Welding aluminium pressure-tight in series with the laser

Challenges

The battery and the battery management controller (BMC) form the beating heart of electric vehicles. The controller monitors, regulates and optimises the performance, safety and service life of the battery by managing parameters such as charging status, temperature and cell voltage. The built-in performance electronics convert the direct current from the battery into the alternating current required for the drive. This generates heat, which can affect the electronics. Modern cooling devices offer a solution. They can be integrated into the BMC housing as a media-tight cover and connected to the vehicle's cooling circuit. The cooling unit must be in direct contact with the performance electronics to ensure effective cooling. This requires the cooling device to be absolutely flat. They should also be lightweight so as not to increase the weight unnecessarily and still meet the pressure test requirements of the car manufacturers. 

"Our customer requested a cooling plate made of drawn aluminium with dimensions of 900 x 200 millimetres - which was a real challenge, even for our most experienced specialists," explains Joseph Gampp, Head of Product Management at Feinwerktechnik hago. But challenging tasks are what drive the team. "After extensive trials and tests with TRUMPF, we have found a reliable solution and can now produce the cooling unit in series," Gampp notes proudly. 

Solutions

With BrightLine Weld, TRUMPF provides a laser welding process that has been proven over the years, enabling fast, non-porous and gas-tight welding of stainless steel. The Multifocus optics developed in 2021 increases the range of applications even further. In combination with BrightLine Weld, it can even be used for pressure-tight welding of aluminium. The optics split the laser beam of a TruDisk laser into a ring and core beam, which in turn are split into four spots and positioned in such a way that a common weld pool is created. The continuously open keyhole prevents the keyhole from collapsing, enabling the creation of a pore-free weld seam without gas inclusions, even during the fast welding process. 

Implementation

Initially, Joseph Gampp and his team tried to weld the aluminium cooling device using existing machines. The problem was that the initially tight weld seams could not withstand the required application pressures and eventually blew open. "That was a deal-breaker for our customer, as the car manufacturer requires pressure pulsation tests before approval," says Gampp, adding, "The entire assembly must withstand a specific pressure at least 100,000 times. As soon as we tried this out on our test components, our weld seams collapsed."  

To address this, hago's specialists collaborated with TRUMPF to develop a stable and, most importantly, production-ready process. At the TRUMPF Laser Application Centre, it quickly becomes evident that all challenges can be overcome with BrightLine Weld and Multifocus optics. The weld seam is sufficiently stable to withstand high pressures.  The parameters can be set so flexibly that the laser can also weld long seams quickly, reliably and distortion-free. This is important because the cooling device must be absolutely flat so that it is in direct contact with the performance electronics in the BMC and can cool them effectively. "We now manufacture the part with a reproducible flatness of less than one millimetre," says Gampp.  

By investing in a TruLaser Cell 7040 laser welding system with BrightLine Weld and welding optics with Multifocus technology, hago has laid the groundwork for series production of the cooling plate. The pre-series with around 3,000 parts has been completed. Within the next six years, over 610,000 cooling devices are expected to roll off hago's production line. "We have achieved what many people believed was impossible," says Gampp, adding proudly: "That's what sets us apart." 

Forecast

The concept of integrated cooling in battery management controllers is relatively new, but has great potential. Joseph Gampp hopes to be able to apply the knowledge gained from his collaboration with TRUMPF to other projects. "The technology aligns perfectly with our strategic direction", he says and is confident that the extensive development efforts will yield positive results. 

Date: 14/05/2025