Development of a scanning touch probe with 5-axis measuring functions

The purpose of this study is to develop a five-axis scanning touch probe with high precision and low contact force. The development of scanning touch probe is consisted of three parts: mechanism design, optical path design, and rotation structure design. The mechanism design contains three parts, Z-axis 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, and 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 work piece only leads to change in the angles of X- and 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. The rotation structure refers to the principle of 5-axis machining design, and the two rotary axes (A- and C-axis) to join the self-developed scanning probe. This design can achieve independent measurements and eliminate the dynamic measurement error that three-axis scanning systems typically have. 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 0.6μm.