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Manufacturing Assembly Handbook PDF

399 Pages·1986·11.871 MB·English
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Manufacturing Assembly Handbook Bruno Lotter Butterworths London Boston Singapore Sydney Toronto Wellington (^ PART OF REED INTERNATIONAL P.L.C. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means (including photocopying and recording) without the written permission of the copyright holder except in accordance with the provisions of the Copyright Act 1956 (as amended) or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 33-34 Alfred Place, London, England WCIE 7DP. The written permission of the copyright holder must also be obtained before any part of this publication is stored in a retrieval system of any nature. Applications for the copyright holder's written permission to reproduce, transmit or store in a retrieval system any part of this publication should be addressed to the Publishers. Warning: The doing of an unauthorized act in relation to a copyright work may result in both a civil claim for damages and criminal prosecution. This book is sold subject to the Standard Conditions of Sale of Net Books and may not be resold in the UK below the net price given by the Publishers in their current price list. English edition first published 1989 Originally published as Wirtschaftliche Montage - Ein Handbuch fur Elektrogeratebau und Feinwerktechnik by VDI-Verlag GmbH, Diisseldorf, West Germany © VDI-Verlag GmbH, Diisseldorf 1986 British Library Cataloguing in Publication Data Lotter, Bruno Manufacturing assembly handbook. 1. Manufactured goods. Assembly I. Title II. Wirtschaftliche Montage. English 670.42 ISBN 0-408-03561-7 Library of Congress Cataloguing in Publication Data applied for Filmset by Mid-County Press, London SW15 2NW Printed and bound by Hartnoll Ltd, Bodmin, Cornwall Preface The rational assembly of electrical and precision engineering products such as domestic appliances, electrical products, do-it-yourself equipment and car accessories has become a decisive competitive factor for quality improvements and cost reductions. The range of solutions offered extends from the economically designed manual assembly station up to highly flexible robot-equipped and computer- controlled assembly cells and systems. In addition to product and operational knowledge, a whole range of methodic and technical expertise in the field of assembly technology is required to identify the most economic option in each and every case and which, by and large, has not previously been available in a practically relevant form for this product range. It is therefore particularly gratifying when such a renowned expert as Bruno Lotter, the Technical Director of an electrical engineering company with production plants at home and overseas, combines his professional experience covering more than 20 years in a comprehensive book. The realization process for an assembly device from the user's point of view was taken as a guideline, the procedure in each phase being illustrated by numerous practical examples. Precision and electrical engineering companies therefore have a guideline at their disposal for the planning and realization of assembly equipment which thoroughly examines all aspects of this modern branch of production technology and gives rise to a whole range of scientific ideas for independent problem solution. I wish the book rapid success and am convinced that it will occupy a permanent position amongst the literature of the relatively young science of assembly technology because it addresses itself to both the practising and student engineer alike. Hanover, April 1986 Hans-Peter Wiendahl Foreword Today, virtually all companies are faced with the urgent necessity to either maintain or regain their competitiveness. Increased productivity is an important requirement in achieving this aim. Since, however, significant advances in productivity are no longer expected in the classical fields of production such as metal machining and forming, etc. increased attention is being focused on the rationalization of assembly processes, and particularly so since the proportion of the assembly costs related to the manufacturing costs of a product is continually increasing. The assembly process must therefore be highly optimized, mechanized and automated in companies which manufacture assembly-intensive products. Assembly can be rationalized from the manual single- station operation up to the point of automation by organizational and technical measures. The possible level of automation of a product is principally determined by two factors, namely the production rate and the product design. The prime object of this book is to identify clearly the possibilities for the rationalization of assembly in relation to the above-mentioned factors. In this respect, an assembly-oriented product design forms the basis for both economic manual assembly and also the fundamental requirement for automated assembly. For this reason, particular emphasis is given to assembly-oriented product design. At low production rates or with complicated assembly processes, in the foreseeable future optimized manual assembly will remain the most economic. For this reason, in this book, assembly technology is not only viewed from the aspect of automation but covers the whole range of systems from entirely manual assembly to fully automated assembly systems. This book is