- Email: [email protected]
Simulation in manufacturing
Computers in Industry
the lines of the displacement hull were also given in the lecture. A brief analysis of the feasibility and utility of the presented method was also done. Bogdanov and Kovachev pointed out that the program package allows interactive adjustment of predetermined geometrical properties of the displacement hull and the lifting surface(s).
II. Hydrodynamics Ship Manoeuvring Response Steps towards international legislation for ship manoeuvrability have motivated the development of theoretical and empirical methods for predicting ship manoeuvring response. One such method, aimed primarily for initial design, was described by N.E. Mikelis (Lloyd's Register of Shipping, U.K.). The use of this method is direct and inexpensive since it requires the input of data only on installed power and on the geometry of ship, propeller and rudder. Mikelis explained that comparisons between simulated and full scale trial manoeuvres for a tanker provide a first verification of the adopted mathematical model. The presentation was entitled "A Procedure for the Prediction of Ship Manoeuvring Response for Initial Design."
Conference Reports
177
Mission Effectiveness R. Hosoda (University of Osaka Prefecture, Japan) and Y. Kunitake (Mitsui Engineering & Shipbuilding Co., Ltd., Japan) introduced a concept of "mission effectiveness" for evaluating the seakeeping performance of ships at the early stage of ship design. In order to evaluate the mission effectiveness, short-term and long-term performance effectiveness was estimated by applying formulations commonly used in estimating ship responses in rough seas with the assistance of probabilistic theories. A method of simulation was also applied to evaluate the overall seakeeping performance of ships in rough seas. Finally, the mission effectiveness which comprises the cost to performance trade-offs was systematically evaluated. In their lecture Hosoda and Kunitake applied the method to the evaluation of seakeeping performance of patrol boats to be operated for a mission °' salvage of ships in distress at sea". The Proceedings of this conference have been edited by P. Banda and C. Kuo and published by North-Holland under the title Computer Ap-
plications in the Automation of Shipyard Operation and Ship Design, V". 1985. xiv + 458 pages. ISBN 0-444-87820-3.
Simulation in Manufacturing The First International Conference on Simulation in Manufacturing which took place in Stratford-upon-Avon, U.K. from 5 - 7 March, 1985 was organised and sponsored by IFS (Conferences) Ltd, Kempston, Bedford, U.K. The aim of the conference, in the words of Conference-chairman Prof. W.B. Heginbotham was "to point the way for exploitation at this time and to indicate what the future holds." He also remarked that "the academic and passive nature of simulation has now been overtaken and complex industrial situations can be represented accurately at an acceptable cost. In-
teractive graphics simulation can be used to model complete dynamic representations of human activity, multi robot cells with parallel operation, automatic assembly situations, automated warehousing and FMS and including 'in process' flow of components and material. Further developments which will incorporate knowledge based systems, will eventually be able to simulate and include the organisational functions like production control, capacity planning and loading and scheduling". A report on the papers delivered is presented below.
178
Conference Reports
Computers' m Industry
1. Simulation - a Management Tool
Risk Avoidance
Risk Reduction in Financial Decision-making
An independent simulation capability is a fundamental requirement for an FMS. In this talk P.L.C. Dunn (CitroEn Industries, U.K.) examined and identified the associated risks in isolation and in combination and discussed the different methods by which a potential FMS-user can select a suitable tool or program to reduce or eliminate these risks. Dunn also discussed some advantages and pitfalls created by this approach.
The installation of large, complex flexible manufacturing systems or computer integrated manufacturing systems represents a major investment for companies, whatever their size. Flexible manufacturing allow companies to benefit from investment in new technology and to counteract the effects of unpredictable external variables. In this talk J.F Wilson (Ingersoll Engineers Inc., U.K.) defined the risks involved in making financial decisions and described how the use of simulation modelling techniques can both quantify and substantially reduce these risks throughout the course of a project to design and install a large manufacturing system. Economic Application of FMS A sound financial appraisal can be carried out if data are available from design simulations. By using the evaluation program in conjunction with a well proven simulation program engineers can select the optimum application from a number of possible investments within a company. P.L. Primrose and R. Leonard (University of Manchester Institute of Science and Technology, U.K.) described how the techniques developed at their institute for investment analysis are capable of being interfaced with simulation programs. They showed that by mutually interchanging data from financial evaluation and simulation, the data used within both techniques become progressively more accurate, thereby increasing both the viability of a specific FMS application and the general expansion of FMS. Effective Simulation? The problems of making simulation effective in the design environment are considerable; design engineers require tools for immediate quantitative checks on their work. N.D. Thomson (IBM UK Laboratories Ltd, U.K.) described what is seen to be an answer, namely generic models on mainframe systems, supplemented by a comprehensive set of packages to provide coarser but more convenient simulation on PC's.
