Effects of gas flow speed on bead geometry and optical emissions during laser powder bed fusion additive manufacturing
ISSN: 1355-2546
Article publication date: 17 April 2023
Issue publication date: 3 July 2023
Abstract
Purpose
Powder bed fusion processes are common due to their ability to build complex components without the need for complex tooling. While additive manufacturing has gained increased interest in industry, academia and government, flaws are often still generated during the deposition process. Many flaws can be avoided through careful processing parameter selections including laser power, hatch spacing, spot size and shielding gas flow rate. The purpose of this paper is to study the effect of shielding gas flow on vapor plume behavior and on final deposition quality. The goal is to understand more fully how each parameter affects the plume and deposition process.
Design/methodology/approach
A filtered-photodiode based sensor was mounted onto a commercial EOS M280 machine to observed plume emissions. Three sets of single tracks were printed, each with one of three gas flow rates (nominal, 75% nominal and 50% nominal). Each set contained single-track beads deposited atop printed pedestals to ensure a steady-state, representative build environment. Each track had a set power and speed combination which covered the typical range of processing parameters. After deposition, coupons were cross-sectioned and bead width and depth were measured. Finally, bead geometry was compared to optical emissions originating in the plume.
Findings
The results show that decreasing gas flow rate, increasing laser power or increasing scan speed led to increased optical emissions. Furthermore, decreasing the gas cross-flow speed led to wider and shallower melt pools.
Originality/value
To the best of the authors’ knowledge, this paper is among the first to present a relationship among laser parameters (laser power, scan speed), gas flow speed, plume emissions and bead geometry using high-speed in situ data in a commercial machine. This study proposes that scattering and attenuation from the plume are responsible for deviations in physical geometry.
Keywords
Acknowledgements
The authors would like to acknowledge Justin Gambone, Russ Dennison and Jason Trotter from GE Research for assisting in the planning and execution of experiments and metallography. This work was sponsored by GE Research center though Office of Naval Research contract N00014-18-C-2010. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the authors and do not reflect the views of the Office of Naval Research, or GE.
Citation
Stutzman, C., Przyjemski, A. and Nassar, A.R. (2023), "Effects of gas flow speed on bead geometry and optical emissions during laser powder bed fusion additive manufacturing", Rapid Prototyping Journal, Vol. 29 No. 7, pp. 1386-1394. https://doi.org/10.1108/RPJ-02-2022-0047
Publisher
:Emerald Publishing Limited
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