Novel R-test measurement system to detect thermally induced volumetric accuracy in horizontal machine tools

Abstract

Because of uneven temperature distributions, machine tools can generate thermal errors, which significantly contribute to machining errors. Previous research has shown that thermal volumetric errors can be directly measured using optical methods or indirectly calculated using error mapping methods. However, these methods are limited to or restricted by specific working conditions. Therefore, our study focused on developing a novel R-test measurement system for realising accurate thermal volumetric error measurements. The R-test measurement system consists of a three-dimensional (3D) ball array plate, R-test detecting head, temperature monitoring module, and data processing module. This system allows the measurement of deviation in the X, Y, and Z directions simultaneously at different fixed points in a 3D cube. Furthermore, considering the temperature and thermally induced volumetric accuracy, it was possible to derive the deformation tendency of the machine tool. An uncertainty analysis and systematic error corrections were conducted. The measurement uncertainty of this system is approximately 4 μm. The thermal volumetric errors were examined using the developed R-test measurement system and an interferometer under the same thermal conditions. The experimental results indicated that the R-test measurement system was able to accurately and rapidly detect thermal volumetric errors. This system provides a measurement technique with a low level of uncertainty, high accuracy, and low cost, which can be used to measure, compensate, and control the thermally induced volumetric accuracy of horizontal machine tools.