2. Control and Planning of Manufacturing Operations
Facility Changes in Manufacturing Plants In their paper M.T. Lilly and J. Driscoll (University of Liverpool, U.K.) detailed research into the simulation of batch manufacturing plants employing either conventional process layouts or advanced Flexible Manufacturing and Group Technology layouts, as changes in layout and manufacturing facilities are undertaken. They explained that the computer utilises on-line graphics and specialist software to interactively generate sequences of facility moves that minimise disruption of production, allowing examination of relayout policies varying from instant changeover to phased relayout over a number of periods. During simulation of a factory's lifespan financial evaluation is made of materials movement, facility relocation and production loss costs with both constant and discounted cash flow values. Production Control Aid FAMS is a Flexible Automated Manufacturing System software package which provides an integrated scheduling and production management tool for the small to medium sized plant. In contrast to other commercial packages the FAMS package has the additional capability to schedule and monitor shop activities in great detail while taking into account material handling, bottlenecks, breakdowns and other unscheduled occurrences. It provides users with interactive modelling capabilities to alert them to critical situations and to enable them to evaluate recovery strategies. P. W. U. Graefe, A.W. Chan (National Research Council of
Computersin Industry Canada) and M. Levi (ICAM Technologies Corp., Canada) described this interactive computer model and expounded on its uses.
Interactive Production Control System A production control system incorporating a dynamic simulation has been developed and fully implemented, and was described by P.D. Spooner (Fyne Management Systems Ltd., U.K.) in his talk. The system is in use since 1984 and is part of an integrated system for the management of the complete manufacturing unit including all the commercial and engineering functions. It consists of a series of modules which can be used to build systems for different plants. The complex dynamic interaction are simulated and updated with data from the shop floor and the system determines optimum scheduling for the work. The effects of the various production controls can be assessed as can the effects of changes. Control under the system significantly reduces lead times and stock levels of both work in progress and finished goods.
3. Simulation - Facilities and Techniques
Using Personal Computers G. Adner, H. Masus and C.G. Wikholm (SaabScania, Sweden) reviewed recently developed working methods for production engineers, based on computer aided simulation of manufacturing systems using personal computers and being used for the study of different system layouts and their limitations. They gave production engineers possibilities to evaluate and test-run different designs of automatic manufacturing systems including flexible industrial robots, machine tools and assembly stations before making decisions about final layouts and related investments. Computer simulation techniques provide production engineers with access to a tool for the design and development of production facilities. Application of Multiprocessing The work at Loughborough University of Technology, U.K. was in response to the need for the development of techniques to further increase the speed of execution of manufacturing system simu-
ConferenceReports
179
lation models. In this lecture E.A. Roberts and N. Shires (Loughborough University of Technology, U.K.) reviewed the progress to date on a multiprocessor dedicated aid to the design of flexible manufacturing systems, which can be regarded as a multiprocessing simulation tool with a highly developed front-end. They discussed how the computational speed can be increased, and described a technique of simultaneous computer processing. They also examined its implications and applications to emulation of manufacturing systems. The talk concluded with a description of the hardware and software implementation of a multitasking version of such a simulation system.
EXPRESS: a Man-Machine Interface Most of the existing simulation systems require a programming language in which the logic of individual activities or events is described. This has always made the tools for designing complicate simulation models more difficult for concomputing users. In this talk J. Shanehchi (Istel Ltd., U.K.) introduced the concept of a man-machine interface for simulation systems which enables users to develop simulation models without requiring in-depth knowledge of computers and computing. The talk concentrated on design characteristics of general interfaces on simulations systems and their applications within EXPRESS, a man-machine interface to SEE WHY.
Criteria for Success R.J. Blightman (P-E International Ltd., U.K.) identified the criteria which a simulation model should satisfy and gave some guidelines on managing a simulation project. The criteria include accuracy, acceptability, speed, flexibility and presentation and Blightman illustrated this by drawing on a number of case studies. A utoMod/A utoGram AutoMod is a collection of software tools for the simulation of industrial systems involving discrete unit material handling components such as Automated Guided Vehicles, Automated Storage and Retrieval Systems, pallet conveyors, towlines, transfer lines, monorails, overhead power and free
180
Conference Reports
conveyor. AutoGram consists of two software components, namely AutoGram-Describe, a subsystem which allows the designer to describe the manufacturing system to be studied and AutoGram-Display which is a system that uses the graphics database and system status information from the model to create a dynamic image of the system being investigated. AutoGram works with AutoMod to provide animated three-dimensional displays of simulated systems and to provide a quick means of digitizing the geometry of the systems. T.A. Norman (Brigham Young University) and V.B. Normal (AutoSimulations Inc., USA) gave an overview of the AutoMod system description language and included examples of pallet conveyor and AGV models.
Selection of Advanced Machine Tools D. Hughes (Kingston Polytechnic, U.K.) focussed attention during his talk on the use of a technique developed to select rather than financially appraise machine tools by providing management with detailed information on future manufacturing requirements. The approach reported on provided decision-makers with additional information on the likelihood of achieving specified loads on particular categories of machine tools. Hughes concluded his talk with two case studies illustrating the use of his technique to select advanced machine tools.
