Early failure modeling and analysis of CNC machine tools

Frequent early failures are the key factors restricting the reliability improvement of CNC (computer numerical control) machine tools. In order to eliminate the early failures of CNC machine tools as much as possible, this paper defined the early failures of CNC machine tools strictly and divided the early failures into sudden early failures and progressive early failures. According to the characteristics of sudden early failures, the corresponding reliability analysis model was established by fishbone diagram and 5M1E (man, machine, material, method, measurement, environment) method. Based on the failure time rather than failure time intervals, the reliability analysis model of progressive early failures, which can reflect the dynamic characteristics of CNC machine tool failures, was established by BBIP (bounded bathtub intensity process) method in NHPP (non-homogeneous Poisson process). The reliability evaluation indexes of progressive early failures were given, and the analysis method of the influence of the relationship between former failure and latter failure on the established reliability model was given. CNC machine tools made in China were taken as the example, and the reliability analysis models of sudden early failures and progressive early failures were established and analyzed, respectively. The conclusion that different product failures of the same model could not be analyzed by the same parameter model is obtained. The results also verify the applicability and correctness of the proposed method, which lay a foundation for the elimination of early failure and the improvement of reliability of machine tools.