Journal of Industrial Engineering and Management Studies

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 (ATS) 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.

Abstract CCC-r chart extended approach of CCC charts, is a technique applied when nonconforming items are rarely observed. However, it is usually assumed that the inspection process is perfect in the implementation control charts imperfect inspections may have a significant impact on the performance of the control chart and setting the control limits. This paper first investigates the effect of inspection errors on the formulation of CCC-r chart, then an economic model is presented in the presence of inspection errors to design control chart so that the average cost per item minimized. The r parameter in the chart is optimized with respect to the economic objective function, Modified Consumer Risk, and Modified Producer Risk.