written based on practical experience for practical application and will give experts in the field of rationalization guidelines for the solution of rationalization problems. Furthermore, it will be of assistance to training establishments and, in addition, give students of production technology a general insight into the state of assembly technology, into systematic planning and realization procedures for assembly operations. Thanks are extended to companies and institutions for the kind provision of material for the presentation of this book and also those who have assisted me by the sacrifice of their spare time. Special thanks are extended to Herr Professor Dr-Ing. Hans-Peter Wiendahl, Director of the Institut fur Fabrikanlagen at Hanover University, for his many valued suggestions and the critical review of the manuscript. Herr Dr Klinger of Messrs Festo is also thanked for his assistance in the preparation of the chapter on controllers. Gratitude is likewise expressed to VDI-Verlag Dusseldorf for their close cooperation and production of the book. Sulzfeld, May 1986 Bruno Loiter vii Chapter 1 Introduction 1.1 Assembly As a general rule, industrially produced products are formed from a large number of single parts produced at different times and by various production processes. The object of assembly is to form a part of higher complexity with specified functions in a specific period of time from the individual parts [1]. As specified in DIN 3593, assembly operations are processes of assembling together and as defined by VDI-guidelines 3239, 3240 and 3244 are functions of workpiece manipulation. The principal activities during assembly are shown in Figure 1.1 including operations such as adjustment and inspection and also the performance of secondary functions such as cleaning and deburring, etc. Material feed by Assembly by - Bunkering - Laying together - Magazining positioning -Transfer suspending - Separating - Filling - Converging saturating - Orienting - Pressing on rotating keying -Turning over screwing slewing force-fitting -Allocation Secondary - Basic forming - Infeed Inspection | operations form-casting - Discharge form-pressing - Measurement ■ Setting - Cleaning - Positioning - Re-forming -Testing ■ Matching - Deburring - Clamping folding • Locking - Fitting - Release riveting - Printing - Material - Marking combinations - Heating welding - Cooling soldering bonding - Other jointing processes binding stitching Figure 1.1 Activity groups employed during assembly (DIN 8593 -IPA Stuttgart) 2 Introduction 1.2 Status of assembly in the production operation In industrial production, the classical production technologies such as metal cutting, re-forming and basic forming, etc. have achieved a high level of automation. Parts are produced at low cost. On the other hand, assembly is largely a manual operation with the interplay of many different functions. In the fields of electrical and precision engineering technology, the wage cost components for assembly are between 25 % and 70% of the total wage costs. The wage costs included in the manufacturing costs of a product are segregated into the following components: • metal-cutting production • non-cutting production • moulded parts production • assembly • testing. It is clearly shown that the assembly operations are the most expensive production stage. Figure 1.2 shows an analysis of three selected products. The rationalization 0 10 20 30 40 50 60 70 80 90 100% Labour cost proportion Figure 1.2 Composition of wage costs for selected precision engineering products potential for assembly is quite evident [2]. However, comparable successes, for example in metal-cutting production technology, are yet to be seen. The principal obstacles to rapid rationalization achievements in assembly are as follows [3]: • The product service life is decreasing, the batch sizes are smaller and the number of variants greater. • Assembly is the last production stage and must continuously be adapted to changing market demands. Status of assembly in the production operation 3 • All the errors in planning, product development and initial production directly affect assembly. • The physical work components of assembly are widely varied and necessitate a high labour involvement to achieve higher flexibility. • Product-specific assembly techniques and organizational forms such as individual work stations, line assembly, erection point assembly and automatic assembly obstruct the implementation of once established solutions to other products. • Products are not designed in terms of assembly considerations. The rationalization of assembly can only be successful if the existing product design is also brought into question. This aspect will therefore be the subject of closer consideration on the basis of practically considered fundamental questions. Chapter 2 Product design as a requirement for economic assembly The development of a product is characterized by the specified product function. The production processes are largely dictated by the design of the individual parts and the product assembly arrangement. Figure 2.1 shows a correlation of cost responsibility and origination of the principal company areas of Design, Parts Manufacture and Assembly in accordance with Reference 4. It is clear that the Design Department only accounts for 12% of the manufacturing costs. However, it largely determines the production processes by the selection of material, tolerances and