Advances in Factories of the Future, CIM and Robotics

500 Pages·1993·24.209 MB·3-537\500

by  Michel Cotsaftis and François Vernadat (Eds.)

MANUFACTURING RESEARCH AND TECHNOLOGY
Volume 1. Flexible Manufacturing: Recent developments in FMS, Robotics
CAD/CAM, CIM (edited by A. Raouf and S. I. Ahmad)
Volume 2. Computer-Aided Design, Selection and Evaluation of Robots (B. O. Nnaji)
Volume 3. Modelling and Design of Flexible Manufacturing Systems (edited by
A. Kusiak)
Volume 4. Flexible Manufacturing: Integrating technological and social innovation
(R T. Bolwijn, J. Boorsma, Q. H. van Breukelen, S. Brinkman and
T. Kumpe)
Volume 5. Proceedings of the Second ORSA/TIMS Conference on Flexible
Manufacturing Systems: Operations research models and applications
(edited by K. E. Stecke and R. Suri)
Volume 6. Recent Developments in Production Research (edited by A. Mital)
Volume 7A. Intelligent Manufacturing Systems I (edited by V. R. Milacic)
Volume 7B. Intelligent Manufacturing Systems II (edited by V. R. Milacic)
Volume 8. Proceedings of the Third ORSA/TIMS Conference on Flexible
Manufacturing Systems: Operations research models and applications
(edited by K. E. Stecke and R. Suri)
Volume 9. Justification Methods for Computer Integrated Manufacturing Systems:
Planning, design justification, and costing (edited by H. R. Parsaei,
T. L. Ward and W. Karwowski)
Volume 10. Manufacturing Planning and Control -A Reference Model
(F. P. M.Biemans)
Volume 11. Production Control-A Structural and Design Oriented Approach
(J.W. M. Bertrand, J. C. Wortmann and J. Wijngaard)
Volume 12. Just-in-Time Manufacturing Systems-Operational planning and control
issues (edited by A.Satir)
Volume 13. Modelling Product Structures by Generic Bills-of-Materials
(E. A. van Veen)
Volume 14. EconomicandFinancial Justification of Advanced Manufacturing
Technologies (edited by H.R. Parsaei, T.R. Hanley and W.G. Sullivan)
Volume 15. Integrated Discrete Production Control: Analysis and Synthesis-
A View based on GRAI-Nets (L Pun)
Volume 16. Advances in Factories of the Future, CIM and Robotics (edited by
M. Cotsaftis and F. Vernadat)
MANUFACTURING RESEARCH AND TECHNOLOGY 16
Advances in Factories
of the Future,
CIM and Robotics
Edited by
Michel Cotsaftis
UR/CENFAR, Fontenay-aux~Roses, France
FrangoisVernadat
INRIA-Lorraine, Metz, France
ELSEVIER
Amsterdam - London - New York - Tokyo 1993
ELSEVIER SCIENCE PUBLISHERS B.V.
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ISBN: 0 444 89856 5
© 1993 Elsevier Science Publishers B.V. All rights reserved.
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V
FOREWORD
Productivity enhancement is a major concern for all manufacturing enterprises. Productivity
enhancement can be achieved in many ways and many facets of this problem have been
investigated over the last decades (design automation, CAD/CAM integration, flexible
manufacturing, robotized activities, cellular manufacturing, JIT, new management strategies,
CIM and enterprise integration, intelligent systems and more recently concurrent engineering
to name a few). A number of methods, tools and technologies have emerged to efficiently
increase productivity and rationalize management of manufacturing enterprises. This does not
mean that complete, packaged, solutions are available or even known in most cases.
Furthermore, a global understanding of the productivity enhancement problem in the context
of the current economic situation, and then for the ones to come, still needs to be assessed.
The aim of the Eighth International Conference on CAD/CAM, Robotics and Factories of the
Future (CARs & FOF 92) held in Metz, France on August 17-19, 1992, was to bring
together experts coming from all over the world, both from academia and industry, to share
their experience and contribute to advances of the many facets of productivity enhancement in
manufacturing enterprises. CARs & FOF' 92 was the eighth event of a series of conferences
sponsored by ISPE (the International Society for Productivity Enhancement).
