A novel method for measuring squareness errors of multi-axis machine tools based on spherical S-shaped trajectories usin
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ORIGINAL ARTICLE
A novel method for measuring squareness errors of multi-axis machine tools based on spherical S-shaped trajectories using a double ball bar Xiaogeng Jiang 1,2 & Jingwei Jia 1,2 & Chang Liu 1,2 & Hao Wang 1,2 Received: 3 June 2020 / Accepted: 19 October 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract This paper presents a novel method to identify the squareness errors of computer numerical control (CNC) machine tools based on double ball bar (DBB) measurements. A series of spherical S-shaped paths are proposed to measure the squareness errors, instead of the generally used circular detection paths since the presented method requires only one experimental setup, and three translation axes are linked, which is more convenient and comprehensive. In this article, the coordinate transformation method and the method for dividing experimental paths evenly are used to solve the asynchronization between actual motion and DBB sampling process. The experimental data is then combined with the product of exponential (POE) model to calculate the three CNC machine tool squareness errors and applied to a spherical spiral testing path with the compensation of the diagnosed errors. The effectiveness of the method is verified by comparing the experimental results before and after the compensation. Keywords Squareness error . Double ball bar . Coordinated motion . Spherical S-shaped path
1 Introduction Multi-axis computer numerical control (CNC) machine tools are currently widely used to manufacture parts with complex features. The part quality mainly depends on the machining accuracy of the CNC machine tools, which is affected by the tool errors. By measuring and compensating various geometric errors of CNC machine tools, it is possible to improve their performance. Geometric errors are one of the critical factors responsible for machine tool errors and are divided into two categories: position-dependent geometric errors (PDGEs) and positionindependent geometric errors (PIGEs). The former, PDGEs, are mainly caused by the defects of the components, while the latter, PIGEs, are caused by the part-dependent machining errors and the assembly errors. In the error modeling process,
* Chang Liu [email protected] 1
Tianjin Key Laboratory of Advanced Mechatronics Equipment Technology, Tiangong University, Tianjin 300387, China
2
School of Mechanical Engineering, Tiangong University, Tianjin 300387, China
PIGEs are treated as constants and remain constant regardless of the position changes. In a three-axis machine tool scenario, the PIGEs of the translational axes are mainly the squareness errors between the three translational axes. That means the difference between the reference straight line inclination of the functional point trajectory (reference trajectory) in a linear moving component with respect to its corresponding principal axis, and about the reference trajectory of another linear moving component with respect to its corresponding linear motion principal axis [1]. The machine
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