dimensions, etc. and is therefore responsible for 75% of the manufacturing costs. Since assembly is the most labour-intensive activity, particular importance is attached to assembly-oriented product design. An assembly- oriented product design is not only the fundamental requirement for automatic assembly, it also forms the basis for economic manual assembly. Its principal objectives are shown in Figure 2.2. In addition to simplification and the directly linked easier control of assembly processes, a higher repeat frequency of assembly processes is also achieved in spite of smaller batch sizes and a large number of product variants [5]. Cost origination 3| 12% 70% 15% % Parts Design Assembly Others production I I 75% 13% 6% 6 % Cost responsibility Figure 2.1 Cost responsibility - cost origination (Gairola) 4 Product design 5 ^^ Assembly-oriented product design * Minimization of assembly time and training r\ time with manual assembly • Implementation of the most simple and reliable equipment used in automatic Objectives assembly • Economic assurance of product quality \-S • Realization of a high repeat frequency of assembly procedures in spite of production of a wide range of product variants ji • Assembly-oriented product design Functions • Standardization of components A_^ • Assembly-oriented design Figure 2.2 Objectives of assembly-oriented product design (Platos-Witte) 2.1 Product design The degree of difficulty of assembly increases with the complexity of the product. Products with a small number of parts are easier to design to be assembly-oriented. As a general rule, resulting from the small number of parts or assembly operations, such products are finish-assembled at one assembly point. On the other hand, the assembly operations must be subdivided for products with a larger number of parts. A condition for this is that a product must be designed so that subassemblies can be pre-assembled. Figure 2.3 shows schematically a subdivision into subassemblies from pre-assembly to final assembly corresponding to assembly progress. The following rules should be observed for the assembly-oriented design of subassemblies and final products: • The whole assembly operation must be subdivided into clearly discernible stages by suitable subassembly formation. • A subassembly must be completed as a unit so that it can continue to be handled and manipulated as a single part. • It must be possible to test a subassembly separately. • Every subassembly should have the minimum possible number of connections to other subassemblies. • Variant-dependent subassemblies should not be included together with variant- neutral subassemblies. • As far as possible, variant subassemblies should have an equal number of installation conditions. To comply with these rules, a so-called base part is of prime importance for the individual subassemblies and the end product [5]. 6 Product design as a requirement for economic assembly _ Prod_u ct _ Final /\ assembly Sub- CO assemblies CO a) ri -*-- m o f~ Sub- Sub- Q. > C assemblies assemblies 1 o F| -—-._> __ -— __A <->Cl > r (^ ■3" CCOO Sub- Sub- Sub- o cCO assemblies assemblies assemblies r~ Pre-assembly t t f Parts production Product complexity > Figure 2.3 Assembly-oriented product subdivision into subassemblies 2.1.1 Base part A base part is defined as the principal part (quite often the base plate or housing) to which further parts are attached in the course of assembly. This term is applicable to both subassemblies and end products. In the field of electronics, a classic example of a base part is the printed circuit board on which all other components are mounted. In the assembly procedure, the base part need not be the first part to be handled; it is rather the part on to which other parts are mounted. It should be designed so that, by subdividing the assembly procedure, transfer from one assembly point to another is possible without any special device. This requirement cannot always be realized. However, with manual assembly in particular, which functions without a workpiece fixture, it should be a specific objective. With progressive assembly with circulating workpiece carriers or automated assembly with workpiece fixtures, to some degree the workpiece carrier or the assembly fixture can assume the function of the base part. Base parts must be designed so that during assembly they are self-centring in the workpiece fixture. The requirement for clamping and therefore the provision of clamping faces on the part should be largely avoided, since clamping workpiece fixtures are more complicated and expensive than workpiece carriers without clamping equipment. With a subdivided assembly operation, i.e. with transfer from one assembly point to another, workpiece fixtures with clamping equipment represent a considerable financial outlay. With a subdivided assembly, and particularly with mechanized assembly operations, the centring accuracy of the base part in the workpiece fixture is important. Base plates or housings as base parts must be designed so that with external centring their external tolerances (see Figure 2.4(a)) must be selected so that with regard to an automatic assembly procedure, the joint points inside the base part can be positioned with adequate accuracy. If this cannot be achieved by external centring, the base part must be equipped with centring holes as shown in Figure 2.4(b). With regard to their

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