This post-conference book puts together some of the most signigicant papers presented at the
conference in selected technical areas as a contribution to productivity enhancement in
manufacturing enterprises. These technical areas can be grouped into four major sections:
Factories of the future, Techniques and tools for automated manufacturing, Robotics, and
Industrial applications.
Factories of the future
The impact of new technologies on modern or future production systems has to be assessed,
and the socio-economical consequences as well as organisational changes have to be analysed.
New ways of managing project development as well as team work will emerge. Furthermore,
enterprise integration, for which enterprise modelling is one of the central issues, still needs to
be the focus of further research. This section groups papers dealing with themes and vision
on factories of the future, new management approaches, manufacturing system integration and
manufacturing information systems.
Techniques and tools for automated manufacturing
This large section collects papers on technical issues dealing with product design and product
engineering, as well as manufacturing system design, analysis and evaluation.
The papers have been organized into seven categories: knowledge-based systems for
manufacturing system simulation, CAED (Computer-Aided Engineering and Design), metal
cutting and assembly processes, manufacturing cell layout, scheduling and multi-level control
of FMS, FMS analysis with Petri nets, and fault diagnosis and maintenance.
The first category contains two papers on the use of knowledge-based systems for advanced
simulation of manufacturing processes.
VI
The second category focuses more on product engineering aspects with two contributions on
finite element analysis, one on product configuration management and one on a CAD/CAE
tool applied to circuit-breaker design.
The third category addresses decision-making in metal cutting and specific problems in
automated assembly.
The fourth category is devoted to manufacturing cell layout using the cellular approach and
covers cell design by machine grouping, machine layout inside a cell (considering materials
handling systems), and workshop layout using the neural network approach.
The fifth category covers scheduling problems and hierarchical control of FMS, while the
sixth category concentrates on the use of Petri nets to model, analyse and control FMS.
The seventh category contains two papers related to system failure and maintenance of
manufacturing systems.
Robotics
Operating technical systems such as robots in high range of parameters, as required by
productivity constraints in factories for tasks performance in the context of current economic
competition, introduces, among other things, new problems in their control, under the two
following main aspects: one is related to appropriate representation of physical phenomena,
another one is in the definition and work out of a control structure to be applied to the system
so that it behaves "intelligently" enough for tasks performance.
With this respect, recent slowdown of robot use in factories at the end of the eighties has
shown limit in totally programmed units, and a need for more decisional flexibility at robot
level for better adaptation to task assignment in unstructured or partially structured
environments.
Advantage has therefore been taken from the CARs &FOF 92 Conference to gather some of
the most interesting advances in robotics in representation and control areas showing possible
orientation toward the goal of providing more flexibility to the robot unit.
The selected contributions are mainly covering the following topics: the representation of the
system, the generation of its trajectory, and its control.
In the first category, there is only one paper on an attractive theoretical representation of
flexible structures. It proposes nice aspects of them and is adequate for numerical workout.
In the second category, five papers have been selected, and they are mainly proposing
solutions to acceptable and precise enough system trajectories, including the case of redundant
structure, which seems to be an interesting alternative for technical cases. Mobile robots are
also considered.
Finally, in the third category, the still very important control problem puts together the last five
contributions. It can be seen that they are essentially proposing new extensions of control
toward larger robustness and larger adaptivity, which are both important key factors for future
robotic structures. These contributions are also seen to have a definite orientation toward
passivity property, here appearing as a strong and useful one.
Although the various texts are by far not covering all aspects of the difficult and not yet solved
problem of the setting of new highly performing robotic units, they are however clearly
Vll
showing a pattern of valuable and interesting approaches to the fascinating problem of
designing a new generation of robots with high enough performance capabilities to be used in
industrial context.
Industrial applications
A few papers on industrial applications have been added to the book to illustrate or
complement previous sections. Papers can be found on such issues as: simulation and control
or scheduling of manufacturing systems, process control, process instrumentation, preventive
maintenance and assembly systems in areas such as steel industry, electrical industry and
discrete parts manufacturing.