(omput~,c.~ :H Indu~'tr~
fele showed under which conditions the system can perform as desired. S1MULAP W Dangelmaier and R. Bachers (Fraunhofer Institute for Production and Automation OPAL W. Germany) are of the opinion that the existence of the parametrized simulation model was inevitable and that it is the latest development in the field of simulation technology. In this paper the parametrized simulation system SIMULAP was described. Using several figures the speakers showed how working with such a system takes place. The weak points of simulation systems in general and of the parametrized simulation system in particular were covered as were the different cases in which it could be successfully employed. FASTSIM In this paper R. Manuelli and G. Guiducci (ELSAG/MECTRON, Italy) gave an outline of FASTSIM, a simulator for the design and performance evaluation of automated systems. This software tool is easy to use, fast and reliable in its quantitative evaluations and of great use to system designers. They also described a case study carried out at their company which demonstrates the application of FASTSIM.
Microcomputer with Graphic Workstation
4. General Applications of Computer Simulation Flexible Assembly System K. Lay and M. Schiefele (Fraunhofer Institute of Industrial Engineering (IAO), W. Germany) showed the modelling and simulation of a subsystem consisting of cycle independent or automatic workstations for different types of products. The simulation program is written in SLAM II, the flow of workpieces described in network statements and special subroutines is realized in FORTRAN. The talk was mainly addressed to the question whether the system could be supplied under consideration of various type mixings and derivations of the ideal conditions. Results of simulation runs with several representative type mixings were presented in which Lay and Schie-
In this paper R. Bedini, A. De Taglia and G. Tani (University of Florence, Italy) dealt with the research carried out at their university which is aimed at adapting an FMS simulation package (GCMS) for mainframe or supermini computers to micros, that is for use in lower capacity, less costly environments. They also examined the methods to improve the performance of the input and output modules (enhanced user friendliness and more powerful and immediate reading and interpretation of outputs) thereby facilitating use of the package on a graphic workstation.
Control Algorithms for FMS Benefits to be gained from the introduction of a FMS have to be set against the high capital costs and problems involved in the system planning,
Computers in Industry
Conference Reports
181
building and control. If the potential benefits are to be adequately evaluated, thorough analytical evaluation is required, with the possible use of mathematical modelling and simulation. Z. Douglieri and R.D. Hibberd (Imperial College of Science and Technology, U.K.) described a simulation program that has been produced to enable the development and assessment of real time scheduling and control algorithms for FMS. It is written in FORTRAN, utilises SIMON routines and has a program consisting of two modules. The first module simulates discretely and deterministically the operations of an FMS and is interfaced to the second module which is devoted to scheduling and controls the flow of components through the FMS. The strategy adopted can be varied from simple priority assignments to complex scheduling algorithms.
Generalised computer simulation models are a tool for the analysis of systems, especially complex areas such as FMS. They provide a realistic, costeffective simulation capability with the advantage of good response times. The use of these models as part of a structured program of systems analysis can reduce investment requirements and improve system performance. R.L Mills (Ingersoll Engineers Inc., U.K.) and J.J. Talavage (Purdue University, USA) described this class of models together with brief details of their development and a selective review of those that are currently available. They concluded their talk with an example of the use of such a simulator which is concerned with the assessment of automatic tool handling within FMS.
Tooling for FMS
Computer Simulation for Planning
In this talk J.M. Kay (Cranfield Robotics & Automation Group, U.K.) expressed the point of view that the flexibility of a manufacturing system is limited by the capabilities of the machine tools and the transport system. To understand the operation of a proposed tool storage and transport system, computer simulation presents itself as a method and to this end two computer models have been created and were considered in detail and described by Kay. They are two simulation packages, TOOLSIM1 and TOOLSIM2, which provide a system designer with a means of testing and improving on ideas and can also be used as a means of incorporating tool availability into the scheduling process.
Simulation provides an aid to good planning and enables precise definition of a system in terms of facility requirements and control logic. The use of graphics facilities to provide animated displays of the simulated system helps to communicate ideas unambiguously. In their talk T.C. Goodhead and T.M. Mahoney (University of Warwick and Austin Rover Group, U.K.) described the use made of a computer simulation package with graphics and interactive facilities during the planning stages of large scale FMS. In their view simulation fulfills the role of quantifying facility requirements and evaluating alternative operating strategies to ensure that the required system performance can be achieved economically.
Simulation Programs
Limited Production of Concentrics 5. FMS Design
Needs, Experience, Facilities A. Carrie (Strathclyde University, U.K.) outlined the needs of user firms and reviewed some experiences with simulating FMS. This was followed by a discussion of the FMS model building process and a review of software facilities, simulations packages and languages. Carrie then brought the three aspects together in a discussion of the further developments required in FMS simulation software.
In this talk R.R. Thettu (Xerox Corp., USA) and S.R. Paidy (Rochester Institute of Technology, USA) presented a simulation model of an FMS proposed for limited production of concentric parts in Xerox copiers and to specify adequate equipment, human, computer and material handling resources before implementation. A general purpose language, SIMAN, has been used to develop a simulation model of this state of the art computer integrated manufacturing facility comprising of nine work centres and an AGVS material handling system. The model has provided timely
182
ConferenceReports
analysis to assess the resource requirements for various production schemes and control strategies which in turn helped in the financial analysis of the limited production facility for the concentrics. Economic Evaluation of Advanced Manufacturing C.R. BoOr and V. Metzler (BBC Brown Boveri & Co. Ltd., Switzerland) illustrated an approach in their talk which can be taken for the planning of complex manufacturing systems and the simulation software used at different phases in the planning. They showed that it is necessary to evaluate at each stage the economics of the alternative designs selected and simulation is therefore coupled with economic analysis. They also presented some results and applications of the simulation.
