Practical Guide to Blow Moulding

217 Pages·37.381 MB·English

by  Lee, Norman

by Norman Lee
Practical Guide to Polyethylene
Practical Guide to Blow Moulding
by
Norman C. Lee
Attractive Design Ltd.
Rapra Technology Limited
Shawbury, Shrewsbury, Shropshire, SY4 4NR, UK
Tel: [phone] Fax: [phone] http://www.rapra.net
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Practical Guide to Polyethylene
©2006 Rapra Technology Limited
ISBN: 1-85957-513-7
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or
transmitted in any form or by any means - electronic, mechanical, photocopying, recording or otherwise
- without the prior permission of the publisher, Rapra Technology Limited, Shawbury, Shrewsbury,
Shropshire, SY4 4NR, UK.
Every effort has been made to contact copyright holders of any material reproduced within the text
and the authors and publishers apologise, if any have been overlooked.
Typeset, printed and bound by Rapra Technology Limited.
Cover printed by Livesey Limited, Shrewsbury
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Practical Guide to Polyethylene
Contents
1 What is Blow Moulding? ................................................................................1
1.1 Introduction .....................................................................................................1
1.1.1 Defi nition ..................................................................................................1
1.1.2 Basic Process ..............................................................................................1
1.1.3 History and Development .........................................................................2
1.2 Types of Blow Moulding .................................................................................4
1.2.1 Introduction ...............................................................................................4
1.2.2 Stretch Blow Moulding .............................................................................6
1.2.3 Extrusion Blow Moulding .........................................................................7
1.3 Material Considerations ................................................................................10
1.3.1 Materials Selection ..................................................................................10
1.3.2 Product Properties and Market Usage ...................................................11
References ...........................................................................................................12
2 Design and Engineering ...............................................................................13
2.1 Design ...........................................................................................................13
2.1.1 Product Design and Development System .............................................14
2.1.2 Process Management Tracking Systems .................................................14
2.2 Basic Design ...................................................................................................15
2.2.1 Basic Design Considerations ...................................................................17
2.2.2 Bottle and Container Design ..................................................................22
2.2.3 Structural Design .....................................................................................27
2.2.4 Design Details ..........................................................................................29
2.3 Selection of Materials ...................................................................................32
2.3.1 Polymer Principles ...................................................................................32
2.3.2 Types of Polymers ....................................................................................32
2.3.3 Amorphous and Crystalline ....................................................................34
2.3.4 Fundamental Properties ..........................................................................34
2.4 Characteristics For Blow Moulding ..............................................................39
2.4.1 HDPE .........................................................................................................39
2.4.2 Acrylonitrile Butadiene Styrene (ABS) ...................................................40
2.4.3 Polycarbonate (PC) ..................................................................................41
2.4.4 Polypropylene .........................................................................................42
2.4.5 Polyphenylene Oxide ..............................................................................43
2.5 Colouring Plastic Materials ...........................................................................44
2.6 Regrind ..........................................................................................................45
2.6.1 Re-grind Specifi cations ............................................................................45
2.6.2 Process Performance ...............................................................................45
2.6.3 Physical Properties ...................................................................................45
2.7 Post Consumer and Industrial Recycled Materials .......................................45
References ...........................................................................................................46
General Reading ..................................................................................................46
3 Mould Design and Engineering ....................................................................47
3.1 Main Characteristics of the Mould ...............................................................47
3.2 Basic Design and Construction Considerations ............................................47
3.2.1 Mould Materials ......................................................................................48
3.2.2 Selection of Materials .............................................................................50
3.2.3 Characteristics of Mould Materials .........................................................50
3.3 Cut Mould versus Cast Moulds .....................................................................52
3.3.1 Cast Aluminium Moulds ..........................................................................52
3.3.2 Cut Moulds ...............................................................................................53
3.3.3 Cast and Cut Moulds ...............................................................................53
3.4 Importance of Fast Mould Cooling ..............................................................53
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3.4.1 Fast Heat Transfer Material Considerations ...........................................53
3.4.2 Manifolds .................................................................................................59
3.4.3 Control of Flash .......................................................................................60
3.4.4 Rate of Cooling ........................................................................................61
3.4.5 Remedies for Flash ..................................................................................61
3.5 The Pinch Off .................................................................................................62
3.5.1 Importance ...............................................................................................62
3.6 High Quality, Undamaged Mould Cavity Finish ..........................................64
3.6.1 Mould Cavity Finish .................................................................................64
3.7 Effects of Air and Moisture Trapped in the Mould .....................................66
