Application on-the-Fly Measurement of CNC Machine Tools

et al. 2021

Meas. Sci. Technol.

The geometric error measurement of computer numerical control (CNC) machine tools is developing towards automation and high precision. This not only improves the measurement efficiency, but also reduces the error caused by the long measurement time. This paper proposes a high-efficiency, automatic method of measuring 21 geometric errors of the three linear axes of CNC machine tools and establishes a comprehensive measurement model. The measurement system and model are applicable to linear axis geometric error measurement for all CNC machine tools. The measurement model was developed using rigid body kinematics theory and combined with the ray-tracing method. It mainly analyses the error crosstalk, system errors caused by optical components, laser beam drift, and non-parallelism errors between the measuring beams. ZEMAX was used to verify the model accuracy. Further, repeatability and comparison experiments were conducted to confirm the reliability and accuracy of the measurement system and model.

Section: Introductionmentioning

confidence: 99%

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

Jia

et al. 2021

Meas. Sci. Technol.

“…These methods can be classified into two categories: direct and indirect [11]. Indirect measurement methods require multi-axis motion of the machine under testing, including an artifact test [12,13], an R test [14,15], a ball bar test [16][17][18], and a tracking interferometer [19][20][21]. Conventionally, these methods have advantages such as high measurement efficiency and simple measurement configuration.…”

Section: Introductionmentioning

confidence: 99%

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

Feng

Int J Adv Manuf Technol

et al. 2020

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.

“…To the best of our knowledge, there is no instrument for directly simultaneously measuring 6DOF geometric motion errors of a rotary axis. There are many kinds of the indirect measurement methods, such as ball bar tests, R test, probing of artifacts, tracking interferometer, and machining tests [19,20,21,22,23,24,25]. These methods can be used to measure geometric motion errors of machine tools, and have the advantages of high measurement efficiency and simple measurement configuration.…”

Section: Introductionmentioning

confidence: 99%

“…These methods can be used to measure geometric motion errors of machine tools, and have the advantages of high measurement efficiency and simple measurement configuration. For example, Holub et al used a self-tracking interferometer in a small three-axis machining center to get all 21 geometric motion errors, and its measurement time was 33 min [19]. Generally speaking, indirect measurement methods have some common disadvantages of requiring complex decoupling and limited measurement range, which make it difficult to conduct an online compensation [22].…”

Section: Introductionmentioning

confidence: 99%

A Method for Simultaneously Measuring 6DOF Geometric Motion Errors of Linear and Rotary Axes Using Lasers

Feng

et al. 2019

Sensors

A novel method for simultaneously directly measuring six-degrees-of-freedom (6DOF) geometric motion errors of CNC machine tools was proposed, and a corresponding measurement system was developed. This method can not only be applied for measuring a linear axis, but also for a rotary axis. A single-mode fiber was used to separate the measuring unit from the laser source in order to ensure system thermal stability and measurement accuracy. The method has the advantages of high efficiency and good accuracy, and requires no complicated decoupling calculation. The positioning error of the linear axis and radial motion error of the rotary axis are measured by laser interferometry and other 5DOF geometric motion errors by laser collimation. A series of experiments were performed to verify the feasibility and effectiveness of the developed measurement system.