Improving Changeover Performance. A Strategy for Becoming a Lean, Responsive Manufacturer

353 Pages·8.072 MB·English

by  R.I. Mclntosh, S.J. Culley, A.R. Mileham and G.W. Owen (Auth.)

Preface
Better revoegnahc performance: design and organizational improvement options
We have been researching industrial changeover performance for nearly 01 years. Our
work has taken us to different sites throughout the UK and mainland Europe.
Diverse industries have been studied, gnivorpT,h revoegnahC ecnalnroJieP si the result
of this research.
Our book joins existing books on this topic. Previous texts have tended to empha-
size refinement to work practice, where local shopfloor teams are usually encouraged
to seek minimal cost retrospective improvement. This approach can lead to markedly
better changeovers, but should not be viewed as an exclusive improvement route.
Similarly, a few texts focus more specifically upon the process hardware, emphasizing
design change to improve changeovers. In some cases, as well, businesses have decided
not to pursue internal retrospective improvement: perhaps more changeover-profi-
cient equipment has been installed, or, occasionally, the services of external design
specialists have been engaged. Our text considers all these options. It concentrates,
however, upon internal retrospective improvement, and proposes a number of tools
that might be used for this purpose. In particular the book describes how organiza-
tional change and design change can be consciously adopted in unison, as part of a
structured overall improvement programme in which the full strategic implications of
seeking better changeover performance are also considered.
Ideas book
Changeover improvement si an on-going topic. The current book assesses changeover
improvement methodologies, concepts and techniques. Space considerations, how-
ever, limit the number of improvement examples that can be included.
We believe that knowledge of previous changeover improvement successes- with
emphasis on either method improvements or equipment modification- can greatly
assist a practitioner. Just as a cook will be aided by an extensive knowledge of possible
ingredients, understanding also the limits of what different ingredients can contribute
and when they might be used, so too those seeking better changeovers will be assisted
by an extensive knowledge of possible improvement options.
x Preface
We propose to follow the current book with a further book that is devoted to
changeover improvement examples. It is intended for use as a 'browse-through'
catalogue. To this end we invite companies to contact us with examples that we might
include. Improvement ideas should be submitted with drawings and/or photographs,
alongside a concise explanation of what has been done. We would also like to know
how the improvement was conceived, how much it cost to implement and what gains
have been achieved. All entries that are accepted will receive a copy of the book upon
publication.
Kindly visit http://www.altroconsulting.com or write to Dr G. W. Owen, Depart-
ment of Mechanical Engineering, University of Bath, BA2 7AY, UK. Email:
G.W.Owen (~ bath.ac.uk.
Indeed, we anticipate that this website will develop into rather more than just a
simple contact point. Ultimately, we hope, it will be built into a comprehensive source
of changeover information, including for example details of service providers, or
details of useful devices and where they can be bought. Perhaps, in time, it will also
become a forum where practitioners across the globe can exchange their experiences,
and by doing so gain ever deeper understanding of this complex topic.
Bath R. I. Mclntosh
January 2001 .S J. Culley
A. R. Mileham
G. W. Owen
stnemegdelwonkcA
We would like to acknowledge the many companies that have participated with us. In
particular we are grateful to different personnel within these companies who have
given their time to us. We would like to single out the assistance of Peter Black,
Mattias Buchmfiller, Paul Davies, Martin Davis, Brian Graham, Bob Guyan, Mark
Hickey, Charles Hill, Johann Illisie, Erik van Leeuwen, Fred Price and John Web-
bern. This book would be greatly diminished without their contribution.
Graham Gest was a fellow researcher at the University of Bath during the early
1990s, concentrating upon classifying changeover improvement options. He proposed
the 'Reduction-In' strategy that is developed further in this book.
Much of the research that this book is based upon was funded by the EPSRC
(Engineering and Physical Sciences Research Council). The authors also gratefully
acknowledge this support.
Finally, the authors are indebted to the Royal Commission for the Exhibition of
1581 for the significant financial contribution made towards the writing of this text.
