Designing process tolerances to minimize loss of nonconforming parts

This paper presents a novel formulation capable of designing process tolerances to minimize the expected loss of the entire process due to nonconforming parts. The proposed model uses the exponential cost-tolerance function to estimate the manufacturing cost and the standard normal probability curve to predict the scrap rate of the operation. The process capability of a machine is applied to standardize the process tolerance; therefore, the allocated process tolerances are not only manufacturable but also cost effective. This feature is advantageous because conventional methods tend to neglect the process capability of equipments and rely too much on experiences and expertise of engineers. Comparison results with other methods reveal that the proposed model is an economic and efficient means of designing process tolerances.