环境温度对数控机床直线运动轴位置偏差的影响

Influence of Ambient Temperature on Positional Deviation of Linear Axis of CNC Machine Tool

机床使用时环境温度的变化,造成补偿后的定位精度变差."固定-支撑"的丝杠安装方式下热误差呈线性规律,据此建立了半闭环直线运动轴位置偏差随环境温度变化的预测模型.测试了半闭环控制运动轴在最高、最低两种环境温度下的位置偏差,拟合得到热误差随环境温度变化的规律.利用位置偏差预测结果,对螺距误差进一步补偿.结果表明:对于半闭环控制的滚珠丝杠进给系统,当环境温升8,℃时,位置偏差最大值由8mm增大到72mm,补偿后降为9.9mm,降低了96.87%,;对于全闭环控制的滚珠丝杠进给系统,当环境温升8℃时,位置偏差由2.5mm增大到17.7mm.根据本文所建立的模型进行补偿,可以提高定位精度的热稳定性,并且当环境温升大于6℃时,利用温度补偿的半闭环控制下定位精度大于全闭环控制下的定位精度.

When the machine tool is in work,ambient temperature change will cause the positioning accuracy after compensation to get worse. In this paper,a semi-closed loop linear motion axis position deviation prediction model was proposed according to thermal error linear law under ball screw fixing-support installation. Under semi-closed loop control system,position deviations of the whole stroke in two environments of the highest and lowest tempera-ture were tested. The law of thermal error changing with ambient temperature was obtained by data fitting. By use of the position deviation prediction results,the pitch error was further compensated for. The results show that for semi-closed loop CNC machine tool,when the ambient temperature rises by 8,℃,the maximum of position deviation increases from 8,μm to 72,μm,while it decreases to 9.9,μm after compensation and the decreasing rate is 96.87%,;for closed-loop CNC machine tool,when the ambient temperature rises by 8,℃,the maximum of position deviation increases from 2.5,μm to 17.7,μm. When the proposed model is adopted to compensate for pitch error,the thermal stability of positioning accuracy can be improved,and when the ambient temperature rise is higher than 6,℃,the positioning accuracy with pitch error compensation under semi-closed loop control system is higher than that under closed loop control system.