Designing a variable control chart for a two-stage production process

Abstract

In this paper, a variable chart has been proposed to study a two-stage serial production process. Measurements of quality characteristics of products processed at each stage are assumed to be independent and follow normal distribution. In order to evaluate performance of the control chart, two cases of equal shifts in both the stages and unequal shifts were considered and results were presented accordingly. The necessary measures are given to calculate the average run length (ARL) for shifted processes. The tables of ARLs are presented for equal and different sample sizes at first- and second- stage. Performance of the proposed control chart is presented using a simulation study.