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26 Apr 2022
Blue diode, adjustable-mode, and ultrafast lasers demonstrate promise for complex welding and cutting processes.
by Mike Hatcher in Munich
Laser applications in electric mobility were in sharp focus on the opening day of the LASER World of Photonics trade show, with several of the industry’s leading firms keen to show what is becoming possible with their latest sources.
In an applications panel session entitled “No e-mobility without lasers” - not that anybody at the Munich event is likely to argue with that conclusion - speakers detailed the myriad challenges faced by the industry, and how a wide variety of lasers could help overcome them.
To the Moon?
The sheer scale of one such challenge was outlined by Reiner Ramsayer from auto parts giant Robert Bosch. Ramsayer, an expert in joining and laser technology at the German company, pointed out the complexity of welding requirements for fuel cell components.
Incredibly, these would require an overall welding length of close to 400 meters for a single vehicle, with Ramsayer pointing out that scaling up production to make 1 million such vehicles would equate to the distance between the Earth and the Moon.
Despite that mind-boggling possibility, Bosch still sees lasers as the preferred technology for the industry’s switch to electric vehicles, with Ramsayer noting the importance of penetration depth and weld reliability for the kind of powertrain products made by the firm.
And there is certainly no shortage of options, with Ramsayer seeing the emergence of blue and green lasers as a positive development for applications needing a small weld depth.
“Lasers have great potential, but a deep understanding of the process is crucial,” Ramsayer concluded. “It’s not just about the laser, it [is about] simultaneous development of the product and the manufacturing process.
Blue power play
Among the latest laser options to hit the market is a 3 kW blue source from high-power diode specialist Laserline. Making its debut on the Munich show floor at this year’s event, the 445 nm “LDM Blue” was also the subject of a presentation by Mathias Schlett from the company.
Schlett highlighted the rapid progress being made in blue industrial lasers, for welding copper in particular. Laserline has now raised its maximum power level from 1 kW in 2018 and 2 kW in 2020, while also improving beam quality. Schlett expects those output powers to continue scaling, just like infrared diode lasers previously.
One specific application being targeted is welding of hairpin contacts, with the latest 3 kW laser able to weld significantly larger components. “The blue laser really enables a simplification of equipment and systems in hairpin welding,” he told attendees.
"In the case of keyhole welding of electrical conductors such as copper hairpins, larger cross-sections can be handled with moderate heat input using blue lasers only," added the firm in a release detailing the new system.
"Where hybrid solutions combining blue and infrared lasers continue to be required, less infrared energy is needed today."
Beyond hairpins, the source could also find applications in the production of power electronics, battery cell assembly, and to weld copper busbars - the metal strips that provide electrical contacts in individual battery cells.
Also targeting busbars is Trumpf, with the industrial laser giant unveiling a new welding system that it claims will help to extend the range of electric vehicles.
“Based on the 8 kW TruDisk 8000 laser, this new busbar welding system features a combination of new processing optics, new weld penetration depth sensors and software,” announced the Ditzinger-headquartered firm.
“All components are optimally matched. The system speeds up battery cell production and brings down the reject rate. The improved quality of the joint between the cells reduces electrical resistance, thereby extending the e-car’s range.”
Flexible beams
Speaking at the application panel forum, Falk Nagel from Coherent’s Rofin-Sinar division stressed that infrared wavelengths still offered the best option for deep-penetration welding, and highlighted the additional capability of the firm’s adjustable ring mode (ARM) 10 kW laser for e-mobility applications.
Like similar systems from other major laser companies, the dynamic beam shaping possible with ARM gives users remarkable control over exactly where and when the power in the beam is delivered to its target.
The Rofin-Sinar team has gone as far as investigating welding dynamics with the system inside a synchrotron, gaining new insights into exactly what is happening in the melt pool.
Nagel sees the flexibility of the system, and the quality of the welds produced, leading to applications in battery cell assembly, battery lid welding, and more besides.
Earlier in the session Scott White from MKS-owned Spectra Physics showed how yet another kind of laser - this time the firm’s picosecond-pulsed IceFyre source - could help cut electrode foils better, for use in lithium ion batteries.
White said that deploying bursts of pulses at a high repetition rate yielded a significantly faster scanning speed than with individual repeated pulses, while retaining or even improving material quality.
He thinks that the approach could offer a “terrific benefit” for the production of both copper-based anodes and aluminum-based cathodes - in doing so, helping to minimize battery failures in future electric vehicles.
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