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Showing papers on "Job shop published in 1993"


Journal ArticleDOI
TL;DR: This paper proposes 260 randomly generated scheduling problems whose size is greater than that of the rare examples published, and the objective is the minimization of the makespan.

2,173 citations


Journal ArticleDOI
TL;DR: A hierarchical algorithm for the flexible job shop scheduling problem is described, based on the tabu search metaheuristic, which allows to adapt the same basic algorithm to different objective functions.
Abstract: A hierarchical algorithm for the flexible job shop scheduling problem is described, based on the tabu search metaheuristic. Hierarchical strategies have been proposed in the literature for complex scheduling problems, and the tabu search metaheuristic, being able to cope with different memory levels, provides a natural background for the development of a hierarchical algorithm. For the case considered, a two level approach has been devised, based on the decomposition in a routing and a job shop scheduling subproblem, which is obtained by assigning each operation of each job to one among the equivalent machines. Both problems are tackled by tabu search. Coordination issues between the two hierarchical levels are considered. Unlike other hierarchical schemes, which are based on a one-way information flow, the one proposed here is based on a two-way information flow. This characteristic, together with the flexibility of local search strategies like tabu search, allows to adapt the same basic algorithm to different objective functions. Preliminary computational experience is reported.

874 citations



Journal ArticleDOI
01 Feb 1993
TL;DR: The use of Lagrangian relaxation to schedule job shops, which include multiple machine types, generic precedence constraints, and simple routing considerations, is explored and compares favorably with knowledge-based scheduling.
Abstract: The use of Lagrangian relaxation to schedule job shops, which include multiple machine types, generic precedence constraints, and simple routing considerations, is explored. Using an augmented Lagrangian formulation, the scheduling problem is decomposed into operation-level subproblems for the selection of operation beginning times and machine types, with given multipliers and penalty coefficients. The multipliers and penalty coefficients are then updated at the higher level. The solution forms the basis of a list-scheduling algorithm that generates a feasible schedule. A procedure is also developed to evaluate the quality of this feasible schedule by generating a lower bound on the optimal cost. Numerical examples are taken from a representative industrial job shop. High-quality schedules are efficiently generated every other day over a three-week period, with costs generally within 4% of their respective lower bounds. The methodology compares favorably with knowledge-based scheduling. >

239 citations


Journal ArticleDOI
TL;DR: Several heuristics are presented for the flowshop scheduling problem with the objective of minimizing mean tardiness, and the various methods that have been devised for minimizing the makespan are modified for this objective.
Abstract: Several heuristics are presented for the flowshop scheduling problem with the objective of minimizing mean tardiness. We consider the cases in which job sequences on all machines are the same (permutation flowshop) and in which they may be different. For the former case, the various methods that have been devised for minimizing the makespan are modified for our objective, while the list scheduling algorithm is used for the latter case. These heuristics are tested and compared with each other on randomly-generated test problems.

125 citations


Journal ArticleDOI
TL;DR: The Vanderbilt Schedule Optimizer Prototype (VSOP), which uses genetic algorithms as search methods for job shop scheduling problems, is discussed and experimental results from a fully implemented VSOP package are presented.
Abstract: The Vanderbilt Schedule Optimizer Prototype (VSOP), which uses genetic algorithms as search methods for job shop scheduling problems, is discussed A job shop is a facility that produces goods according to prespecified process plans, under several domain-dependent and common sense constraints The scheduling of orders in a job shop is a multifaceted problem VSOP uses domain-specific chromosome representations, recombination operators, and local enumerative search to increase efficiency Experimental results from a fully implemented VSOP package are presented >

116 citations


Journal ArticleDOI
TL;DR: A new capacity sensitive ORR procedure called path based bottleneck (PBB) is proposed and tested in job shop environments that have not been previously explored, and it is shown that in many cases, the shortest processing time (SPT) dispatching rule is a superior performer than a due-date based rule like critical ratio (CR); a conclusion which is contrary to the existing research.
Abstract: We investigate the performance of capacity-sensitive order review and release (ORR) procedures in job shop environments that have not been previously explored. Previous research has ignored the case of job shops which must perform to very tight due-dates because of time-sensitive customers. We propose and test a new capacity sensitive ORR procedure called path based bottleneck (PBB) in such environments, along with the modified infinite loading (MIL) procedure which has been shown to work well in several studies. We compare the performance of these two controlled release rules with that of immediate release rule under different conditions of capacity utilization and customer specified exogenous duedates. Our results indicate that PBB performs well in lowering total costs when due-dates are tight, while MIL is a better procedure with relatively loose to medium due-dates. We also show that in many cases, the shortest processing time (SPT) dispatching rule is a superior performer than a due-date based rule like critical ratio (CR); a conclusion which is contrary to the existing research in this area. In addition, the shop floor control policies recommended are shown to be sensitive to the cost structure of the firm. The managerial implications of this research in providing effective shop floor control in job shops operating under tight due-date conditions are also discussed.

