Development of a 3D Laser Ball Bar Measurement System and Error Analysis of a Serial-Parallel Type Machine Tool

• Main Authors: Hai Wang, 王海
• Other Authors: 范光照
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/36680560008634149061

博士 === 國立臺灣大學 === 機械工程學研究所 === 92 === Techniques for performing accuracy testing of CNC machine tools can be found in many standards, such as the ISO 230. Most of the existing linear measurement instruments are one dimensional, such as the laser interferometer or step gauge. For the circular test of 2D motion, as specified in the ISO 230-4, some instruments have been developed, such as the, double ball bar (DBB), Contisure, and the latest laser ball bar (LBB). Although these instruments are capable of 2-axis error measurements, they are still sensitive to one dimension only. Conventional techniques for assessing machine tool accuracy conforming to ISO-230 specifications should adopt a variety of precision instruments, such as laser interferometer and optics, straightedge, electronic level, double ball bar, etc. It is a time-consuming process when changing different equipment for different accuracies. For multi-axis machines, where the spindle can swing, the error calibration is more difficult. A novel design, which integrates the merits of LBB and LTS (laser tracking system) is proposed in this research for the three dimensional measurements of moving object in real time phase. This system is based on the spherical coordinate principle containing only one precision Laser linear measurement device and two precision Laser rotary encoders in the gimbals base with a precision linear guide for slider motion. Such a system can be dragged by any 3D moving target with a magnetic head and freely moved in the space. Three sensors simultaneously record the ball positions and transform into the Cartesian coordinate in real time. It aims to measure the tool position relative to the worktable at any working point no matter the inspected machine is of 3D Cartesian type or parallel type multi-axis machines. The design of the instrument is discussed and the errors attributes are analyzed to enhance its accuracy. Practical applications will be addressed with respect to different error measurements, such as linear errors, circular errors, volumetric errors, and to different types of machine tools, such as Cartesian type and parallel type. The measuring result is compared to a commercial instrument, the maximum difference is around 2μm. All can be done simply with the developed 3D LBB system.