Quality Control
Duy Duong-Tran; Romina Dastoorian; Lee Wells
Abstract
Exponential Weighted Moving Average (EWMA) control charts have been widely used in Statistical Process Control (SPC) to detect small and persistent process shifts. In theory, EWMA control limits monotonically increase over time to account for the continual growth of the EWMA statistic’s variance. ...
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Exponential Weighted Moving Average (EWMA) control charts have been widely used in Statistical Process Control (SPC) to detect small and persistent process shifts. In theory, EWMA control limits monotonically increase over time to account for the continual growth of the EWMA statistic’s variance. However, these control limits are often assumed constant and are set to their respective asymptotic limits to simplify the process of applying and analyzing EWMA control charts. One-sided EWMA charts are often implemented when it is only desirable to detect shifts in a specific direction. When using one-sided EWMA charts, reflecting boundaries (resets) can be used to prevent the statistic from drifting too far from the chart’s control limit, which can delay shift detection. There have been several research efforts into designing and studying the performance of one-sided EWMA charts with reflecting boundaries. However, these efforts have maintained the constant control limit assumption. When implementing a reflecting boundary, the EWMA statistic’s variance is constantly being reset to zero, which may significantly affect the constant control limit assumption’s validity. The focus of this paper is to understand behavior of the one-sided EWMA control charts with constant and time-varying limit assumption through simulation studies.
Statistical Process
Teuku Mirwan Saputra; Hernadewita Hernadewita; Akmal Yudha Prawira Saputra; Lien Herliani Kusumah; Hermiyetti ST
Abstract
Enhancing the process capability is a must in quality improvement of process manufacturing in the industry. Usually, Statistical Process Control (SPC) is applied in measure the activity of quality improvement. In this case, the statistical process control used to measure the process capability of molding ...
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Enhancing the process capability is a must in quality improvement of process manufacturing in the industry. Usually, Statistical Process Control (SPC) is applied in measure the activity of quality improvement. In this case, the statistical process control used to measure the process capability of molding machine regarding of force result of inner contact rubber button in plastic industry. The forces of inner contact rubber button which produce by molding machine already become the critical point as a judgment of malfunctions or not. Meanwhile, the forces problem still found in molding machine that affected to the inner contact rubber button as defect product. Furthermore, as shown of SPC, the process capability of molding machine was 0.63. This mean the process capability is still need the improvement. As the result of quality improvement was made by applied of Poka-Yoke, the process capability of molding machine was improved to 1.65.