A Hierarchical Production Planning and Finite Scheduling Framework for Part Families in the Flexible Job-shop (with a case study)

Tendency towards optimization in last decades has resulted in creating multi-product manufacturing systems. Production planning in such systems is difficult, because the calculated optimal production volume must be consistent with the limitation of production system. Hence, integration has been proposed to decide about these problems concurrently. Main problem in integration is how we can relate production planning in the medium-term timeframe to scheduling in the short-term timeframe. Our contribution creates production planning and scheduling framework in the flexible job-shop environment with respect to the time-limit of each machine in order to produce different part families in the automotive industry. Production planning and scheduling have an iterative relationship. In this strategy, information flow is transformed in a reciprocative way between production planning and scheduling in order to satisfy the time-limit of each machine. The proposed production planning has a heuristic approach and renders a procedure to determine the production priority of different part families based on the safety stock. Scheduling is performed with ant colony optimization and assigns machines in order of priority to different part families on each frozen horizon. Results showed that the proposed heuristic algorithm for planning decreased parts inventory at the end of planning horizon. Moreover, the results of the proposed ant colony optimization were near the optimal solution. The framework was performed to produce sixty-four different part families in the flexible job-shop with fourteen different machines. The output of the approach determined the volume of production batches for part families on each frozen horizon and assigned different operations to machines.