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Flexible assembly systems: The scheduling problem for multiple products
Journalof ManufacturingSystems Voluroe12/No. I
Cumulative Abstract Index
more sides. Parts of this type are difficult because features on different sides may interact with each other:, cutting one group of features first may make the part such an odd shape that it is difficult to clamp for subsequent operations. These interactions must be carefully considered when grouping and ordering the machining operations. The machinlst program has been designed to be an integral part of CAD systems, facilitating the generation of manufacturing plans. Keywords: Process Planning, Operations Planning, Expert ;System, ClqC Machining Center
that should make the model consistent, conceptually uniform and easy to understand.
Antomato Top-Down
odel, Hierarchical Control
A Oumt~fcat/on of the Value ofFlezib//ity, G. Hutchinson, V. Sinh& pp. 47-57 Man~.e~s of production systems are often faced with the decision of acquiring production capacity to meet forecast demand. Return on investment (ROI) models have traditionally been used, but unfortunate results have occurred in some instances, because the benefits of flexibility were not quantified. This paper concentrates on two aspects of flexibility, the ability to change manufacturing mission and capacity. They are shown to have quanlifutble economic value in a particular situation by use of a decision theoretic model. System parameters of interest are investigated to estimate their influence, including uncertainty. Keywords:Rcx~l~h'ty,InvestmentAnalysis, Decision Thec~, Uncmamty
The Cutting Path and Tool Selection Problem in ComputerAided Process P/arming, J. Bard, T. IV~o,pp. 17-26 This paper is concerned with minimizing the sum of the tool setup and volume removal times associated with metal cutting operations on a flexible machine. The problem is of interest to most repetitive manufacturers because any reduction in processin s time tnmslates directly into cost savings. Finding optimal solutions, though, has proven quite difficult for manufacturing engineers due to the large number of cutting paths and tool combinations that may be selected. The problem is modeled as an integer program but transformed by relaxing some of the constralnts into one of finding a minimum cut on a simple network. After obtaining a tentative solution at this step, an efficient, but suboptimal, procedure is used to generate alternative process plans. These are seen to speed convergence during branch and bound. Overall performance is judged by examining a wide variety of test problems derived from actualmanufacturing data. Keywords: Flexible Manufacturing Systems, Computer Aided Process Planning, Metal Cutting, Integer Programming
Schedulingand Machining ofJobs ThroughParallelNonidentical Machine Cel/s, E. Watson, P. Egbelu, pp. 59-68 Process planning and scheduling are two functions commonly encountered in any manufacturing system. Despite the well-recognized interdepeadencies between them, research in these areas have progressed separately as if there is virtually no relationship between the two. The result of such separate development in terms of manufacturing systems planning can lead to the adoption ofpelicies that are far trom optimal. In this paper, a modeling approach that integrates the functions of job scheduling and process planning in cells with parallel and nonidentical machine groups is presented. A heuristic algorithm is developed that allocates the jobs to machines while at the same time generates the best machining perameters to use for each job in order not to violate any job and machine related restrictions. The basis of optimization is the mlnimi1Jtfionof total manufacturing cost. Ke~nvor~: Schedulmg,Processplanning, Optimiz~oa, Machining Cells, Parallel Processing
Flexible Assembly Systems: The Scheduling Problemfor Multiple Products, M. Donath, R. Graves, D. Carlson, pp. 2%34 Flexible assembly systems (FAS) promises to be an efficient processing approach for producing small and medium-sized batches of products. One vitally important element which affects the achievement of high performance by the FAS is its scheduling/ dispatching component operating within the production planning a n a control system (PPCS). A detailed definition of the FAS scheduling process is given and key differences between this process and the classical simple job shop scheduling process are discussed. A mathematical model is developed for the minimize makespan problem, and it is shown that the problem is NPcomplete, that it is one of the most difficult problems in the class of decision problems that can be solved by polynomial time nondeterministc algorithm (NP). The design of heuristic solution procedures is also discussed. Keywords: Scheduling, Dispatching, Complexity Analysis, Algorithm Design, Flexible Assembly Systems
1989~ V o l . 8 / N o . 2 A Framework for Understanding Flexibilityof Manufacturing Systems, D. Oupta, J. Buzacott,pp. 89-97 The concept of"flexibility"has been a recurringtheme in the recentoperationsresearchliteraturepertainingto manufacturing. Although flexibility is recognized for its strategic importance to the future of manufacturing, critical underpinnings of this conc.ept are not well understood. This paper presents a comprehenszve study of flexibility and proposes a scheme for assessing "value of flexibility", a surrogate flexibili~ measure. The paper also provides valuable conceptual foundat/ons for the development of quantitative models dea!ing with economic evaluation of investments in the flexibly automated manufacturing systems. eywords: Flexibility, Flexible Manufacturing Systems, urrogate Measures, Value of Flexibility, Economic Justifications
Reference Model for Manufacturing Planning and Control Systems, F. Biemans, C. Vissers, pp. 35-46 A reference model for a manufacturing planning and control system (MPCS) is presented, which represents a MPCS as a hierarchical organization of cooperating decision-making units. The model is an abstract specification of an integrated MPCS, and a milestone in its top-down design. Moreover, the model provides a reference for a common terminology and concepts. The model could play the same role in the development of a computerized MPCS that the open systems interconnection reference model of the international organization for standardization does in the development of computer networks. This paper proposes a structure as well as a distribution of tasks over the deczsion-making units in the model. The model is jnstfied on the basis of criteria
An IntelligentInformation System for an Automated Integrated Man~acturing System, D. Weber, C. Moodie, pp. 99-I 13 The recent years of manufacturing research have been governed by the trend toward integration of automation islands into
69
Cumulative Abstract Index
more sides. Parts of this type are difficult because features on different sides may interact with each other:, cutting one group of features first may make the part such an odd shape that it is difficult to clamp for subsequent operations. These interactions must be carefully considered when grouping and ordering the machining operations. The machinlst program has been designed to be an integral part of CAD systems, facilitating the generation of manufacturing plans. Keywords: Process Planning, Operations Planning, Expert ;System, ClqC Machining Center
that should make the model consistent, conceptually uniform and easy to understand.
