A Comparative Study of Methods on Evaluating Process Performance for Asymmetric Tolerances with Consideration of Process Yield and Quality Loss

• Main Authors: Mei-Yao Wu, 吳美瑤
• Other Authors: Chao-Lung Yang
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/m7j398

碩士 === 國立臺灣科技大學 === 工業管理系 === 102 === Process capability indices provide numerical measures on process performance, which have been widely used as one of practical tools for quality assurance. In manufacturing industries, there are two cases with manufacturing tolerances, one is called symmetric tolerance and the other is called asymmetric tolerance. However, most of researches in the literature are focused on cases while the manufacturing tolerance is symmetric, which have been shown to be inappropriate for evaluating process performance with asymmetric tolerance. Therefore, in this thesis, we focus on asymmetric tolerances and use the index for evaluating process performance. Several available methods for constructing confidence intervals of the index are examined and discussed. These methods include two types of sampling distribution approach (SD*, SD), four types of bootstrap approach (SB, PB, BCPB, PT), generalized confidence interval approach (GCI) and Bayesian approach (BA). A series of simulations is conducted to calculate the coverage rate (CR) and mean of lower confidence bounds (MLCB) under various parameters. The simulation results show that the GCI and BA approaches seem to work very satisfactory. Therefore, these two approaches can be recommended for evaluating process performance with asymmetric tolerances. Finally, an application example is presented for illustration.