Abstract: It has been reported that the downtime due to cutting tool failure is more than one third of the total forced downtime of the machine tool. Therefore, it is very important for improving the machine tool operation reliability to investigate the gradual reliability and its sensitivity of the cutting tool. A non-stationary Gamma process which is a continuous-time, continuous-state and monotone increasing stochastic process with independent increment is employed to describe the wear process of the cutting tool. The gradual state function of the cutting tool with the periodical compensation for wear and the invariant machining condition are formulated according to the principle that the machining error is not more than the given machine tool machining accuracy in two cases. One has the assumption that the cutting tool has not the machining error and the detection of the wear of the cutting tool is accurate. The other is the contrary one. Then, the corresponding gradual reliability is derived. On this basis, the sensitivity of the gradual reliability is analyzed. It is described by the numerical examples how to improve the operation reliability of the cutting tool using the proposed gradual reliability model and its sensitivity analysis results. The more feasible theory and method for improving the cutting tool operation reliability with the periodical compensation for wear and the invariant machining condition than the existed works might be provided by this work.

Key words: Cutting tool, Gamma process, Gradual reliability, Sensitivity analysis