Abstract: The ball screw feed drive system of CNC(computerized numerical control)machine tools is characterized as multi-heat sources with strong time-varying heat rate. But the past work was scarely focused on the time-varying of the heat sources. This fact results in inaccuracy of predicting temperature rise and thermal error of the screw. In this paper， the heat rates of the multi-heat sources were captured by virtue of the FEM integrated with Monte Carlo method. Consequently， relationship of the ratio of each heat source to the total heat rate of the system with the running time was obtained. Then， based on heat ratios of the heat sources， the heat rates of the heat sources were determined using torque current of the servo motor in the ball screw feed drive system. Finally， numeric prediction model of temperature rise and thermal error of the screw was put forward based on finite difference method of one-dimension heat conduction equation， and the accuracy of the prediction method was verified by experimental results.

Key words: CNC machine tool, ball screw feed drive system, temperature field, heat conduction, thermal error