Multiperiod LP models for simultaneous production planning and scheduling in multiproduct batch plants

Abstract: "Production planning and scheduling are intimately linked activities. Since the production goals set at the planning level must account for the ability to implement them at the scheduling level, ideally both activities should be analyzed simultaneously. However, this in general is 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, (1989b) 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 cleanup 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.