6. Industrial Case Studies Getting the Best Simulation has much to offer in improving cost effectiveness. The purpose of the talk delivered by B.W. Hollocks (Istel Ltd., U.K.) was to present guidelines for the use of simulation with full benefits. Hollocks illustrated this by describing the course of a major simulation project in heavy manufacturing industry. "FORSSIGHT'" In the lecture om FORSSIGHT M.J. Birch, H.P. Feszezur (British Aerospace), T.J. Terrel and R.J. Simpson (Lancashire Polytechnic, U.K.) detailed how a chosen sub-system of the FMS is represented by ~ dynamic mimic diagram on a colour graphics display to provide interactive simulation facilities for the user. They placed emphasis on the modular approach used throughout all stages of the model development and showed that this form of flexible simulation is able to accommodate all phases of plant automation. Cycle Manufacturing T.M. Gough described events which have taken place at his place of employment - T.I. Raleigh Ltd., U.K. The company has been modernising its production methods and this has involved sub-
~"omputer,~ m Industry
stantial investments in new plant and management systems. In 1982 a decision was taken to employ simulation techniques to assist in planning the investment program. The company has also been involved in work scheduling for which it employs an MRP system to plan at a macro level. Simulation is therefore used to support developments in the engineering project, to schedule the plant when it is implemented, to properly plan plant investment and to operate this efficiently after implementation. 7. Late Papers Computer Simulation The main purpose of the talk presented by N.R. Greenwood (General Electric Industrial Automation Europe), P. Rao (GEC Research and Development, U.S.A.) and M. Wisnom (Structural Dynamics Research Corp., U.K.) was to demonstrate the viability of sophisticated factory simulation packages, in particular the system developed by General Electric. The packages were designed to run on the DEC Vax range of computers but it is also possible to implement a notable portion of the software on the IBM PC and the Data General. The packages will also be released in Europe. GRASP Robots are used increasingly for industrial tasks and it is essential that the design planning and installation of robot workplaces proceed smoothly. M.C. Bonney (Loughborough University of Technology, U.K.), J. Moser (ITT/AMTC, Belgium) and Y.G. Young (BYG Systems Ltd., U.K.) described the evaluation and use of a Graphic Robot Simulator called GRASP. In the first part of the lecture GRASP itself was described and the speaker provided an overview of its major features and functionality. The second part focussed on a case study which detailed some of the results obtained from a thorough evaluation of the package used in a industrial environment, giving a potential user a good idea of how and where savings could be achieved. GPSS and Production Sectors The existing conventional methods of designing production sectors are incapable of providing suf-
Computers in Industry
ficient evidence of the actual time-dependent behaviour of the system. It is necessary to obtain data for analysing the production process and simulation modelling has become a tool for obtaining this information. Its objective is to derive relations between the structure of the production sector and its productivity and utilization. The General Purpose Simulation System (GPSS) language was chosen for modelling production sectors. J. Zajickova (Research Institute of Technology and Economy in Mechanical Engineering, Czechoslovakia) described this in the lecture and gave examples to illustrate the points made. In the application of simulation modelling to problems of production sectors effective simulation algorithms have been developed and experience gained with operating small and larger models. A basis is created for optimization with regard to designs of technical control systems, thereby increasing the economic effectiveness of production systems designed with the the aid of this method.
Life Cycle Simulation M.A.M. Rogers (ICI plc, U.K.) described how the technique known as visual interactive modeling has been developed and packaged for application to batch manufacturing of chemicals. The concept of life cycle simulation in connection with batch processes was explained and the methodology organisation and software techniques for its effective implementation were described. Transfer Line Performance The results of a computer simulation study on the performance of a transfer line for diesel engine
ConferenceReports
183
block manufacture was presented by K.K. Hon and N.M. Ahmad (University of Birmingham, U.K.). The model they described incorporated data on machine breakdown, inter-operational stock capacity and other parameters. They also reported on the computer simulation runs they had made to evaluate machine breakdown effect, the effect of machine replacement on line output and machine utilization.
High Variety Small Batch FMS This talk focussed on the vital role played by visual interactive simulation in a project at a company which manufactures small batches of varied components which seldom repeat. M.W. Looney and A.H. Warby (Inbucon Management Consultants Ltd., U.K.) showed that the simulation exercise confirmed that the proposed FMS concept was viable. It enabled the specification of the major hardware items and led to the establishment of system operating rules.
Automotive Body Shop Using SLAM H K.R. Morrison (Ford Motor Co., U.S.A.) discussed the formulation of an automotive body shop facility using SLAM II. Increased use of automation creates a need simulation analyses and the speaker addressed formulation problems posed by job splitting, out of sequence jobs, workstation breakdowns and user interactions. The Proceedings of the Conference were jointly published by IFS Publications Ltd., U.K. and North Holland, Amsterdam, The Netherlands. VIII + 3 8 4 pages. ISBN 0-903608-84-7 and 0-444-877320. Price Dfl. 225.
the lines of the displacement hull were also given in the lecture. A brief analysis of the feasibility and utility of the presented method was also done. Bogdanov and Kovachev pointed out that the program package allows interactive adjustment of predetermined geometrical properties of the displacement hull and the lifting surface(s).
