Analytical And Experimental Investigation Of Milling Chatter

The process of metal milling chatter is a complicated nonlinear dynamic behavior among milling machine, cutting tools and workpiece, and it is a kind of self-excited vibration which is often caused by dynamic chip thickness. This kind of vibration may lead to the change of relative position between workpiece and cutting tool, and the surface quality and efficiency of the cutting tool could be reduced. By inferring the dynamic milling force in the process of milling, the nonlinear dynamic model was established on the basis of existing theoretical of milling chatter, and the inference conclusion was verified by the experimental method. The main contents of this research include some aspects as follow:1) According to the inference dynamic milling force, the physical model of milling chatter which is produced by position feedback was deduced. A 2-DOF delayed differential equations with nonlinear coupled milling force were proposed. By solving the eigenvalue of DDE, the stability of equilibrium of the system was analyzed and the expression of critical delayed near the equilibrium point was obtained. By multi-scale method, the approximate analytic solution of equations was discussed, and the analysis of the characteristics of milling chatter caused by delayed feedback was investigated.2) Based on the two degree freedom of dynamics model, the stability limit diagram was drawn by the semi-discrete method, and the relationship of bifurcations conditions and eigenvalue of the system was discussed. Using the Simulink simulation of the vibration equations, the dynamic milling process was numerically simulated. Under the different milling parameters, the change curves of displace and acceleration in the process of dynamic milling were obtained. The simulation results indicated the process efficiently and quickly, and were in accordance with the stability limit diagram.3) Through the experiment method, the phenomenon of stable milling and chatter was observed and analyzed. The effect of the speed, cutting depth and cutting width on the stability of the milling was analyzed, and comparing the phenomenon of experiment and the conclusions of theory, the relative conclusions in the real milling process were verified. Some new phenomenon appears according to this experiment, and these problems were also analyzed and summarized in this paper. The results of the experiment analysis have guiding significance for the selection of miller parameter and vibration control and improvement of the theoretical model.