<title>Influence of beam quality when welding with Nd:YAG and CO<formula><inf><roman>2</roman></inf></formula> lasers</title>

Abstract

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 CO<SUB>2</SUB> lasers now used. The solid-state laser displays a greater basic absorption of its beam wavelengths by technically relevant materials than the CO<SUB>2</SUB> 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 CO<SUB>2</SUB> laser manufactured by TRUMPF with different beam quality and power were used for the experiment. Whereas the CO<SUB>2</SUB> 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 large focal diameters. A drastic influence of the beam quality on processing efficiency was demonstrated for the CO<SUB>2</SUB> laser using identical processing parameters apart from the beam quality.