Showing papers on "Job shop published in 1979"

A Simulation Study of Predictable Due-Dates

Abstract: This paper describes a simulation study of assigning attainable or predictable due-dates in hypothetical labor and machine constrained job shop settings of varying size and structure. Several predictable due-date assignment rules are developed based on conditional estimates of individual job flow time derived from initial simulation runs. Mean lateness, mean earliness and mean missed due-dates are used as measures of shop performance to compare the various predictable due-date rules under conditions of varying dispatching rules and shop size and structure. Results indicate that due-dates assigned based on expected job flow time and shop congestion information may provide more attainable due-dates than rules based solely upon job characteristics. In addition, better due-date performance appears to be achieved when due-date oriented dispatching rules are employed and when the shop system is not structurally complex.

Complexity of Scheduling Shops with No Wait in Process

Abstract: We show that obtaining minimum finish time schedules with no wait in process is NP-Hard for flow shops, job shops and open shops. Specifically, it is shown that the two processor job and open shop problems are NP-Hard even when jobs are restricted to have no task of length zero. The two processor flow shop problem is NP-Hard if jobs with only one task are permitted. Note that Gilmore and Gomory Gilmore, P., R. Gomory. 1964. Sequencing a one state-variable machine: A solvable case of the travelling salesman problem. Oper. Res.12 655--679. have obtained a polynomial time algorithm for the two processor flow shop for the case where every job has two tasks. The 4-sum and 2-pair problems are also shown NP-Hard.

A stochastic dominance ordering of scheduling rules

Abstract: This paper applies stochastic dominance (SD) preference-ordering criteria to job shop scheduling rules. A simulation model of a hypothetical dual-constrained job shop is used to derive several measures of shop performance for a number of dispatching/due-date scheduling policies. The results presented suggest that previous research conclusions concerning the relative performance of dispatching scheduling rules may need to be reconsidered if production schedulers are risk-averse utility maximizers.

A machine loading procedure which considers part complexity and machine capability

Abstract: The research described in this paper is concerned with machine loading for jobs entering a job shop. The loading method proposed assigns jobs to machines based on the best match of job attributes with machine capability. A piece part coding system similar to the Opitz method is used to define the job characteristics and a machine capability matrix is specified for each processor in the shop. A loading algorithm called the ‘score rule’ assigns jobs to machines. Shop congestion is also considered in the algorithm.

Priority updating procedures in dynamic job shop simulation studies: the impact on measures of performance under different due date assignment rules

Abstract: In job shop simulation studies the effects of local priority dispatching rules have been studied extensively. Among these, due-date oriented priority rules (such as slack, slack/remaining operation, critical ratio) have been found to be effective and useful in practice. These priority dispatching rules are dynamic in nature, that is, the state of the priority entity changes continuously over time. Therefore, one should theoretically update the priorities of jobs waiting in a queue every time a machine at a work center becomes available. This is an extremely costly procedure even in experimental simulation studies.