Reliability Analysis Of VMC600 Machining Center

China is a large manufacturing country,manufacturing products in the number of the world has been leading,but has not been among the world's manufacturing powers.With the increasing growth of the national economy,industry and manufacturing industry have long been the main characteristics that weigh whether a country is strong,whether its comprehensive national strength is strong and whether it has international competitiveness.The advantages and disadvantages of processing center and other major equipment manufacturing reflect the comprehensive strength of the country's equipment manufacturing industry.However,most of the equipment manufacturing industry in China is still at the low and middle level,and the reliability level of domestic processing center is low,which is also one of the current problems.Therefore,improving the reliability of processing center in China is also listed as one of the main development directions.This paper studies the reliability of 8 VMC600 machining centers on the production line of a technical college.After 24 months of failure data collection,a total of 67 groups of effective data were collected.Based on the data,this paper makes a preliminary analysis of the data,analyzes the failure frequency,maintenance time and responsibility of the machining center,and looks for the weak links of the machining center.On the basis of hazard analysis(FMECA)and fault tree analysis(FTA),the failure mode and cause analysis of the machining center are respectively carried out.First,nine functional subsystems are divided and the fault modes are classified.The CA quantitative analysis method in FMECA is applied to calculate the hazard degree of each fault mode and functional subsystem.The analysis results provide effective data for the designer and reference for the maintainer.The subsystem was set as a unit and a top event,and the final cause of the fault was set as a basic event,and all possible causes of the fault were analyzed.The fault analysis was carried out for each subsystem,and effective improvement suggestions and measures were proposed for the prominent fault problems and hidden troubles of the subsystem.Then the reliability modeling and evaluation of machining center are carried out.WPP diagram was generated by calculating the fault data and fitted with the existing model curve to confirm the use of two-parameter Weibull distribution.Then the least square method was used to fit the two-parameter Weibull distribution,and finally the Kolmogorov-Smirnov test was used to test the fitting degree of Weibull distribution.The results showed that the interval time of machining center followed the fitting estimated Weibull distribution model.By means of reliability modeling,the mean time between failures,mean maintenance time and intrinsic availability of machining center are calculated.Finally,the reliability distribution of VMC600 machining center is carried out based on AHP.The indicator layer,criterion layer and scheme layer were set,and the average failure time interval index of reliability distribution was set as 800 h.Then,four reliability distribution criteria were determined: failure hazard degree,system maintainability,failure frequency and cost ratio.Membership vector and fuzzy matrix are used to allocate the coefficients of each subsystem.At last,the average trouble-free time allocated by the new machining center was calculated,and the scheme layer was used to allocate each functional subsystem to obtain the final time of reliability allocation.