The Research On Preventive Maintenance Strategy Of CNC Machine Tool Based On RCM

With its efficient, quick, good processing capacity, CNC Machine Tool, as on ofthe most important manufacturing equipment, is used more and more widely in thevarious sectors. However, because the maintenance item and the maintenancefrequency of the traditional maintenance of CNC machine tool are built on theexperience, there are some problems, such as the formulation of maintenance strategyis rough, the way of maintenance is incorrect, and with the high cost of maintenance,the availability is low. So this paper is intended to provide a scientific method for theformulation of CNC machine preventive maintenance strategy. Based on reliability-centered maintenance ideas, referenced the domestic and foreign achievements on themaintenance strategy of CNC machine tool, studied of two aspects. On the one hand,through analytic hierarchy process and Monte Carlo simulation method, converted thecomplex tedious qualitative analysis process of reliability-centered maintenance toquantitative calculation. On the other hand, with considering forced maintenancecaused by the two kinds of sudden faults during preventive maintenance cycle,respectively established the preventive maintenance cycle decision model withavailability and average maintenance costs as optimized object. The specific researchwork and conclusions are as follows.In order to make the complex problem is simplified, adopted the hierarchyanalysis and expert scoring way, and combined with linear weighting method isestablished numerical control machine tool important degree level evaluation model.Meanwhile, through Monte Carlo simulation determined how important the evaluationfactors of subsystems are, enhanced the robustness of the model. Combined experts'experience and quantitative calculation instead of the traditional logic diagrammethod of the decision to confirm the various subsystems important degree level,made qualitative analysis steps of reliability-centered maintenance quantitative, andreduced the influence of subjective factors.It is the premise of developing the preventive maintenance strategy to be familiarwith life distribution of the preventive maintenance subsystem. So first processedcensored data of CNC machine tool subsystems, and estimated reliability. Then basedon the information of data and graph to make preliminary judgment and assumptions of life distribution of the system, and estimated parameters the model. Finally, testedthe model by linear related inspection and K-S method, and compared the results ofthe different parameters estimation method with K-S method, then took the bestestimate, improved the estimation and the accuracy of the test results.Through the analysis of the fault of the CNC machine subsystem in thepreventive maintenance cycle, respectively established the availability model and theaverage cost of maintenance model of the first n cycle of preventive minor repairs andan overhaul of the cycle. Analyzed and explored the actual application of the modelwith different parameters. with considering forced maintenance caused by the twokinds of sudden faults during preventive maintenance cycle, and compared with thetraditional preventive maintenance decision, the model is more comprehensive, moreflexibility, and more widely.Aim at the bottleneck that during the model establishing process of currentpreventive maintenance decision lacked of data support, established the equipmentmaintenance management information system, and provided the convenience forscientific research institutions and enterprises to collect and manage maintenanceinformation and make proper maintenance decision.Cited a horizontal NC lathe as an example, analyzed it by. the method in thispaper. Established the model to evaluate how important each subsystem is, andaccording to the route of preliminary data processing-model primary-parameterestimation-model test, established the life distribution model of electrical system.Finally with availability and average maintenance costs as the target established themodel for preventive maintenance cycle decision-making and determined thepreventive maintenance optimal cycle of the electrical system of the horizontal NClathe.