(A) hierarchical production planning in line production system

Abstract

This thesis deals a hierarchical production planning problem for a line production system. A hierarchical procedure is proposed for the following three phases : aggregated production planning, family disaggregation and item disaggregation. For the first phase problem, an LP formulation is developed with the objective of minimizing the sum of inventory holding cost and overtime labor cost, which can be solved on a rolling horizon basis. For the second phase problem, the first period``s solution of the aggregated plan is disaggregated to families in a way which maximizes line efficiency. For the last phase, the family production quantity is disaggregated to items such that the flow time is minimized. In this regard, item-flow model and batch-flow model are proposed to determine the batch size and operation sequence of each item. In the item-flow model, the case with two items is solved optimally, whereas a heuristic procedure is presented for the case with multi-item. And in the batchflow model, a heuristic and a way to find a lower bound are proposed. A example problem is solved to illustrate the above models.