Integration of production planning and scheduling in manufacturing systems

In this paper, the formalization of an optimization problem is presented with the aim of integrating medium-term production planning with short-term production scheduling. The decision variables of the proposed model are both continual and combinatorial. The former are relevant to the lot-sizes and the timing of operations, whereas the latter mainly refer to the assignment and the sequencing of operations over resources. Actually, in the proposed formalization, only continual variables are considered, assuming that all combinatorial issues are a-priori fixed. However, simple criteria are provided in order to assess the optimality of a certain choice of the values of the combinatorial variables.