M. COTSAFTIS and F. VERNADAT
Metz, November 1992
Advances in Factories of the Future, CIM and Robotics
M. Cotsaftis and F. Vernadat (Editors)
© 1993 Elsevier Science Publishers B.V. All rights reserved. 3
Future Factories and Today's Organizations
P. Robert Duimeringa, Frank Safayenia and Lyn Purdyb
department of Management Sciences, University of Waterloo, Waterloo, Ontario, N2L 3G1,
Canada
bCentre for Administrative and Information Studies, University of Western Ontario, London,
Ontario, N6A 5C2, Canada
Abstract
This paper will draw from our experience during the past five years with organizations
which are trying to improve their manufacturing activities using a variety of techniques and
technologies. The paper will raise issues about how we are currently thinking about
manufacturing systems, the kinds of solutions we consider as potentially feasible, and the
difficulties organizations encounter implementing these solutions. Specifically, the paper will
examine the Just-in-Time (JIT) and Computer Integrated Manufacturing (CIM) approaches as
integrated manufacturing systems, and consider the impact of these systems on the
manufacturing organizations in which they are implemented. A conceptual framework of the
JIT system, developed through past research, will be utilized along with other organizational
theory to point out shortcomings in some of the implicit assumptions underlying the CIM
approach, and to examine how truly integrated manufacturing systems can be designed,
regardless of the techniques or technologies chosen. The argument will be advanced that the
only way for future factories to be effective is by 1) considering manufacturing activities in the
context of the overall organizational system, 2) redesigning organizations to accommodate
manufacturing activities, and 3) rethinking the ways advanced manufacturing technologies can
be utilized, not only in terms of their theoretical potential, but also in terms of the concrete
realities of organizations.
1. INTRODUCTION
In response to increasing international competitive pressures over the past decade, Western
manufacturers have focused a great deal of attention on attempts to improve manufacturing
activities through the adoption of new techniques and technologies. Among the new strategies
being pursued, two dominant themes have emerged. The first is the Just-in-Time (JIT)
manufacturing system, originally developed by the Toyota Motor Company of Japan, which
includes a range of techniques aimed at simplification and waste reduction within the
manufacturing system. The second is the Computer Integrated Manufacturing (CIM) approach,
in which computer based information systems are utilized to link islands of automation, islands
of information, and flexible technologies throughout the manufacturing operation.
While the development and adoption by industry of these two strategies has occurred more
or less independently and their compatibility is not well understood, both approaches are
generally assumed to be advantageous to manufacturing organizations attempting to improve the
competitiveness of their operations. For example, both systems claim to contribute to increased
productivity by improving organizational integration, product quality, as well as manufacturing
4
flexibility and responsiveness. As such, future factories can be expected to combine some of
the characteristics of both the JIT and CIM approaches.
Empirically, however, what is known about the success of the two manufacturing
approaches within industry is rather limited. As a total system, JIT has been shown by Toyota
and other Japanese firms to be an effective strategy for improving productivity when
implemented appropriately [eg. 10]. CIM on the other hand is still largely an unproven
manufacturing approach with very few well documented case studies. Most of the literature
describing CIM considers the system from a purely hypothetical perspective, and tends to
consist mainly of predictions made about the success of the system based on the "theoretical
potential" of CIM technology [eg. 4,7]. It is also worth noting that the degree to which either
of the two strategies has been successfully implemented by Western manufacturers has been
very limited. The limited success is often related to the assumptions about the organizational
context in which these systems are implemented. For example, organizations often assume that
they can implement JIT without modifying their organizational structure [6,13]. Similarly, with
respect to CIM, incorrect assumptions related to human resources have been shown to result in
sub-optimal performance of advanced technological systems [12].
The objective of this paper is to examine JIT and CIM as integrated manufacturing systems,
and to consider the relative impact of these systems on the manufacturing organizations in
which they are implemented. The paper will utilize a conceptual framework of the JIT system
which has been developed through our past research, as well as other organizational theory, in
order to point out critical shortcomings in some of the assumptions underlying the CIM
approach and highlight some of the organizational issues which must be addressed for future
factories to effectively utilize either JIT or CIM.
