In batch manufacturing, a fraction of the batch, or ''lot,'' may require reworking because its members fail to conform to standards A rework station ''undoes'' the previous operation, so that the nonconforming members can go through the same operation additional times. This paper explores how policies dealing with these nonconforming members affect the cycle time of a facility. Two different operating policies can be followed In one, the ''mother'' lot is held back while the ''child'' sub-lots-are reworked, after which all members are reunited for the next operation, Tn the other, the mother lot is allowed to proceed to the next operation while the child is held back; reworked members are then introduced by one of three methods: In the first, the reworked members of each mother lot are introduced by themselves. In the second, a minimum order quantity of reworked members is designated and a new lot introduced when this level is reached. In the third, the reworked members are added to the-next mother lot that visits the operation. In this paper, queuing models are developed for these policies, and the policies are simulated with regard to cycle time. Simulation of a wafer fabrication model is used to determine the effectiveness of these policies and their impact on cycle time.
