An improved thermal model for machine tool bearings

Thermal model for machine tool spindle is of great importance to machine tool design. Traditionally, the thermal contact resistance between solid joints and the change of the heat generation power with the bearing temperature are often ignored when thermal characteristics of a machine tool spindle are analyzed. This has caused inaccuracies in the thermal model. With the heat source models and the heat transfer models from Bossmanns and Tu [Journal of Manufacturing Science and Engineering 123 (2001) 495–501, International Journal of Machine Tools & Manufacture 39 (1995) 1345–1366], a model including the thermal contact resistance at solid joints based on a fractal model and the change of the heat generation power, viz. the amount of the heat generation per second, with the bearing temperature increases is developed. The complete thermal model is used to simulate the temperature distribution in grinding machine housing with a conventional spindle bearing. Compared with experiment, it is shown that the completed model is much more accurate than the traditional model which ignores the two important factors above. The thermal expansion of the housing system is analyzed.