Electroplating production scheduling by cyclogram unfolding in dynamic hoist scheduling problem

This article presents a scheduling problem that exists in electroplating lines. An electroplating line is an automated manufacturing system which covers machine parts with a coat of metal. It consists of a set of tanks that chemically process the items and hoists that transport the items between workstations. Scheduling the movements of these hoists is commonly called a hoist scheduling problem. The most common approaches to the problem are cyclic hoist scheduling problem and dynamic hoist scheduling problem (DHSP). This article presents a DHSP solution method. The method divides the problem into real time and non-real time. Special schedules, called cyclograms, allow minimisation of the length of non-real time calculations. A notion of the problem is introduced, an outline of a scheduling system is presented, as well as the heuristic algorithm itself. The results of the described method, referred to as a cyclogram unfolding method, are compared to several cases available in the literature.