Extrusion Blow Molding A Practical and Comprehensive Guidebook Ottmar Brandau Apex Container Tech Inc. First published in 2013 © Ottmar Brandau. All rights reserved No part of this publication may be reproduced or transmitted in any form or by any means, electronic, or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. This book and all its contents are protected under copyright by the publisher. Operators, engineers, and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, or experiments described in this book. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have professional responsibility. To the fullest extent of the law, the author does not assume any liability for any injury or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use of any methods, instructions or ideas contained in the material herein. ISBN: 978-0-9919901-0-8 Cover Design by Lana Turcic-Brandau. She can be reached at: [email protected] Cover photos by Bekum America Corporation and the author By the same author: Stretch Blow Molding – Second Edition On 300 pages Mr. Brandau explains the ins and outs of this exciting technology. He delves in the material, explores the different machine types, and details all facets of the process including the single-stage process. Available at amazon.com Bottles, Preforms, Closures – Second Edition Mr. Brandau and 4 contributors illustrate the various design and process variables to make a complete PET package. A section on injection molding of preforms offers as yet the most insightful advice on perfecting the art. Available on amazon.com The Rapid Guide to Perfect Preforms Mr. Brandau and Mr. Unterlander share their detailed knowledge of the injection molding process of preforms by giving concrete advice on 35 common preform problems. Printed in a unique format this book should be part of every tool box. Available at https://www.hbmedia.info/petplanet/book6 The Guide to Extrusion Blow Molding can be purchased at www.blowmolding.org/Extrusion_Blow_Molding_Book.html List of Contributors I would like to thank the companies that have allowed me to use their photos and diagrams. A special tank you to Klaus Mischkowski for his excellent drawings. AGR International, Inc. www.agrintl.com Aignep Pneumatic, Italy www.ai gnep.it ALPS, USA www.alpsleak.com Barr Inc., USA www.robertbarr.com Bekum America Corporation, USA www.bekumamerica.com Berg Chilling Systems Inc., Canada www.berg-group.com Blow Mold Tooling, Canada www.blowmold.com BMC Controls, UK www.bmc-controls.co.uk Clorox Company, USA http://www.thecloroxcompany.com Compair, UK http://www.compair.com Conair, USA www.conairgroup.com Coretech Systems, USA http://www.coretechsystems.org/ Cumberland, USA http://www.cumberland-plastics.com/ Delta Engineering BVBA www.delta-engineering.com Distilled Water Company, USA www. thedistilledwatercompany.com