Precision measurement method of “cradle-type” five-axis machining center

Abstract

This study mainly measures the accuracy of closed impeller machining machines in aerospace. However, this machining center is different from others and belongs to a “cradle type” five-axis machining center. The measuring difficulty of cradle-type five-axis machining center is that the error accuracy of X, Y, Z, B, and C axes can meet the requirements when the Y-axis moving speed reaches 80 m/min and the maximum acceleration is 10 m/s2; and the C-axis maximum angular acceleration is 1.25 rad/s2; and the maximum angular velocity is 60 rpm. Therefore, the 24 theoretical models of accuracy error measurement for cradle type are derived at first. Combined with the theoretical model, the straightness of X, Y, and Z and the positioning accuracy of X, Y, Z, B, and C axes are measured by laser interferometer. In X, Y, Z, and C axes detection, two methods are adopted and compared. Then, the overall processing accuracy is measured through trial-cutting parts. The measurement results show that the second way (with temperature sensor) is better than the first measurement. Compared with the device without normal temperature sensor, the measurement of X-axis repeated positioning accuracy and positioning accuracy are improved by 8.5% and 23.6%, respectively. The positioning accuracy of Y-axis is improved by 16.7%. The repeated positioning accuracy and positioning accuracy of Z-axis are improved by 78.9% and 72.1%, respectively. The repeated positioning accuracy and positioning accuracy of the C-axis are improved by 20.4% and 7%, respectively. At the same time, it is also measured that the repeated positioning accuracy of B-axis is 15 μm. Finally, through the processing and testing of the trial-cutting parts, the processing error of the inclined cone table profile is 20 μm, which is far less than the design parameters of the original cradle-type five-axis machine tool. It provides efficient theoretical guidance and practical reference for similar five-axis machine tool measurement methods in the future.