Showing papers on "Job shop published in 1976"

A Simulation Study of Operating Policies in a Hypothetical Dual-Constrained Job Shop

Abstract: This paper describes a simulation study of the relative impact of due-date assignment, dispatching and labor assignment decision rules on the performance of a hypothetical dual-constrained job shop. Six criteria are used to measure the performance of the decision rules. They are mean flow-time, variance of flow-time, mean lateness, variance of lateness, proportion of jobs late, and total labor transfers. Multiple regression is the principal method of analysis of the results of the experiments. This technique provides regression coefficients and analysis of variance statistics for the decision rules for the various performance measures. Since the objective of this study is to go beyond simple statements of the significance of the various decision rules, the multiple regression results are used with analysis of variance statistics to indicate the relative impact of the decision rules. The regression coefficients and the omega squared ω2 indices [Hays, W. L. 1962. Statistics. Holt, Rinehart and Winston, New York, 406--408.] indicate that the relative importance of the due-date assignment, dispatching and labor assignment decision rules is dependent upon the measure of performance considered. In addition, the relative importance and optimality of the dispatching rules is dependent upon the due-date tightness for selected performance measures.

The production capacity of job shops with limited storage space

Abstract: Suppose the number of jobs which can be stored in front of the machines in a job shop is limited. As a result, arriving jobs for which there is no space in the shop will form a shop queue. The production capacity or maximum departure rate of jobs from the shop will depend on the way in which jobs are selected from the shop queue for release to the machine queues. For a job shop with two identical machines and random routing of jobs a number of release rules are compared. It is shown that the production capacity is increased when the number of jobs in the shop is kept less than the available storage space. Among release rules independent'of job processing times and number of operations the optimum release rule is shown, using dynamic programming, to be the idle machine rule, i.e. only release a job to the shop when a machine would otherwise be idle.

Due-Dates and Instantaneous Load in the One-Machine Shop

Abstract: The due-date assignment problem occurs when due-dates are assigned within, rather than outside, a job shop. This study explores the importance of instantaneous and future shop loads in setting due-dates in shops operating under due-date dependent queue discipline. The assignment of due-dates to arriving jobs in an m-machine shop is formulated as a stochastic dynamic programming problem in the first part of this study. A computational experiment using dynamic programming is performed in the second part and due-dates are developed for specific instantaneous load conditions in a simulated one-machine shop. The importance of instantaneous and future shop loads for assigning due-dates in a one-machine shop, with constant interarrivals and exponential service times, is shown.

Organizational segmentation and labor transfer policies in labor and machine limited production systems

Abstract: This paper describes a simulation study to examine the effects of different organizational structures on the performance of a dual-constraint job shop production system. A hypothetical shop in which machines and workers are constraining resources is the setting of the study. The shop consists of divisions comprised of work centers which contain machines to which workers are assigned. There are fewer workers than machines. Variations in organizational structure are achieved by segmenting a fixed number of work centers equally into varying numbers of divisions. Mean flow-time, flow-time variance, and worker transfers between divisions and work centers are used as performance measures. Changes in organizational segmentation are shown to affect the performance of the production system and the effects are dependent on the extent to which workers can be transferred between the divisions of the system.

Two issues in the evaluation of job-shop schedules

Abstract: Two issues are examined concerning the evaluation of job-shop schedules. First, machine and labor cost/utilization are suggested as alternatives to physical utilization criteria. Secondly, an exploration is made of the use of Kiviat Charts as a means of integrating multidimensional criteria for the overall evaluation of the quality of job shop schedules.

A Model to Evaluate Job Shop Productive Capability

Abstract: A composite measure for assessing the productive capability of a job shop manufacturing system is proposed. The methodology for developing this probabilistic measure, the capacity rating index, is indicated. A framework is provided to indicate how the methodology might be applied to production planning problems.

Optimal control of job shop queues with subcontracting

Abstract: An optimal production policy in a job shop queue specifies, for minimum cost, the number of servers, amount of overtime, and the maximum queue length allowed before subcontracting takes place. This paper examines the development and application of such a policy.

A work progress forecasting algorithm for a job shop manufacturing facility

Abstract: The research described in this paper has addressed itself to the development of on algorithm to forecast potential job costs and throughput times in a job shop. The algorithm utilizes historically repetitive relationships between cumulative job costs find time which are defined as cost curves. The algorithm was developed and evaluated using actual historical data from a large job shop production facility. Evaluation tests showed the cost forecast mechanism to be an effective early predictor of actual total job costs. The throughput time forecast mechanism was found to be less effective as an early predictor, but valuable as an early warning indicator of potential scheduling problems and irregularities.