Study On Preventive Maintenance Decision Technology Of CNC Machine Tools Based On Performance Of Fault Rate

Numerical control machine is widely used in the processing of many crucial partsas machine tools in modern manufacturing, with extremely high reliability. By thestatistics, maintenance costs of numerical control machine tools accounted for20%-30%of the entire life-cycle costs. Hence it is of great significance to improve thereliability of CNC machine tools and reduce the loss, of which study on preventivemaintenance decision and establishing reasonable maintenance mode is conducted.With integration of Mechanical&Electrical-hydraulic technology, numericalcontrol machine tools standed for machining centers and CNC punching machine arecomplex equipment, so it’s different from the failure mechanism of traditionalmanufacturing equipment. Scheduled maintenance system based on the bathtub curvehas not adapted to the maintenance management of CNC machine tools. Therefore,preventive maintenance decision model on account of actual fault rate performance isproposed via using failure data gathered from CNC machine tools, which is based onthe research of failure mechanism and failure principle for CNC machine tools.Different prevention maintenance method is used in different stages of NC machinecombined with the characteristics of the failure rate curve. By the research object ofCNC bending machine, refinement maintenance management of CNC machine tools onthe basis of preventive maintenance decision theory and Japan’s Total ProductiveMaintenance is put forward, and the application of preventive maintenance decisiontheory based on the performance of fault rate is discussed. The main work andcontribution of this paper is as follow:①By the introduction of traditional reliability theory, the features of fault ratecurve including the common fault rate curve type and characteristics are explored. Inaddition, the framework of preventive maintenance decision based on the analysis ofCNC machine tools fault rate curve model is established, of which CNC machine toolsis used as the research object.②On the discussion of quantitative modeling method of failure rate curve model,the fault rate curve model on the basis of abundance failure data gathered from sometype of CNC bending machine is set up. According to the analysis of fault rate curvemodel based on subsystem and service stage of CNC machine tools, fault mechanismand preventive maintenance decision-making management is discussed. ③At fist, maintenance decision-making model is achieved through maintenancefrequency and maintenance interval time, which is solved by the target of minimum feeper unit time, maximum availability and security. Then, Constant Failure Rate andInereasing Failure Rate divided on characteristics of fault rate are studied respectively.On the principle of minimum expected total downtime for maintenance cycle analysis,time delay model is established in Constant Failure Rate. With the goal of maximumavailability, maintenance opportunity by using the mixed weibull model fitting failuredata is optimized.④The application of preventive maintenance decision theory in enterprise basedon the characteristic of fault rate is discussed. Refinement maintenance managementsystem of CNC machine tools is put forward, which is controlled by check list in thewhole life-cycle; In technical level, the maintenance strategy of CNC machine tools isstudied. Meanwhile, vital maintenance position and reasonable maintenance method isconfirmed by fault hazard degree.