Abstract: Taken into account of the variation of the transient chip and cutting angle， a dynamic model was proposed for the ex-circle computerized numerical control (CNC) lathing based on the regenerative chatter theory. By applying digital simulation technique， a software package was developed to do simulations for available experimental data. The simulation results clearly showed the nonlinear relation between the limited cutting width and the spindle speed， and the spindle speed has more effect on the chatter than other factors. The stability increases with increase of the equivalent stiffness or the damping ratio in vibrating system， but it will decline when the directional coefficient， cutting overlapping coefficient or cutting stiffness increases. And the shapes of the lobes are simultaneously changed. However， the natural frequency of the vibrating system has no effect on the shapes of the stability lobes， and the lobes integrally move to the right with its increase. These results provide theoretical basis for chatter suppression.

Key words: regenerative chatter, CNC(computerized numerical control) lathing, dynamic modeling, digital simulation, stability analysis