Roboncs & Computer-Integrated Manufacturing, Vol 1, No 3/4, pp 227-230, 1984 0736-5845/84 $3 00 + 0 00 Pnnted m the 1) S A All rights reserved Pergamon Press Ltd

• Paper

SOME APPROACHES TO INTEGRATION

J. H A T V A N Y

Computer and Automation Institute, Hungarian Academy of Science, H-1502 Budapest, POB 63, Hungary

The integration of CAD and CAM is one of the weightiest of the so far unsolved (or only partially solved) problems that are proving to be grave obstacles to the computer-integrated manufacturing systems that we have all envisaged over a number of years. There are two main reasons for this. One is the failure to apply a design methodology conducive to integration; the other is the lack of a clearly suitable principle around which the integration should take place. The lack of a methodical, overall system design directed towards integration from the outset is due not so much to the absence of suitable methodologies (in fact, quite a few have been developed), as to their failure to gain acceptance in industrial practice.

As regards the integrative principle that can provide the core around which a CAD/CAM system can be built, opinions differ widely. One fashionable trend considers geometric modelling to be the "all-saving" principle. Others allot this role to process planning, family-of-parts classification, databases and their management, distributed systems architectures and their implementations. Following their various traditions, various coun- tries are pursuing different courses based on these and other principles.

It is apparent (and appreciated by all the countries concerned) that none of the methods that they have separately or jointly developed is as yet suitable for the fool-proof design and implementation of the "factory of the future". However, they all have something to offer and have allowed spectacular progress to be made. There is widespread agreement that it is only the synthesis of the extant approaches, the deepening of our theoretical understanding, and above all the acquisition and sharing of much practical experience that can lead to a usable ' ' science" of integration.

INTRODUCTION It is gradually becoming apparent to persons throughout the world who are concerned with investment strategies in the manufacturing industries that the age-old concepts of "returns on investment" are no longer applicable to the present-day world.

The classical criteria, their object functions, and optimization procedures are based on the search for stability, and the accompanying assumption of an unchanging product mix, an unchanging technology, producing for an unchanging market, using the same raw materials, the same energy, the same manpower, all at unchanging cost. In today's environment not one of these assumptions is true. We are living in an era of rapidly changing products, costs, and condi- tions, involving a highly dynamic situation in which the search is no longer for stability, but for survival.

The failure to realize this new situation in time has led to the bankruptcy of major enterprises and has contributed to mass unemployment and to drastic changes in the industrial profiles of a number of countries. In the socialist countries it has led to a temporary deceleration of industrial growth, to the inadequate penetration of new technologies, and to

a chronic (apparent) shortage of labour. The realiza- tion that the survival of a modern industrial potential requires a different approach to the outdated search for stable equilibrium has been forced upon indus- trial strategists. Balanced and harmonic growth today requires a quantum increase in the ability of industry to change products, to change technologies, and to change its cost structures swiftly and easily.

The means for achieving these aims are the pro- perties of

• flexibility and • adaptiveness.

It has long been shown by the production engineering community that the best way to achieve these goals is through the integrated computer con- trol of the entire design and manufacturing opera- tion. Consequently there has been a very large surge of interest in policy-making bodies throughout the world in the more rapid dissemination of integrated, computer-controlled systems that will:

• allow the production of small batches with the

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228 Robotics & Computer-Integrated Manufacturing • Volume 1, Number 3/4, 1984

productivity and efficiency of mass-production techniques; and enable swift changes to be made in product structure at minimal or zero investment costs.

Recently, attention has been focused on the prob- lem o rwhy it appears to be such a slow and expen- sive procedure to integrate existing CAD and CAM subsystems into single, co-operative, flexible com- plexes. Since this problem is now the centre of inter- national attention, we shall attempt to examine it in somewhat more detail.

OBSTACLES TO INTEGRATION The following have been recognized as the main

barriers to CAD/CAM integration:

• inadequate human relations, skills, and motiva- tion;

• unsuitable systems design and investment prac- tices;

• insufficient reliability of equipment.

As regards the human factor, the classical organ- ization of most factories today encourages "empire building". In the era of the Tayloristic division of labour, the professional engineers and technicians also became so specialized and compartmentalized that many of them now have little or no vision out- side their own narrow field. Combined with the strictly hierarchical structures that are still dominant in most industrial plants, this factor breeds a power- ful resistance to all those types of change, where traditionally separate functions are integrated and the accustomed boundaries are broken down. On the contrary, most medium and lower-level mana- gers are expressly motivated to increase the impor- tance of their "own" department and to resist out- side encroachment of their authority.