90 citations


Journal ArticleDOI
TL;DR: In this paper, the authors discuss some possible approaches to the problem and describe the experience of setting up a system to collect such data in a major UK company and the potential uses of such a database.

83 citations


Journal ArticleDOI
TL;DR: Results of this research indicate a departure from previous results in the dual resource constrained job shop, and shows that selection of the rule that governs where the worker should move is the most important choice.

77 citations


Journal ArticleDOI
TL;DR: The proposed dispatching rule adapts itself to the variation in the shop floor utilization level and assigns appropriate weights to the process time and due date information accordingly and is found to perform quite well with respect to mean flow time, mean tardiness and variation in tardy.

67 citations


Journal ArticleDOI
TL;DR: The problem of finding maximum throughput schedules is NP-hard for no-wait flowshops with two machine centers having one or more parallel machines and all the problems in two-machine openshop and jobshop are shown to beNP-hard even if each job has only two tasks.

Journal ArticleDOI
TL;DR: This paper presents a model-based heuristic cell system redesign methodology to deal with long-term demand changes, validated and applied to system designs generated from several data sets published in the literature.
Abstract: Cellular manufacturing systems have been proposed as an alternative to the job shop since they provide some of the operational benefits of a flow line production process, while retaining to some extent the flexibility of job shops. However, this must be balanced against the possibility of additional initial investments in equipment to form the cells and a certain loss in manufacturing flexibility, particularly in terms of the ability to deal with long-term demand changes. This paper presents a model-based heuristic cell system redesign methodology to deal with such demand changes. The methodology is validated and applied to system designs generated from several data sets published in the literature. Results show that different kinds of demand changes incur distinct kinds of costs. Further, characteristics of cell designs that can handle long-term demand changes at least cost are identified.

Journal ArticleDOI
TL;DR: In this article, the authors investigate the impact of routeing flexibility, machine flexibility, and product-mix flexibility on the performance of a manufacturing plant using simulation modelling as the primary tool.
Abstract: This paper provides investigative insights into the impact of routeing flexibility, machine flexibility, and product-mix flexibility on the performance of a manufacturing plant. The study employs simulation modelling as the primary tool. The facility modelled is an automobile engine assembly plant consisting of a FMS (flexible manufacturing systems), job shop, and assembly line. A variety of experiments, with the FMS exhibiting one or more of the above three flexibilities at different levels, were simulated on the model. In each experiment the manufacturing performance as given by flow time and work-in-process inventory was tracked. The experiments focused first on the FMS itself, and then on the entire plant. Measures for the three flexibilities are introduced. The simulation results are analysed in detail. The results indicate significant performance benefits in context of the FMS, but little in context of the overall plant

Journal ArticleDOI
TL;DR: In this paper, the authors compared a traditional job shop with the same factory structured as a hybrid factory containing a cellular manufacturing unit, based on job shop simulation using differing combinations of capacities, allocations of jobs between the cell and the rest of the factory and levels of productivity improvements achieved in the cell.
Abstract: This paper compares a factory structured as a traditional job shop with the same factory structured as a hybrid factory containing a cellular manufacturing unit. The comparison is based on job shop simulation using differing combinations of capacities, allocations of jobs between the cell and the rest of the factory and levels of productivity improvements achieved in the cell. Performance is evaluated in terms of flow times and delays for the cell, the non-cell remainder of the factory and for the normal functional factory. The simulation model was designed to eliminate possible confounding issues of machine reliability, operator skill, unique manufacturer specific part characteristics, factory layout and different scheduling techniques. The result is a systematic evaluation of cellular manufacturing, some general conclusions as to the particular circumstances that favour the use of cells and a set of implications for management practice.

Journal ArticleDOI
TL;DR: In this paper, the problem of selection between sequencing and dispatching as a scheduling approach in a job shop setting is investigated, and makespan performance using the two different approaches is compared through simulation experiments, under such dynamic manufacturing environments as machine breakdowns, specification changes and rush jobs.
Abstract: The problem of selection between sequencing and dispatching as a scheduling approach in a job-shop setting is investigated Makespan performance using the two different approaches is compared through simulation experiments, under such dynamic manufacturing environments as machine breakdowns, specification changes and rush jobs Based upon the experimental results, a new approach that switches sequencing to dispatching according to the manufacturing situation is proposed, to make the best use of both sequencing and dispatching approaches

Journal ArticleDOI
TL;DR: In this article, a broad-based simulation study of the performance of two-stage group scheduling heuristics in a job shop cell is presented, where shop factors include: setup to runtime ratio, cell load level and variability of inter-arrival times.
Abstract: This paper describes a broad-based simulation study of the performance of two-stage group scheduling heuristics in a job shop cell. The objective of this study was to examine the direct and interactive effects of a variety of shop factors on the performance of the best, previously reported, group scheduling heuristics. A set of traditional single-stage scheduling heuristics were examined as well. Shop factors considered include: setup to runtime ratio, cell load level and variability of inter-arrival times. An assumption common to group scheduling research which provides for an equal division of the part family into subfamilies is also examined. This is accomplished through the creation of an alternative scenario where the majority of the parts are assigned to one subfamily, i.e. one subfamily dominates the part family population. The effects of set up to runtime ratio and cell load have been examined in previous group scheduling research, but not in conjunction with the inter-arrival time variability fac...

