Economic Design of Statisticl Process Control Charts With Imperfect Process Adjustment and Tampering

摘要

The existing literature on economic design of X process control charts generally assumes perfect process adjustment, such that the process mean is returned to an exactly centered "in control" state following any real or false alarm control chart signal. This paper presents a model which demonstrates the effects of imperfect process adjustment on the economically designed control chart parameters. The intent is to demonstrate that the optimal control limit width depends on the precision with which the process can be adjusted. The greater the process adjustment error, all else constant, the wider will be the optimal control limits, in order to alleviate the potential for process over-control and tampering effects.