Fong Kee, Taiwan www.fki.com Graham Engineering Co., USA www.grahamengineering.com Hill Learning Systems, USA www.hetacfluidpower.com Hunkar Laboratories, USA www.hunkarlabs.com Kautex Werke, Germany www.kautexinc.com Lectro Engineering Co., USA www.lectroengineering.com Maguire, USA www.maguire.com Moog Inc., USA www.moog.com MTM Systems, USA http://www.mtmsystems.com Noria Corporation, USA www.noria.com Nordic Sensors, Canada www.nordicsensors.com Chevron Phillips Chemical Company LP www.cpchem.com Proco Machinery, Canada www.procomachinery.com Schaub Chiler Service, USA www.chillers.com/ Guide to Extrusion Blow Molding Contents List of Contributors 6 Contents i Introduction 1 1. Machine Types 5 1.1 SHUTTLE MACHINES 5 1.1.1 Blow-and-Drop Machines 6 1.1.2 Tie-bar-less Machines 8 1.1.3 Clamp-mounted Deflashers 10 1.1.4 Clamp-mounted Deflasher with Intermediate station 11 1.1.4 Independent Deflashing Station 12 1.1.5 Take-out Robots 13 1.1.6 Horizontal Machines 14 1.2 RECIPROCATING (“RECIP”) MACHINES 16 1.3 ACCUMULATOR HEAD MACHINES 17 1.4 WHEEL MACHINES 19 1.5 COMPARISON OF THE DIFFERENT EBM MACHINE TYPES 20 1.5.1 Output 21 1.5.2 Tonnage 22 1.5.3 Extruder 23 1.5.4 Die Diameter 24 1.5.6 An Example 24 2. Machine Components 29 2.1 EXTRUDER 29 i Table of Contents 2.2 CLAMP DESIGNS 33 2.2.1 Direct-Acting Cylinder 33 2.2.2 Toggle Clamp 35 2.2.3 Electric Clamp 36 2.3 BLOW PINS 37 2.4 CUTTING DEVICES 40 2.4.1 Swing knife 40 2.4.2 Spear Knife (also called stab knife) 41 2.4.3 Squeegee or Pinch Knife 42 2.4.4 Hot Knife 43 2.4.5 Specialty Knife 44 2.5 HEAD TECHNOLOGIES 44 2.5.1 Splitters 44 2.5.2 Mandrel Head 46 2.5.3 Torpedo Head 47 2.5.4 Spiral Head 49 2.5.5 Head Tooling 50 2.6 PUNCH 51 2.6.1 Clamp-mounted Deflashers 51 2.6.2 Stationary Punch 52 2.6.3 Independent Punch/Trimmer 52 2.7 TOP AND BOTTOM BLOW 54 2.8 IN MOLD LABELING (IML) 55 3. Parison Programming (or Wall Thickness Control) 57 ii Guide to Extrusion Blow Molding 3.1 FUNCTION OF THE PROGRAMMER 57 3.2 PROGRAMMER COMPONENTS 59 3.3 PROGRAMMER SYSTEMS 62 3.3.1 Time-based System 62 3.3.2 Position-Based System 63 3.4 MOUNTING CONSIDERATIONS 65 3.5 PROGRAMMING THE PROGRAMMER 66 3.6 MULTI-CAVITY HEADS 70 3.7 OVALIZATION 71 3.8 OVALIZATION PROCEDURE 73 3.8 MOVING DIES DURING EXTRUSION 76 4. EBM Materials 79 4.1 PRODUCTION OF PLASTICS 79 4.2 AMORPHOUS, CRYSTALLINE, AND SEMI-CRYSTALLINE 84 4.3 SOLID AND MELT DENSITY 86 4.4 MELT FLOW INDEX 87 4.5 VISCOSITY AND SHEAR 88 4.7 THE FUTURE OF PLASTICS 90 5. Material Flow from the Extruder to the Die 91 5.1 EXTRUSION SCREW 91 5.2 CHANNEL FLOW 97 5.3 TEMPERATURES 99 5.4 PARISON SWELL 101 iii Table of Contents 6. Blowing a Container 105 6.1 INFLATING THE PARISON 105 6.2 SHUTTLE MACHINES 109 6.3 RECIPROCATING MACHINES 115 6.4 ACCUMULATOR HEAD MACHINES 115 7. Co-Ex Molding 119 7.1 CO-EX FOR DECORATION 120 7.2 