The impact of defects on a process with rework

In this paper, we attempt to quantify the impact of defects on various system performance measures for a production process with 100% inspection followed by rework. In the literature, the number of defects (feedback loops) is assumed to be a random variable having a geometric distribution. We model the number of defects as a random variable having any general discrete distribution, and investigate the impact of the defect distribution on system performance measures such as yield, production lead time, and work-in-process inventory. We provide management guidelines for short term control decisions such as identifying potential bottlenecks under increased workloads and allocating additional resources to release bottlenecks. In order to meet the long term goal of continuously decreasing defect levels, we propose a budget allocation method for process improvement projects.