Gap Inspection and Alignment Using a Vision Technique for Laser Butt Joint Welding

Abstract

The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and penetration. Laser butt joint welding is one of the most accurate welding processes, because the laser ,spot size and welding gap are only 0.1-0.2 mm, and sometimes even smaller. It usually takes a long time to set up the welding operation, because the focused laser beam must be aligned with the centre of the welding gap, and the gap should be smaller than half the beam diameter. During the actual operation of laser butt welding, the laser beam must be properly aligned at any welding position. Also, the gap size must be maintained at a reasonable size or inspected on-line to make sure that it is small enough so that the laser beam cannot pass straight through the welding gap. This criterion limits the applicability of laser butt joint welding. A CCD camera and several image process techniques were employed in this research to capture the welding seam track, and determine the proper welding path and gap size. The results showed that the laser beam can be automatically aligned with the centre of the welding gap at any welding position, and the gap size can be inspected to make sure that it is always smaller than half the spot size.