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Laser powder bed fusion of metallic components (PBF-LB/M) is gaining acceptance in industry. However, the high costs and lengthy qualification processes required for printed components create the need for more effective in-situ monitoring and testing methods. This article proposes multispectral Optical Tomography (OT) as a new approach for monitoring the PBF-LB/M process. Compared to other methods, OT is a low-cost process monitoring method that uses long-time exposure imaging to observe the build process. However, it lacks time resolution compared to expensive thermographic sensor systems. Monochromatic OT (1C-OT) is already commercially available and observes the building process layer-wise using a single wavelength window in the NIR range. Multispectral OT (nC-OT) utilizes a similar setup but can measure multiple wavelength ranges per location simultaneously. By comparing the classical 1C-OT and nC-OT approaches, this article examines the advantages of nC-OT (two channel OT and RGB-OT) in reducing the false positive rate for process deviations and approximating maximum temperatures for a better comparison between different build processes and materials. This could ultimately reduce costs and time for part qualification. The main goal of this contribution is to assess the advantages of nC-OT compared to 1C-OT for in-situ process monitoring of PBF-LB/M.
In-situ monitoring of the Laser Powder Bed Fusion build process via bi- chromatic optical tomography
(2022)
As metal additive manufacturing (AM) is entering industrial serial production of safety relevant components, the need for reliable process qualification is growing continuously. Especially in strictly regulated industries, such as aviation, the use of AM is strongly dependent on ensuring consistent quality of components. Because of its numerous influencing factors, up to now, the metal AM process is not fully controllable. Today, expensive part qualification processes for each single component are common in industry.
This contribution focusses on bi-chromatic optical tomography as a new approach for AM in-situ quality control. In contrast to classical optical tomography, the emitted process radiation is monitored simultaneously with two temperature calibrated cameras at two separate wavelength bands. This approach allows one to estimate the local maximum temperatures during the manufacturing process, thus increases the comparability of monitoring data of different processes. A new process information level at low investment cost is reachable, compared to, e.g., infrared thermography.
Bei der Realisierung von Oberflächen-Schutz-System (OSS) auf Betonflächen ist die tatsächlich erreichte Dicke der Beschichtung ein wesentlicher Parameter, der über die Funktionalität und Langzeitstabilität der aufgetragenen Schicht entscheidet. Die Firma IBOS und die BAM haben in den letzten Jahren gemeinsam einen funktionstüchtigen Prototyp eines Messgeräts zur zerstörungsfreien Schichtdickenmessung für Bodenbeschichtungen entwickelt. Hierin wird die Abkühlkurve eines vorher erwärmten Bereichs berührungslos mit einer IR-Kamera erfasst und mit einem Modell verglichen, was die Bestimmung der Schichtdicke ermöglicht. Im Rahmen dieses Beitrags wird die Umsetzung der Methode unter Laborbedingungen und in der Praxis auf der Baustelle erläutert und diskutiert.