Study On Surface Topography Simulation Of Micro-milling Aluminum Alloy LF 21

Aluminum alloy LF 21 has strong reflection ability to visible light,heat and electromagnetic waves,and its waveguide slit structure is widely used in waveguide radar antenna.The surface roughness of the sidewall of the waveguide slit directly affects the electrical performance of the antenna.However,aluminum alloy LF 21 has low strength and hardness,and high plasticity.Under the influence of cutting force,the phenomenon of plastic flow of materials is very common,and processing defects such as material extrusion and accumulation are inevitable.Coupled with the poor rigidity of the slit itself,it might be easily deformed under the influence of cutting force,clamping force,cutting heat,residual stress and other factors.The surface roughness of the sidewalls of the waveguide slits processed by conventional milling is difficult to guarantee.Micro-milling technology can meet the requirements of high-precision machining of meso-scale parts/structures with complex geometric features.It is considered to be a potentially effective processing technology of rustproof aluminum alloy waveguides.However,micro-milling tool has a small diameter and low rigidity.Under the processing conditions where the feed per tooth is equivalent to the arc radius of the cutting edge,the tool deformation and tool wear are serious,and the micro-milling system has complex dynamic response characteristics,which will result in a complex formation mechanism of the surface morphology of the slit array structure,and the surface roughness is difficult to predict.What’s more,the effects of micro-milling,such as material elastic recovery,the minimum cutting thickness,and friction effects,on the surface of the workpiece after processing cannot be ignored.Therefore,this paper studies the simulation of surface morphology and prediction of surface roughness micro-milling aluminum alloy LF 21.The specific research contents are as follows:Combining cutting theory with cutting process simulation technology,a simulation model of the micro-milling aluminum alloy LF 21 process is established based on DEFORM 3D,and the tool wear prediction of aluminum alloy LF 21 micro-milling is realized.What’s more,the quantitative relationship between the tool nose radius and the tool wear is deduced.Further,taking the minimum cutting thickness as the boundary,the author establishes a micro-milling force model considering the effect of tool wear and tool runout.Combined with the micromilling machining mechanism and characteristics,the dynamic model of the micro-milling system is established.Based on the dynamic flexibility coupling method,combining the Timoshenko beam theory and the hammering test,the tool tip frequency response function is obtained,and the modal identification is used to obtain the system dynamics model parameters.On the basis of the existing trochoid theory,combined with tool wear,tool radial runout,tool flexible deformation,system dynamic response,etc.,the cutting trajectory model at discrete points of axial micro-element on any cutting edge is deduced.With the time step as the increment,the trajectory of all the discrete points of the axial micro-elements of the cutting edge is solved,and the simulation result of the workpiece surface topography after processing is derived based on the principle of tool path reproduction.Using the APP design tool of MATLAB,the author develops a simulation software for the sidewall surface topography of the slit array structure,which realize the micro-milling force signal preprocessing,the parameter identification of micro-milling force model and tool radial runout model,surface topography simulation and surface roughness prediction of the slit sidewall and other functions.This paper realizes the simulation of surface morphology and prediction of surface roughness micro-milling waveguide slit sidewall under any cutting parameters.This paper can provide theoretical and technical basis for the optimization of cutting parameters in micromilling waveguide slits,which is beneficial to the industrialization and application of micromilling technology in LF 21 waveguide slits.