Maximizing ROI by minimizing process variability

There seems to be an apparent dilemma between the increasingly popular concepts of total quality management (TQM), and the environmental stress screening (ESS) concepts of reliability engineering. TQM tends to reduce the variability of the process and the defects in the process, while reliability engineering tends to induce the defects in the manufacturing process in the plant so they will not escape into the use environment. The author addresses that issue and shows how by adjusting the screening strength during the ESS process at a desired capability index level, return-on-investment (ROI) can be maximized. The methodology presented indicates that the ROI is more sensitive to costs due to process variability than to the relative cost constants. This methodology presents a model by which the effect of screening strength on the process capability index and the ROI can be identified