Economic design of cumulative count of conforming charts under inspection by samples

This paper deals with the economic issues involved in the design of control charts for high quality manufacturing processes. The cumulative count of conforming (CCC) chart has been shown effective for such processes. However, the applicability of the conventional CCC chart is limited to the case that items are inspected one by one in the order of production. When items are inspected lot by lot or sample by sample without preserving or according to the original production ordering, modification is needed. In this paper, it is proposed to monitor the cumulative number of samples inspected until a nonconforming sample is encountered. An economic model is developed for designing such a generalized CCC chart. Numerical examples are given and sensitivity analysis is performed to demonstrate the use of the economic design model.