The product cycling problem in systems with uncertain production yields

The author addresses a production planning problem for a single machine producing multiple parts, where the yield rate (fraction acceptable) for each part may be uncertain, and the production policy is to cycle through the set of parts. She analyzes a simplified version of the problem that, although still quite complex, becomes solvable as a result of several properties that are demonstrated. The major simplifying assumption is that inventory for each product is zero when its production run begins. A procedure with a fixed-point flavor is developed to determine the cycle duration and the associated production policies (yield loss adjustment factors). An iterative scheme is suggested to incorporate heuristically the impact of the yield adjustment experiments; however, it is found that in most situations, only a single iteration is needed. The resulting plan is viewed as a basis for specifying targets that provide guidelines for controlling the system while considering long-term aggregate tradeoffs. In particular, the model of the planning problem captures both the effect of setup times and, at an aggregate level, the impact of yield uncertainty (not just average yields) on capacity utilization. >