旋转台几何误差的在机测量与辨识

On-machine measurement and identification for the geometric errors of rotary table

旋转台是多轴数控机床的基本组成部件,其几何误差对加工精度具有显著的影响。以旋转台轴线的4项定位误差及6项运动误差的测量与辨识为目标,利用标准球和接触式测头设计简易、高效的综合误差在机测量方案,提出基于综合误差的分步辨识方法。首先,在旋转工作台上安装高度不等、位置不一的标准球以构建测量点系,并在不同旋转角度下,利用直线轴的插补运动带动高精度测量头测量球心误差。然后,依据小误差理论和齐次变换原理依次构建4项定位误差和6项运动误差的分步辨识模型,辨识出全部误差项。在带旋转轴的机床上进行实验验证与实际应用,结果表明:利用辨识结果计算的预测值与实际测量值相比,绝对误差不超过0.004 mm;利用辨识误差项修正后的工件在机测量结果与三坐标测量值相比,绝对误差也不超过0.006 mm,满足了高精度的应用要求。该方法具有操作简单、占机时间少、辨识精度高的特点,适合加工现场的快速、短周期标定。

Rotary table is a basic component of multi-axis CNC machine tool,and its geometric error has significant impact on the machining accuracy. Taking the measurement and identification of four location errors and six motion errors of rotary table axis as the target,a simple and efficient comprehensive error on-machine measurement scheme is designed using the standard balls and touch-trigger probe.A multiple-step identification method based on comprehensive error is proposed. Firstly,the standard balls are installed at different altitudes and locations on the rotary table to construct the measurement point system. The deviations of the ball centers are measured by a high precision touch-trigger probe installed on the machine spindle at diffident rotation angles. Secondly,the multiple-step identification models of the four location errors and six motion errors are constructed based on the small error theory and homogeneous transformation principle one by one,and all the error terms are identified. The experiment verification and practical application were carried out on the machine tool with rotation axis. The results show that the absolute residual error is less than 0. 004 mm when comparing the predicted value calculated from the identified result with that the actual value measured by the touch-trigger probe. The absolute residual error is less than 0. 006 mm when comparing the measured result obtained with the touch-trigger probe and corrected using the identified error with the measurement result using 3D coordinate measuring machine. The measurement results show that the proposed method meets the requirement of high precision industrial applications. The method is simple to operate,consumes less machine time,has high identification precision,and is suitable for the quick and short cycle calibration on machining site.