五轴加工刀触点路径非线性误差补偿与修复方法

自由曲面五轴加工时,两个旋转坐标参与线性插补会引起刀具与曲面的实际切触点(刀触点)偏离预设的刀触点线性轨迹,形成刀触点路径的非线性误差。为有效降低该误差,提出一种基于理想刀触点路径的非线性误差补偿与修复方法。通过分析刀具姿态变化引起刀触点路径非线性误差的产生机制,分别建立机床运动学变换模型和刀触点路径的非线性误差模型,根据当前插补刀心点求出与之相应的插补刀触点,再求出插补刀触点与刀触点路径间的空间距离和垂足位置坐标,进而分别确定非线性误差的补偿距离和方向,对插补刀心点的位置进行实时修复后,再完成对5个进给轴的伺服控制。仿真结果表明,该方法能有效降低刀触点路径的非线性误差,对提高五轴线性插补时刀触点轨迹的控制精度具有实用价值。

Method on Compensation and Correction of CC Path Nonlinear Error for Five-axis Machining

While five-axis machining for the freeform surface,deviation is easily produced between the cutter contacting(CC)points and the given linear CC path because of the two rotation coordinates participating in the linear interpolation process,and the nonlinear error of the CC path is simultaneously formed.In order to effectively reduce the error,a nonlinear error compensation and correction method based on the ideal CC path was proposed.By analyzing the mechanism of the nonlinear error of CC path caused by the cutter’s attitude being changed,the machine tool kinematics transformation model and the model of the CC path nonlinear error were established respectively.The CC point was obtained firstly according to the current interpolation cutter center point.Secondly,the foot point coordinate and the spatial distance between the CC point and the CC path were calculated.The third step was to determine the compensation distance and direction of the nonlinear error respectively.After the position of the tool center point being real-time corrected,the servo control of the five feed axes would be carried out.The simulation results showed that the method can effectively reduce the nonlinear error of the CC path and had practical value for improving the control accuracy of the CC point trajectory during five-axis linear interpolation.