Failure cause analysis of machine tools using digraph and matrix methods

Abstract This paper presents a methodology to analyze the failure causes of a machine tool using digraph and matrix methods. The machine tool failure causality digraph models a failure cause taking into consideration its failure contributing events and their interaction in terms of the cause–effect relationship, i.e. causality. The machine tool failure causality function is determined from the machine tool failure causality matrix. The matrix is obtained from the digraph, which is characteristic of the failure cause. The function is useful not only for failure cause analysis but also for comparison and evaluation of the failure cause. The coefficients of similarity and dissimilarity based on the function are also proposed. These coefficients are useful for comparison of two failure causes of a machine tool. In addition, the machine tool failure causality index, derived from the machine tool failure causality function, is proposed, which evaluates and ranks the failure causes of a machine tool.