공정 개선을 위한 가변 샘플링 간격을 이용한 계수치 관리도의 최적 설계

The proposed design method minimizes bias, i.e., an average time to signal for the shift of process from the target value (ATS) curve, as well as it applies a VSI method to an attribute control chart for detecting a process shift efficiently. First, the results of the factorial experiment obtained by various parameter circumstances show that the VSI control chart using nearly unbiased ATS design provides the smallest decreasing rate in ATS among other charts for all experimental cases. Second, we represent that a process change is rapidly detected when short sampling interval  approximate to min . In addition, the change of the sampling interval may not influence in a set of control chart parameters. Third, we demonstrate ATS curve has large bias establishing the parameter of VSI control chart using the Shewhart method. However, the proposed design method for the development of a control chart robust of sample size and control parameter size. Finally, We present an optimization model that may efficiently provide optimal ATS values for process parameters in a steady state, and that may efficiently establish parameters of correct control chart by supplying an optimization algorithm.