With respect to design and implementation prac- tices, the main obstacle has been the failure to take a top-down, integrated view of the overall system in the early stages. It has been the general practice in early attempts at system-building first to select machine-tools appropriate to the product mix and to buy them; then to find controls to fit the machines and to buy them; to find an attractive-looking (and momentarily available) CAD system and to buy it; finally, when all these pieces have already been bought or ordered, to try to piece them together into a system. In most cases, the result led to a gross breach of deadlines, of costs, and of the quantity and quality (qualifications) of the manpower required to commission the system. Furthermore, the completed systems failed to meet the original productivity,

economy, reliability, and accuracy targets previously set. Not only was this harmful to the performance of the organizations concerned, but it also demoralized the persons involved and discouraged them from further integration.

Following these unpleasant experiences (which were characteristic of the first systems in all coun- tries), attempts were made to introduce strictly top- down "structured" design approaches along the lines advocated earlier for the production of computer software. Whilc these experiments have been useful in introducing a new conceptual framework to the job of systems design, their manual implementation proved to be too complex and the purely unidirec- tional top-down approach to analysis did not comply with the requirements of real-life design situations in industry.

A further complication was added with the rapid introduction of microprocessors. These led many people to think that since each component of a sys- tem could now be run autonomously and the link between them was "only" a matter of software, overall design was not really necessary after a l l - - i t would instead be enough to build autonomous "cells" and "islands" and then to link these "somc- how" to each other. This view is today causing just as many losses as the other errors did earlier.

It is only quite recently that leading manufacturcrs and investors arc recognizing the fact that only those integrated systems which havc methodically bcen designed for this purpose from the start can bc built and operated economically. Otherwise, they will again find themselves in that most expensive and wasteful of all situations: of having to "debug the system with a soldering iron".

On reliability, even a vcry primitivc calculation will show that if two pieces of equipment each with 90% reliability are intimately interlinked (i.e. each has to bc operative for the other to operate) , then the resulting reliability of the complex is 81%. For a flexible manufacturing system consisting of, say, six machines, a work transport system, washing sta- tion, measuring station, etc., it is therefore easy to see that the reliability of each component module would have to be well over 99% for the system to be operating for 90% of the time. For most machine- tool factories, control factories, and system compo- nent suppliers this requirement involved a quantum jump in the quality of their products, for which they were unprepared in terms of materials, processes, measurement, and testing techniques and equip- ment, personnel skill, organization, and attitudes. Yet without these changes the idea of an integrated system with acceptable performance indiccs is illus-

Some approaches to integration • J. HATVANY 229

ory. The results achieved to date are still far from satisfactory, though some sophisticated methods for improving systems reliability, despite the use of "unreliable" components, have also emerged.

METHODS OF INTEGRATION No country in the world has yet claimed to have a

complete set of workable procedures for integrating the subsystems of a total manufacturing operation. The approaches currently being applied differ according to the traditions, resources, economic sys- tems, and aims of the various countries. Neverthe- less, there is considerable cross-fertilization ~24 and general optimism.

Work in the U.S.A. has been clustered around two focal points. One of these is in the use of geometric modelling as the underlying unifying principle of CIM systems. However, only recently have the prac- tical limitations of this approach been appreciated and greater efforts have been made to incorporate process planning, fixture design, tooling, etc. into the integrative process. The other approach, though far more arduous, has achieved some highly important results--an analysis of the overall structure of the CIM process, followed by the definition of critical interfaces for product data definition, graphic file exchange, etc. While much fault can be found with some of the initial results, there can be no doubt that today these represent the single most important step taken towards methodical systems integration.

In Japan a concurrent scheme of two strategies has been operating since the mid-1960s. The first of these strategy components has been a succession of Government-sponsored and organized projects for the theoretical and experimental study of long-term fundamentals (DNC, followed by the "Methodol- ogy of Unmanned Manufacturing" and now the "Flexible Manufacturing System Complex with Laser"). Each of these projects has helped to develop a national terminology; a consensus among management, government, labour, financiers, and technicians on long-term aims and limitations; a framework for shorter-term company tactics; a gen- eral appreciation of the need for standardization and the limitations it imposes; and finally a sound found- ation for training the CAD/CAM engineers of the future.

Parallel with their active and enthusiastic partici- pation in these long-term projects, the Japanese companies have developed mainly pragmatic methods for integrating machine tools and transport equipment into flexible manufacturing systems. Machining information--generally in ISO or RS tape format--is transmitted to standard CNC units

in what is little more than an accelerated BTR (behind-the-tape reader) mode, and is stored there (mostly in bubble memories). The "tape" informa- tion is generated off-line, by computer-aided manual NC programming procedures, but these are very rarely linked organically to CAD or even to CAPP. On the other hand, two integrative features are very advanced indeed: one of these is the one-line scheduling of the systems (which in fact pulls the whole act together at a very high level); the other is the advanced monitoring and failure-detection apparatus that makes "unmanned machining" poss- ible in the second and third shifts.

