A study of multivariate process capability indices in manufacturing processes

Process capability indices are assumed as an important tool for measurement of performance of a manufacturing process [1]. Single quality variable is considered in case of univariate process capability indices (UVPCI) for example Cp, Cpk and Cpm where as multiple quality variables are considered in multivariate process capability indices (MVPCI) [1, 2]. UVPCIs are extensively studied by a large number of researchers and practioners. However, till today no efficient MVPCI is developed for the assessment capability of a process with proper application in manufacturing processes. This paper therefore highlighted on the application of the different multivariate process capability indices developed so far in three different case studies, forging, centrifugal casting, and hardening and tempering processes [1, 2]. The results are compared with percentage conforming products as well as amongst the indices themselves. The results show that hardening and tempering is the most and forging is the least capable process.