Research On Five-axis Machining Technology Of Aviation Blade Based On Kinematics And Dynamics

As the most important part of the aero-engine,the aero-blade has the structural characteristics of thin thickness and rapid curvature change,which is extremely difficult in the actual machining process.The five-axis CNC machining technology is one of the most effective methods to achieve the machining of aviation blades because of the advantages of high precision and variable tool axis attitude.For the blade inlet and outlet edges and other difficult machining positions,after using CAM software for tool trajectory planning,it is found that the tool axis attitude between adjacent tool contacts is very easy to change abruptly,which causes the angular velocity and angular acceleration of the machine tool rotation axis to surge,even beyond the kinematic parameters allowed by the machine tool,resulting in excessive milling force and large elastic deformation of the blade.Therefore,based on the kinematic and kinetic characteristics constraints of the rotary axis in the five-axis CNC machine tool,this topic focuses on the optimization method of the tool axis vector and machining deformation control strategy at the sharp change of leaf body curvature,which is of great significance to improving the machining quality of aviation blades,and the main research contents are as follows:Based on the kinematic characteristics constraint of the rotary axis of the five-axis CNC machine tool,the transformation of the tool position file to the CNC file is completed by establishing its kinematic model and using the method of inverse kinematic transformation.For the problem of kinematic parameter overrun caused by excessive tool axis rotation angle between adjacent tool contact points,the tool axis vector optimization algorithm under the machine tool coordinate system is used to determine the local optimization interval and complete the tool axis vector optimization within the overrun interval.The least squares method is used to solve the kinematic parameter overrun problem at the connection between the optimized interval and the non-optimized interval,and the kinematic parameters of the rotary axis are limited to the reasonable range of the machine tool so as to improve the machining quality of the aviation blade.The milling force model of the ball-head milling cutter is established by Advantedge FEM machining simulation software.Orthogonal experiments are designed to obtain the combination of each group of milling parameters,and the milling force values corresponding to each group of milling parameters are obtained by machining simulation.The linear regression method is used to analyze the milling parameters,and the regression coefficients of each parameter term are solved by Box-Cox transformation,and then the empirical formula of the milling force prediction model is obtained.Based on the simulation machining results,milling force experiments are designed for verification so as to obtain the milling force values within the error tolerance and provide data support for the subsequent application of loads in the finite element analysis of the blade.For the kinetic problems such as excessive milling force caused by the sudden change of machine tool kinematic parameters,the machining deformation at the contact point between the tool and the leaf body is studied by simplifying the analysis of the finite element model of the aeroblade and focusing on the machining deformation at the contact point between the tool and the leaf body.Based on the complex surface modeling of the blade surface,the mapped mesh method is used to complete the meshing of the blade part.The ANSYS Workbench software is used to load the milling force component in the form of a load at the selected mesh nodes,and the information of the position with the largest deformation is obtained by analyzing the deformation of the leaf body at each node.According to the relationship between milling force,elastic deformation,and axial milling depth,an iterative algorithm is used to optimize the deformation volume so as to establish a prediction model for the elastic deformation volume of the leaf body.For the multi-objective optimization problem of machining deformation and machining efficiency,by selecting four basic milling parameters such as milling depth as the optimization variables,solving the function expressions with machining deformation and material removal rate as the optimization objectives,and then establishing a multi-objective function optimization model The NSGA2 genetic algorithm is used to set the initial parameter values,and the Pareto optimal solution set of the milling parameters is obtained by iterative calculation.Based on the optimized results,the optimal range of milling parameters is verified by using Vericut virtual machining simulation and five-axis experiments,and the machining deformation before and after optimization is compared on a three-coordinate measuring platform to further verify the reliability of the optimized results.