Fuzzy analysis for higher effectiveness of control chart

摘要

This paper addresses the problems occurring in the control chart and develops a new way to improve the evaluation process of this widely used tool. Classical limitation of control chart is its inability to accurately diagnose the out of control situation. In the Shewhart's control chart, the effects of the variation of the process points plotted on the control chart are not taken into account for evaluation; which can be misleading for finding the out of control situation. For a more perfect evaluation, the variation of the positions of these points is needed to be incorporated. The research deals with this classical limitation of the control chart. Through a real illustrative example, this paper introduces the concept of fuzzy control chart as a tool for verifying level of variation, and trend in quality characteristics incorporating uncertainty by introducing linguistic variables to identify the position of the points in the control chart. The use of linguistic labels provides better neural view to inspectors for acceptance or rejection of process, offering different strategic options for company to choose etc.