Correlation Between LPBF Gas Shield Homogeneity and Part Quality : A Matter of Flow Characterisation

With the strong growth of the metal additive manufacturing market, OEM and end-users are facing more and more stringent specifications to comply with standards for highly critical applications. Gas shielding delivered in Laser Powder Bed Fusion (LPBF) build chambers, is known to have a significant influence on the quality and reproducibility of manufactured components. By removing the by-products produced by the laser/powder interaction from the build platform such as vaporized metal (condensates) or spatters, this gas shielding strongly contributes to maintain a homogeneous quality throughout the part. Nevertheless, literature and feedback from the field have highlighted heterogeneity in velocities, consistency in time, and limitations on existing instrumentation, often correlated with downgraded part quality. This presentation deals with the results obtained through the development of a modular autonomous 3-axis robot, able to characterize gas shield velocity fields homogeneity in LPBF build chambers. Effects of changes in nozzle design for process improvement, correlation with CFD calculations and part quality have also been studied.

In this work, a 3-axis robot has been developed by Air Liquide-R&D to conduct automated mappings of instant gas velocities along the build plate. Measurements are possible on every kind of build chamber configuration, with different types of embed sensors. Ability to characterize gas flow at different heights, leverages the understanding of gas flows and provides valuable data to the user.