Green disk lasers are the superior tool among industrial lasers operating in the visible wavelength regime, whenever a combination of high power and very good beam quality is desired. We report latest lab and application results, showing the potential of the technology beyond today´s commercially available products and use cases. TRUMPF´s green TruDisk lasers are based on a well-established and proven thin disk oscillator design with an added internal-resonator nonlinear crystal for the generation of second harmonic of 515 nm. Power level and beam parameter product of these devices have significantly been improved recently, leading to a commercially available product of 2 kW in combination with a 100 µm fiber core diameter and NA 0.1. Here, we report results on our new 3 kW green TruDisk laser, showing the progress achieved in making this power-enhanced laser a stable, reliable tool for industrial applications. Moreover, lab results will be presented that indicate the potential for further power scaling beyond 3 kW output power. The benefits of visible laser light in comparison to standard IR laser wavelengths around 1000 nm in terms of machining highly reflective materials are demonstrated. Due to the much higher absorption at room temperature, process stability, efficiency and reproducibility are significantly improved. The green laser light enables spatter-free weld connections of copper parts, and welding in heat conduction mode, such as on multiple layers of copper foils. This makes green TruDisk lasers an extremely versatile and easy-to-use tool for a range of applications, for example in the context of eMobility and power storage.
We report on industrial high-power lasers in the green wavelength regime. By means of a thin disk oscillator and a resonator-internal nonlinear crystal for second harmonic generation we provide 2000 W continuous-wave laser radiation at a wavelength of 515 nm, transported by a fiber with a 150 µm core diameter and NA 0.1. Application tests show that this laser is perfectly suited for copper welding due to the superior absorption of the green wavelength compared to IR, which allows the production of spatter-free weld spots and seams with an unprecedented reproducibility in diameter and welding depth. Now with 2 kW available power in the green, the welding performance for high quality welds can be increased compared to the already available 1 kW green laser system. The higher power leads to a larger melt volume and higher process efficiency. It is also possible to weld other materials with high quality results, for example stainless steel or aluminum. A particular advantage compared to the common IR lasers is the ability of the green laser for heat conduction mode because of the higher absorption. But due to the high beam quality also high-quality deep penetration welding is applicable, with the comfort to use scanner optics with a big field of work. This offers a whole range of new applications, e.g. remotedeburring of copper parts or producing a shiny copper surface by using shielding gas in addition. A further significant benefit of the green wavelength is that the surface condition does not influence the welding process, which allows to skip many expensive preprocessing steps such as tin-coating. Especially for e-mobility tasks the green 2 kW laser source is a suitable option for increasing productivity and quality: One example are copper foil stacks for battery production, which can be welded with higher speed and reduced spatter formation without ultrasonic pre-welding.
We report on industrial high-power lasers in the green wavelength regime. By means of a thin disk oscillator and a resonator-internal nonlinear crystal for second harmonic generation we provide 2000 W continuous-wave laser radiation at a wavelength of 515 nm. Careful shaping and stabilization of the polarization and spectral properties leads to an excellent optical-to-optical efficiency (pump to green) above 55%. The beam parameter product is designed and measured to be below 7 mm∙mrad which allows the transport with a fiber of 150 μm core diameter and standard numerical aperture of 0.1. Fiber and beam guidance optics are adapted to the green wavelength, enabling low transmission losses and stable operation. The laser, beam guidance as well as a chiller and the common customer interfaces are packaged within a compact footprint of less than 1 m². The green laser is equipped with a wide range of sensors and interfaces, enabling the user to integrate the laser in a production network and to benefit from features such as condition monitoring and predictive maintenance. Application tests show that this laser is perfectly suited for copper welding due to the superior absorption of the green wavelength compared to IR, which allows the production of spatter-free weld spots and seams with an unprecedented reproducibility in diameter and welding depth. With the new green 2 kW laser, the welding performance for high quality welds can be increased compared to the already available 1 kW system.
KEYWORDS: Copper, Continuous wave operation, Laser welding, Disk lasers, Laser applications, Near infrared, Laser sources, Resonators, High power lasers
We present application results of welding copper with multi-kW truly continuous-wave Disk Lasers at the green wavelength of 515 nm. By spatially combining three commercially available 1 kW TruDisk 1020 lasers, 3 kW of green cw laser radiation is provided by a fiber with 200 μm core diameter. We achieved the following highlights by applying this laser source to copper sheets of different thicknesses: Sputter-free full penetration welding of 0.7 mm thickness has been demonstrated with excellent quality and a feed rate of 25 m/min, much faster than comparable IR wobble processes. In deep penetration welding mode, high-quality welds with depths of 1 mm and 2 mm have been obtained with feed rates of 18 m/min and 8 m/min, respectively, even in thick copper sheets, i.e., at maximum heat dissipation. 3 kW of green cw radiation allow welding depths <3.5 mm. Having proven the large potential of multi-kW green cw lasers, we give an overview on the current lab results on the power scaling of the disk laser sources. We demonstrate <2 kW green cw power with a BPP of 2.5 mm·mrad, as well as <3 kW green cw power with a BPP of 5 mm·mrad, both devices being realized with a compact footprint of less than 1 m2. Summarizing, our application results prove the high-power green cw disk lasers to be the perfect choice for high-performance welding of copper with an excellent quality.
New processes and lasers are required to optimize and improve processes for laser welding of batteries. Highly reflective materials cause problems due to lack of absorption, stability, spatter and brittle intermetallic phases. We present solutions for battery welding using pulsed green lasers and nanosecond pulsed IR lasers. Green laser improved process stability and spatter formation between 0.1-0.8 mm penetration depth could be avoided. Nanosecond welding process differs from normal keyhole welding and formation of intermetallic phases can be suppressed. Analysis is based on highspeed camera measurements and metallurgical studies, showing significant improvement in the process and weld quality.
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