Development of a three dimensional scanning touch probe with high precision and low contact force

This study aims to develop a three dimensional scanning touch probe with high precision and low contact force. The overall design has two parts, mechanism design and optical path design. The mechanism design contains three parts, Zaxis system, XY-axis system, and probe mechanism. The Z-axis system applies the characteristic of the thin sheet spring to move vertically. In the design of XY-axis system, a micro-beam is employed, through which length, width, thickness of the micro-beam and corresponding dimensions of the leaf spring are designed according to the selected contact force. The freedom degree is limited to three. And the center of the mechanism is equipped with a stylus to inhibit displacement of the Z-axis. The contact between the probe and the workpiece only leads to change in the angles of Xand Y-axes, achieving the feature of 2-degree freedom. To enable rapid change for the probes, this study designs a probe mechanism, reliability of which is analyzed and validated with ANSYS software, so that the design of 3-degree freedom mechanism is completed. The sensor has a laser diode to coordinate with Position Sensor Detector (PSD) which works with the optical path designed to measure placement of Z-axis and angle placement of XY-axis. By validation through an experiment, the three dimensional scanning touch probe developed by this study has a measuring range of ±1mm×±1mm×1mm, and unidirectional repeatability of 0.6um.