A multi-site supply network planning problem considering variable time buckets - A TFT-LCD industry case

Due to the increase in the variety of demands from downstream customers, companies are required to expand their production capacity by way of adding more plants. Many enterprises encounter difficulties in production planning because manufacturing environments have changed from traditional single-plant to current multiplants. Therefore, the production planners must develop an integrated multi-site planning approach to coordinate all production resources of multiple plants within the enterprise. As the company may possess many manufacturing plants that are located in different places geographically, the planners will face production allocation problems in the multi-site environment. The decisions may involve the manufacturing routings of demand products and production quantities among multi-plants. As a result, a monolithic model of the multi-stage and multi-site production planning problem is proposed in this paper. The contribution of this planning model is to combine two different time scales, i.e., monthly and daily time buckets. In addition, we also consider other practical planning characteristics and constraints. For example, production transformation functions, capacity consumption constraints, materials supplying constraints, inventory balancing equations and so on. Through optimization procedures, the information on production and procurement in the multi-plant network is derived. Besides, an example from a thin film transistor- liquid crystal display (TFT-LCD) manufacturer case in Taiwan is illustrated for explaining the monolithic planning model.