Measurement Performance Evaluation of a Non-Contact Narrow Shape Measurement with Direction Switching

Abstract

The narrow inner geometry of machine parts requires high-precision machining and geometric inspection for high-performance products such as hydraulic components. However, it has been difficult to measure 3D inner surface geometry with conventional measurement methods. It is also difficult to measure the reference or datum surface and the narrow inner surface profile by the same measuring tool. Therefore, a novel optical measuring probe that can measure both the narrow profile and the datum surface by a thin probe that can be inserted into the narrow space and measuring the distance in the radial and depth directions was developed. To realize this measuring method, a distance measurement probe based on FMCW (Frequency Modulated Continuous Waves) method and a novel measurement direction switching technology using polarization direction control were developed. Experimental results show that the dimensional measurement accuracy by each measurement direction is micrometer order. The measurement results of a test piece with complex geometries showed good agreement with those obtained by CMM (Coordinate Measuring Machine).