Modeling, analysis, and removal of chatter marks in flexible turning

Abstract

Chatter is a kind of self-excited, unstable vibration in almost all machining processes. Existing studies have been focusing on the pre-chatter stage, developing various techniques to detect, predict, and suppress chatter. In real applications, chatter will inevitably happen under certain cutting conditions, with generating chatter marks on the workpiece surface. Additional operations are required to remove chatter marks before the finish machining. It is noted that chatter marks will easily induce chatter again, resulting in worse surface quality. This paper quantitatively analyzes the effects of chatter marks on the stability of the process by modeling chatter marks with a periodically modulated depth of cut. Stability lobes show that the existence of chatter marks greatly reduces the stability limit. Furthermore, chatter mark removal using spindle speed variation (SSV) is proposed. Extended high-order full-discretization method using Lagrange interpolation is developed to analyze the effect of SSV on chatter marks removal. It is shown that SSV can remarkably improve the stability limit even with chatter marks. Finally, machining experiments of thin-walled discs are conducted to verify the deterioration effect of chatter marks on the stability limit and show that chatter marks can be effectively removed by the SSV.