Mechanism of Thermal Deviation Characteristic in Spindle System of Machine Tools

Thermal deviation in machine tools often caused by spindle rotation, feed motion, or environment temperature change has been widely studied but most of these studies have concentrated on improving or compensating for thermal deviation. No study has covered generating mechanism of thermal deviation, however, and guidelines remain to be established for improving their design. We studied thermal deviation in the spindles of machine tools and propose a thermal deviation model in the spindle taking into consideration the generation mechanism, finding that: (1) The thermal time constant that differs between spindle speed-up and slow-down occurs due to a large difference in the heat capacity of each spindle component. (2) The thermal time constant that decreases with increasing spindle speed occurs due the effect of heat capacity or the heat transfer rate of spindle components.