New Capability Indices for Evaluating the Performance of Multivariate Manufacturing Processes

Generally, an industrial product has more than one quality characteristic. In order to establish performance measures for evaluating the capability of a multivariate manufacturing process, several multivariate process capability indices have been developed in the past few years. Among them, Taam's MCp and MCpm indices have the drawback of overestimation and Hubele's three-component capability vector lacks simplicity in practice. In this article, taking the correlation among multiple quality characteristics into account, we develop two novel indices; NMCp and NMCpm. Using two numerical examples we demonstrate that the true performance of multivariate processes are accurately reflected in our NMCp and NMCpm indices and in their associated interval estimates. Finally, simulation results show that our indices outperform both those of Taam and Hubele. Copyright (C) 2009 John Wiley & Sons, Ltd.