screw Profile 40
5.5.3 Compression Ratio .40
5.5.5 Drive Design 41
5.6 Injection Pressure 42
6.1 Hydraulic Clamp System 46
6.3 Clamp Unit Specifications . 50
7 Mold 55
5 S.4 Helix Angle . 41
6 Clamp Unit . 45
6.2 Hydro-Mechanical System . 47
6.4 Ejector System 51
7.1 Mold Components . 55
7.2 Types of Molds . 62
7.2.1 Cold Runner Molds . 62
7.2.2 Hot Runner Molds 64
7.2.3 Other Mold Types 66
7.3 Ejection . 67
7.4 Projected Area 68
7.5 Mold Venting . 70
7.6 Mold Cooling . 71
8Control 76
8.1 Processing Functions . 76
8.2 Control Functions 77
8.3 Process Control . 81
9 Robotics and Granulators . 83
9.1 Robotics . 83
9.2 Granulators . 84
10.1Mold Setup 86
10.2 Process Methods . 89
10.3 Process Setup 90
10.4 Mold Start-up . 93
10.5 Process Documentation 95
11 An Overview – The Cycle . 97
11.l The Cycle – Defined . 97
11.2The Importance of Cycle Time 98
10 Getting 86xi
l 1.3 The Greater Importance of “Good Production” . 100
12The Ten Keys to Successful Molding 102
12.1 Adequate Mold Venting . 102
12.2 Proper Mold Cooling . 105
12.3Using the Right Screw 106
12.4Selecting the Appropriate Valve 111
12.5 Controllingthe Heat Profile 113
12.6 Using Back Pressure Wisely . 119
12.7 Controlling the Injection Rate 120
12.8 Managing Screw RPM and Residence Time . 124
12.9 Performance Measurement 128
12.10Preventive Maintenance Program 130
13 Thermoset Molding 132
13.1 Thermoset Materials . 132
13.2 Machine Modifications . 134
13.3Processing Modifications 135
14Safety 137
14.1 Safety Requirementsof ANSI B15 1.1 137
14.2 Safety Rules to Follow 140
15 Recognizing Molding Problems 143
15.1 Process Problems 143
15.1.l Brittleness of Parts . 143
15.1.2 Bubbles and Voids . 144
15.1.3 Burned Material . 145
15.1.4 Cloudy or Hazy Parts . 146
15.1.5 Drool 147
15.1.6 Flash 148
15.1.7 Flow Lines 149
15.1.8 Gate Blush 149
15.1.9Inadequate Color Mixing 150
15.1.10 Jetting 152
15.1.11Knit Lines . 152
15.1.12 Part Deformation 153
15.1.13 Poor Screw Recovery 154
15.1.14 Short Shots 155xii
15.1.15 Sink Marks 156
15.1.16 Splay . 157
15.1.17 Warped Parts . 158
15.2 Component Wear Problems 159
16Terminology . 165
17 Other Molding Notes 186
17.1 Special Molding Processes 186
17.1.1Two Color Molding 186
17.1.3 Gas Assist Molding 189
17.1.4 Powder Injection Molding . 189
17.1.2 Turret Molding 188
17.1.5 Intrusion Molding 191
17.1.6 Other Molding Processes 191
17.2 Molding Operation Items 192
Appendices . 194
A Injection Molding Materials . 194
B Properties of Common Plastics . 196
C Recommended Plastic Drying Data 199
D Useful Data 200
Abbreviations and Symbols 200
Calculations 201
Conversions 202
E Velocity Control on Injection Molding Machines . 203
Nozzle Adaptors (End Caps) 209
F Procedure for Application of Bolt Torque on
References . 211
Index . 212
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