Influence of machine vibration on finished surface in bonnet polishing and its suppression

Abstract

High-precision polishing of free-form surfaces is necessary for advanced optical components. The 7-axis CNC polishing machine with virtual pivot system, in which the three rotation axes on the spindle side intersect at one point, can easily polish free-form surfaces since it can change the precession angle without changing the machining position. However, at the reversal point of the toolpath, a large torque is instantaneously applied to the rotating axis, causing the machine to vibrate and the polishing accuracy to decrease. In this study, we investigated the effect of vibration on polishing accuracy, and proposed a toolpath that suppresses it. Finally, an experiment using bonnet tool showed the proposed toolpath decreased the Z∆q value of surface waviness after polishing from 17.0 to 9.91.