II. Hydrodynamics Ship Manoeuvring Response Steps towards international legislation for ship manoeuvrability have motivated the development of theoretical and empirical methods for predicting ship manoeuvring response. One such method, aimed primarily for initial design, was described by N.E. Mikelis (Lloyd's Register of Shipping, U.K.). The use of this method is direct and inexpensive since it requires the input of data only on installed power and on the geometry of ship, propeller and rudder. Mikelis explained that comparisons between simulated and full scale trial manoeuvres for a tanker provide a first verification of the adopted mathematical model. The presentation was entitled "A Procedure for the Prediction of Ship Manoeuvring Response for Initial Design."
Conference Reports
177
Mission Effectiveness R. Hosoda (University of Osaka Prefecture, Japan) and Y. Kunitake (Mitsui Engineering & Shipbuilding Co., Ltd., Japan) introduced a concept of "mission effectiveness" for evaluating the seakeeping performance of ships at the early stage of ship design. In order to evaluate the mission effectiveness, short-term and long-term performance effectiveness was estimated by applying formulations commonly used in estimating ship responses in rough seas with the assistance of probabilistic theories. A method of simulation was also applied to evaluate the overall seakeeping performance of ships in rough seas. Finally, the mission effectiveness which comprises the cost to performance trade-offs was systematically evaluated. In their lecture Hosoda and Kunitake applied the method to the evaluation of seakeeping performance of patrol boats to be operated for a mission °' salvage of ships in distress at sea". The Proceedings of this conference have been edited by P. Banda and C. Kuo and published by North-Holland under the title Computer Ap-
plications in the Automation of Shipyard Operation and Ship Design, V". 1985. xiv + 458 pages. ISBN 0-444-87820-3.
Simulation in Manufacturing The First International Conference on Simulation in Manufacturing which took place in Stratford-upon-Avon, U.K. from 5 - 7 March, 1985 was organised and sponsored by IFS (Conferences) Ltd, Kempston, Bedford, U.K. The aim of the conference, in the words of Conference-chairman Prof. W.B. Heginbotham was "to point the way for exploitation at this time and to indicate what the future holds." He also remarked that "the academic and passive nature of simulation has now been overtaken and complex industrial situations can be represented accurately at an acceptable cost. In-
teractive graphics simulation can be used to model complete dynamic representations of human activity, multi robot cells with parallel operation, automatic assembly situations, automated warehousing and FMS and including 'in process' flow of components and material. Further developments which will incorporate knowledge based systems, will eventually be able to simulate and include the organisational functions like production control, capacity planning and loading and scheduling". A report on the papers delivered is presented below.
178
Conference Reports
Computers' m Industry
1. Simulation - a Management Tool
Risk Avoidance
Risk Reduction in Financial Decision-making
An independent simulation capability is a fundamental requirement for an FMS. In this talk P.L.C. Dunn (CitroEn Industries, U.K.) examined and identified the associated risks in isolation and in combination and discussed the different methods by which a potential FMS-user can select a suitable tool or program to reduce or eliminate these risks. Dunn also discussed some advantages and pitfalls created by this approach.
The installation of large, complex flexible manufacturing systems or computer integrated manufacturing systems represents a major investment for companies, whatever their size. Flexible manufacturing allow companies to benefit from investment in new technology and to counteract the effects of unpredictable external variables. In this talk J.F Wilson (Ingersoll Engineers Inc., U.K.) defined the risks involved in making financial decisions and described how the use of simulation modelling techniques can both quantify and substantially reduce these risks throughout the course of a project to design and install a large manufacturing system. Economic Application of FMS A sound financial appraisal can be carried out if data are available from design simulations. By using the evaluation program in conjunction with a well proven simulation program engineers can select the optimum application from a number of possible investments within a company. P.L. Primrose and R. Leonard (University of Manchester Institute of Science and Technology, U.K.) described how the techniques developed at their institute for investment analysis are capable of being interfaced with simulation programs. They showed that by mutually interchanging data from financial evaluation and simulation, the data used within both techniques become progressively more accurate, thereby increasing both the viability of a specific FMS application and the general expansion of FMS. Effective Simulation? The problems of making simulation effective in the design environment are considerable; design engineers require tools for immediate quantitative checks on their work. N.D. Thomson (IBM UK Laboratories Ltd, U.K.) described what is seen to be an answer, namely generic models on mainframe systems, supplemented by a comprehensive set of packages to provide coarser but more convenient simulation on PC's.
