Entire product capability analysis chart with asymmetric tolerances index Spa

Abstract

This study proposes the S_pa-product capability analysis chart (S_pa-PCAC), which can widely represent multiple process capabilities with asymmetric tolerances of Smaller-the-Better, Larger-the-Better, and Nominal-the-Best characteristics. Process capability index S_pa is generated based on index S_pk, which uses asymmetric tolerances to reasonably measure process capabilities. The interval estimates of the indices are derived to reliably assess process capabilities. The Six-Sigma-based quality-level and its connection with the process yield are introduced in the capability zone of S_pa-PCAC to check if the process capabilities can meet the requirements. One example of an entire product is given for application.

Keywords: Six-Sigma; asymmetric tolerances; capability zone; process capability index; product capability analysis chart.