Unknown Surface Modeling Method Based on High-precision CMM

Abstract

Reverse engineering is typically applied to solve the CAD model of unknown parts. As modern industry requirements on the accuracy of complex surfaces increase, setting up the high-precision CAD modeling of unknown complex surface parts through reverse engineering becomes an interesting research topic. Here, we present a method that combines manual measurement and automatic measurement with a high-precision coordinate measuring machine (CMM) to measure unknown complex-surface to obtain CAD model. In this study, the unknown complex-surface was fixed on the CMM worktable, and cancelling the probe compensation function of PC-DMIS before measurement. Then, 490 measuring points were obtained by manually moving the probe with a diameter of 5mm to measure surface. The measured points generated the CAD model, the CAD model was offset a probe radius, and determined the rough contours of the surface. This CAD model was automatically measured in a CMM, and the function of the “automatic measurement model” was iterated to obtain a high-accuracy CAD model. Each measurement was arranged with 20×20 measuring points. The accuracy of the CAD model obtained by each iterative measurement would be improved, and finally a high-precision CAD model was obtained. After 7 iterations, the final accuracy of the unknown surface CAD model was as high as 0.004 mm as compared to that of the actual part.