3.7.1 Polished Moulds ......................................................................................66
3.7.2 Moisture ...................................................................................................66
3.8 Injection of the Blowing Air .........................................................................66
3.8.1 Injection Blowing Air ..............................................................................66
3.8.2 Blowing Devices .......................................................................................67
3.9 Ejection of the Piece from the Mould ..........................................................67
3.9.1 Ejection Methods .....................................................................................67
3.9.2 Manual Ejection .......................................................................................68
3.9.3 Automatic Ejection ..................................................................................68
3.9.4 Hydraulic Systems ....................................................................................68
3.10 Pre-Pinch Bars ..............................................................................................68
3.10.1 Top Pinch ................................................................................................68
3.10.2 Bottom Pinch .........................................................................................68
3.11 Bottle Moulds ..............................................................................................68
3.11.1 Neck Ring and Blow Pin Design ............................................................68
3.12 Dome Systems ..............................................................................................70
3.12.1 Dome Blow Pin ......................................................................................70
3.12.2 Trimming Types ......................................................................................71
3.13 Pre-Finished System .....................................................................................71
3.13.1 Pre-Finished Neck Rings ........................................................................71
3.14 Unusual Problems ........................................................................................71
3.14.1 Special Features .....................................................................................71
3.14.2 Irregular Shaped Parts ...........................................................................72
3.15 Computer Aided Design and Engineering for Mould Making .................73
3.15.1 Application in Mould Making ..............................................................73
3.15.2 Systems and Methods ............................................................................73
3.16 General Mould Buying Practices ...............................................................77
3.16.1 Mould Procurement ..............................................................................77
3.16.2 Request for Quotation ..........................................................................77
3.17 Mould Maintenance Program ...................................................................78
3.17.1 The Moulds Used to Produce Polyvinyl Chloride (PVC) and
Polyethylene Terephthalate ..................................................................78
3.17.2 Moulds for PE ........................................................................................78
3.17.3 Mould Cooling Lines .............................................................................78
3.17.4 Guide Pins and Bushings ......................................................................78
3.17.5 Striker Plates and Blow Pin Plates ........................................................78
3.17.6 Pinch off .................................................................................................79
3.17.7 Shut Down .............................................................................................79
Acknowledgements ............................................................................................79
References ...........................................................................................................79
Further Reading ..................................................................................................79
4 The Extrusion Blow Moulding System .........................................................81
4.1 Extruder .........................................................................................................81
4.2 Drive ...............................................................................................................82
4.2.1 Motors ......................................................................................................82
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4.3 Gear Box ........................................................................................................83
4.4 Screw Support Bearings ................................................................................83
4.4.1 Life of Thrust Bearings ............................................................................83
4.5 Extruder Feed ................................................................................................84
4.5.1 Feed ..........................................................................................................84
4.6 Hopper ..........................................................................................................85
4.6.2 Feed Throat ..............................................................................................85
4.7 Single-Screw Extruder ...................................................................................86
4.7.1 Barrel Construction .................................................................................86
4.7.2 Zone Heating ...........................................................................................86
4.7.3 Venting ....................................................................................................86
4.7.4 Wear Resistant Barrels ............................................................................87
4.7.5 Grooved Barrels .......................................................................................87
4.7.6 Pressure Generation ................................................................................87
4.8 Melt Filtration ...............................................................................................87
4.9 The Screw .......................................................................................................87
4.9.1 General-Purpose Screw ...........................................................................87
4.9.2 Screw Zones .............................................................................................88
4.9.3 Dedicated Screws .....................................................................................88
4.9.4 Barrier Screws ..........................................................................................89
4.9.5 Wear-Resistant Screws .............................................................................89
4.9.6 Mixing Pins and Sections .........................................................................90
4.9.7 Distributive and Dispersive Mixing .........................................................90
4.10 The Extrusion Blow Moulding Head and Die Unit ....................................91
4.10.1 Centre-Feed Die ....................................................................................92
4.10.2 Side-Feed Dies ........................................................................................93
4.10.3 Wall Thickness .......................................................................................93
