Thermal Properties of a Hydrostatic Air Spindle (1st Report)

Analysis and Control of Thermal Deformations

Abstract

The purpose of this study is to evaluate and control thermal deformations of a hydrostatic air spindle for ultraprecision machine tool. According to measurements, the spindle growth to Z direction amounts more than 6 pm in some cases. Such quantity of deformations is not negligible for ultraprecision machining, and counter plans are discussed in the paper. It reports that numerical analysis is effective for foreseeing thermal deformations. As a result of theoretical analysis based on thermo hydrodynamic lubrication theory, numerically calculated value of the thermal displacements fits well to measured value. So, it is able to foresee the deformations. And the thermal deformation can be decreased effectually by supplying air to the spindle in lower temperature than that of the thermostatic chamber, in which the machine is settled. And in addition, by changing the temperature of the air supply, due to the pasture of time from the beginning of the rotation, settling time of the deformations can be shortened evidently. As above, this study makes some proposals about thermal properties of a hydrostatic air spindle and proves them theoretically and experimentally.