Development of a surface scanning touch probe for micro-CMM

This paper presents a surface scanning touch probe with low touch force for micro-CMM. The displacements of the probe are detected by a 2-DOF mechanism, which is comprised of a round frame, a tungsten stylus and a leaf spring fixed to the base. The design of the stylus is mounted at the centre of a stiff round frame, which in turn is fixed to a leaf spring; meanwhile, a live center which is installed in the center of the leaf spring to inhibit the Z-axis displacement error. When the probe touches the object, it only causes angular displacement of XY-axis. Therefore, it could achieve the characteristics of 2-DOF. In the design of optical path, a collimated LD is used as a light source and a 2D Position Sensor Detector are adopted as sensing components. Both of them are combined into the aforementioned mechanisms, then integrated with a rotation mechanism. Moreover, AC-axis servo motors were used to be a driver in rotation mechanism. Furthermore, a bearing was used as a guiding element with the rotating mechanism motor's driver. They could be installed on a micro-CMM to achieve complex surface scanning measurement. Finally, the experiment tests show that the measuring range of the probe is ±1 mm and ±1mm in X and Y directions, the measuring standard deviation is 55 nm, probing force is smaller 0.11 N/mm.