4.10.4 Accumulator Head ................................................................................93
4.10.5 Die and Mandrel ....................................................................................93
4.10.6 Die Swell ................................................................................................94
4.10.7 Parison Adjustment ..............................................................................94
4.10.8 Die Shaping ............................................................................................95
4.10.9 Parison Programming ............................................................................96
4.10.10 Blow-up Ratio ......................................................................................97
4.11 Mould Clamping Systems ............................................................................98
4.11.2 Clamping System Requirements ...........................................................98
4.11.3 Clamp Operation ...................................................................................98
4.11.4 Press Types .............................................................................................98
5 Extrusion Blow Moulding Advanced Systems ..........................................103
5.1 Co-Extrusion Blow Moulding ......................................................................103
5.1.1 Arrangement of Extruders for Co-Extrusion ........................................103
5.1.2 Multi-Layered Structures .......................................................................103
5.1.3 Co-Extrusion Systems .............................................................................103
5.2 Three-Dimensional Blow Moulding ...........................................................105
5.2.1 Introduction to 3-D ...............................................................................105
5.2.2 3-D Extrusion Processes .........................................................................106
5.2.3 Suction Blow Moulding .........................................................................106
5.2.4 Parison Manipulation ............................................................................110
5.2.5 3-D Extrusion Systems ...........................................................................111
5.2.6 Head Adapter Radial Wall System ........................................................114
5.3 Double Walled Parts and Containers .........................................................116
6 Injection and Stretch Blow Moulding Machines .......................................117
6.1 Introduction .................................................................................................117
6.1.1 Injection Moulding Process ...................................................................118
6.2 Process Characteristics .................................................................................118
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6.2.1 One step Machine .................................................................................118
6.2.2 Two Step Process ...................................................................................120
6.2.3 Moulding Process ..................................................................................120
6.3 Tooling .........................................................................................................121
6.3.1 Introduction ...........................................................................................121
6.4 Stretch Blow Moulding ...............................................................................127
6.4.1 Introduction ...........................................................................................127
References .........................................................................................................129
7 Safe and Effi cient Set-up, Start-up, Operation, Shutdown
Procedures and Safety ................................................................................131
7.1 Start-up ........................................................................................................131
7.1.1 Start-Up Preparations ............................................................................131
7.1.2 Melt Temperature .................................................................................131
7.1.3 Warming up an Empty Machine ...........................................................132
7.1.4 Warming up a Full Machine .................................................................132
7.1.5 Initial Operation and Purging ..............................................................132
7.1.6 Commencing Moulding – Manual Operation ......................................133
7.1.7 Commencing Moulding – Automatic Operation .................................133
7.1.8 Changing Conditions and Dimension Verifi cation ..............................133
7.1.9 Recording Production Conditions ........................................................134
7.2 Safety in Normal Machine Operation ........................................................134
7.2.1 Operation ...............................................................................................134
7.2.2 Safety Considerations ............................................................................134
7.3 Shutting Down ............................................................................................135
7.3.1 Temporary Stops ....................................................................................135
7.3.2 Overnight Stops .....................................................................................136
7.3.3 High Temperature Work .......................................................................137
7.3.4 Heat-Sensitive Materials .......................................................................137
7.3.5 Purge Materials .....................................................................................137
7.3.6 Shutting Down an Injection Blow Moulding Machine .......................137
7.3.7 Check Recommendations ......................................................................138
References .........................................................................................................138
8 Fault Finding – Causes and Effects .............................................................139
8.1 Introduction .................................................................................................139
8.2 Troubleshooting ..........................................................................................139
8.3 Brainstorming ..............................................................................................139
8.4 Problems and Causes ...................................................................................140
8.4.1 Background Sounds of the Plant ..........................................................142
8.4.2 Quality Problems ...................................................................................142
8.4.3 Machine and Equipment Problems ......................................................142
8.4.4 Importance of Consistent Material .....................................................143
8.4.5 Process Settings .....................................................................................143
8.4.6 Ambient Conditions ..............................................................................143
8.5 Preventive and Corrective Actions .............................................................143
8.5.1 Corrective Actions .................................................................................143
8.5.2 Corrective-Action Team ........................................................................145
8.5.3 Root Cause .............................................................................................145
