Advancements in laser material processing, particularly in EV battery production, require innovative solutions. Dynamic beam control of fiber lasers has emerged as a promising technology to meet these needs. This contribution examines the challenges in EV battery production and the solutions provided by these lasers. Through dynamic beam control, fiber guided lasers enable precise and efficient welding of copper and aluminum components. Adjustable beam parameters such as intensity, shape, and size enhance precision, productivity, and material utilization. These capabilities of dynamic beam-controlled lasers drive innovation in manufacturing processes for the EV industry and beyond.
We report technological advances in thin-disk laser technology enabling further scaling of average output power and beam quality. A newly developed resonator design serves as a universal building block for industrial-grade thin-disk lasers from 6 to 24 kW. The robust resonator design allows for power levels beyond 12 kW from a single disk with a beam parameter product (BPP) of ~ 4 mm*mrad. By polarization combining of the output of two resonators, i.e. two laser disks, the power can be doubled to up to 24 kW while maintaining the good beam quality. The mentioned properties render the new TruDisk lasers ideal for high-throughput laser material processing. With slight modifications of our setup we also achieve a BPP of ~ 2 mm*mrad with < 8 kW output power. The optical setup provides two fiber outputs, switchable on a < 100 ms timescale, that can be equipped with different types of exchangeable processing fibers for maximum productivity and flexibility. It is possible to use TRUMPF’s BrightLine Weld (BLW) technology in combination with a 50/200 µm dual-core fiber at each fiber port. The BLW technology allows for distribution of the laser power between the 50 µm fiber core and a 200 µm ring, enabling a significant increase in productivity and quality in welding. We use BLW with a 50/200 µm dual-core fiber for welding of stator hairpins for electric drives at a quality and speed unattained so far.
KEYWORDS: Beam shaping, Laser welding, Copper, Optical coherence tomography, Laser applications, Solid state lasers, Aluminum, Energy efficiency, Disk lasers, High power lasers
Recently, a new laser welding technology called BrightLine Weld has been introduced by TRUMPF. It is based on applying a TruDisk thin-disk solid-state laser with a so called two-in-one fiber delivery optical cable. In combination with a novel system of variable laser power coupling into the inner as well as the outer fiber core, an application-tailored laser power distribution is created. This enables a new degree of freedom through beam shaping for laser keyhole welding. The process benefits are significantly higher achievable feed rates during welding, minimal spatter formation and highest weld seam qualities. This paper presents latest results on welding of steel, aluminum and highly reflective materials such as copper using BrightLine Weld. The welding of gear parts has been performed exploiting the full feed rate performance with highly alloyed steels. Endurance strength tests show that the weld seam characteristics of these novel high-speed welds fulfill state-of-the-art requirements. We also report on results in weld penetration depth monitoring, applying optical coherence topography (OCT) to copper welding samples. Due to the keyhole stabilization in a wide range of feed rates and their respective penetration depths, the keyhole depth monitoring becomes widely applicable and supports the process especially in terms of reliability. Furthermore, an outlook on full penetration welding of tubes and profiles will be given. We will show first application results demonstrating the impact of BrightLine Weld on spatter prevention both on the top and on the bottom side of the weld seam.
Due to their numerous advantages in system technology, especially fiber optic beam delivery, solid state lasers have become state of the art for welding. Even so the obstacle of the so called "spatter regime" has been waiting for an industrial solution in order to gain high productivity.
In general the spatter regime occurs in a distinct welding speed range. With deep penetration welding applications like in power train the spatter regime shows up at welding speeds of 5 to 6 m/min. Beyond 6 m/min the mass loss due to weld spatter reaches a level resulting in undercuts of the weld seam and potentially internal porosity, both of which reduce the mechanical strength properties of the part. Moreover, if spatter particles are present or dislodged when welded parts are being assembled, the gear box itself may incur in-service damage.
This report presents recent results addressing this problem and demonstrates significantly reduced spatter when welding at high speed, which today has only been achievable with CO2 laser beam welding. This new process approach is based on applying the disk laser with a special new beam forming method. The welding speed can be increased significantly and the energy efficiency of the process can be reduced dramatically.
New technological developments in high power disk lasers emitting at 1030 nm are presented. These include the latest generation of TRUMPF’s TruDisk product line offering high power disk lasers with up to 6 kW output power and beam qualities of up to 4 mm*mrad. With these compact devices a footprint reduction of 50% compared to the previous model could be achieved while at the same time improving robustness and increasing system efficiency. In the context of Industry 4.0, the new generation of TruDisk lasers features a synchronized data recording of all sensors, offering high-quality data for virtual analyses. The lasers therefore provide optimal hardware requirements for services like Condition Monitoring and Predictive Maintenance. We will also discuss its innovative and space-saving cooling architecture. It allows operation of the laser under very critical ambient conditions.
Furthermore, an outlook on extending the new disk laser platform to higher power levels will be given. We will present a disk laser with 8 kW laser power out of a single disk with a beam quality of 5 mm*mrad using a 125 μm fiber, which makes it ideally suited for cutting and welding applications.
The flexibility of the disk laser platform also enables the realization of a wide variety of beam guiding setups. As an example a new scheme called BrightLine Weld will be discussed. This technology allows for an almost spatter free laser welding process, even at high feed rates.
In continuous wave keyhole-mode laser welding of high strength steel alloys hot cracking can occur. The hot crack susceptibility depends on the mutual interaction of several factors like the welding parameters, the alloy composition and the weld fixturing. In this paper we focus on the influence of the welding parameters and investigate the dependency of the laser power, the welding speed and the laser wavelength on the crack formation. X-ray images are used to visualize the hot crack patterns, which exhibit a pronounced periodicity. To influence the hot crack formation, the incident energy input into the process was adapted. For specific welding parameters, we show exemplarily the prevention of hot cracking by the use of a twin-spot optics.
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