Joining of multiple sheets in a butt-joint configuration using single pass laser welding with multiple spots

The introduction of high-power single mode fiber lasers has given deeper and narrower welds than previously seen using lasers. In some cases, the weld becomes too narrow and must be expanded to fit the geometrical shape of a given welding task. Instead of using only one beam, it was suggested to split the beam into multiple spots placed in a prespecified pattern. In this way, the dimensions of the weld pool could be controlled. In this work, the spots are placed on a row perpendicular to the welding direction. This provided the ability to control the final weld face by controlling the width and depth of penetration independent of each other with minimum heat input. An examination was conducted on how the weld cross section is influenced by spot distance, number of spots, power, and focus. It is shown that a weld seam can be widened in steps by using multiple spots, and the depth can be controlled independently from the width by adjusting the laser power. It is possible to produce a rectangular like cross section of the weld by choosing correct design parameters. For a pattern with multiple spots on a row, equal depth of penetration in the weld bead is reached if the edge spots have 5%–10% more power than the center spots. Basic rules for design of spot patterns are given for a configuration with a single mode laser and spot diameter of Ø85 μm. The ability to bridge gaps is increased in multispot welding compared to multiple single passes. The technique shows promising results in welding parts which resembles the conditions of a real production regarding robustness and tolerances.