数控机床进给系统热源发热率辨识与热误差预测

Heat Source Rate Identification and Thermal Error Predictions of Ball Screw Feed Drive System for CNC Machine Tools

数控机床进给系统具有热源多且各热源发热率时变性强的特点.但以往研究对各热源发热率的时变性关注较小,因此很难实现丝杠温升和热误差的精确预测.本文将Monte Carlo(MC)模拟集成FEM方法捕获到进给系统各热源的发热率,进而确定了各热源发热率占系统总发热率的比例--分配比随系统运行时间的变化规律.然后,基于进给系统各热源的发热率分配比,提出利用进给系统伺服电机的力矩电流计算各热源发热率的方法.最后,基于一维热传导方程的有限差分法,提出了丝杠温升和热误差的数值预测模型,并利用试验验证了模型预测的精确性.

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 onedimension heat conduction equation, and the accuracy of the prediction method was verified by experimental results.