Research On The Process Of Cycloidal Milling Of 300M Ultra-high Strength Steel

300M ultra-high strength steel is widely used in aerospace,automobiles,ships and other fields because of its good mechanical properties such as high strength,high transverse plasticity,high fracture toughness,and excellent fatigue characteristics and good corrosion resistance.However,because of its good mechanical properties,it will have excessive cutting force,serious tool wear,poor surface quality and other phenomena in the machining process.With its unique cycloidal trajectory,cycloidal milling improves the adverse effects that occur in conventional milling during machining.Therefore,it is necessary to carry out relevant research on the 300 M steel cycloid milling process,select the appropriate milling process parameters to improve the processing efficiency and reduce the processing cost,and provide a basis for the selection of 300 M steel cycloid milling processing technology.Taking 300 M steel as the research object,the cycloid milling test was carried out,the influence of milling parameters on cutting force and surface roughness was studied,and finally the milling parameters were optimized by multi-objective optimization.The main contents are as follows:(1)Theoretical model of milling forces for cycloidal milling developed.The real motion trajectory of the tool during cycloidal milling is analyzed,and the equation of the motion trajectory between the tool center and the tip is obtained.The geometry of the chip is constructed by numerical method,and the instantaneous cutting thickness is obtained by solving the transcendental equation,so as to establish the dynamic model of milling force.(2)Milling force experiment and analysis.In order to obtain the cutting force coefficient in the milling force model,an experiment is designed to compare the cutting force coefficient extracted from general slot milling with the cutting force coefficient extracted from cycloidal milling,and the cutting force coefficient extracted from cycloidal milling is fitted.It is found that the coefficient extracted from cycloid milling cannot be used to predict the milling force of cycloidal milling,and the milling force model established has a high degree of agreement with the actual value.The single-factor and orthogonal experiments were designed to explore the variation law of milling force with milling parameters,and an empirical model of milling force was established,and the empirical model fitting results obtained were good and met the engineering requirements.(3)Measurement and analysis of surface roughness and tool wear.The single-factor experimental results show that the surface roughness increases with the increase of cutting speed,feed per tooth and milling depth,and decreases with the increase of cycloid trajectory radius,and the change law is analyzed and explained.The response surface experiment was used to analyze the multi-factor interaction to analyze the milling parameters,establish the polynomial of surface roughness,and analyze the variance of the model,and the model had good significance.Using traditional milling and cycloidal milling to process grooves of the same width and depth,observing the tool wear,it is found that cycloid milling can reduce the wear of the tool,and several forms and mechanisms of tool wear are analyzed.(4)The parameter optimization problem of NSGA-II algorithm is carried out.Taking the cutting speed,feed per tooth,axial depth of cut and cycloid radius as constraints,the milling parameters were optimized with the minimum surface roughness and maximum material removal rate as the objective functions,and the optimal parameter combination was obtained.The optimal parameter combination was verified and the surface quality was found to be improved.