The effect of the stabilization period on the economic lot scheduling problem

The Economic Lot Scheduling Problem (ELSP) is the problem of scheduling production of several items in a single facility, so that demands are met without stockouts or backorders, and the long run average inventory carrying and setup costs are minimized. One of the general assumptions in the ELSP is that the yield rates of a given manufacturing process are constant, or 100%, after setup. However, this assumption may not be true for certain manufacturing processes, in which the yield rates are quite low just after setup, and then increase over time. This period is called a stabilization period and yield rates gradually increase during this period until they reach the target rates, which are set empirically or strategically. The purpose of this paper is to clarify the effect of the stabilization period by applying the stabilization period concept to the ELSP, which has been widely applied to many production systems. In this paper, the problem is tackled in three stages: Firstly, we formulate a model and develop an algorithm, which provides a lower bound for a minimum cost. Secondly, we develop a heuristic procedure using the time-varying lot size approach. Finally, we solve a special case of the ELSP to find an upper bound using the common cycle approach.