CO-EX FOR POST-CONSUMER RESIN 121 7.3 BARRIER LAYER CO-EX 122 7.4 FOUR-LAYER CO-EX WITH BARRIER 123 7.5 FIVE-LAYER CO-EX WITH BARRIER 124 7.6 SIX-LAYER CO-EX WITH BARRIER 124 7.7 SEVEN-LAYER CO-EX WITH BARRIER 125 7.8 CO-EX EQUIPMENT 125 7.9 RUNNING CO-EX EQUIPMENT 127 8. Basic Hydraulics, Pneumatics, and Machine Control 129 8.1 HYDRAULICS 129 8.2 PNEUMATICS 136 8.3 MACHINE CONTROL 138 8.4 PID LOOPS 141 8.5 STATISTICAL PROCESS CONTROL (SPC) 144 9 Setting Up an EBM machine 147 9.1 CHANGE-OVER DIFFERENCES 147 9.2 PREPARATION 148 9.3 SETUP SHEETS 149 9.4 REMOVING OLD TOOLING 149 iv Guide to Extrusion Blow Molding 9.5 PURGING THE EXTRUDER AND HEAD 150 9.6 MOUNTING THE NEW TOOLS 151 9.7 MOUNTING DIES AND PINS 153 9.8 STARTING UP THE MACHINE 155 9.9 QUALITY CHECKS 157 10. Mold and Head Tooling 159 10.1 MOLD CONSTRUCTION 159 10.2 PINCH-OFF DESIGN 163 10.3 VENTING 165 10.4 FLASH DESIGN 167 10.5 HEAD TOOLING 169 10.6 PUTTING IT ALL TOGETHER – AN EXAMPLE 172 11. Container Design Considerations 175 11.1 DESIGN PROCESS 175 11.2 DESIGN CONSIDERATIONS 176 12. Quality 179 12.1 SAMPLING INTERVAL AND RESPONSIBILITY 179 12.2 NECK DIMENSIONS 181 12.3 WALL THICKNESS MEASUREMENTS 183 12.4 DROP TEST 185 12.5 TOP LOAD TEST 185 12.6 UN TESTING 187 13 Auxiliary Equipment 189 13.1 CHILLER 189 13.1.1 FUNCTION 189 v Table of Contents 13.1.2 PIPING 191 13.1.3. ANTI-FREEZE 194 13.1.4 FLOW IN COOLING SYSTEMS 195 13.1.5 CALCULATION OF CHILLED WATER REQUIREMENTS 196 13.2 COMPRESSOR 199 13.3 MATERIAL FEED 200 13.4 GRINDER 202 13.5 SPIN TRIMMER 204 13.6 DRYER 205 13.7 SURFACE TREATMENT 209 13.7.1 FLAMERS 209 13.7.2 CORONA TREATMENT 210 13.7.3 COLD PLASMA DISCHARGE TREATMENT 211 13.7.4 FLUORINATION TREATMENT 211 13.9 PACKAGING SYSTEMS 212 13.10 LEAK TESTER 219 13.11 Cooling formula 221 13.12 MONITORING ENVIRONMENTAL CONDITIONS 222 14. Process Troubleshooting Guidelines 225 15 Troubleshooting Common Problems 229 15.1 AIR BUBBLES 229 15.2 BAD PARTING LINES 230 15.3 BOTTOM WEBBING 231 15.4 CONDENSATION MARKS 231 15.5 CONTAMINATION 233 15.6 CONTAINER DEFORMATION 234 15.7 CONTAINER RUPTURE 235 vi Guide to Extrusion Blow Molding 15.8 CURTAINING 235 15.9 DISCOLORATION OR UNEVEN COLOR APPEARANCE 236 15.10 DIE LINES 238 15.11 DOUGHNUT FORMATION 239 15.12 DULL FINISH 240 15.13 EXCESS MATERIAL IN BASE 241 15.14 GELS IN BOTTLE 242 15.15 HANDLE WEBBING 243 15.16 HOLES 244 15.17 INSUFFICIENT TOP LOAD 245 15.18 MATERIAL DEGRADATION 246 15.19 MOISTURE BUBBLES 246 15.20 NECK “EARS” 247 15.21 NECK CHOKES 248 15.22 OVAL NECKS 249 15.23 ORANGE PEEL 250 15.24 PANELING OR PANEL SINK 251 15.25 POOR FLASH SEPARATION 251 15.26 ROCKER BOTTOM 252 15.27 SIDEWALL FLASH 253 15.28 WELD (“SPIDER “) LINES 254 15.29 UNEVEN WALL DISTRIBUTION 255 15.30 UNMELTS 255 15.31 VENTING ISSUES 256 15.32 WEAK BASE SEAM 256 15.33 WEAK SPOTS IN SIDE WALL 257 vii Table of Contents 16.