Integrated Scheduling of Material Handling and Manufacturing Activities for Just-In-Time Production of Complex Assemblies

This paper considers the simultaneous scheduling of material handling transporters (such as Automatic Guided Vehicles or AGVs) and manufacturing equipment (such as machines and workcenters) in the production of complex assembled products. Given the shipping schedule for the end-items, the objective of the integrated problem is to minimize the cumulative lead time of the overall production schedule (i.e., total makespan) for on-time shipment, and to reduce material handling and inventory holding costs on the shop-floor. The problem of makespan minimization is formulated as a transportation integrated scheduling problem, which is NP-hard. For industrial sized problems, an effective heuristic is developed to simultaneously schedule manufacturing and material handling operations by exploiting the critical path of an integrated operations network. The performance of the proposed heuristic is evaluated via extensive numerical studies and compared with the traditional sequential scheduling approach. The superiority of the integrated heuristic is well demonstrated.