A dynamic input/output control system for job shop manufacturing operations

Abstract

A dynamic job shop control system with a combined input/output control mechanism is developed for achieving improved shop performance. The problem is modelled such that at periodic intervals, the best combination of input and output variables for the forthcoming period are identified. The purpose of the control system is to determine the set of jobs to be released into the shop (input variables) and the capacity levels of machines (output variables) for a planning period such that a composite cost function is minimized.

The problem is mathematically formulated as a 0-1 linear mixed integer program (MIP). An iterative based heuristic optimizing algorithm incorporating the MIP is developed. The control algorithm is compared with another job shop control system where only the input is assumed variable. The two systems are compared by computer simulation and results indicate significant improvements for most of the performance measures evaluated. Significant reductions in the mean and variance of the manufacturing lead time with a better distribution among its parts were also achieved.