The Application of Mathematical Model for Production Planning in a Polystyrene Factory

In this study, production planning for a polystyrene factory is addressed. The research case study is a plant that produce polystyrene beads. The main products, polystyrene beads, can be classified into 2 types which are clear beads and opaque beads. Moreover, clear and opaque polystyrene beads can be further categorized into 3 and 5 sub-products, respectively. Generally, the production processes are usually sequenced based on the melt flow index, in order to reduce the number of transition period. During the transition period, plastic beads are being wasted, which lead to higher setup cost. Furthermore, the main raw materials, used for production, are obtained from crude oil. Hence, the raw material cost is fluctuated by world crude oil price. Due to the previous mentioned problems, this research proposed the mathematical model for polystyrene production planning, to determine the optimal lot-size, and sequence by considering multiple period planning, to overcome the variations of raw material prices. The computational time was used to evaluate the performance of proposed model. The results indicated that the computation time of proposed model increases exponentially as the planning forecast period is longer. Thus, a heuristic approach should be developed for solving long time planning in future research.