Effective allocation of idle time in the group technology economic lot scheduling problem

The group technology economic lot scheduling problem (GT-ELSP) addresses the issue of scheduling the products, classified into groups, on a single facility. The objective is to develop a schedule that minimises the sum of average inventory holding and setup costs over the infinite planning horizon. Previous research on this class of problems has assumed the cycle idle time to be equally divided among various sequence positions and has varied the frequency of production of individual products. We propose a heuristic that maintains constant frequency of products and varies the idle time among the sequence positions. We address the feasibility issue of the GT-ELSP and show that our heuristic, based on the time varying lot size approach, yields low-cost quality solutions that aid practical implementation. We tested our heuristic on a large set of randomly generated problems to assess its efficacy over the solutions of earlier proposed heuristics.