Precision measurement of rail form error in a closed type hydrostatic guideway

Abstract

In this paper, a measuring device and measuring method are proposed to measure the rail profiles of a closed type guideway with submicrometer accuracy. The device is applied to hydrostatic bearing table and a mixed two-probe method (MTPM) is applied to measure the rail profile and linear motion error of the device. The effectiveness of the proposed measuring device is experimentally verified in two ways: In the case of the vertical direction, linear motion errors of the device tested on the upper and lower rail, respectively, are compared. In the case of the horizontal direction, the measured rail profiles using the proposed device are compared with directly measured profiles using a straight-edge and two probes (SEM). In the experiments on the vertical rail, both linear motion errors of the measuring device obtained from the upper rail and the lower rail show good agreement and the measurement accuracy is in a range of ±0.11∼±0.15 µm. In the experiments on the horizontal rail, the measured rail profile by the MTPM agreed well with the profile measured by SEM. However, because the rail has an abruptly varied surface, the measurement accuracy in this case deteriorated to a range of ±0.19∼±0.26 µm. From the experimental results, it is confirmed that the proposed measuring device with the MPTM is very effective to measure closed type multiple rail profiles with submicrometer accuracy.