Reliability Evaluation of CNC Machine Tools Based on Function Monotonicity

To improve the deficiency of previous reliability evaluation methods of CNC machine tools, an evaluation method based on function monotonicity is proposed to evaluate the reliability of CNC machine tools. First, residual correlation method is used to eliminate abnormal data. Second, an empirical distribution function of CNC machine tools is established through mean rank method. Furthermore, reliability models of CNC machine tools are developed, and model parameters are estimated through maximum likelihood method. A comprehensive evaluation method is adopted to select the optimal distribution function, which is the model used in our study. Finally, the interval of mean time between failures is estimated on the basis of function monotonicity. The proposed method is also used to evaluate the reliability of a certain CNC lathe. Results verify the feasibility and effectiveness of the proposed method.