Research On Compilation Method And Application Of Load Spectrum Of NC Turret Based On Mixed Distribution

Due to the lack of load data of CNC machine tools,the product can’t be assessed the true life accurately at the design stage.Besides,due to the lack of load spectrum at the reliability test stage,resulting in a load factor that does not match the actual conditions.In order to solve these problems,the method and application of load spectrum of NC turret are studied in this paper.In order to obtain the true load conditions of CNC machine tools,it’s necessary to go to enterprise and collect the process parameters.According to the on-site process parameters of the CNC machine tools,the cutting force acquisition test is carried out to acquire cutting load data.However,CNC machine tools processing conditions are complex and have more external sources of interference and other factors,which result in cutting load data analysis and processing difficulties.In order to solve these problems,this paper studies the key technology of load spectrum of NC turret,such as decision of the process parameter,the noise reduction of load signal,parameter extrapolation of the load,the compilation and application of load spectrum.The contents in this paper can be organized as follows:1)According to the on-site process parameters,36 typical process parameters and the proportion of the use of the corresponding are determined.The cutting force acquisition device of CNC lathe is built,the determination of sampling frequency and cutting test steps are determined.On this basis of these,the cutting force acquisition test is carried out to obtain the load signal of NC turret.2)The characteristics of CNC lathe processing and load signal of NC turret are analyzed,which contains singular value and noise signal.Based on this,the improved wavelet adjacent coefficient method is proposed to realize the noise reduction of load signal.3)According to the load characteristics of the NC turret,the parameter extrapolation model of the load of NC turret is established based on mixed distribution.Monte Carlo Markov chain method and rain count method are used to realize the combination of 36 typical process parameters of load signal.According to the fitting characteristics of the combined load,the mixed Weibull distribution model of load average and Weibull distribution model of load amplitude are established.Aiming at the difficult problem in the selection of basis function in mixed distribution model,the neighbor likelihood ratio method is proposed.Based on the correlation analysis of the load amplitude and average,the Copula function is used to establish the joint distribution of load average and amplitude.Finally,according to the load extrapolation frequency and the joint distribution model,the program load spectrum of the NC turret is established under constant cutting torque.4)The reliability test plan of the NC turret is developed based on analyzing the basic flow of the reliability test,which includes the determination of the reliability test time,the solution of the minimum number of test samples and the test loading scheme.Finally,the software of load spectrum generator is designed by MATLAB,which is based on the research content of this paper.