A gap-detection technique for laser beam butt welding

There are many factors that affect quality of the laser beam welds. Excessive gap in the joint is one of the most common reasons that cause weld faults, if the gap width can be measured in real-time, special techniques can be applied to eliminate or reduce weld faults. This paper reports a gap-detection technique. This technique uses dual-spot detection technology, which senses the light emission from the welding process. The light transmitted through the gap in front of the weld pool is a key signal that can be calibrated to tell the gap width. The second signal comes from the weld plume that indicates the health of the welding process. When these signals are fed into a close loop controller, a control system for laser beam welding with a better gap bridging capability has been developed.