Multispot laser welding for increased gap bridgability

Laser beam welding is a promising technology to enable automated high-quality welding procedures at significantly higher processing speeds compared to conventional processes. However, its usability is often limited by gap bridgability. This disadvantage is related to the small laser beam spot sizes that require low gap sizes for joining, which are often practically not available, and the desired welding without additional filler materials to enable high processing speeds without direction restrictions. New possibilities of beam shaping for process control are also available now for high-power laser processing and they show promising results. The resulting complex effects require additional investigation to understand the mechanisms and the use of the technologies for process improvements. Therefore, in this work, advanced beam shaping optics with up to four separate laser beam spots was used to understand the impact of multiple-spot welding on the process dynamics and gap bridgability. Gap bridgability was measured by an opening gap setup, while spatter amounts as indicators of process dynamics were measured by high-speed imaging. It was shown that multiple-spot laser welding can increase the gap bridgability, probably due to the initiated melt flow toward the joining partners. Symmetric separation of the keyholes toward the sheets increased the gap bridgability, while additional low-intensity spots in the center were able to stabilize the melt pool and reduce spattering.