Development of an optical measuring system for integrated geometric errors of a three-axis miniaturized machine tool

Miniaturized machine tool (mMT) is one kind of downsized machine tool derived from conventional machines to manufacture miniature parts. However, it is extremely difficult to calibrate an mMT due to its small dimension. This paper presents a novel method that uses laser diode and optics to measure integrated geometric errors (three translation errors and three rotational errors). The squareness error between two axes is calculated by the least-square method. These seven errors are acquired simultaneously in one setup for each motion direction. The proposed measuring system consists of laser diodes, beam splitters, and 2D position sensing detectors (PSDs). The relationship between the PSD readings and the geometric errors calculated by the algorithm based on homogeneous transformation matrix is derived according to the configuration of measured mMT. Simulation is carried out to prove the validity of this algorithm. Sensitivity analysis based on the mounting errors of system components is also presented in this paper. Finally, an experiment is executed to verify the feasibility of the proposed measuring method.