Economic Design of EWMA Chart for variable Sampling Interval with sampling at fixed times

• Main Authors: Yen-Hsin Chang, 張燕欣
• Other Authors: Chao-Yu Chou
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/32086543237757781585

碩士 === 國立雲林科技大學 === 工業工程與管理研究所碩士班 === 92 === Using control chart to monitor process in production to reduce defective items result from production variability. Exponentially Weighted Moving Average（EWMA） control chart have more sensitivity and detection ability than traditional Shewhart control chart in monitoring small variability. As the result, the study choose EWMA control chart to monitoring process. Furthermore the study not only consider the statistic part but also economy part. Reynolds（1996）discover the variable sampling interval with sampling at fixed times（VSIFT）have greater detection efficiency than fixed sampling interval（FSI）. Moreover have lower sampling cost in the same detection ability. Therefore, we construct the economic design model of VSIFT EWMA control chart to determine the value of six control parameters （i.e., smooth exponential, the sampling size, fixed sampling interval, subinterval numbers, the control limit, and the warming limit）of optimal combination. The aim is make the time cost per unit to get the minimum cost target and find out the effect of parameters to control parameters and cost by sensitivity analysis.