Process capability: A New Criterion for Loss Function–Based Quality Improvement

Response surface methodology (RSM) – the method most preferred by quality engineers – is a natural and effective tool to achieve the desired process quality. Most of the current literature on process quality does not focus on information relating to how much better or worse a process is and also the degree of the process performance. On the other hand, although the process performance criteria are able to predict process capability, they cannot provide significant information relating to the process quality in terms of rate of rejects and losses. Therefore, this paper takes into account these two concepts and defines a criterion based on the process capability indices for the upside-down normal loss function (UDNLF). The proposed approach determines the optimal settings of a given process by minimizing the expected UDNLF which is defined in terms of and indices. The proposed procedure and its merits are illustrated on the basis of an example