Efficient air flow control for remote laser beam welding

Abstract

Efficient air flow control plays a crucial role for the reliability of remote laser beam welding applications.Local air flows are helpful to suppress unfavorable interactions between laser radiation and welding fumes as a result of absorption and/or scattering effects. On the other hand, local and additional global flows have to be applied for emission control to protect optical components and workpieces from contamination and to avoid harmful air pollution of the atmosphere. However, the appropriate design of complex air flow systems under the additional condition of preferably low overall gas consumption is still a challenging task because a high number of decisive factors and a multitude of possible interactions complicate the pure empirical selection and positioning of suitable flow components and the adjustment of the numerous control parameters. This paper presents the results of a combined and complementary approach of experimental and theoretical investigations to meet these challenges. The experimental work was focused on the aspects of interaction mechanisms between the laser beam and the welding fume. Besides the characterization of process emissions some of the requirements of stable remote processing with maximum penetration depth are revealed. In contrast, the theoretical work describes a general methodology on how to support the optimization of the cabin air flow by means of Computational Fluid Dynamics (CFD) models in combination with Design-of-Experiments (DoE) approaches.

Impact of fume particles in the keyhole vapour

“…Especially when processing with a CO 2 laser, where plasma forming is expected, an application of shielding gas can significantly improve the energy input by blowing the plasma away from the laser beam circumference. When processing with a fiber laser, Mahrle et al [20] found that a gas flow of 2 m/s applied by a shielding gas nozzle from a rectangular position to the straight upwards directed vapor plume is sufficient to suppress interactions between the laser beam and the plume. It seems that a reduction of the particle density in the plume reduces the energy absorption and/or scattering by the plume.…”