Optimal Scheduling for Automated Two-Machine Manufacturing Systems with Intermediate Operations

Abstract

This paper deals with scheduling problems of minimizing the maximum completion time (i. e., the makespan) for automated manufacturing systems in which n jobs are processed on two machine centers Ma and Mb in this order, and there is an intermediate washing station (WS) between Ma and Mb, which is also used for storing the jobs completed on Ma (work-in-process, WIP). The job transportation between Ma and WS is done by a robot RTA and the job transportation between WS and Mb by another robot RTB. This paper gives an algorithm that can efficiently solve the problem exactly even when the job loading/unloading times are non-negligible and the job washing times are job-dependent. Furthermore, this paper gives more efficient algorithms for the special cases in which the washing station is set in input AS/RS (Automated Storage/ Retrieval System) or output AS/RS so only one transportation robot is necessary.