New method and system of automatically moving a CMM probe tip into holes with submillimeter diameter and high aspect ratio

The demand of measuring the internal topography of holes with submillimeter diameter and high aspect ratio is increasing. However, moving a coordinate measuring machine (CMM) probe tip into a submillimeter hole manually is extremely difficult because the diameters of the probe tip and the hole are extremely small to be seen clearly with human eyes. An automatic measuring method and system is presented in this study to simplify the operation and improve the measuring efficiency. A micro CMM system was built. Two cameras were used to image the probe tip and the holes to be measured. The obtained images were magnified, and the edges of the probe tip and the holes were extracted. The image coordinates of the center points of the probe tip and the hole were obtained. The center coordinate values of the probe tip and the hole in the world coordinate system were achieved using the principle of binocular stereo vision. The probe tip was moved into the holes by the differences in the obtained coordinate values. Experiments were conducted. The effectiveness of the proposed method and system was verified by moving the probe tip into a hole with 1 mm diameter. This method can be used to assist in the measurement of deep submillimeter holes, especially in nonbatch measurement situations.