Work-in-progress optimization of cyclic manufacturing systems with assigned throughputs

This paper shows that it is possible to formalize and to put in a proper form an optimization problem consisting in the optimization of the work-in-progress (WIP) in a manufacturing system, while ensuring a minimum value for the throughput of each product. The decision variables involved in this problem are the lot sizes for the various products and components and the system initial state, as regards the number of tokens in each place of the net. In spite of the limited modelling capability of timed event graphs, the considered structure of manufacturing systems is by no means trivial. Actually, the fact that the set of decision variables includes the lot sizes makes the production flows in the system optimized in practice. The main novelty of this paper with respect to previous works concerns the possibility of dealing with situations in which no machine acts as a bottleneck one. The optimization problem arising is thus more difficult than the two-level optimization problem.