Quality defaults and work-in-process inventory

The objective of this paper is to analyze the interactions between quality defaults and work-in-process (WIP) inventory. A model is presented where defects produced in one station can only be detected at the next station. In this model the amplification effects between WIP and quality defaults are evaluated under the assumption that defective items are reworked or replaced by good ones and that arrivals are Markovian. The main conclusion is that under quite general conditions the inventory between the two stations will keep growing without limit for any failure rate. This result provides a rationale for the Just-in-time practice of limiting the inventory and indicates that the expected throughput not always increases by increasing the WIP inventory buffer.