Live Axis Turning

Abstract

The goal of this research is to develop a new method to create Non-Rotationally Symmetric (NRS) optical surfaces that overcomes the limitations of the current techniques and is fast, accurate and inexpensive. The term Live-Axis turning (LAT) has been coined to describe a lightweight, linear-motor driven, air bearing slide that can be used to fabricate NRS surfaces. The system described was developed at the Precision Engineering Center (PEC) in an effort to create a long-range fast tool servo to fabricate future NASA optics. The slide designed for the system is a triangular cross-section, lightweight (0.6 kg) honeycomb aluminum slide driven by a linear motor (64 N maximum force) resulting in an acceleration capability of 10 g. Additionally, a damper was added to the system to investigate the effects of physical damping on surface quality. The LAT axis was mounted on a Nanoform 600 diamond turning machine and both flat surfaces and tilted flat surfaces were machined to assess the performance of the system, which has a rise time of less than 2 msec. The 12.5 mm diameter flat surfaces had surface finishes of 16 nm without damping and 14 nm with damping, with both having a figure error of less than ½ wave. 25 mm diameter tilted flat surfaces, using a maximum stroke of +/- 1 mm at 5 Hz, had a surface finish of 24 nm without damping and 20 nm with damping. The figure error for the damped and undamped parts was +/- 25 microns.