2. THEORETICAL FRAMEWORK
2.1. Total Cycle Time Reduction as a Common Goal in JIT and CIM
Before considering the differences between JIT and CIM, it is worth noting one important
similarity between the two systems. In particular, underlying both systems is the idea of "total
cycle time reduction" as a key factor leading to improved manufacturing productivity. In JIT, a
major (but by no means exclusive) focus of the system is on production throughput time
reduction, achieved primarily through the reduction or elimination of inventory buffers
throughout the manufacturing system. By implementing a range of JIT techniques, designed to
let manufacturers operate with low inventory levels, production throughput times can be
significantly reduced. In the CIM system, the concept of cycle time reduction is enlarged to
include not only production cycle times, but also administrative cycle times, such as order
processing cycle times and product development cycle times. By utilizing computer based
information technologies which allow for instantaneous information transmission and data
sharing, as well as flexible manufacturing technologies capable of producing in very small
batches, it is argued that the CIM system can dramatically reduce both production and
administrative cycle times simultaneously [7].
Theoretically, the relationship between cycle time and manufacturing productivity has
recently been identified in the literature [8,14,15]. For example, Wacker [15] has formally
shown that when reduced throughput time is taken as the overriding goal of a manufacturing
system, other goals which have been traditionally assumed to be contradictory, cease to behave
as such. Consequently, underlying both JIT and CIM is a common (and apparently valid)
assumption that reducing cycle times can lead to improved productivity levels.
2.2. Implications of Reduced Cycle Time in the JIT System
Some of the differences between JIT and CIM arise when one considers how the two
systems address the question of reduced cycle times. Through our past research on JIT, we
have developed a conceptual framework for understanding the JIT system and its implications
for manufacturing organizations [5,6,13], based on the theory of cybernetic systems [1,2]. In
5
particular, the framework considers the impact of reductions in the level of inventory (ie.
reduced cycle times) on the functioning and structure of manufacturing organizations.
Theoretically, the role of inventory within a manufacturing system is viewed as a buffer
which handles variability between interrelated manufacturing processes. The significance of
inventory as a buffer lies in the fact that it decouples interrelated processes from one another,
thereby preventing the variability of one process from having an immediate impact on another.
Some examples might be as follows. Suppliers shipping an incorrect part, machines breaking
down in production, and unexpected worker absenteeism can all be considered as variabilities
in the production system, which can be absorbed by high levels of inventory such that
production operations can continue without disruptions. For instance, there may be enough
stock on hand to give the supplier time to send another shipment, to allow time to repair a
malfunctioning machine, or for other workers to continue production even if one worker does
not show up for work.
Other sources of manufacturing variability might include organizational functions, such as
design engineering or marketing. For example, product designs which incorporate a large
number of non-standard components or frequent changes in the production schedule generated
by the marketing department both constitute sources of variability from the point of view of
manufacturing, which have traditionally been absorbed by high levels of inventory.
Since the presence of inventory tends to minimize the impact of variability in the system,
significant inventory reductions will decrease the time it takes for variability in one process or
organizational function to have an impact on another by increasing the coupling, or degree of
interdependence, between interrelated activities. In the context of the preceding examples,
small amounts of inventory mean that the wrong part from a supplier, machine breakdowns,
absent workers, non-standard design components, or sudden schedule changes will rapidly
disrupt the manufacturing system.
If the organization cannot use inventory for handling variability in a low cycle time
manufacturing system, alternative courses of action must be taken to avoid disruptions.
Essentially, two possible options are available. The first involves reducing variability at the
source, and the second has to do with increasing variability handling mechanisms at the point of
impact within production. Considering the above examples, variability reduction might include
such activities as pressuring suppliers to ensure consistently correct shipments, preventive
maintenance to reduce the likelihood of machine breakdowns, modifying the employee reward
structure to discourage absenteeism, ensuring the use of standardized components in design,
and levelling production schedules to filter out market fluctuations. Strategies aimed at
increasing variability handling within the system might involve developing emergency shipping
procedures to handle late supplier shipments, having back-up equipment available in case of
machine breakdowns, developing a multi-functional work force such that workers can be
reassigned in the case of absenteeism, and increasing the flexibility of manufacturing processes
to cope with high levels of component variety or unstable production schedules.