8.6 Packaging ....................................................................................................146
8.7 Scrap .............................................................................................................147
8.7.1 Contaminated Material .........................................................................147
8.7.2 Reworked Parts ......................................................................................147
9 Auxiliary Equipment: Design, Function, Operation, and Safety ..............149
9.1 Bulk Material Handling Systems .................................................................149
9.2 Dryer ............................................................................................................149
9.2.1 Hot Air Dryers ........................................................................................149
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9.2.2 Dryer Operation ....................................................................................150
9.2.3 Dryer Safety ...........................................................................................151
9.3 Blenders and Metering Equipment (Feeders) ............................................151
9.3.1 A Volumetric Blender ............................................................................152
9.3.2 Gravimetric Systems .............................................................................152
9.3.3 Metering and Blending Equipment .....................................................152
9.3.4 Machine Operation ...............................................................................152
9.4 Machine Safety ...........................................................................................153
9.5 Hopper Loader ............................................................................................153
9.5.1 Loader Operation ..................................................................................154
9.6 Water Temperature Controllers .................................................................154
9.6.1 Operation ...............................................................................................155
9.7 In-line Inspection and Testing Equipment ................................................155
9.7.1 Laser Measurement ...............................................................................155
9.7.2 Ultrasonic Testing ..................................................................................155
9.7.3 Vision Systems .......................................................................................156
9.7.4 Mechanical .............................................................................................157
9.8 Conveyors ....................................................................................................157
9.9 Granulators ..................................................................................................158
9.10 Safety ........................................................................................................158
10 Finishing ......................................................................................................161
10.1 Planning for the Finishing of a Blow Moulded Part ...............................161
10.1.1 Product Design ....................................................................................161
10.1.2 Mould Engineering .............................................................................162
10.1.3 Process Planning ..................................................................................163
10.2 Removing Domes and Other Sections ......................................................167
10.3 Flash Removal ............................................................................................167
10.3.1 The Cutting Machine – Round Parts versus Parts with Corners ........167
11 Decoration of Blow Moulded Products .....................................................169
11.1 Testing Surface Treated Parts ..................................................................169
11.2 Spray Painting ...........................................................................................170
11.3 Screen Printing ..........................................................................................170
11.4 Hot Stamping ............................................................................................172
11.5 Pad Printing ...............................................................................................172
11.6 Labels and Decals ......................................................................................174
12 Glossary .......................................................................................................175
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Practical Guide to Polyethylene
8
Practical Guide to Blow Moulding
Preface
Blow moulding has evolved from the ancient art of glass blowing and it is used to advantage with
plastic materials specifi cally because these materials can be engineered to provide a variety of
properties. These properties have been developed over a period of time beginning with celluloid,
which was fi rst used to blow mould baby rattles and novelties in the 1930s. Linear low-density
polyethylene was used in the 1940s for high production bottles; polyethylene terephthalate (PET) was
used to make soda bottles by the injection blow moulded stretch method, to the highly sophisticated
multilayered containers and automotive fuel tanks in the last decade, and complicated twisted
shapes by the three dimensional blow moulding method in the last few years.
The plastic industry as a whole, blow moulding in particular, is driven to take advantage of
material development and computer technology with microprocessors, the latter enabling process
programming of machines and robots. The machine and mould builders responded by developing
robust sophisticated equipment.
The author has been personally involved in the development of the industry since the early 1960s.
During the 1980s he recognised the need for individuals in the industry to keep up with new
developments and advances in materials, processes and equipment, and he developed a series of
blow moulding seminars, which were held by the Society of Plastic Engineers. Key experts from
the industry (listed below) were selected to present the latest and greatest advances in materials,
equipment and processes.
Each of these has infl uenced the content of this book – Practical Guide to Blow Moulding. It is
presented in simple language describing the basics of blow moulding as well as latest state-of-the-
art and science of the industry.
A key feature is the approach of discussing the ‘basics’ then taking the reader through the entire
process from design development through to fi nal production.
Finally I wish to acknowledge the hard work of the Blow Moulding Quality Engineer, Loretta Lee
from WhiteRidge Plastics in assisting me with the manuscript and diagram production without
which this work would not have been possible.
Ralf Abramo, Sr., – R.J. Abramo Associates
John Bergerhouse – Equistar Corporation
Karl Bruning – Formally Bekum America Corporation
Gary Carr – Bekum America Corporation
Lewis Ferguson – Parisons
Andrew Fricke – Formally Hunkar Laboratories Inc.
Paul Geddes – B&G Products, Inc.
John HSU – Cincinnati Milacron Corporation
Richard Morgan – Formally with Cincinnati Milacron Corporation now with Wilmington
Machinery
John McNamara – Formally Blow Moulding Specialties, Inc
Robert Jackson – Jackson Machinery, Inc.
Robert Slawska – Proven Technology, Inc.
Bruce Vogel – Portage Casting & Mold, Inc.
Mitra Yousefi – Industrial Materials Institute NRC/CNRC
Ron Walling – Advanced Material Center, Inc.