Research On Cutting Parameters Optimization Of Micro Milling And Modeling Of Micro Milling Force

In the aerospace,biomedical,electronics,automotive and other industries,micro-cutting technology is widely used to manufacture precision micro-components nowadays.Micro milling technology is one of micro cutting technology,which is mainly used for maching micro parts with complex micro structure or curved surface.If the cutting parameters are too small,the tool edge arc radius(r0)of micrometer scale is easy to cause the size effect in micro milling,and the micro milling force changes nonlinearly with the decrease of feed rate per tooth(fz),which may result in the poor surface quality of workpiece,the increase of burr number and the increase of tool wear.Therefore,choosing appropriate cutting parameters and avoiding excessive micro milling force will help to improve the surface quality and machining efficiency of workpiece and reduce the generation of burr.Main research contents of this paper are as follows:(1)Research on the influence of cutting parameters on the surface quality.First of all,the micro milling A17075-T6 single factor experiment is designed by feed rate per tooth(fz),the axial cutting depth(ap)and the spindle speed(n).Based on the non-linear change of micro milling force and the arc radius of micro milling tool,the minimum cutting thickness(hmin)range of 0.2r0-0.4r0 is determined.Then,the fz/r0 value is used as the basis for quantitative analysis.The strong size effect area,the transition size effect area and the weak size effect area are divided according to the strength of the edge size effect,and the micro milling size effect zone is established.Finally,under the strong size effect area and the weak size effect area,by analyzing the effects of changing cutting parameters on the top burr width,surface roughness and micro-milling force of the micro-slot,which proves that the main purpose of micro milling cutting parameter optimization is to avoid cutting parameters in the strong edge size effect zone.The above conclusions provide theoretical basis for the selection of micro milling cutting parameters,and also have important reference value in improving the surface quality.(2)Optimization of micro milling cutting parameters based on response surface method.In order to optimize the four process parameters of micro milling A17075-T6:fz,ap,n and tool overhang(1),a rotatable central composite micro milling straight slot test was designed based on the second-order response surface method.The response prediction model of micro milling is established by using the least square method,and the fitting degree between the experimental value and the predicted value is good.The significance of regression equation was tested by variance analysis,and the influence of micro milling cutting parameters on micro milling force and top burr was studied.The results show that ap and fz have a significant linear effect on the micro milling force and the top burr in a certain range of process parameters,and the effect decreases in turn,while n and l have no significant effect.According to the optimal response values(minimum micro milling force,minimum top burr width,minimum surface roughness),the optimized combination of micro milling process parameters is obtained:n is 11394r/min,fz is 5.8?m/z,apis 11.6?m,l is 20.9mm.(3)The micro milling force modeling considering the radial runout and lag angle of the tool.Firstly,based on the analysis of cutting path of tool tip,considering the tool radial runout and tool lag angle,a new calculation model of instantaneous undeformed cutting thickness in micro milling is established.Then considering the principle of micro milling,based on the conventional three-dimensional milling force model and the instantaneous cutting thickness model,the micro milling force prediction model is established.The micro milling force test results and prediction results have a high degree of fit.The above conclusions provide theoretical basis for the selection of micro milling process parameters,and also have important reference value in improving the surface quality,which is helpful for the rapid application of micro milling technology in industrialization.