基于冗余联动的六轴联动数控机床加工轨迹误差优化

针对数控机床实际加工轨迹与理论轨迹存在误差的现象,提出利用六轴联动数控机床冗余联动特点优化该误差的方法。建立了一类六轴联动数控机床的运动学模型,并研究了其冗余联动特点。根据刀具接触点运动规律,以冗余旋转联动轴的运动优化刀具中心点运动轨迹误差和刀具轴线转动轨迹误差,从而实现加工轨迹误差的优化。在实际六轴联动数控机床上进行了抛光加工实验,通过应用所提出的轨迹误差优化算法,减小了抛光过程中的加工轨迹误差,降低了工件表面粗糙度,且保证加工后表面具有较高的均匀一致性,提高了抛光表面质量,从而验证了所提出方法的有效性。

Optimization of Machining Trajectory Error Based on Redundant Linkage in Six-axis Linkage CNC Machine Tool

To minimize the error between actual processing trajectory and theoretical trajectory in computer numerical control (CNC) machine tool, an error optimization method with the redundant feature of six-axis linkage CNC machine tool was proposed. Firstly, the kinematic model of a type six-axis linkage CNC machine tool which had three linkage axes and three rotation linkage axes was established. Then, the feature of redundant linkage of machine tool was researched, and the redundant rotation linkage axis was defined. With the trajectory model of contact point between tool and workpiece, the trajectory errors models of tool center point and axis vector were established. The errors models showed that the values of them depended on the motion of rotation linkage axes. The motion of redundant rotation linkage axis was applied to adjust the motions of all linkage axes. The values of the two errors became the minimum when the sum of the motion of rotation linkage axes became the minimum. And, it made the values of the processing trajectory error became the minimum at the same time. To demonstrate the validity of the optimization method, two polishing experiments were made in a six-axis linkage CNC machine tool. An experiment was made in the five-axis linkage mode that the redundant rotation linkage axis was motionless, and another experiment was made in the six-axis linkage mode. Because the lower machining trajectory error made the lower surface roughness and the higher of its consistency, compared with the five-axis linkage mode, the processing result in six-axis linkage mode was more excellent. The validity of the method was verified by the results of experiments.