2. Control and Planning of Manufacturing Operations
Facility Changes in Manufacturing Plants In their paper M.T. Lilly and J. Driscoll (University of Liverpool, U.K.) detailed research into the simulation of batch manufacturing plants employing either conventional process layouts or advanced Flexible Manufacturing and Group Technology layouts, as changes in layout and manufacturing facilities are undertaken. They explained that the computer utilises on-line graphics and specialist software to interactively generate sequences of facility moves that minimise disruption of production, allowing examination of relayout policies varying from instant changeover to phased relayout over a number of periods. During simulation of a factory's lifespan financial evaluation is made of materials movement, facility relocation and production loss costs with both constant and discounted cash flow values. Production Control Aid FAMS is a Flexible Automated Manufacturing System software package which provides an integrated scheduling and production management tool for the small to medium sized plant. In contrast to other commercial packages the FAMS package has the additional capability to schedule and monitor shop activities in great detail while taking into account material handling, bottlenecks, breakdowns and other unscheduled occurrences. It provides users with interactive modelling capabilities to alert them to critical situations and to enable them to evaluate recovery strategies. P. W. U. Graefe, A.W. Chan (National Research Council of
Computersin Industry Canada) and M. Levi (ICAM Technologies Corp., Canada) described this interactive computer model and expounded on its uses.
Interactive Production Control System A production control system incorporating a dynamic simulation has been developed and fully implemented, and was described by P.D. Spooner (Fyne Management Systems Ltd., U.K.) in his talk. The system is in use since 1984 and is part of an integrated system for the management of the complete manufacturing unit including all the commercial and engineering functions. It consists of a series of modules which can be used to build systems for different plants. The complex dynamic interaction are simulated and updated with data from the shop floor and the system determines optimum scheduling for the work. The effects of the various production controls can be assessed as can the effects of changes. Control under the system significantly reduces lead times and stock levels of both work in progress and finished goods.
3. Simulation - Facilities and Techniques
Using Personal Computers G. Adner, H. Masus and C.G. Wikholm (SaabScania, Sweden) reviewed recently developed working methods for production engineers, based on computer aided simulation of manufacturing systems using personal computers and being used for the study of different system layouts and their limitations. They gave production engineers possibilities to evaluate and test-run different designs of automatic manufacturing systems including flexible industrial robots, machine tools and assembly stations before making decisions about final layouts and related investments. Computer simulation techniques provide production engineers with access to a tool for the design and development of production facilities. Application of Multiprocessing The work at Loughborough University of Technology, U.K. was in response to the need for the development of techniques to further increase the speed of execution of manufacturing system simu-
ConferenceReports
179
lation models. In this lecture E.A. Roberts and N. Shires (Loughborough University of Technology, U.K.) reviewed the progress to date on a multiprocessor dedicated aid to the design of flexible manufacturing systems, which can be regarded as a multiprocessing simulation tool with a highly developed front-end. They discussed how the computational speed can be increased, and described a technique of simultaneous computer processing. They also examined its implications and applications to emulation of manufacturing systems. The talk concluded with a description of the hardware and software implementation of a multitasking version of such a simulation system.
EXPRESS: a Man-Machine Interface Most of the existing simulation systems require a programming language in which the logic of individual activities or events is described. This has always made the tools for designing complicate simulation models more difficult for concomputing users. In this talk J. Shanehchi (Istel Ltd., U.K.) introduced the concept of a man-machine interface for simulation systems which enables users to develop simulation models without requiring in-depth knowledge of computers and computing. The talk concentrated on design characteristics of general interfaces on simulations systems and their applications within EXPRESS, a man-machine interface to SEE WHY.
Criteria for Success R.J. Blightman (P-E International Ltd., U.K.) identified the criteria which a simulation model should satisfy and gave some guidelines on managing a simulation project. The criteria include accuracy, acceptability, speed, flexibility and presentation and Blightman illustrated this by drawing on a number of case studies. A utoMod/A utoGram AutoMod is a collection of software tools for the simulation of industrial systems involving discrete unit material handling components such as Automated Guided Vehicles, Automated Storage and Retrieval Systems, pallet conveyors, towlines, transfer lines, monorails, overhead power and free
180
Conference Reports
conveyor. AutoGram consists of two software components, namely AutoGram-Describe, a subsystem which allows the designer to describe the manufacturing system to be studied and AutoGram-Display which is a system that uses the graphics database and system status information from the model to create a dynamic image of the system being investigated. AutoGram works with AutoMod to provide animated three-dimensional displays of simulated systems and to provide a quick means of digitizing the geometry of the systems. T.A. Norman (Brigham Young University) and V.B. Normal (AutoSimulations Inc., USA) gave an overview of the AutoMod system description language and included examples of pallet conveyor and AGV models.
Selection of Advanced Machine Tools D. Hughes (Kingston Polytechnic, U.K.) focussed attention during his talk on the use of a technique developed to select rather than financially appraise machine tools by providing management with detailed information on future manufacturing requirements. The approach reported on provided decision-makers with additional information on the likelihood of achieving specified loads on particular categories of machine tools. Hughes concluded his talk with two case studies illustrating the use of his technique to select advanced machine tools.
