Performance of CCC-r control chart with variable sampling intervals

Abstract

The CCC-r chart is developed based on cumulative count of a conforming (CCC) control chart that considers the cumulative number of items inspected until observing r nonconforming ones. Typically, the samples obtained from the process are analyzed through 100% inspection to exploit the CCC-r chart. However, considering the inspection cost and time would limit its implementation. In this paper, we investigate the performance of CCC-r chart with variable sampling interval (CCC-r_VSI chart). The efficiency of CCC-r_VSI chart is compared with fixed sampling interval (FSI) scheme of CCC-r chart (CCC-r_FSI chart) and CCC_VSI chart. The comparison results show that CCC-r_VSI chart is more efficient than the CCC_VSI chart in reducing the average time to signal (<em>ATS</em>) and also CCC-r_VSI chart performs better than CCC-r_FSI chart. In addition, some sensitivity analyses are performed to illustrate the effect of the input parameters on the performance of CCC-r_VSI chart.