Integrated production planning and scheduling using backward/forward scheduling simulation

This paper deals with release time planning to reduce lead times of jobs in make-to-order production environments. In traditional MRP-based planning system, lead times are estimated using historical data and past experience without precisely considering capacity constraints. The proposed method in this paper is based on precise backward and forward scheduling simulation. First, backward simulation in which simulation starts at each due date of job and sends it through the shop floor based on the backward sequence of its part routing is applied. Next, forward simulation is applied to modify the release times obtained by backward simulation. A genetic algorithm is also used to minimize lead times of jobs in the final step. Numerical experiments of planning and scheduling with processing time uncertainty are carried out to examine the effectiveness of the proposed method.