SIMULTANEOUS PRODUCTION PLANNING AND SCHEDULING IN MULTIPRODUCT BATCH PLANTS

Production planning and scheduling are intimately linked activities. The production goals set at the planning level depend on marketing considerations but must account for the ability to implement them at the scheduling level. Hence, ideally, planning and scheduling should be analyzed simultaneously. However, this is in general a very difficult task given the large combinatorial nature of just the scheduling problem in itself. In this work, based on a previously developed LP flowshop scheduling model by Birewar and Grossmann that can effectively aggregate the number of batches belonging to each product, a multiperiod LP model is proposed for the simultaneous production planning and scheduling of multiproduct batch plants that may consist of one or several nonidentical parallel lines. Inventory costs, sequence-dependent clean-up times and costs, and penalties for production shortfalls are readily accounted for in this model. The actual schedule to achieve the production goals predicted by the planning problem is derived by applying a graph enumeration method to the results from the simultaneous planning and scheduling model or by any other scheduling method. Several examples are presented to illustrate the proposed method. © 1990, American Chemical Society. All rights reserved.