Manufacturing Assembly Handbook

399 Pages·1986·11.871 MB·English

by  Bruno Lotter (Auth.)

Manufacturing Assembly Handbook
Bruno Lotter
Butterworths
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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