Graph-Assisted Cyclic Hoist Scheduling for Environmentally Benign Electroplating

Abstract

Hoist scheduling is a class of production scheduling of batch systems in the manufacturing industries. Cyclic hoist scheduling (CHS) is a type of hoist scheduling that deals with the scheduling that involves one hoist and produces some type of product in a multistage production line. The only “resource” in the production is the hoist for which various operations compete with each other in every production cycle. Currently available CHS approaches, regardless of whether they are algorithmic or heuristic based, are almost all designed to maximize the production rate by optimizing hoist movements; environmental issues are not a concern during development of the hoist schedule. This paper introduces a methodology for solving a general CHS problem where the production rate and waste reduction are simultaneously taken into account. Using this methodology, all feasible hoist schedules for a given CHS problem can be rapidly identified using a graph-assisted search algorithm. The schedules are then evaluated in terms of waste minimization capability, using the corresponding operational strategies. In evaluation, the system dynamics associated with each selected feasible hoist schedule is examined. A final hoist schedule is the best for maximum production rate and minimum waste generation. The efficacy of the methodology is demonstrated by solving an industrial electroplating example.