TRUMPF high-power laser dynamic beam shaping technology creates opportunities for the electric vehicle industry

It is reported that researchers from TRUMPF in Germany reported research on using dynamic beam shaping of high-power lasers to improve the productivity of hairpin stators, creating opportunities for the electric vehicle industry. Relevant research was published in "PhotonicsViews" under the title "Unlocking opportunities for the EV industry with beam shaping of high-power lasers".

The electric vehicle (EV) industry is experiencing unprecedented growth, driven by the global shift toward sustainable transportation. Laser welding has become an important technology in the industry, providing a convenient way to reduce production costs and expand manufacturing options for new battery and electric drive technologies. Although lasers have developed rapidly and power levels have reached 24kW or higher, how to effectively apply such high laser power in the welding process remains a challenge.

This article explores the gap between available laser power during hairpin welding and translating it into higher productivity. These limitations, especially in melt pool dynamics, prevent the full potential of high laser powers from being realized. To address this challenge, researchers have explored innovative beam shaping methods to overcome these limitations and utilize higher laser power during welding. Through detailed demonstrations, researchers show how new beam shaping techniques can be applied to make higher laser powers practical in welding, boosting productivity to unprecedented levels. This research not only helps optimize laser welding of electric vehicle components, but also opens the door to wider applications of advanced manufacturing technology.

superimposed laser beams

Welding the contacts of various batteries or electronic drives (mainly made of aluminum, copper and steel) requires a low-spatter process with low heat input and no pores in the weld. Additionally, the penetration depth and volume of molten material should be kept to a minimum. To meet these requirements, the process must be stabilized by controlling the shape and dynamics of the keyhole and surrounding molten pool.

In view of these characteristics, the researchers adopted a TRUMPF BrightLine Weld welding method to control the welding process by stabilizing the keyhole. This is achieved by superimposing two laser beams (a core beam and a ring fiber beam). This will have a stabilizing effect on the keyhole and surrounding molten pool. This innovative technology is used in a wide range of applications involving copper, aluminum and steel components, such as in the electric vehicle industry.

Figure 1 shows the beam profile of the superimposed laser beam from the TruDisk BrightLine Weld laser source in the focal plane. The sketch shows two beams superimposed and directed into the keyhole. The keyhole opening therefore has a conical shape compared to the case without the ring beam, which is the main effect for stabilization during machining. This phenomenon not only creates stable keyholes but also allows a significant increase in molten material near the surface. Both effects are critical to reducing spatter and void formation.

Figure 1 Effect of BrightLine Weld on the welding process. The laser beam is coupled to the inner fiber core and the coaxial ring fiber.

Table 1 Experimental configuration

Welding results

The laser-based hairpin welding process represents a significant challenge as it requires precise and fast connections while minimizing void formation, heat input and spatter. Preventing instabilities and achieving precise connections in hairpin stator designs requires a deep understanding of the process. At the same time, there is a need to maintain high process efficiency, minimize material loss, and optimize cycle times while maintaining structural integrity. Multimode lasers with 2-in-1 fiber guide function are mainly used for welding copper hairpins. The laser power is high and the quality requirements are strict. Compared to other high-power beam shaping technologies, TRUMPF's BrightLine welding technology (available for disk lasers and fiber lasers) is able to utilize the full laser power. Optics for fiber coupling are designed to support interchangeable fibers and integrate multiple beam outputs while maintaining beam quality integrity.

Figure 2 BrightLine Weld is an optical wedge used to adjust the power distribution between the core and ring fiber.

To address the challenges of short process times and minimizing spatter and porosity, BrightLine Weld technology was used to ensure a strong, conductive connection that significantly reduces porosity and spatter compared to processes using core fibers alone (see Figure 3). Dynamically adjusting the laser power split ratio between the core and ring fibers during the welding process provides a synergistic approach that combines fast processing times with reduced porosity generation. Throughout the welding process, the laser power alternates between the core and ring fibers to optimize the results. Although spatter is reduced, a small amount of spatter can still be observed under this process strategy.

Figure 3 Comparison of welding performance of the TruDisk 8000 multimode laser using single-core, static and dynamic BrightLine Weld processes. Corresponding spatter and pore images show improved speed and quality of the dynamic BrightLine mode process.

To address the challenges of short processing times and minimization of spatter and porosity, the application of BrightLine Weld technology ensures a robust conductive connection that significantly reduces porosity and spatter compared to processing using core fiber alone (see Figure 3). Dynamic adjustment of the laser power distribution ratio between the core and ring fibers during the welding process provides a synergistic approach that combines fast processing times with reduced pore generation. Throughout the welding process, the laser power alternates between the core and the ring fiber to optimize the welding effect. After adopting this process strategy, although the spatter was reduced, a small amount of spatter was still observed.

Source: Yangtze River Delta Laser Alliance