Reliability Analysis And Evaluation Method Of Domestic CNC Machine Tools

CNC machine tool is the basic equipment of machine tool manufacturing industry,which reflects the comprehensive strength of a country.Compared with similar machine tools abroad,there is a gap in MTBF,the main index of domestic CNC machine tools.Most of the domestic machine tool manufacturers lack the accumulation of reliability data,and do not grasp the reliability analysis and evaluation methods,and can not determine the key factors affecting the failure of machine tools,which has become the main problem restricting the development of the reliability of CNC machine tools in China.This topic comes from the Ministry of Industry and Information Technology's "Highend CNC Machine Tools and Basic Manufacturing Equipment" major scientific and technological project: the domestic CNC system brain-changing engineering for typical Aeroengine Parts Manufacturing(2017ZX04011013).This paper mainly analyses the fault data of CNC machine tools,identifies the key parts that affect the failure of machine tools,and studies the reliability evaluation method based on the fault data and performance test data.The main contents of this paper are as follows:(1)Introduced the characteristics of reliability data of CNC machine tools,established the collection process of reliable data,and used the quartile distance(IQR)method to eliminate the outliers of collected data,screened out the valid data needed for later evaluation.By using the method of failure mode and impact analysis,the frequent failure modes,causes and locations of CNC machine tools are obtained.Through quantitative analysis of the harmfulness of the whole machine tool,the more harmful failure factors of machine tools are sequenced and corresponding improvement measures are formulated,which provides reference for designers in improving the reliability of machine tools.(2)The reliability evaluation method based on fault time interval is studied.The failure data are processed by the principle of total fault time method,the distribution model is screened preliminarily by graphic method and Chichi information criterion,the machine tool distribution model is determined by correlation test and K-S test,the machine tool distribution model is determined by correlation test and K-S test,and the reliability evaluation of NC machine tool based on fault time interval is completed.(3)In the case of small sample data,the fault data of NC machine tools are less,so the reliability evaluation method based on Bayesian theory is studied.Fault data of similar machine tools are regarded as prior distribution of NC machine tools,and then the posterior distribution is inferred according to Bayesian theory.Its functional expression is obtained.The posterior distribution is calculated iteratively by OpenBUGS software,and the posterior distribution function is obtained to evaluate the reliability of NC machine tools.(4)The reliability evaluation of CNC machine tools based on performance degradation data is studied.Based on the measured data of positioning accuracy of NC machine tools,a linear regression model is established.The rationality of the model is tested by correlation,and the reliability evaluation method based on pseudo-life data is studied.At the same time,the linear Wiener degradation model of CNC machine tools is established to estimate the parameters and obtain the reliability function image,so as to complete the reliability evaluation.