A Micro Positioning Tool Post using a Piezoelectric Actuator for Diamond Turning Machines

Abstract

A micro positioning tool post, “Piezo Tool Post”, which was designed for high-resolution tool servo system of ultra-precision diamond turning machines, was developed and tested. The tool post utilizes a wire-cut parallel spring mechanism, a PZT stack and a capacitance gage to measure the displacement up to ±25 μm. To eliminate the non-linearities of PZT actuator and to improve the stiffness and response, two types of closed-loop controllers were applied to the tool post : (A) one with a notch filter ; and (B) one with state feedback using a state observer. Both controller were able to achieve a band width of several hundred Hz without resonant peaks, a resolution of <5 nm, static stiffness of >2.4 kN/μm and static stability. But it was proved that only controller (B) can improve the dynamic compliance at the resonances. The actual resolution of depth-of-cut control of <25 nm was determined by cutting tests on aluminum alloy. © 1988, The Japan Society for Precision Engineering. All rights reserved.