Antomato Top-Down
odel, Hierarchical Control
A Oumt~fcat/on of the Value ofFlezib//ity, G. Hutchinson, V. Sinh& pp. 47-57 Man~.e~s of production systems are often faced with the decision of acquiring production capacity to meet forecast demand. Return on investment (ROI) models have traditionally been used, but unfortunate results have occurred in some instances, because the benefits of flexibility were not quantified. This paper concentrates on two aspects of flexibility, the ability to change manufacturing mission and capacity. They are shown to have quanlifutble economic value in a particular situation by use of a decision theoretic model. System parameters of interest are investigated to estimate their influence, including uncertainty. Keywords:Rcx~l~h'ty,InvestmentAnalysis, Decision Thec~, Uncmamty
The Cutting Path and Tool Selection Problem in ComputerAided Process P/arming, J. Bard, T. IV~o,pp. 17-26 This paper is concerned with minimizing the sum of the tool setup and volume removal times associated with metal cutting operations on a flexible machine. The problem is of interest to most repetitive manufacturers because any reduction in processin s time tnmslates directly into cost savings. Finding optimal solutions, though, has proven quite difficult for manufacturing engineers due to the large number of cutting paths and tool combinations that may be selected. The problem is modeled as an integer program but transformed by relaxing some of the constralnts into one of finding a minimum cut on a simple network. After obtaining a tentative solution at this step, an efficient, but suboptimal, procedure is used to generate alternative process plans. These are seen to speed convergence during branch and bound. Overall performance is judged by examining a wide variety of test problems derived from actualmanufacturing data. Keywords: Flexible Manufacturing Systems, Computer Aided Process Planning, Metal Cutting, Integer Programming
Schedulingand Machining ofJobs ThroughParallelNonidentical Machine Cel/s, E. Watson, P. Egbelu, pp. 59-68 Process planning and scheduling are two functions commonly encountered in any manufacturing system. Despite the well-recognized interdepeadencies between them, research in these areas have progressed separately as if there is virtually no relationship between the two. The result of such separate development in terms of manufacturing systems planning can lead to the adoption ofpelicies that are far trom optimal. In this paper, a modeling approach that integrates the functions of job scheduling and process planning in cells with parallel and nonidentical machine groups is presented. A heuristic algorithm is developed that allocates the jobs to machines while at the same time generates the best machining perameters to use for each job in order not to violate any job and machine related restrictions. The basis of optimization is the mlnimi1Jtfionof total manufacturing cost. Ke~nvor~: Schedulmg,Processplanning, Optimiz~oa, Machining Cells, Parallel Processing
Flexible Assembly Systems: The Scheduling Problemfor Multiple Products, M. Donath, R. Graves, D. Carlson, pp. 2%34 Flexible assembly systems (FAS) promises to be an efficient processing approach for producing small and medium-sized batches of products. One vitally important element which affects the achievement of high performance by the FAS is its scheduling/ dispatching component operating within the production planning a n a control system (PPCS). A detailed definition of the FAS scheduling process is given and key differences between this process and the classical simple job shop scheduling process are discussed. A mathematical model is developed for the minimize makespan problem, and it is shown that the problem is NPcomplete, that it is one of the most difficult problems in the class of decision problems that can be solved by polynomial time nondeterministc algorithm (NP). The design of heuristic solution procedures is also discussed. Keywords: Scheduling, Dispatching, Complexity Analysis, Algorithm Design, Flexible Assembly Systems
1989~ V o l . 8 / N o . 2 A Framework for Understanding Flexibilityof Manufacturing Systems, D. Oupta, J. Buzacott,pp. 89-97 The concept of"flexibility"has been a recurringtheme in the recentoperationsresearchliteraturepertainingto manufacturing. Although flexibility is recognized for its strategic importance to the future of manufacturing, critical underpinnings of this conc.ept are not well understood. This paper presents a comprehenszve study of flexibility and proposes a scheme for assessing "value of flexibility", a surrogate flexibili~ measure. The paper also provides valuable conceptual foundat/ons for the development of quantitative models dea!ing with economic evaluation of investments in the flexibly automated manufacturing systems. eywords: Flexibility, Flexible Manufacturing Systems, urrogate Measures, Value of Flexibility, Economic Justifications
Reference Model for Manufacturing Planning and Control Systems, F. Biemans, C. Vissers, pp. 35-46 A reference model for a manufacturing planning and control system (MPCS) is presented, which represents a MPCS as a hierarchical organization of cooperating decision-making units. The model is an abstract specification of an integrated MPCS, and a milestone in its top-down design. Moreover, the model provides a reference for a common terminology and concepts. The model could play the same role in the development of a computerized MPCS that the open systems interconnection reference model of the international organization for standardization does in the development of computer networks. This paper proposes a structure as well as a distribution of tasks over the deczsion-making units in the model. The model is jnstfied on the basis of criteria
An IntelligentInformation System for an Automated Integrated Man~acturing System, D. Weber, C. Moodie, pp. 99-I 13 The recent years of manufacturing research have been governed by the trend toward integration of automation islands into
69