Adaptation of Dual Cooling Jacket to a Machine Tool Spindle andFeed-Forward Control of its Temperature and Thermal Deformation. 1st Report, Development of Algorithm and Assessment of Dual Cooling Jacket System.

Abstract

The spindle head unit of most precision machine tools is temperature-controlled by forced circulation of liquid lubricant or coolant in order to reduce its thermal deformation. However, an over cooled or thermally unstable coolant may cause an unacceptable temperature distribution in the head unit. Thus it was proposed to incorporate two concentric cooling jackets into the unit. The inner jacket is for heat exchange with the undercooled oil, and oil at a constant temperature is circulated through the outer one so that the temperature distribution of the head unit may become uniformly moderate. Next, the feed-forward temperature control system was developed to control the oil temperature prior to heat generation at the spindle bearings. With a spindle head model and such an oil-temperature control device, it was demonstrated both from the experiment and the numerical simulation that the dual cooling jacket stucture is practically effective in decreasing the thermal displacement of the machine tool spindle as well as the machine tool itself in accordance with the related feed-forward temperature control system.