Introduction
The importance of good changeover performance in multi-product manufacturing
environments is becoming ever more widely understood. Certainly, the academic
community has devoted considerable attention to this topic. There is also a greater
awareness of changeover issues within manufacturing industry. This applies to indus-
tries as diverse as presswork, plastic moulding, pharmaceutical, foodstuffs, printing
and domestic consumables. Many other industries can also be nominated, including
those that are concerned primarily with assembly operations. Whereas there was a
particular early focus upon changeover improvement within the presswork industry,
this si no longer the case. It is now recognized that any business where a range of
products is to be manufactured on non-dedicated equipment should be conscious of
its changeover capability.
Awareness of changeover issues should include an awareness ofw hat better change-
overs might contribute to business performance. The rewards can often be substan-
tial. One option is simply to devote any time that is saved to increasing production
volume. At one site, for just one line, we estimated that this could contribute an
additional profit of nearly s million per annum. Yet in many respects this is a crude
exploitation of an improved manufacturing capability. Often it is more advantageous
to exploit this new capability instead by increasing the frequency with which change-
overs are conducted. Products are manufactured in smaller batches. Many potential
benefits are possible by manufacturing this way, not least of which are those that arise
by being more flexible, or more responsive to customer requirements. At the same
time, for example, significant inventory reductions might also be achieved. Using
a very basic analysis, halving changeover time while at the same time doubling the
number of changeovers that take place can potentially permit a 50 per cent inventory
reduction.
Much of the current attention to changeover issues can be attributed to Shigeo
Shingo's pioneering work. His changeover book A Revolution in Manufacturing." The
'SMED' System ~ is rightly recognized as a reference text. Yet it is now nearly 20 years
since Shingo's changeover work became widely known. Our book aims to update
Shingo's work. We argue that emphasizing procedural improvements to shopfloor
activity, as largely described by Shingo's single minute exchange of die (SMED)
methodology, 2 can be re-examined in the light of what has been learnt over these
last two decades. We suggest that a wider, more comprehensive approach to
changeover improvement can be adopted; an approach that addresses diverse issues
2 Improving revoegnahC ecnamrofreP
that can otherwise significantly diminish the results that an improvement initiative
achieves.
It is now generally agreed that the philosophy of mass manufacture, which has long
been at the heart of volume manufacturing practice, has become obsolete. 6-3 The
limitations of mass manufacturing have become apparent as competitive performance
criteria have broadened, where the prominence of price and cost efficiency, which
have been a primary justification of mass manufacture, have declined. 9-7 Increasingly
a business now has to compete simultaneously on price, product quality, product
differentiation, delivery performance, and rapid product development. ~1 These
objectives must be achieved additionally without compromising overall productivity,
while still retaining excellent control of costs and staying abreast of technological
advance. 13,14
Traditional mass manufacturing techniques, in which businesses typically employ a
rigid process technology, are ill-matched to accommodate all these demands. 51
Instead a responsive, multi-product, small-batch, low-inventory, flexible manufactur-
ing capability is required to enable an organization to compete successfully in today's
volatile and congested markets. A change towards such a manufacturing capability
has gradually come about since the early 1980s as JIT (Just-ln-Time) manufacturing
techniques have increasingly been adopted. 71"6~ Subsequently, JIT manufacturing
techniques have largely become embodied in ~world-class' manufacturing ~ 02 and
'lean'/'agile' manufacturing. 22"12 A highly prominent component of these modern
manufacturing philosophies si the need for better changeover performance. 32 v2
This book is uniquely concerned with changeover performance- what it is, what it
can contribute and how to improve it. We will assess what constitutes a changeover.
We will consider the potential strategic impact of improved changeover performance.
We will also consider in detail how to set about achieving significantly faster, higher-
quality changeovers. Examples of the approach we advocate, drawn from case
studies, will be provided. We will investigate the many pitfalls or difficulties that
a changeover improvement initiative can face.
It has frequently been asserted in the past that better changeovers should be
achieved principally by continuous, incremental improvement activity, conducted
by a shopfloor team and concentrating upon changing existing work practices and
procedures. Although this approach has prevailed when seeking retrospective
improvement, this need not represent the only possible approach, nor indeed, in many
cases, the best. ~2 For example, there are factors that can influence the outcome of an
initiative that are likely to be beyond the influence of a shopfloor team. Potential
limitations to team activity, among many other considerations, should be understood.