Journal ArticleDOI
TL;DR: Computational results indicate that significant due date performance improvement over traditional dispatching rules can be obtained by using a new approach that decomposes the dynamic problem into a series of static problems.

Journal ArticleDOI
TL;DR: The results of this investigation reveal that the mixed flowtime prediction models provide significant improvements in job shop due-date estimation performance, and Statistically significant performance improvements are obtained in both the average lateness and fraction tardy jobs for mixed estimates.

Journal ArticleDOI
TL;DR: In this article, a two-phase methodology is presented as an aid to organizing job shop production in a cellular manufacturing system, where the first phase selects the machines to be kept on the shop floor and assigns parts to the machines retained.
Abstract: A two-phase methodology is presented as an aid to organizing job shop production in a cellular manufacturing system. The first phase (selection/assignment phase) selects the machines to be kept on the shop floor and assigns parts to the machines retained. The second phase (partition/reassignment phase) establishes a partition of the set of parts and corresponding cells of machines and reassigns some of the operations with a view to eliminating some intercell material movements. This phase is repeated until a partition meeting the operator's requirements is obtained. The results obtained with this method on several examples found in the literature are consistently equivalent to or even better than those hitherto proposed, in terms of intercell moves.

Journal ArticleDOI
TL;DR: Results of the simulation experiments show that the CPFT combined with the adaptive adjustment approach (CPFT-ADJ) provides overall improved performance compared to the dynamic and static versions of the CON, TWK, and CPPT procedures for less complex job structures.

Journal ArticleDOI
TL;DR: In this paper, the authors compared the benefits realized by the development of a multi-skilled workforce with the benefits of additional workforce staffing in a dual resource constrained hybrid job-shop.
Abstract: In many manufacturing organizations, increasing process flexibility is becoming more important while the reliance on product cost to measure manufacturing performance is being lessened As a result, companies are placing more emphasis on developing a cross-trained workforce in an effort to improve the flexibility of their operations Having a cross-trained workforce allows managers to move workers around to adjust to temporary overloads in the shop Another approach to increasing process flexibility is through the addition of labour to create a capacity buffer Adding more labour improves flexibility since it reduces the average utilization in the shop thereby reducing the possibility of any overload occurring in the first place This paper compares the benefits realized by the development of a multi-skilled workforce with the benefits realized by additional workforce staffing Both strategies exhibit improvement in the simulation of a hypothetical dual resource constrained hybrid job-shop Results sugges

Journal ArticleDOI
TL;DR: A decomposition algorithm for this procedure is presented that efficiently solves problems with large-scale deterministic equivalents of up to 66,000 variables.
Abstract: This paper presents a method for finding optimal flows in a dynamic network with random inputs into the system and congestion limits on flow. This model has been used in deterministic settings to represent dynamic traffic assignment and job shop routing. This paper builds on the deterministic results to show that a globally optimal solution in the stochastic problem may be obtained by a sequence of linear optimizations. A decomposition algorithm for this procedure is presented that efficiently solves problems with large-scale deterministic equivalents of up to 66,000 variables.

Journal ArticleDOI
TL;DR: In this article, the authors focus on the scheduling phase of flexible manufacturing systems (FMSs) and establish six decision points involved in the operations among parts, AGVs and machines.

Journal ArticleDOI
S. T. Enns1
TL;DR: In this article, the authors investigated flowtime prediction under conditions where Jackson's decomposition principle can be applied and developed four models in which due-date setting rule parameters are based on predicted flowtime.
Abstract: This paper investigates flowtime prediction under conditions where Jackson's decomposition principle can be applied. Four models in which due-date setting rule parameters are based on predicted flowtime are developed and compared. Simulation results show both job characteristic and dynamic shop load information to be useful in predicting flowtimes. Analysis of prediction deviations shows that good predictions lead to errors which are approximately normally distributed. The variance of prediction errors can also be analytically determined. Therefore, quoted delivery dates can be set which are consistent with a desired level of delivery performance.

