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.