Production planning in the molded pulp packaging industry

Abstract

Production planning in molded pulp packaging companies involves decisions about setting up appropriately the production process to meet the demands of different products. This production process comprises stages such as blending, molding and drying, and the major challenges for the production planning occur in the molding stage, where the mix of products manufactured simultaneously depends on the combination of molds attached to the molding machine, called molding pattern. Thus, the problem lies in deciding which molding patterns should be used, how long each pattern should be used and the production sequence that they should be scheduled. In this study we propose a novel optimization approach to deal with this problem by considering some possible settings for the molding machine based on specific technological constraints. These preset settings are included into a mixed integer programming model to define the molding patterns and to deal with the production lot sizing and scheduling decisions. Since the molding patterns are defined by the approach, three types of production setup times and costs (some of then are sequence-dependent) must be also calculated and taken into account in the planning decisions. Computational tests with real data from a Brazilian molded pulp plant show that the production plans generated by this approach are suitable in practical settings, as well as define molding patterns different from those commonly used and simultaneously reduce setup times and costs, when compared to the production plans of the company.