(omput~,c.~ :H Indu~'tr~
fele showed under which conditions the system can perform as desired. S1MULAP W Dangelmaier and R. Bachers (Fraunhofer Institute for Production and Automation OPAL W. Germany) are of the opinion that the existence of the parametrized simulation model was inevitable and that it is the latest development in the field of simulation technology. In this paper the parametrized simulation system SIMULAP was described. Using several figures the speakers showed how working with such a system takes place. The weak points of simulation systems in general and of the parametrized simulation system in particular were covered as were the different cases in which it could be successfully employed. FASTSIM In this paper R. Manuelli and G. Guiducci (ELSAG/MECTRON, Italy) gave an outline of FASTSIM, a simulator for the design and performance evaluation of automated systems. This software tool is easy to use, fast and reliable in its quantitative evaluations and of great use to system designers. They also described a case study carried out at their company which demonstrates the application of FASTSIM.
Microcomputer with Graphic Workstation
4. General Applications of Computer Simulation Flexible Assembly System K. Lay and M. Schiefele (Fraunhofer Institute of Industrial Engineering (IAO), W. Germany) showed the modelling and simulation of a subsystem consisting of cycle independent or automatic workstations for different types of products. The simulation program is written in SLAM II, the flow of workpieces described in network statements and special subroutines is realized in FORTRAN. The talk was mainly addressed to the question whether the system could be supplied under consideration of various type mixings and derivations of the ideal conditions. Results of simulation runs with several representative type mixings were presented in which Lay and Schie-
In this paper R. Bedini, A. De Taglia and G. Tani (University of Florence, Italy) dealt with the research carried out at their university which is aimed at adapting an FMS simulation package (GCMS) for mainframe or supermini computers to micros, that is for use in lower capacity, less costly environments. They also examined the methods to improve the performance of the input and output modules (enhanced user friendliness and more powerful and immediate reading and interpretation of outputs) thereby facilitating use of the package on a graphic workstation.
Control Algorithms for FMS Benefits to be gained from the introduction of a FMS have to be set against the high capital costs and problems involved in the system planning,
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building and control. If the potential benefits are to be adequately evaluated, thorough analytical evaluation is required, with the possible use of mathematical modelling and simulation. Z. Douglieri and R.D. Hibberd (Imperial College of Science and Technology, U.K.) described a simulation program that has been produced to enable the development and assessment of real time scheduling and control algorithms for FMS. It is written in FORTRAN, utilises SIMON routines and has a program consisting of two modules. The first module simulates discretely and deterministically the operations of an FMS and is interfaced to the second module which is devoted to scheduling and controls the flow of components through the FMS. The strategy adopted can be varied from simple priority assignments to complex scheduling algorithms.
Generalised computer simulation models are a tool for the analysis of systems, especially complex areas such as FMS. They provide a realistic, costeffective simulation capability with the advantage of good response times. The use of these models as part of a structured program of systems analysis can reduce investment requirements and improve system performance. R.L Mills (Ingersoll Engineers Inc., U.K.) and J.J. Talavage (Purdue University, USA) described this class of models together with brief details of their development and a selective review of those that are currently available. They concluded their talk with an example of the use of such a simulator which is concerned with the assessment of automatic tool handling within FMS.
Tooling for FMS
Computer Simulation for Planning
In this talk J.M. Kay (Cranfield Robotics & Automation Group, U.K.) expressed the point of view that the flexibility of a manufacturing system is limited by the capabilities of the machine tools and the transport system. To understand the operation of a proposed tool storage and transport system, computer simulation presents itself as a method and to this end two computer models have been created and were considered in detail and described by Kay. They are two simulation packages, TOOLSIM1 and TOOLSIM2, which provide a system designer with a means of testing and improving on ideas and can also be used as a means of incorporating tool availability into the scheduling process.
Simulation provides an aid to good planning and enables precise definition of a system in terms of facility requirements and control logic. The use of graphics facilities to provide animated displays of the simulated system helps to communicate ideas unambiguously. In their talk T.C. Goodhead and T.M. Mahoney (University of Warwick and Austin Rover Group, U.K.) described the use made of a computer simulation package with graphics and interactive facilities during the planning stages of large scale FMS. In their view simulation fulfills the role of quantifying facility requirements and evaluating alternative operating strategies to ensure that the required system performance can be achieved economically.
Simulation Programs
Limited Production of Concentrics 5. FMS Design
Needs, Experience, Facilities A. Carrie (Strathclyde University, U.K.) outlined the needs of user firms and reviewed some experiences with simulating FMS. This was followed by a discussion of the FMS model building process and a review of software facilities, simulations packages and languages. Carrie then brought the three aspects together in a discussion of the further developments required in FMS simulation software.
In this talk R.R. Thettu (Xerox Corp., USA) and S.R. Paidy (Rochester Institute of Technology, USA) presented a simulation model of an FMS proposed for limited production of concentric parts in Xerox copiers and to specify adequate equipment, human, computer and material handling resources before implementation. A general purpose language, SIMAN, has been used to develop a simulation model of this state of the art computer integrated manufacturing facility comprising of nine work centres and an AGVS material handling system. The model has provided timely
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analysis to assess the resource requirements for various production schemes and control strategies which in turn helped in the financial analysis of the limited production facility for the concentrics. Economic Evaluation of Advanced Manufacturing C.R. BoOr and V. Metzler (BBC Brown Boveri & Co. Ltd., Switzerland) illustrated an approach in their talk which can be taken for the planning of complex manufacturing systems and the simulation software used at different phases in the planning. They showed that it is necessary to evaluate at each stage the economics of the alternative designs selected and simulation is therefore coupled with economic analysis. They also presented some results and applications of the simulation.
