Online monitoring of 3D printing of steel via optical emission spectroscopy

Giuseppe Pignatelli; Anne Strasse; Andrey Gumenyuk; Igor Gornushkin

doi:10.1515/mt-2021-2082

Article

Online monitoring of 3D printing of steel via optical emission spectroscopy

Giuseppe Pignatelli
Giuseppe Pignatelli (M.Sc. in Science and Engineering of Materials) was born in 1987, obtained a bachelor and master’s degree in material science, and is a Ph.D. scholar at BAM institutes, Berlin, with a project about online optical monitoring of metal additive manufacturing.
, Anne Strasse
Anne Strasse (M.Sc. in Production Engineering) was born in 1985 and is a research assistant at BAM working on in-situ monitoring of defect formation during the laser metal deposition process.
, Andrey Gumenyuk
Andrey Gumenyuk (Ph.D. in engineering from the Technical University of Aachen) was born in 1970 and is a group leader at BAM of the "Laser Beam and Hybrid Welding" group.
and Igor Gornushkin
Igor Gornushkin (Ph.D. in chemistry from the University of Florida) was born in 1958 and is a senior scientist at BAM in the group of chemical and optical sensors.

Published/Copyright: February 21, 2022

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From the journal Materials Testing Volume 64 Issue 1

Abstract

Additive manufacturing by laser metal deposition (LMD) requires continuous online monitoring to ensure quality of printed parts. Optical emission spectroscopy (OES) is proposed for the online detection of printing defects by monitoring minute variations in the temperature of a printed spot during laser scan. A two-lens optical system is attached to a moving laser head and focused on a molten pool created on a substrate during LMD. The light emitted by the pool is collected by an ultraviolet–visible (UV–vis) spectrometer and processed. Two metrics are used to monitor variations in the surface temperature: the spectrally integrated emission intensity and correlation coefficient. The variations in the temperature are introduced by artificial defects, shallow grooves, and holes of various widths and diameters carved on a substrate surface. The metrics show sufficient sensitivity for revealing the surface defects, except for the smallest holes with an under-millimeter diameter. Additionally, numeric simulations are carried out for the detection of emission in the UV–vis and near-infrared (NIR) spectral ranges at various surface temperatures. It is concluded that both the metrics perform better in the NIR range. In general, this work demonstrates that spectrally resolved OES suits well for monitoring surface defects during 3D metal printing.

Keywords: additive manufacturing; laser metal deposition; optical emission spectroscopy; optical sensor; process control

Corresponding author: Igor Gornushkin, BAM Federal Institute for Materials Research and Testing, Berlin, Germany, E-mail: igor.gornushkin@bam.de

About the authors

Giuseppe Pignatelli

Giuseppe Pignatelli (M.Sc. in Science and Engineering of Materials) was born in 1987, obtained a bachelor and master’s degree in material science, and is a Ph.D. scholar at BAM institutes, Berlin, with a project about online optical monitoring of metal additive manufacturing.

Anne Strasse

Anne Strasse (M.Sc. in Production Engineering) was born in 1985 and is a research assistant at BAM working on in-situ monitoring of defect formation during the laser metal deposition process.

Andrey Gumenyuk

Andrey Gumenyuk (Ph.D. in engineering from the Technical University of Aachen) was born in 1970 and is a group leader at BAM of the "Laser Beam and Hybrid Welding" group.

Igor Gornushkin

Igor Gornushkin (Ph.D. in chemistry from the University of Florida) was born in 1958 and is a senior scientist at BAM in the group of chemical and optical sensors.

Acknowledgement

The authors cordially thank Drs. Simon Altenburg, Nils Scheuschner, Christiane Maierhofer, and other colleagues from the ProMoAM project for their crucial contribution to this work. G.P. also acknowledges the research opportunities to fulfil his doctorate. I.G. and G.P. acknowledge Prof. Dr. U. Panne and Dr. K. Rurack for their support in this work.

Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
Research funding: This research has been funded by BAM within the focus area Material under BAM’s ProMoAM project.
Conflict of interest statement: The authors declare no conflicts of interest regarding this article.

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Published Online: 2022-02-21

Published in Print: 2022-01-27

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https://doi.org/10.1515/mt-2021-2082

Keywords for this article

additive manufacturing; laser metal deposition; optical emission spectroscopy; optical sensor; process control