Proceedings of the
9th International Conference of Asian Society for Precision Engineering and Nanotechnology (ASPEN2022)
15 – 18 November 2022, Singapore

Aspects of spindle balancing and consequences on ultra-precision machining

Byron R. Knappa, Dan Oss and Dave Arneson

Professional Instruments Company, 7800 Powell Road, Hopkins, Minnesota, 55343, USA


Spindle balancing is of critical importance for direct machining optical surfaces-particularly in applications requiring surface form and finish on the nanometer-level. However, various aspects of balancing and its effects on precision machining remain misunderstood including the effects of unbalance on error motions. In this work, the consequences of unbalance vibration on error motion is explored deterministically by measuring error motions of a high speed air bearing spindle as a function of balancing grade. Another critically important issue addressed is torque ripple due encoder eccentricity that creates a vibration masked as unbalance. Incorrect diagnosis of the cause of this "apparent" unbalance vibration and attempts to correct it using balancing can lead to significant errors. Finally, a compensation approach is demonstrated to reduce the apparent unbalance caused by encoder eccentricity using error mapping.

Keywords: Precision balancing, spindle metrology, encoder error correction, torque ripple

PDF Download