To summarize these concepts, if organizations are to operate with short cycle times by
lowering levels of inventory, increased interdependence implies that the level of variability
impacting the production system must either be reduced at the source, or handled effectively at
the point of impact by increasing variability handling capability within production.
2.3. Cycle Times and Manufacturing System Integration
Conceptually, there is a direct relationship between the preceding concepts and the idea of
an integrated manufacturing system. One may talk about a truly integrated manufacturing
system as one in which different interrelated organizational tasks and activities are carried out in
concert with one another. That is, an integrated manufacturing system is one in which
variability reduction and variability handling are performed effectively. Organizational
integration can therefore be considered in terms of its relationship to manufacturing and
administrative cycle times. An organization which, through effective variability reduction and
handling, is able to generate its required production or administrative outputs in very short cycle
6
times could be described as being well integrated. An organization which requires long cycle
times to generate its required outputs could be described as being poorly integrated.
An integrated manufacturing system cannot be achieved without addressing the question of
how the production activities are affected by the other functional activities being performed
elsewhere within the organization. For appropriate variability reduction and variability handling
to take place, effective coordination of these interrelated activities becomes absolutely
necessary. Our research on the JIT system, for example, has shown that in successful JIT
organizations, lower production cycle times correlated not only with a broader range of
organizational activities aimed at reducing variability and increasing variability handling
mechanisms, but also with higher degrees of cross-functional communication and coordination,
and a tendency to structure the organization along product rather than functional lines [5,6].
The relationship between lower cycle times and organizational changes is related to the idea
of increased interdependence. As cycle times are reduced, interdependence increases within the
organization along a particular orientation, namely the direction defined by the information and
material flow lines associated with particular products. Consequently, there is a need for
increased communication and coordination along this direction, creating a strong pressure to
modify the organizational structure along product lines rather than functional lines. Hence,
system integration is achieved in successful JIT organizations through the basic redesign of the
organizational structure as well as a redesign of interrelated processes and functional activities.
The main issue in designing low cycle time manufacturing systems, therefore, involves
addressing the question of how variability is reduced or handled within the organizational
system. Whether this is accomplished using technology, people, or any other method is not the
crucial issue. What is important is the manner in which interrelated activities are designed,
organized and coordinated throughout the organizational structure in order to achieve the goal of
reduced cycle times. The focus of the remainder of this paper will be to examine the CIM
system in this context by considering the approaches used by CIM to achieve organizational
integration and handle system variability.
3. CIM AS AN INTEGRATED MANUFACTURING STRATEGY
The preceding discussion has argued that integration within a manufacturing organization
involves addressing the question of how variability is reduced or handled throughout the
organizational system.. In highly integrated manufacturing organizations, characterized by low
manufacturing and administrative cycle times, effective variability reduction and handling
necessitates changes in how interrelated processes and functional activities are coordinated and
organized. That is, manufacturing system integration is viewed primarily as an issue of
organizational system design.
When the CIM approach is considered in the context of this conceptual framework,
however, it becomes apparent that the CIM system implies a different approach for achieving
manufacturing system integration. Essentially, it is argued in the literature, that the CIM system
brings about organizational integration (ie. reduced administrative cycle times) by automating
the flow of information between interrelated processes and organizational functions (islands of
automation) using advanced information technologies [4,7]. In addition, cycle times are
reduced within production through the use of flexible manufacturing technologies (such as
robotics, FMS, automated guided vehicles, automated storage and retrieval systems, etc.),
which are capable of quickly processing a broad range of products in small batches. That is,
the main approach used in the CIM system for dealing with organizational variability is to
increase the level of flexibility, in order to handle variability at the point of impact within the
production operation. As such, both integration and variability handling within the CIM system
are essentially assumed to be purely technological issues, rather than organizational issues.
The following sections of this paper will examine these assumptions in detail, by raising
issues related to the ideas of integration and flexibility as they pertain to the CIM system. The
technological approach of CIM will be considered in the context of today's organizational