Journal ArticleDOI
01 Sep 1993
TL;DR: A hybrid approach between two new techniques, Genetic Algorithms and Artificial Neural Networks, for generating Job Shop Schedules (JSS) in a discrete manufacturing environment based on non-linear multi-criteria objective function is described.
Abstract: This paper describes a hybrid approach between two new techniques, Genetic Algorithms and Artificial Neural Networks, for generating Job Shop Schedules (JSS) in a discrete manufacturing environment based on non-linear multi-criteria objective function. Genetic Algorithm (GA) is used as a search technique for an optimal schedule via a uniform randomly generated population of gene strings which represent alternative feasible schedules. GA propagates this specific gene population through a number of cycles or generations by implementing natural genetic mechanism (i.e. reproduction operator and crossover operator). It is important to design an appropriate format of genes for JSS problems. Specifically, gene strings should have a structure that imposes the most common restrictive constraint; a precedence constraint. The other is an Artificial Neural Network, which uses its highly connected-neuron network to perform as a multi-criteria evaluator. The basic idea is a neural network evaluator which maps a complex set of scheduling criteria (i.e. flowtime, lateness) to evaluate values provided by experienced experts. Once, the network is fully trained, it will be used as an evaluator to access the fitness or performance of those stimulated gene strings. The proposed approach was prototyped and implemented on JSS problems based on different model sizes; namely small, medium, and large. The results are compared to the Shortest Proceesing Time heuristic used extensively in industry.

Journal Article
TL;DR: An optimization algorithm is developed whose performance is comparable to that of the best algorithms for the standard one machine problem, and Embedding this algorithm into a modified version of the Shifting Bottleneck Procedure that uses the tighter one machine relaxation discussed here results in a considerable overall improvement in performance.
Abstract: : We study the one machine scheduling problem with release and delivery times and the minimum makespan objective, in the presence of constraints that for certain pairs of jobs require a delay between the completion of the first job and the start of the second (delayed precedence constraints). This problem arises naturally in the context of the Shifting Bottleneck Procedure for the general job shop scheduling problem, as a relaxation of the latter, tighter than the standard one machine relaxation. The paper first highlights the difference between the two relaxations through some relevant complexity results. Then it introduces a modified Longest Tail Heuristic whose analysis identifies those situations that permit efficient branching. As a result, an optimization algorithm is developed whose performance is comparable to that of the best algorithms for the standard one machine problem. Embedding this algorithm into a modified version of the Shifting Bottleneck Procedure that uses the tighter one machine relaxation discussed here results in a considerable overall improvement in performance on all classes of job shop scheduling problems.

Journal ArticleDOI
TL;DR: Results on benchmark problems indicate that the resulting heuristic is superior to other commonly used heuristics, and the combined algorithm yields results comparable to several optimal scheduling algorithms, yet with vastly fewer and simpler iterations.

Journal ArticleDOI
TL;DR: In this article, a new lower bound for the job shop scheduling problem is developed based on a two-job relaxation, which can be solved efficiently by using geometeric methods.

Journal ArticleDOI
TL;DR: By using the model as an enhancement to a company's MRP system, the cost effects of redeploying its workforce were simulated and the model served a strategic role in workforce expansion and deployment decisions.
Abstract: Many manufacturing firms that use Material Requirements Planning MRP cannot deliver products on schedule and within budget. Faced with bewildering bottlenecks, erratic process flows, and unrealistic due dates, they are unable to develop accurate schedules for their raw material acquisitions, workforce, and equipment. Their MRP plans must be translated into a workable schedule, one which determines when individual tasks will be performed by workers at work centers. There is a clear need for such an enhancement to MRP, a means to operate on detailed task data, yet capable of producing a schedule that directly relates to the MRP plan, the master production schedule, and the resource plan. We describe a method for determining feasible and cost-effective schedules for both labor and machines in a job shop. The method first sequences tasks at resources and then minimizes overall earliness and lateness cost by solving a series of maximum flow problems. By using the model as an enhancement to a company's MRP system, we simulated the cost effects of redeploying its workforce. Although the model was not used for real-time scheduling, it served a strategic role in workforce expansion and deployment decisions.

Journal ArticleDOI
TL;DR: In this article, a cost-based due date assignment methodology is proposed, which uses two pre-specified parameters: an estimate of job flow time and the probability of the job being tardy.
Abstract: In this paper, a cost-based due date assignment methodology is proposed. The method uses two pre-specified parameters: an estimate of the job flow time and the probability of the job being tardy. An optimization model is presented to find the best tardiness probability of the job based on a total cost function involving the work-in-process inventory and the tardiness costs. Using the results of the correlation analysis performed on a wide set of shop, job and job’s route related variables, ten models are constructed to estimate the flow time of a job in the shop. The models are then compared based on the simplicity of the model and the standard deviation of the estimate errors. One of the models is recommended and tested to check if it can be used in different shop scenarios. As a result, it is observed that the model performs satisfactorily in all the shop conditions considered in this study.