Passive vision measurement for robust reconstruction of molten pool in wire and arc additive manufacturing

Abstract Robust measurement of molten pool in wire and arc additive manufacturing can help better understand the geometrical size of fabricated parts and even offer feedback to control this process. Most of existing detection methods are not sufficient to express full geometric features of molten pool. In this paper, a novel passive vision sensing system using a single camera is designed based on the refraction principle of a biprism. Intrinsic and external parameters of left-right virtual cameras and their relative position are solved through a planar pattern, and an image pair is rectified by transmission projection. A global-based iterative matching algorithm is optimized for calculating the left-right parallax images of the image pair, and coordinates of space points are calculated via the triangle measuring method. The proposed sensing system and algorithms are validated by a standard cylinder. The results show that the width error of the calculated cylinder appearance is approximately 3.02% and the maximum height error is 4.15%. Finally, molten pool geometry in gas metal arc (GMA) additive manufacturing is restructured, proving the effectiveness of the virtual binocular vision system and the accuracy of the reconstruction algorithms.