Research On Milling Force Modeling And Optimal Control Of Ball-end Milling Cutter For Machining Titanium Alloy Blades

On the basis of mastering the deformation of titanium alloy blade and the wear rule of ball end milling cutter,the establishment of milling force model is the basis of improving machining efficiency and quality.In this paper,through theoretical analysis,finite element simulation and milling experiment,the deformation law of the ball end milling cutter when machining titanium alloy blade is systematically studied,and the milling force model based on the deformation of the blade during machining and the wear of the surface after the ball end milling cutter is established.Finally,based on the optimization of milling parameters,the milling force is optimized,and finally the purpose of deformation control is achieved.The machining deformation of titanium alloy blade was studied.The 3D model of titanium alloy blade was built by UG.In this paper,the process of interaction between milling force and deformation is analyzed,and the iterative cycle model is established.Firstly,through 16 groups of four factor four level orthogonal experiments,the empirical formula of milling force in three directions is obtained,and combined with iterative cycle analysis,it is changed to the iterative formula of axial milling force and milling depth.Through the finite element analysis of ANSYS software,the specific deformation of each milling position on both sides of titanium alloy blade was obtained,and the deformation before and after iteration was compared.After considering the iterative cycle,there is a difference between the actual deformation and the initial deformation at each milling position.At the maximum deformation,the deformation after iteration is reduced by 59 microns compared with the initial one.The shear force model of the front face of ball end milling cutter is studied.The geometric model of the ball part of the ball end milling cutter with spiral edge is analyzed.Through the analysis,the instantaneous undeformed milling thickness in the model is obtained,and the shear force model of the front face of the ball end milling cutter is preliminarily established.The model is transformed into XYZ force by coordinate axis,and the meshing limit is considered in plane and curved surface(including titanium alloy blade).The shear force coefficient of the rake face is obtained by theoretical analysis and experimental solution.By substituting the deformation of workpiece into the undeformed shear force model,the shear force model considering the deformation of workpiece is obtained.The friction effect model of ball end milling cutter is studied.The wear of back face is analyzed,and the curve of wear with milling length is obtained by fixed parameter experiment.Through the single factor experiment,the influence of each parameter on the back face wear is studied.The conclusion is that the influence of the spindle speed is the largest,followed by the feed per tooth,and the influence of the milling depth is the smallest.The theoretical model of friction effect force on the unit length of the ball end milling cutter is established by the micro element method,and the friction effect force model of the ball end milling cutter in the X and Y directions is obtained.Three ball end milling cutters with different wear amount are used to measure the force respectively,and then compared with the tool without wear,the coefficient solution experiment is done to obtain three coefficients of the friction effect force model of the rear cutter face.The total milling force model based on blade deformation and tool wear is obtained by vector superposition of the shear force model of the front face and the friction force model of the back face of the ball end milling cutter in all directions,which is verified by experiments.The optimization of machining parameters based on the milling force model of titanium alloy blade is studied.Four basic milling parameters in the process of titanium alloy blade machining are determined as the variables to be optimized.Two objective functions,which aim at the minimum milling force and the shortest machining time,are added to form a multi-objective optimization function.The constraints are defined and the milling parameters are optimized by Matlab genetic algorithm toolbox.After optimizing the parameters,the milling force becomes smaller and the machining time is shortened,which shows that the optimization can provide some reference for the selection of actual parameters.