EFFECT EVALUATION OF LOT SPLITTING IN JOB SHOP SCHEDULING

Abstract

ABSTRACT As the lot splitting concept has been used widely to reduce the makespan in a production system, most researches investigate the flow shop production systems and the job shop production systems have received much less attention relatively. This study investigates the application of lot splitting in a job shop production system with setup times which cannot be omitted more thoroughly. The research is divided into two phases. First, The addressed job shop scheduling problem is illustrated by a disjunctive graph, then a shifting bottleneck based heuristic is developed to solve the addressed scheduling problem without lot spitting. Following, each product is split into some consistent sublots, and a neighborhood searching procedure is then applied for finding a good solution. Two kinds of objectives that are minimizing makespan and early/tardiness penalties are evaluated. In order to investigate the influence of the number of sublots, due dates and setup times on a job shop production system with regard to the corresponding objective considered, some experiments are conducted. The experimental results shown that the lot splitting can effectively reduce makespan and early/tardiness penalties in the job shop scheduling problem. Two consistent sublots make the largest benefit, however, the benefits are gradually reduced with increasing the number of sublots.