A comprehensive understanding of what an improvement initiative is likely to involve
Introduction 3
should be in place before the initiative gets underway. An initiative should involve
more than simply selecting a production process to work upon, engaging shopfloor
personnel, seeking to maximize 'external time' effort (see below) and setting arbitrary
improvement targets.
A major theme of this book will be the potential contribution of design to achieve
better changeovers, by physically changing the existing manufacturing system. We
will investigate how design may be applied either as an alternative or complementary
strategy to seeking improvement by organizational change. This is a topic that, to
date, has received little attention. Design for changeover may occur retrospectively, or
may be applied to new equipment as supplied by the original equipment manufac-
turer. This book is targeted primarily at those seeking to improve their manufacturing
operations but, by setting out generic design rules, it can also help original equipment
manufacturers to respond to customers who are increasingly demanding changeover-
proficiency in the specification of their new equipment. 43-92
The book is structured for use by manufacturing industry. Different chapters will
be of particular interest to managers and to production personnel. In general, the
earlier chapters are aimed at senior business managers, where the strategic require-
ment for rapid changeover will be investigated, and our overall methodology for
changeover improvement will be described. Later chapters are more focused on
achieving improvement in detail, addressing topics that are of particular relevance
to improvement practitioners- those who are responsible for effecting change on the
shopfloor. Throughout the book we shall propose different tools and documentation
(as later summarized by Figure 7.15) that might assist the improvement effort.
Apart from those directly concerned with manufacturing operations, our discussion
of design issues should be of use to original equipment manufacturers. In addition, by
highlighting how the disciplines of changeover and maintenance can significantly
impinge upon one another, we believe that sections of our text will also be useful to
maintenance staff.
Finally, we have also attempted to write a book that is relevant for academic
purposes. To do so without unduly disrupting the text for industrial readers we have
provided our references - and, often, a brief explanation of the point we are drawing
from them- at the end of each chapter. Nevertheless, it is still sometimes necessary to
describe our thinking in detail in the main body of the text, particularly concerning
the development of the different tools that we propose. A summary of the topics of
each chapter is presented in Figure 1.1.
What constitutes a changeover needs to be defined if changeover activity is to be
investigated. Some important definitions are presented below that will be applied
throughout this book. Other definitions will be introduced where appropriate later in
the text. A full glossary is presented in Appendix .1
Figure 1.1 The content and likely relevance of different chapters
Introduction 5
To date, changeover improvement has been very closely associated with Shigeo
Shingo's 'SMED' methodology (which will be discussed in detail in later chapters).
Apart from investigating the advantages and potential limitations of adopting
the 'SMED' methodology, the term 'SMED' will not be used in our text. The term
'set-up reduction' (SUR) is also likely to be encountered in academic and industrial
literature, as is the term 'make ready', which can be used when describing changeover
activity in the printing industries. These terms similarly will not be used in this book.
As noted below, the preferred terminology, which will be used throughout, will be
variations of 'improving changeover performance'.
Improved changeover performance" faster and higher-quality
changeovers
In general, we shall refer to ~changeover improvement ,~ 'a better changeover' or
'improving changeover performance' in preference to 'a faster changeover'. Although
the likely major thrust of any improvement initiative will be to reduce the change-
over's duration, a practitioner may also seek to improve the changeover's quality. A
higher-quality changeover will occur when line parameters at the completion of the
changeover have been set more precisely, possibly allowing, for example, a higher
production rate, reduced scrap, higher product quality or greater line reliability. 53 73
The term 'changeover improvement' embraces improvement of this nature. The term
'faster changeover' will be used, but only when the duration of the changeover alone is
under consideration.
The total elapsed time for a changeover, cT
A changeover si the complete process of changing between the manufacture of one
product to the manufacture of an alternative product- to the point of meeting
specified production and quality rates. The total elapsed time for a changeover, ,~T
is shown in Figure 1.2.
