Design analysis and applications of a 3D laser ball bar for accuracy calibration of multiaxis machines

Conventional techniques for measuring the volumetric errors of Cartesian coordinate machine tools are time consuming using a laser interferometer or step gauges. For multiaxis machines, where the spindle can swing, volumetric error calibration is even more difficult. In this study, a novel 3D laser ball bar (3D-LBB) has been developed for the easy setup and rapid measurement of the tool position relative to the worktable at any working point of multiaxis machines. The instrument makes use of one laser ball bar and two rotary laser encoders to detect the target path in the spherical coordinate system. The design of the instrument is discussed, and the error attributes are analyzed to enhance the instrument's accuracy. Applications to the volumetric error measurement of a robot and two types of machine tools have demonstrated the high-precision capability of this 3D laser ball bar.