Qualification of high-power 532 nm cw fundamental mode CBC fiber lasers for innovative processes and systems for macro material processing of pure copper materials for electromobility, power electronics and automation
Battery-powered drive systems will be used for almost all mobility systems in the future. Parts and components made of materials such as copper and aluminum with very good electrical and thermal conductivity are key components for energy storage systems, power electronics, control and required cooling structures, among others. Laser processes are advantageous for the flexible processing (joining, separating, additive manufacturing, particularly selective laser beam melting) of the materials mentioned. Near-infrared (NIR) lasers with brilliant beam quality are used, which also offer high spatial resolution. The minimum intensity required for sufficient process stability and process efficiency when using NIR laser radiation generally only allows processes in keyhole mode for copper (formation of a vapor capillary required).
The high degree of reflection of copper for processing with classic NIR lasers is a limiting factor. Stable processes without sharpeners in the molten phase, such as heat conduction welding or solid-phase processes such as heat treatment/annealing, are not possible with NIR laser radiation for copper, or only possible with restrictions. For lasers in the visible range with a wavelength of 532 nm (green), the actual measured absorption on polished copper at room temperature increases from 1070% to 3% compared to NIR fiber lasers with 42 nm, and for the technically relevant temperature range up to the melting point from 10% to 29%, thus allowing an increase in process efficiency by a factor of 3 to be expected.
As part of the CBC-Green research project, the task was therefore set to realize the welding of copper materials using a green fundamental mode laser from CIVAN Advanced Technologies. KH Arnold Maschinenfabrik GmbH & Co. KG (Fa. Arnold) was assigned the task of developing a beam guidance and modulation system within the research association, which was to be integrated into an existing system at Fraunhofer IWS.
In the first step, it was necessary to design an optics box that shapes the raw beam accordingly and uses a beam guide to redirect the laser beam so that it reaches the component. For the optics box, the calculations required for the design of the mirrors were carried out based on the laser's caustic data and the requirements for creating the demonstrator. The optics box was designed and manufactured based on the calculated data. The individual parts of the optics box were assembled on site at Arnold and delivered to Fraunhofer IWS. There, the beam guide in the existing Fraunhofer IWS system was revised so that the green laser used here could be used. At the same time, the optics box was installed and integrated into the control system. Our commissioning engineer had programmed the interfaces here according to the project participants' wishes so that the green laser could be used on the system via the machine control system. While the laser was being tested, Arnold was available to provide support and make any necessary adjustments for the remainder of the project period.
Project partners:
thyssenkrupp Systems Engineering GmbH
Fraunhofer IWS Dresden
Siemens AG Corporate Technology
CIVAN Advanced Technologies (Israel)