Rubber Processing and Production Organization

Rubber Processing and Production Organization

Rubber Processing and Production Organization Philip K. Freakley Institute of Polymer Technology Loughborough University of Technology Loughborough, United Kingdom Plenum Press New York and London

Library of Congress Cataloging in Publication Data Freakley, Philip K. Rubber processing and production organization. Includes bibliographies and index. I. Rubber industry and trade. I. Title. TSI890.F7 1985 678'.2 ISBN -13: 978-1-4612-9452-8 001: 10.1007/978-1-4613-2375-4 e-isbn-13: 978-1-4613-2375-4 84-24835 1985 Plenum Press, New York Softcover reprint of the hardcover 1st edition 1985 A Division of Plenum Publishing Corporation 233 Spring Street, New York, N.Y. 10013 All rights reserved No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording, or otherwise, without written permission from the Publisher

To Viv, for helping to unsplit infinitives

Foreword The absence of a book dealing with rubber processing has been apparent for some time and it is surprising that a straightforward text has not been produced. However, this book goes far beyond the scope of a simple technical approach and deals with the full spectrum of activities which lead to successful and profitable product manufacture. The need to deliver a product to a customer at the right time, at the right cost, and at the right quality is a basic premise on which the book is based. The increasingly stringent demands of customers for products that can be introduced directly into an assembly or production line without goodsinwards inspection, are placing increasing pressures on the manufacturer. As a result, it is becoming essential to achieve and sustain product quality and consistency, by the monitoring and control of manufacture, at a level which renders all products saleable. The book has been written to satisfy the needs of practitioners in the rubber industry and is certainly not another descriptive text which is only read for interest when more important matters are not pressing. My close cooperation with Philip K. Freakley during the writing of the book has resulted in the incorporation of many of the viewpoints and methods which I have developed and refined during more than 38 years in the rubber industry. Since I feel that my own company is at the forefront of the application of computers to rubber product manufacture, it has been possible to draw upon sound practical experience of their applications in both the management and technical areas of rubber company activity, and then to project these applications forward some five years. In many of its aspects, the subject matter of the book looks to the future and anticipates technical and organizational methods which rubber companies will need to assimilate and apply, in order to maintain and improve their performance. I strongly recommend this book for all company staff involved in rubber product manufacture. Works Director, Woodville Polymer Engineering Ltd. R. W. Garfield vii

Preface The primary aim of this book is to provide technical, engineering, and management staff in rubber product manufacturing companies with a detailed and practical guide to manufacturing systems. In recent years the need to achieve greater productivity and precision in manufacture, in order to satisfy the increasingly stringent demands of customers, has stimulated a much greater interest in manufacturing methods than has hitherto been apparent. The changes thus initiated have now been substantially accelerated by the advent of the microprocessor, with all its attendant implications for automation, process monitoring, and production organization. The style of the book owes much to its emphasis on computer methods and the adoption of the systems approach to manufacturing, both of which have been extensively developed in the area of general production engineering and management. It is also unique in using the commercial viewpoint to put the technical details of processing operation performance into an economic perspective. The basis of the systems approach is the recognition that the development or improvement of a manufacturing facility can be divided into two major stages, which are known as analysis and synthesis. In analysis the basic elements of a manufacturing system are identified and dealt with separately, with the objective of understanding and subsequently improving them. Synthesis is then concerned with the reassembly of the improved elements into a system which fully exploits all the advantages to be gained from them. However, because of the interactions and dependencies which inevitably occur among elements, improved system performance cannot be guaranteed without an understanding of the principles and practice of synthesis. Many technical activities (and texts) concentrate upon analysis to the almost total exclusion of synthesis. This may account for the difficulties which are often experienced in demonstrating that improved profitability accrues from technical progress in manufacturing methods. In this book Chapters 2 to 6 are primarily concerned with analysis, dealing with material ix

x PREFACE behaviour and the main processes of the rubber industry. Chapters 7 to 11 then address the complex task of assembling or synthesizing the individual processes into efficient manufacturing systems, capable of achieving high productivity and profitability. Because of its objective of providing a practical guide to product manufacture, the book concentrates upon the efficient utilization of currently available equipment. Design of machinery is only covered insofar as it is necessary to support the selection of equipment for purchase; theoretical methods are only introduced where they can be directly applied to the improvement of process performance. While a detailed understanding of microprocessor systems and mathematical methods may be necessary to implement some of the techniques dealt with in the book, the concepts involved and their applications should be readily apparent. Managers will be able to gain a clear overview of the resources needed to implement the suggested techniques and the benefits to be derived from them. Institute of Polymer Technology Loughborough University of Technology, U.K. Philip Freakley

