Intermittent process measurement of a freeform surface profile with a circular triangulation laser probe on a machining center

摘要

This paper describes the development of a non-contact type system for measuring a freeform surface on a machine tool. A laser probe, model OTM-3A20 made by Wolf & Back Co., was integrated into a CNC machining centre as a non-contact sensor. An adjustment device for the laser probe was designed to minimise the cosine error caused by assembly inaccuracy. An alignment test of the measuring laser beam was carried out using a calibrated specimen. The systematic accuracy of the circular triangulation laser probe and a standard triangulation laser probe, with respect to the surface roughness, surface slope, and coating colour of the workpiece, was investigated by using an HP5529A laser interferometer system. The measuring system, which consists of a personal computer, a CNC controller of a machining centre, a Renishaw MP10 touch-trigger probe system, and the controller of the laser probe system, was integrated information-technically. Automatic measuring software was developed for the purpose of measuring path simulation, generation of NC codes, and error analysis of the measured data. The profile error of the tested object, measured by the laser probe and the coordinate measuring machine respectively was found to be within 45 μm. In this case, the tolerance of the designed part is about 50μm, so the developed system can be applied to the inspection of mould production in bakelite according to the experimental results.