摘要:

The goal of this paper is to solve a continuous time production planning problem, where production rates are assumed to be piecewise constant. The problem is then to determine not only the rates, but also the times, called switching times, at which these rates may change. An iterative procedure is proposed where, at the first step, optimal rates are determined given the switching times and, at the second step, new switching times are added given the rates.Alinear programming model is proposed and discussed for the first step. Several rules to remove or add switching times are also analyzed. Computational experiments are presented comparing two versions of the procedure and showing its efficiency

ISSN:0740-817X    

DOI:10.1080/07408170008963882

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

We extend the concept of CONWIP control to a job shop setting, in which multiple products with distinct routings compete for the same set of resources. The problem is to determine the fixed overall WIP level and its allocation to product types (WIP mix) to meet a uniformly high customer service requirement for each product type.Weformulate an optimization problem for an open queuing network model in which customer orders pull completed products from the system. Then, assuming heavy demand, we derive a throughput target for each product type in a closed queuing network and provide a simple heuristic to find a minimum total WJP and WIP mix that will achieve an operating throughput close to this target. In numerical examples, theWIPmix suggested by this approach achieves the customer service requirement with a relatively low totalWIP

ISSN:0740-817X    

DOI:10.1080/07408170008963883

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A multiple-product facility consisting of a manufacturing process and a finished product warehouse for several types of products is considered. An (R,r) continuous-review inventory control policy is applied to each type of product in the warehouse. The demand arrival processofeach typeisassumed to be Poisson. The processing times and the set-up times are arbitrarily distributed. We have developed an iterative proceduretoapproximately compute the average inventory level of each product in the warehouse under different priority schemes

ISSN:0740-817X    

DOI:10.1080/07408170008963884

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The increasing market demand for product variety forces manufacturers to design mixed-model assembly lines on which different product models can be switched back and forth and mixed together with little changeover costs. This paper describes the design and implementationofan optimization-based scheduling algorithmformixed-model compressor assembly lines at Toshiba with complicated component supply requirements.Aseparable integer optimization formulation is obtained by treating compressor lots going through a properly balanced line as undergoing a single operation, and the scheduling goal is to delivery products just in time while avoiding possible component shortage. The problem is solved b y using Lagrangian Relaxation (LR). Several generic defects of LR leading toslowalgorithm convergence are identified based on geometrical insights, and are overcome by perturbing/ changing problem parameters. Numerical testing shows that near-optimal schedules are efficiently obtained, convergence is significantly improved, and the method is effectiveforpractical problems. The system is currently under deployment at Toshiba

ISSN:0740-817X    

DOI:10.1080/07408170008963885

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

We address the Parallel-Machine Flexible-Resource Scheduling (PMFRS) problem of simultaneously allocating flexible resources, and sequencing jobs, in cellular manufacturing systems where the cells are configured in parallel.Wepresent a new solution methodology for the PMFRS problem called the Nested Partitions (NP) method. This method combines global sampling of the feasible region and local search heuristics. To efficiently apply the NP method we reformulate thePMFRSproblem, develop a new sampling algorithm that can be used to obtain good feasible schedules, and suggest a new improvement heuristic. Numerical examples are also presented to illustrate the new method.

ISSN:0740-817X    

DOI:10.1080/07408170008963886

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This research considers the problem of schedulingjobs on parallel machines with an unrestricted due date and additional resources. The objective is to minimize the total absolute deviation ofjobcompletion times about the common due date. This problem is motivated by restrictions that occur in the handling and processing of jobs in certain phases of semiconductor manufacturing and other production systems. It is shown that the problem is polynomial when there exists one single typeofadditional resource and the resource requirements per job are zero or one.

ISSN:0740-817X    

DOI:10.1080/07408170008963887

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Many companies face the strategic decision of deciding on the number of Distribution Centers (DCs), their location, and which customers they serve. One objective for a company facing this decision is to maintain acceptable service while minimizing the fixed costs of operating the DCs, inventory holdingcostsat theDCs, and transportation costs between plants andDCs, andDCsand customers. For insight into this problem, we develop an analytical model for a stylized version of it. However, since the general versionofthe problem is NP-Hard, we also develop heuristic procedures. We solve a variety of example problems to test the performance of these heuristics relative to optimal solutions and a lower bound based on a relaxation of the original problem. Managerial insight based on our computational studies is provided.Wealso present a small case-study example motivated byourinteraction with Frito-Lay, Inc

ISSN:0740-817X    

DOI:10.1080/07408170008963888

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

We investigate how knowledge of future arrivals can be used to control bulk server diffusion and oxidation processes in semiconductor manufacturing to reduce the average waiting time of lots. While past research has dealt with the control of bulk server queueing systems, only a few studies have addressed the use of knowledge of future arrivals, and those studies were limited to a single server system. We extend prior strategies for the single product-single server case to a multiple product-multiple server case, and devise a control strategy that is tested through the use of simulation. The performance of the new policy is compared to that of the optimal control strategy ignoring future arrivals (i.e., a Minimum Batch Size strategy). Results indicate that the new strategy performs well under a wide variety of circumstances. To demonstrate the control strategy performance in a realistic setting, a detailed simulation model of the diffusion area of an existing wafer fab was developed. The model was run with several start rates and the results compared to those from a Minimum Batch Size strategy. Results indicate that the new strategy performs well over a wide range of start rates.

ISSN:0740-817X    

DOI:10.1080/07408170008963889

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

We considertheproblem of minimizing maximum lateness in a job shop.Aconceptually simple simulation based procedure described in a recent paper by Hodgsonet al[1] is modified to provide improved schedules. Computational experimentation is provided to identify the conditions under which the approach is most viable, and to report the procedure's performance on known test problems.

ISSN:0740-817X    

DOI:10.1080/07408170008963890

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor