High Speed Precision CNC Machine Tools Reliability Technology Research

In recent decades, domestic CNC machine tools enterprise learning foreignadvanced technology, relying on independent innovation and strengthen the scientificresearch ability and strengthen the cooperation with university and some other ways,make the technology level of domestic production of CNC machine tools is increasedgreatly, reduced the gap with foreign advanced machine tool manufacturing enterprises.In the field of high-end CNC machine tools, however, there are still large gaps in thedomestic CNC machine tools reliability level and the advanced world level, this can’tmeet the requirements of our users, so lead to the high-grade CNC machine toolsimports increased, also reduces the domestic market share of high-end CNC machinetools. So improve the reliability of home-made numerical control machine tool is ofgreat significance.The paper is part of the national major scientific research projects, established thereliability of failure data record and analyzed field failure data of one series CNClathes of a domestic factory. Fits distribution function and probability density curvewith several group of failure data,assuming that obey weibull distribution, and thenrespectively using the least-squares fitting method and GM (1,1) direct modelingmethod to estimate model parameters, Select the best model by fitting the results, andthen through the selected model get the Point and interval estimations of the mean timebetween failure(MTBF).The failure mode effect and criticality analysis(FMECA)method were used forCNC lathe machine and subsystems Analysis shows that the hydraulic system failurerate is highest, and the electrical system harm degree is the highest, followed by themain transmission and spindle system and tool holder system, these four subsystems isthe weak link of CNC lathe, and puts forward improvement for these four subsystems.In the paper, using expert evaluation method in the aspect of reliability prediction,and the hydraulic system, electrical system, the main transmission and spindle system, tool holder system is considered as a reference, calculating the average failure rate ofthe machine tool is expected values close to the observed value. In terms of reliabilitydistribution, using the method of combining the fuzzy theory and the traditionalmethods, considering the influence of the damage degree and the average repair time,through the expert evaluation method for rating the weight of each influence factor,setting up the weight assembly of influence factors and membership degree,distribution coefficient is obtained by fuzzy change, And in accordance with theprinciple of distribution subsystem failure rate. Finally according to the results of thereliability prediction of the failure rate of each subsystem redistribution, so that eachsubsystem failure rate more reasonable allocation.