A new lot sizing model for deteriorating items with production compressibility

This paper presents a new mathematical formulation for determining optimal Production-inventory policies in the case of dealing with multiple deteriorating products and dynamic demands. The deterioration of each product type occurs at a randomly distributed rate. Production rates for each product type are decision variables, such that process compressibility is assumed to be existed. In other words, each product type could be produced more rapidly by paying more than normal production speed. Consequently, process compressibility is contributed with time / cost trade-off. This trade-off is considered as a nonlinear relation. As the proposed model is a concave minimization program, a new particle swarm optimization algorithm is developed for solving large instances of the problem. Computational experiences report the efficiency and efficacy of the model the algorithm to obtain good quality production plans.