A high-precision laser method for directly and quickly measuring 21 geometric motion errors of three linear axes of computer numerical control machine tools

Abstract

Error compensation has become an important means of improving the manufacturing and processing accuracy of computer numerical control (CNC) machine tools. Quick and precise measurement of the various geometric motion errors (GMEs) of CNC machine tools is crucial. We propose a novel laser method for the efficient and direct high-precision measurement of the 21 GMEs of a three-axis CNC machine tool, or three linear axes of a five-axis tool. A corresponding system was developed, comprising a fiber-coupled laser unit, sensor head, target unit, and beam-steering unit. The beam-steering unit was designed to perform high-accuracy 90°rotation of the measuring beam, and the target unit was designed to be sensitive to 18 GMEs of the three linear axes. Stability, repeatability, and comparison experiments were conducted to verify the performance of the proposed system. The results showed that the stability of the position error measurement is ± 6.3 nm. For straightness error measurement, the stability, repeatability error, and residual are within ± 60.3 nm, ± 0.5 μm, and ± 0.7 μm, respectively. These are within ± 0.12 arcsec, ± 0.5 arcsec, and ± 0.5 arcsec for the pitch and yaw measurements, and within ± 0.37 arcsec, ± 1.5 arcsec, and ± 1.0 arcsec for the roll measurements, respectively. For squareness error measurement, the repeatability error and residual are within ± 0.6 arcsec and ± 1.6 arcsec, respectively. Compared with a laser interferometer, the proposed system can measure the 21 GMEs of a three-axis machine tool with one-step installation. Without accuracy loss, the measurement efficiency is approximately 45 times higher than that of a laser interferometer, thus providing a new quick and accurate measurement method of GMEs and error compensation of CNC machine tools.

Comprehensive measurement model of geometric errors for three linear axes of computer numerical control machine tools

“…To improve the adaptability of measurement system and model, the same method was used to establish comprehensive measurement models for other types of CNC machine tools. The analysis showed that there are two different measurement modes in the measurement process because of the different types of machine tools [33]. In general, the default measurement mode occurs when the target unit moves with the work table.…”

“…To achieve quick and accurate measurement of the geometric errors of the linear axes of CNC machine tools, our research team proposed a series of measurement systems to direct measure simultaneously the 6DOF geometric error of a single linear axis [29][30][31][32]. A novel method for automatically measuring 21 geometric errors of the three linear axes of CNC machine tools with one-step installation was proposed, and a corresponding measurement system was developed [33,34]. Furthermore, the differences between the two measurement modes were analyzed [35].…”

A novel method for measuring radial and axial errors in a cylindrical coordinate system using a combined double ball bar

“…The advantage of these methods is that the results obtained generally do not include unnecessary error factors such as repeated installation and positioning errors of the measuring device. Feng et al [28][29][30] proposed methods for directly measuring multi-degree of freedom (DOF) geometric errors based on the principle of laser measurement, and the measurement efficiency of the new method is higher than that of conventional laser interferometer measurement. However, many equipment and lenses must be installed when using this method.…”

Simultaneous measurement method of six-degree-of-freedom absolute position and attitude based on light spots

“…In recent years, Liu et al have succeeded in measuring the 6-DOF geometric motion errors of a long linear stage simultaneously by combining the geometrical optics method and laser interferometer method 11 . Zheng F et al use two CCRs and one beam splitter (BS) to comprise a six-error sensing component and propose a direct method for simultaneously measuring six geometric motion errors (GMEs) of a single linear axis, and finally, realize the measurement of 21 GMEs of three linear axes of a machine tool 12 . These systems are implemented on mechanical platforms that require high precision displacement stages.…”