6. Industrial Case Studies Getting the Best Simulation has much to offer in improving cost effectiveness. The purpose of the talk delivered by B.W. Hollocks (Istel Ltd., U.K.) was to present guidelines for the use of simulation with full benefits. Hollocks illustrated this by describing the course of a major simulation project in heavy manufacturing industry. "FORSSIGHT'" In the lecture om FORSSIGHT M.J. Birch, H.P. Feszezur (British Aerospace), T.J. Terrel and R.J. Simpson (Lancashire Polytechnic, U.K.) detailed how a chosen sub-system of the FMS is represented by ~ dynamic mimic diagram on a colour graphics display to provide interactive simulation facilities for the user. They placed emphasis on the modular approach used throughout all stages of the model development and showed that this form of flexible simulation is able to accommodate all phases of plant automation. Cycle Manufacturing T.M. Gough described events which have taken place at his place of employment - T.I. Raleigh Ltd., U.K. The company has been modernising its production methods and this has involved sub-
~"omputer,~ m Industry
stantial investments in new plant and management systems. In 1982 a decision was taken to employ simulation techniques to assist in planning the investment program. The company has also been involved in work scheduling for which it employs an MRP system to plan at a macro level. Simulation is therefore used to support developments in the engineering project, to schedule the plant when it is implemented, to properly plan plant investment and to operate this efficiently after implementation. 7. Late Papers Computer Simulation The main purpose of the talk presented by N.R. Greenwood (General Electric Industrial Automation Europe), P. Rao (GEC Research and Development, U.S.A.) and M. Wisnom (Structural Dynamics Research Corp., U.K.) was to demonstrate the viability of sophisticated factory simulation packages, in particular the system developed by General Electric. The packages were designed to run on the DEC Vax range of computers but it is also possible to implement a notable portion of the software on the IBM PC and the Data General. The packages will also be released in Europe. GRASP Robots are used increasingly for industrial tasks and it is essential that the design planning and installation of robot workplaces proceed smoothly. M.C. Bonney (Loughborough University of Technology, U.K.), J. Moser (ITT/AMTC, Belgium) and Y.G. Young (BYG Systems Ltd., U.K.) described the evaluation and use of a Graphic Robot Simulator called GRASP. In the first part of the lecture GRASP itself was described and the speaker provided an overview of its major features and functionality. The second part focussed on a case study which detailed some of the results obtained from a thorough evaluation of the package used in a industrial environment, giving a potential user a good idea of how and where savings could be achieved. GPSS and Production Sectors The existing conventional methods of designing production sectors are incapable of providing suf-
Computers in Industry
ficient evidence of the actual time-dependent behaviour of the system. It is necessary to obtain data for analysing the production process and simulation modelling has become a tool for obtaining this information. Its objective is to derive relations between the structure of the production sector and its productivity and utilization. The General Purpose Simulation System (GPSS) language was chosen for modelling production sectors. J. Zajickova (Research Institute of Technology and Economy in Mechanical Engineering, Czechoslovakia) described this in the lecture and gave examples to illustrate the points made. In the application of simulation modelling to problems of production sectors effective simulation algorithms have been developed and experience gained with operating small and larger models. A basis is created for optimization with regard to designs of technical control systems, thereby increasing the economic effectiveness of production systems designed with the the aid of this method.
Life Cycle Simulation M.A.M. Rogers (ICI plc, U.K.) described how the technique known as visual interactive modeling has been developed and packaged for application to batch manufacturing of chemicals. The concept of life cycle simulation in connection with batch processes was explained and the methodology organisation and software techniques for its effective implementation were described. Transfer Line Performance The results of a computer simulation study on the performance of a transfer line for diesel engine
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block manufacture was presented by K.K. Hon and N.M. Ahmad (University of Birmingham, U.K.). The model they described incorporated data on machine breakdown, inter-operational stock capacity and other parameters. They also reported on the computer simulation runs they had made to evaluate machine breakdown effect, the effect of machine replacement on line output and machine utilization.
High Variety Small Batch FMS This talk focussed on the vital role played by visual interactive simulation in a project at a company which manufactures small batches of varied components which seldom repeat. M.W. Looney and A.H. Warby (Inbucon Management Consultants Ltd., U.K.) showed that the simulation exercise confirmed that the proposed FMS concept was viable. It enabled the specification of the major hardware items and led to the establishment of system operating rules.
Automotive Body Shop Using SLAM H K.R. Morrison (Ford Motor Co., U.S.A.) discussed the formulation of an automotive body shop facility using SLAM II. Increased use of automation creates a need simulation analyses and the speaker addressed formulation problems posed by job splitting, out of sequence jobs, workstation breakdowns and user interactions. The Proceedings of the Conference were jointly published by IFS Publications Ltd., U.K. and North Holland, Amsterdam, The Netherlands. VIII + 3 8 4 pages. ISBN 0-903608-84-7 and 0-444-877320. Price Dfl. 225.