Increased process stability during laser beam welding by high-frequency beam oscillation

Fig. 1: Processing head with resonance scanner

The goal of one of the research projects recently finalized at the Laser Zentrum Hannover e.V. (LZH) was to increase the process speed and stability during laser beam welding. High-frequency beam oscillation was applied to achieve a variable formation of the vapor capillaries and to reduce the energy per section as compared with the double focus technique. A processing head was not only designed and built, but also charcterized and optimized. The results were verified by sample processing of aluminum and in part zinc-coated steel materials.

During this research project several scanner processing heads for high-frequency beam oscillation were designed and realized. First trials have shown that in order to achieve a significant reduction in process pores high beam oscillation frequencies are necessary during the welding of aluminum AA5182. Thus, a high-frequency resonance scanner was designed with oscillation frequencies of up to 3710 Hz at arbitrarily adjustable usable oscillation strokes of more than 2 mm.

Aside from results with regard to pore reduction and increase of gap bridging, findings were also obtained about the influence of high-frequency beam oscillation on the capillary geometry and weld pool size.

This renders possible a more process-reliable welding of aluminum materials with high process stability and reduced energy per section than has so far been possible using the double focus technique. Thus, the application spectrum of existing systems is enlarged. Additional expenses when using a high-frequency resonance scanner processing head were evaluated and showed that the requirements are met for an economic use of the procedure in industrial applications.

The examinations were funded by the Federal Ministry of Economics and Technology through the German Federation of Industrial Research Associations “Otto von Guericke” (AiF) and supported by the Research Association on Welding and Allied Processes of the German Welding Society (DVS).

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The Laser Zentrum Hannover e.V. (LZH) carries out research and development in the field of laser technology and is supported by the Ministry of Economic Affairs, Labour and Transport of the State of Lower Saxony (Niedersächsisches Ministerium für Wirtschaft, Arbeit und Verkehr).