Positional Shift of Melt Tracks at Oblique Beam Incidence in Laser Powder Bed Fusion and Laser Welding

The influence of an oblique angle of incidence of a laser beam on the position of the formed melt track in a powder bed is investigated experimentally. We introduce techniques for an accurate determination of geometric displacement effects to measure its precise position and shape. With increasing oblique incidence, an expanding lateral displacement is found that cannot be explained solely by geometric projection effects. Possible sources are considered and discussed, such as powder consolidation, intensity dependent displacement of the weld root, and a remaining contribution supposedly resulting from complex process dynamics during the interaction of laser and alloy in the melt zone. Compensation of the track displacement is necessary to achieve dimensional accuracy of printed parts.