Evaluation and compensation of laser-based on-machine measurement for inclined and curved profiles

摘要

On-machine measurement is being applied increasingly commonly to inspect deviations in machining, without removing the workpiece from the machine. A laser-based non-contact method has been introduced to measure complex profiles highly efficiently, but the accuracy of its measurement has not been assessed and compensated for. To improve the accuracy of the measurements of inclined and curved profiles using a laser displacement sensor, this study evaluates and compensates for deviations in the measured values by using compensation strategies. The factors influencing measurement accuracy are analyzed and the phenomenon of secondary reflection is explained on the basis of laser triangulation. For an inclined profile, the strategy whereby angle compensation is carried out followed by displacement compensation is used. For a curved profile, a corrected formula in which the coefficients are calculated according to the measurements is applied. The two patterns of coarse and fine compensation rely on the choice of the correction coefficient determined by the adaptive requirements of assessing accuracy. The results show that the surface roughness, measuring environment, and positional errors are less important than the inclination angle and displacement in affecting the accuracy. For the inclined profile, the measurement accuracy improved to -7.4 mu m similar to+6.7 mu m after compensation. For the curved profile, the deviations decreased by 71.5% and 91.9% compared with the original after coarse and fine compensations, respectively. Furthermore, the compensation strategies can be applied to the measurement of complex profiles in future work. (C) 2019 Elsevier Ltd. All rights reserved.