Acknowledgments A number of people have given generously of both their time and expertise to ensure that the treatment of the very broad range of topics covered in this book is both accurate and consistent in contributing to the subject of "rubber product manufacturing systems." First and foremost, Roy Garfield, Works Director of Woodville Polymer Engineering Ltd., was unable to carry through his original intention of coauthorship, due to unavoidable pressures of work, but has maintained an encouraging interest and enthusiasm for the book. He undertook the substantial task of reading and discussing the manuscript with the author as it was produced, with the result that an eminently practical and industrially relevant approach has been maintained throughout. Chapters 10 and 11 were read by Dr. Malcolm R. Hill of the Management Studies Department of Loughborough University of Technology and the former chapter by his colleague, Mr. Nigel Coulthurst. Many useful comments and suggestions flowed from their detailed appraisal of these two chapters, which have contributed substantially to their coherence. A number of processing machinery manufacturers have provided detailed illustrations and have assisted the author by discussion of the design, operation, and control of their equipment. The majority of these contributions are acknowledged in the text. Last, but certainly not least, the author would like to thank Mrs. Joyce Deaville of Woodville Polymer Engineering Ltd., who typed the manuscript and coped with some very substantial additions and modifications, and Mrs. Barbara Green of the Institute of Polymer Technology, who undertook the exacting task of labeling the illustrations. xi

Contents 1. RUBBER PRODUCT MANUFACTURING SYSTEMS 1 1.1. Introduction... 1 1.2. The Systems Concept... 3 1.3. The Selection and Operation of Tests for Unvulcanized Rubber... 5 1.4. The Prediction, Monitoring, and Control of Process Performance... 7 1.5. Production Organization 8 References..... 13 2. MATERIALS BEHA VIOR AND TESTING 15 2.1. 2.2. 2.3. 2.4. 2.5. Introduction.... Flow Properties of Raw Elastomers and Rubber Mixes Measurement of Flow Properties Thermal and Heat-Transfer Properties Vulcanization Characteristics References 15 16 21 29 32 40 3. PRINCIPLES OF MIXING AND INTERNAL MIXERS 3.1. Introduction.... 3.2. The Mechanisms of Mixing 3.3. Elements of Internal Mixer Design 3.4. Practical Mixing Variables 3.5. Flow Instabilities.... 3.6. Laboratory Simulation of Full-Scale Mixing References............. 43 43 44 48 56 64 65 67 xiii

xiv 4. SCREW EXTRUSION AND CONTINUOUS MIXING CONTENTS 69 4.1. 4.2. 4.3. 4.4. 4.5. 4.6. 4.7. Introduction Elements of Extruder Construction Hot-Feed Extruders.... Cold-Feed Extruders.... Design of Extruder Heads and Dies Determination and Control of Extruder Operating Characteristics Continuous Mixing References 69 70 74 75 79 94 100 108 5. CALENDERING AND MILLING 111 5.1. 5.2. 5.3. 5.4. 5.5. 5.6. 5.7. Introduction... The Operating Characteristics of Two-Roll Mills Mill and Calender Roll Temperature Control Calender Configurations and Operations Roll Deflection and Methods of Correction Feeding, Sheet Cooling, and Batch-OfT Equipment Determination and Control of Calender Operation Characteristics References 111 111 118 119 121 124 126 129 6. HEA T TRANSFER AND VULCANIZA TlON METHODS 131 6.1. 6.2. 6.3. 6.4. 6.5. 6.6. Introduction Heat Transfer Prediction of State of Cure Molding.... Batch Vulcanization Continuous Vulcanization References 131 131 140 146 172 174 181 7. PROCESS CONTROL AND QUALITY CONTROL 183 7.1. The Interaction of Process Control and Quality Control 183 7.2. Specifications... 184 7.3. Process-Capability Studies 192 7.4. Process Monitoring 217

CONTENTS 7.5. Process Control 7.6. Quality Control References xv 241 254 264 8. PLANT LA YOUT AND OPERA TlONS METHODS 267 8.1. General Considerations....... 267 8.2. Transport and Storage in Manufacture 271 8.3. Handling Methods and Operations at Work Stations 280 8.4. Planning and Allocating Space 288 8.5. Layout Synthesis and Evaluation 296 8.6. Installing and Commissioning a Layout 309 References... 313 9. COMPANY PHILOSOPHY, ORGANIZA TlON, AND STRA TEG Y 315 9.1. Philosophy.............. 9.2. Company Organization......... 9.3. Market Research and Company Development References.............. 315 316 336 351 10. THE ECONOMICS OF MANUFACTURING OPERA TlONS 353 10.1. The Flow of Cash Through a Company 10.2. Cost Identification and Analysis Methods 10.3. Standard Costs... 10.4. Business Plans and Budgets 10.5. Budgetary Control References.... 353 356 369 377 391 395 11. PRODUCTION MANAGEMENT 11.1. Production Planning 11.2. Purchasing and Inventory Control 11.3. Implementing the Production Plan References.... 397 397 412 431 442 INDEX... 445