Fuel cell technology was considered a niche market for a long time. Due to the transition phase in energy generation and the search for alternative drives, the market demand might grow notably. For efficient mass production an increase of throughput in welding of metal bipolar plates, used to build the stacks in a fuel cell, is needed. High welding speeds require fast scan systems and high power lasers, both  available. However, it’s the welding process itself which determines the maximum reachable speed. Weld seam failures such as humping effects and undercut occur when a certain speed limit is exceeded.

Blackbird Robotersysteme set up a test rig integrating the 2D scan head intelliSCAN from SCANLAB and HOLO/OR’s latest development the Flexishaper, a full range adjustable beam shaper. The necessary beam shape was determined based on welding process simulations. The layout of the utilized beam shaper is the result of a combined optical design, integrating both diffractive optical elements (DOE) and scan system. The processing tests demonstrated to shift the speed limit of failure free welding speed from 45 m/min up to 70 m/min.

Adopting processing experience with DOEs

Thin sheet welding of bipolar plates has similar requirements to  laser powder bed fusion (LPBF) processes. Both require scan field sizes up to 500 x 500 mm² with a typical processing speed around 1m/s and below. Also in metal 3D printing the processing speed is not limited by the speed of the scanner or the available laser power, but it is mostly the process itself which limits the throughput. Thus, the encouraging laser welding results are the first step on the way to further optimize  LPBF processes as well.

“Our joint company holding creates the trust that is necessary for such a close cooperation to explore innovative solutions. Only in a setup like this you can openly analyze the upcoming market requirements and transfer the outcome in an optical design” recounts Georg Hofner, CEO SCANLAB.

“Our sister companies provide a construction kit for us, which we can translate into tangible benefits for our markets and customers based on our specific experience and application knowledge” adds Karl Christian Messer, CEO Blackbird Robotersysteme.

“This is exactly the kind of cooperation that creates high value products by combining our unique beam shaping expertise with our sister companies market deep understanding” concludes Israel Grossinger, Owner and President of HOLO/OR.

The next steps will be to test the laser welding concept in a larger scale setup and to pursue different applications in parallel. As the fiberSYS meets requirements of both LPBF and laser welding processes, the integration of DOEs into this scan system, particularly suited for multi head laser machines, was included in the development road map.