Dynamic Analysis Of Chatter System For Micro-milling And Simulation Of Milling Process

Micro-milling has Strong competitiveness in the manufacturing. With the improvement of science and technology and the progress of society, the demand for complex Optoelectronic components with micro-size is growing no matter in civil use or in national defense industry. Thus micro-milling is playing a very important role in the milling process. However, the chatter which accompanies the milling process often affects the processing properties of machine tools, life of tool and machining quality of workpiece, even produce the noise pollution. Based on the above mentioned, this paper analyzed the main chatter form-regenerative chatter in milling process. Meanwhile the paper established the cutting process dynamic model for the two degrees of freedom based on the cutting parameters of the milling process (N, r, ae, kt, kr) and the dynamics parameters of the chatter system(kx, ky, (?)x, (?)y,ωnx,ωny),then the stable curve of the cutting process was obtained using MATLAB software. Thus the appropriate cutting parameters were selected according to the limit cutting conditions predicted by stable curve. This paper mainly analyzed the laws that how the changes of the system dynamics parameters effected the stability limit depth of cut. And then got to know the factors not only made the stable curve changes in the vertical coordinate direction; there were also changes in the horizontal axis. And the paper also analyzed the factors'effect on the minimum limit depth of cut, and the result showed that the change of the number of teeth for tools is most sensitive to the minimum limit depth of cut. At the same time, using the two degrees of freedom dynamic model and the cutting system parameters, it calculated the average milling force in X, Y directions.In addition, chose a group of cutting parameters which is below the critical cutting conditions according to the stability curve. Based on the cutting parameters, Did the finite element simulation and cutting experiments in cutting process and contrast analysis results.then tested the rationality of the dynamics model and the reliability of the simulation model. Using Deform-3D,got the diagram of the stress and strain in five states, when the cutter was getting ready to cut into the workpiece, cut into the workpiece at 1/4 diameter of the cutter, cut into the workpiece at 3/4 diameter of the cutter, exactly completely cut into the workpiece and the cutter got into stable cutting. Then analyzed the elastic flow,the plastic flow in the workpiece and the macroscopic situation that the material removed from the surface of the workpiece, according to the diagram and the situation that when there is a large number of plastic deformation in the workpiece. And it also analyzed the force on the workpiece during the milling process using the Deform-3D software. In the five above states, the cutting force showed a gradual increase. But in the third state, the cutting force has a sharp increase which was the largest one in the five states. And then the force decreased, indicating that there is a flexible accumulation process during the cutting process. This process made the load of the cutter became larger and the force increased dramatically.As to the experiments, this paper tested the cutting force on the X, Y, Z three directions in the machining centre using LiYang MVL1300. The data from the Deform software was compared with experimental cutting force data. Although there was deviation among the comparison, they basically correspond with each other in the trend. This proved that the simulation model was reliable. The curve is also reliable according to the experiment and the simulation (flutter didn't occur when it below the critical cutting conditions). When we compared the experimental data with the theoretic average milling force, we got to know that there was deviation, but they were in the same magnitude. This also proved the rationality of the theory.This paper had gotten help from the special project of ministry of science and technology for international cooperation and exchanges(2010DFA72000) and special funded projects of the doctoral program of higher education for ministry of education (200801831024)...