Influence of beam quality when welding with Nd:YAG and CO2 Lasers

Solid-state lasers with high beam quality are now available in the power range up to 4 kW. Since the beam of this laser type can be transmitted via flexible optical fiber for processing complex automotive structures, this laser has increasingly become an interesting alternative to the CO2 lasers now used. The solid-state laser displays a greater basic absorption of its beam wavelengths by technically relevant materials than the CO2 laser and thus a theoretically better coupling characteristic. However, in view of the relatively poor beam quality of the solid-state laser, the question as to whether greater processing efficiency can result still remains open. Welding experiments using transferable processing parameters were carried out to obtain reliable data for a direct comparison of both laser types. The most powerful Nd:YAG laser (HAAS HL 3006D) now available on the market as well as two CO2 laser manufactured by TRUMPF with different beam quality and power were used for the experiment. Whereas the CO2 laser shows advantages at low welding speeds and high welding depths, the solid-state laser can compensate for the distinctly poorer beam quality in the case of higher welding speeds that are typical for sheet-metal working. In this area, the Nd:YAG laser even showed distinct advantages when using larger focal diameters. A drastic influence of the beam quality on processing efficiency was demonstrated for the CO2 laser using identical processing parameters apart from the beam quality.