| Summary: | 碩士 === 國立雲林科技大學 === 工業工程與管理研究所碩士班 === 93 === Traditional Shewhart Control Chart is a useful tool in detecting the shift of process average but it is insensitive to small process average change. Exponentially Weighted Moving Average Control Chart (EWMA) and Cumulative Sum Control Chart were developed to improve the ability in detecting small process shifts. The control chart with variable sample sizes and sampling intervals (VSSI) proposed by Arnold and Reynolds in 2001 has same purpose in improving the ability of detecting the change of process. Some researches proposed design of control chart under preventive maintenance policy that can decrease the production cost.
This study develop an economic design of VSSI CUSUM Control Chart under the strategy of preventive maintenance and using Genetic Algorithm in searching the optimum parameters (larger sample size, smaller sample size, long sampling interval, short sampling interval, warning limit, control limit) to make the expected cost per time unit be the lowest. Results of this study show that the optimum of AATS for the economical design of VVSI CUSUM was lower about 6.5% compared with that of traditional CUSUM Control Chart. Moreover, the expected cost per time unit was lower about 9.8% than traditional CUSUM Control Chart.
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