Three-dimensional Stability And Deformation Of Thin-walled Part In High Speed End Milling

With the development of aerospace technology,thin-walled parts are being widely used in the engineering.Because of their complexity under loading and the higher shape precision,it is difficult for thin-walled parts to carry out the force analysis according the classical theory.Therefore,the thin-walled parts are one of the complex manufacturing processes in the world.One of the most prominent problems in their manufacturing process is the machining deformation,and one of the very important factors affecting the deformation is the chatter.Accordingly,during the processing of thin-walled parts, the machining deformation and cutting stability are to be studied and controlled in order to improve the machining accuracy and surface quality.A method combined experiment with theoretical model and computer simulation was proposed in this dissertation to study machining deformation and three-dimensional stability of 2A12 aluminum alloy thin-walled parts,which could provide a theoretical guide for predicting and controlling the machining deformation of thin-walled parts.The three-dimensional stability model of milling thin-walled parts is established on the basis of the model of Altintas and Budak.It can derive the three-dimensional stability lobes of the spindle speed,axial and radial depths by Matlab7.0.It can be found intuitionisticly and accurately the interrelation between the cutting parameters and the effect on the stability by the three-dimensional stability lobes.Accordingly,it can select the most excellent cutting parameters under the condition of the stability. Moreover,the interrelation between the cutting force coefficents and the cutter parameters is built by studying the cutting mechanics and cutting force model to analyze the influence of the helix angle,normal rake angle,tooth number and radial cutting depth on the three-dimensional stability lobes.Then,the stability of cutting system and selection for the optimal parameter can be analyzed which can forecast the stability of the cutting system to improve the cutting efficiency of the machine tool.It can provide a theoretical guide for the parameters optimization of milling thin-walled parts.The elastic deformation of milling thin-walled parts is predicted using a theoretical deformation equations model,which is established on the basis of reciprocal theorem. The elastic deformation of the 2A12 aluminum thin-walled parts in end milling process is simulated by using FEM software ANSYS10.0.In the process of simulating,the influences of linear loads,location of the cutter,thickness of the part on the deformation of the thin-walled plates are analyzed,and the elastic deformation is forecasted at the condition of the different influence factor,which lays a theoretical foundation for analyzing and forecasting the deformation of milling thin-walled parts.The elastic-plastic deformation of milling thin-walled part is analyzed,and the theoretical elastic-plastic deformation equations model and the boundary conditions for the cantilever part are established on the basis of the equations of Von Karman.The elastic-plastic deformation of the 2A12 aluminum thin-walled parts in end milling process is calculated by using FEM software ANSYS10.0.Moreover,it considers the influence of bending springback on the elastic-plastic deformation.The bending springback is considered in the calculation of elastic-plastic deformation.The internal cause of bending springback and the influence factors are analyzed.The elastic-plastic deformation is calculated under the effect of multi-factor coupling by FEM software ANSYS10.0 and Matlab.The deformation experimentation of milling 2A12 aluminum thin-walled parts is processed,and the deformation is measured on a CMM 775,which validates the correctness of the elastic-plastic deformation model.It provides a theoretical guide for the controlling technology of the machining deformation of thin-walled parts.Integrating the deformation theory and three-dimensional stability,the three-dimensional stability model of different tool position is established for thin-walled parts.Three-dimensional stability lobes of the axial cutting depth,spindle speed and tool position are plotted by Matlab.The experiment validates the stability model of tool position,which can guide the selection of cutting parameters in the process of milling thin-walled part and control the stabilized cutting process.It can improve the machining efficiency and precision in the process of milling thin-walled plate.The model of the maximum material removal rate without chatter is established by cutting theory and numerical calculation.When the material removal rate is maximal, the exit immersion angle is only related with the cutting force coefficient which is related with the helix angle,normal rake angle,friction factor and the chip deformation coefficient.Therefore,it can seek the most optimal cutting parameter pairs at the condition of stability to obtain the maximum material removal rate.The specific example validates the mathematical model of the maximum material removal rate.This project is supported by National High Technology Research and Development Program of China(Grant No.2008AA042405) as well as National Basic Research Program of China(Grant No.2009CB724401).