Axial thermal error compensation method for the spindle of a precision horizontal machining center

Thermal error of spindle has great influence on the performance of the machine tool. In order to alleviate those impacts, an axial spindle thermal error compensation method is introduced in this paper. Firstly the temperature field and thermal deformation of the spindle system are simulated by finite element analysis (FEA) with a high accuracy, as the boundary conditions are set according to the measured parameters such as the speed of the spindle, temperatures of coolant oil, and ambient temperature etc. Secondly, magnetic temperature sensors and non-contact tool setting system are used to test the temperature data and axial thermal deformation respectively. Additionally Spearman´s rank correlation analysis is employed to determine the place and the number of critical temperature points which are closely correlated to spindle axial thermal deformation. By establishing a model between spindle temperature field and its axial thermal deformation and compensating the thermal error with predicted data which are sent to the CNC system directly, the axial thermal error at varying spindle speeds is effectively reduced up to 92 percent, from more than 225 microns to within 20 microns. Therefore, the spindle thermal error is reduced and the machining accuracy can be kept at a high level.