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Inert Gas Flow Speed Measurements in Laser Powder Bed Fusion Additive Manufacturing

Published

Author(s)

Jordan Weaver, Alec Schlenoff, David Deisenroth, Shawn P. Moylan

Abstract

Laser powder bed fusion (LPBF) is an additive manufacturing technology that uses a laser to selectively melt powder feedstock to build parts in a layer-by-layer process. For metals-based LBPF additive manufacturing, the interaction of the laser and powder feedstock creates byproducts such as a plume, spatter, and powder ejecta. Directional gas flow, typically nitrogen or argon, is used to remove or mitigate the negative effects of these byproducts. This report documents and presents gas flow measurements using hot-wire anemometers (HWA) for two different nozzles on a commercial LPBF machine and two different gasses at the NIST Additive Manufacturing Metrology Testbed (AMMT). The AMMT gas flow system generates comparable volumetric flow rates with argon and with nitrogen, which result in comparable flow speed profiles for both gasses. There are significant differences in the gas speed profiles along the gas flow direction (Y-position) and minimal differences perpendicular to the gas flow direction (X-position) with both machines. The speed differences with Y-position are in part due to the elevated inlet and outlet nozzles from the build platform. The average speed only decreases slightly from the inlet to the outlet despite these differences in the speed profiles. The grid nozzle on the commercial machine with a downward facing row of channels at the base of the nozzle increases the gas speed close to the build platform; however, non-uniform speed profiles remain. Gas speed and therefore gas speed measurements with HWAs are highly dependent on Z and Y position. This should be considered when prescribing machine performance protocols. Additional suggestions for measuring and reporting gas flow are made as well as recommended future experiments and simulations to assist in machine performance standards.
Citation
Advanced Manufacturing Series (NIST AMS) - 100-43
Report Number
100-43

Keywords

Hot-wire anemometer, gas flow speed, machine performance, plume, spatter, qualification, additive manufacturing

Citation

Weaver, J. , Schlenoff, A. , Deisenroth, D. and Moylan, S. (2021), Inert Gas Flow Speed Measurements in Laser Powder Bed Fusion Additive Manufacturing, Advanced Manufacturing Series (NIST AMS), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://doi.org/10.6028/NIST.AMS.100-43, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=933065 (Accessed May 23, 2022)
Created October 19, 2021, Updated January 4, 2022