Ongoing research work at the leading Japanese universities is aimed at the development of geometric modelling and process planning systems (GEOMAP, TIPS), which hopefully will allow the numerous extant FMS plants to take a step towards CAD/CAM integration. At the same time, the fac- tories are exploiting the previous efforts invested in standardization by offering a broad spectrum of manufacturing "modules", "cells", and "islands", which can--at a relatively low system-level--be fairly easily linked and then integrated by high-level scheduling.

In Europe, the U.S.S.R. and Germany have a long-standing tradition (dating back to the late 1920s) of concern with the scientific determination of cutting technologies. This has led, in the Soviet Union and the two post-War German States, to the concentration of much effort on computer-aided parts classification, process planning (cutting-condition determination, machine and tool selection, optimal trajectory determination), the establishment of machinability databanks, etc. In due course, the highly developed suites of programs developed for these purposes came to be regarded as the principal mode for designing manufacturing systems for inte- grating CAD and CAM, and for providing data to scheduling. Internal part representations were based on the process classification schemes. In recent years, however, academic research has been oriented towards increasing the weight of geometri- cal modelling as the integrative factor.

In the U.S.S.R. there is currently an immense con- cemtration of resources on the rapid implementation of FMS in a very large number of plants. (For exam- ple, 16 agricultural machinery plants are now simul- taneously installing such systems.) The key word is standardization: they are all using the same comput- ers, the same control units, the same modular soft- ware system (MEMO), with many standardized sub- systems, standard tooling, pallets, fixtures, etc. 3 In these systems the link to CAD is rather tenuous, but

230 Robotics & Computer-Integrated Manufacturing • Volume 1, Number 3/4, 1984

the process planning systems (and their links to scheduling and manufacture) are very powerful. A rather similar approach is also being adopted in Czechoslovakia.

France and Hungary have traditions in mathemat- ical abstraction and analysis. In both these countries, computer-based systems have been developed and are being industrially tested for the analysis and synthesis of large, highly integrated systems. Taking as their points of departure the ideas originally proposed by Hori and Ross in the U.S. and later embodied in the IDEF programs, researchers have sought to integrate these with the facilities of Petri- nets, relational databases, simulation techniques, interactive graphics, etc. to offer the designer a broad palette of inter-related design tools. The ini- tial industrial experiences have pleased users in both countries.

The U.K. and France have, together with the U.S.A., long been pioneers of numerical geometry and later of geometric modelling. (B6zier first inte- grated the design and manufacture of car-bodies; Braid invented set-theoretic solid modelling.) In both these countries an intimate integration of design and manufacture has been achieved in a few selected areas (mainly automative and aeroscope). Similarly integrated CAD/CAM systems are now appearing, e.g., for mould and die manufacture. None of these, however, has links to scheduling and management.

West Germany and Norway have embarked on an ambitious project to interface extant modules through standard linkages.

Finally, mention should be made of the work being conducted in a number of countries (e.g., The

Netherlands, U.K., Japan, U.S.S.R.) to develop multi-layer, multi-user database management sys- tems that will hopefully cover the whole area and facilitate integration. It is hoped that these will later operate in a distributed mode through local-area networks. (The la t t e r - -and particularly their stan- d a r d i z a t i o n - a r e of course themselves powerful fac- tors for integration.)

In conclusion it is apparent (and appreciated by all the countries concerned) that none of the methods that have been separately or jointly developed are as yet suitable for the fool-proof design and implemen- tation of the "factory of the future". However, they all have something to offer and have allowed great progress to be made. There is widespread agreement that it is only the synthesis of the extant approaches, the deepening of our theoretical understanding, and above all the acquisition and sharing of much more practical experience that can lead to a usable "science" of integration.

REFERENCES 1. Ellis, T.M.R., Semenkov, 1.1. (Eds.): Papers on

"Design and implementation of integrated CAD/CAM systems" from France, G.D.R., Norway, U.S.S.R., ('zechoslovakia~ F.R.G., Japan, Finland. In Advances in CAD~CAM. Amsterdam, North-Holland. 1983.

2. Kochan, D. (Ed.): Papers from Hungary, F.R.G., Bul- garia, Japan, G.D.R., Czechoslovakia, Holland, France. In Integration o f CAD~CAM. Amsterdam, North-Holland. 1984.

3. Orlovski, G.V. (Ed.): EVM v Proyektirovaniya i Proiz- vodstvc. Leningrad, Mashinostroenie. 1983.

4. Papers from U.S.A., F.R.G., Japan, Norway, Hungary. In PTK 83. Die Zukun fi der Fabrik. Munich, Carl Hanser. 1983.