Effect of vibration assistance on chatter stability in milling

Vibration-assisted machining is a process in which external vibration at certain amplitude and frequency is superimposed to the original cutting motion. It has been demonstrated that vibration assistance is able to improve tool life and surface quality in milling process. This research presents an analytical model in predicting the chatter stability in vibration-assisted milling process. The tool-workpiece separation caused by the modified tool tip trajectory with assisted vibration is investigated. The instantaneous uncut chip thickness and varying time delay are obtained numerically. A dynamic model with varying time delay caused by the vibration assistance is developed, and semi-discretization method is used to determine the chatter stability with different frequencies and amplitudes of vibration assistance. The simulations are validated by experimental results, and it is shown that the vibration assistance does not improve the critical depth of cut, but generates new stability lobes between the original two adjacent lobes corresponding to no vibration assistance. The results provide guidance in determining appropriate milling and vibration assistance parameters to ensure the process stability.