Set-up period
What we have termed the ~set-up period' is the readily defined interval when no
manufacture occurs. It is important to differentiate between activities which take
place during the set-up period and those which are required to set a machine up
(i.e. to adjust it for production): the two need not be the same. For example, pre-
setting of tooling is an adjustment activity that occurs during external time. Similarly,
for many changeovers, final adjustment of the machine only occurs once preliminary
production has commenced- in the 'run-up period'.
Run-up period
The run-up period starts when manufacture of product B is commenced, and con-
tinues until steady production at full capacity occurs, at consistently acceptable
product quality. In our experience the duration of the run-up period can be up to
ten times the duration of the set-up period. Many commentators only define a
changeover as the time from 'good piece to good piece', but this definition takes no
6 Improving revoegnahC ecnamrofreP
erugiF 2.1 evitatneserpeR line output during changeover
account of the run-up of the line or machine, where full production has still not been
achieved. s3 This book will demonstrate how the set-up period and the run-up period
are related to one another and why, therefore, it is wrong to consider the set-up period
in isolation as representing the elapsed time for a changeover.
Figure 2.1 shows one possible way that run-up may occur. Other run-up regimes
also exist, which are entirely different from the gradual and uninterrupted increase in
production that Figure 2.1 presents. These will be discussed later in the book. The
difficulty of establishing when the run-up period ends and when true volume produc-
tion begins will also be discussed.
Internal time
, ::: :,~, ,:::::: ~ ::: :::: :: :,::, :~:::::::: :~:~:::::::::::::::::::::::::::: :~ ~:~~::: :,:: : ::: ~::::: ::::::: :: ~::: ::::::: : ~:::::: ~ :~::~::,,,:::::: ::::::, :~::~:::::: ~ :::: ~ ~ ~ ~ ~::, :: : :~ ::::~,~ :~,~, :::::~:~ ~:: ~: ::: :~::::,:, :~::::: :~:::: ,:::: :::: :~:~:::,: :~:: : ::::~:~:~:;:~: ::: :::::,:::::::::,: :,:::::::, :~::: ~ :~:: ~: ::,::: ::::::::::, :~:::: ~: ~::::::::::::: ,::::~:~:~:~,
Based on an original description by Shingo, 93 internal time is usually taken to refer to
the period during changeover when no manufacture occurs. The term 'internal time'
needs to be used with considerable caution, however, because it could be argued that
it also includes the run-up period (which Shingo did not adequately distinguish).
Sparing and qualified use of the term 'internal time' will be made in this book,
which includes both the set-up period and the run-up period- the period .oT An
'internal time activity' is thus, by our interpretation, an activity that cannot occur
during external time. A major thrust of improvement to date, based on the work of
Shingo, has been to isolate and move tasks that are needlessly conducted in 'internal
time' into external time (often without altering the tasks in any other way).
Introduction 7
External time
Shingo's term 'external time' applies to the period before the line or machine ceases
manufacture. It is frequently used in connection with preparatory activities prior to
halting production.
Run-down period
:~:~:~:::~:~:~:,~:~:~:~:~:~:~:~:~,~,~,=~=,=;:;:,::~:,:~:~=~:~:~: :~:~:~=~=~,~=~,~:~:~::~:,:~:~,~=:,:~ ~=~*~;~=~=~=~=~=~=~=~;~~=~=~=~=;~;~=~=~~~;~~=~~;~=~;~;~=~~;~;=~=~;~=~=~=~=~=~=~
Figure 3.1 shows that under some circumstances a manufacturing process may
occasionally experience a run-down period, as the line or machine is slowed down
and halted. ~4 A linear, non-interrupted run-down period is illustrated.
Changeover activity
~=~=~=~=;~=~=~=~;~=~=~=~==~=~=~=~=~~=~=~=~=~~=~=~=~~==~~=~=~=~=~=~=~==~=~=~=~~+~==~~=~=~===~=~=~=~=~=~+~+~
Changeover activity comprises each and every task that must occur for a changeover
to be successfully completed (culminating in full production at a specified product
quality). These tasks may be conducted before the line has halted, while the line
is halted or during run-up. Some tasks required to complete a changeover might
be undertaken by personnel who are not part of the immediate shopfloor environ-
ment.
Figure 3.1 Line output during changeover when including a run-down period