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Towards multi-sensor monitoringand control of Directed Energy Deposition using a Laser Beam
University West, Department of Engineering Science, Division of Production Systems. (KAMPT)ORCID iD: 0000-0002-2527-1048
2023 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [sv]

Under senare år har omfattande insatser gjorts för att främja mer hållbara flygtransporter i Europa. De konventionella tillverkningsmetoderna som används inom flyg- och rymdindustrin kräver betydande mängder råmaterial, vars utvinning, bearbetning och användning har negativa miljöeffekter. Därför finns det ett starkt incitament att utveckla nya, mer material-effektiva tillverkningsmetoder.

Additiv tillverkning (AM), även känd som 3D-printining, har fördelen att direkt komma nära den slutliga formen på strukturer genom att lägga till material endast där det behövs, något som minimerar spill och förbättrar materialanvändningen. Dock utgör införandet av AM komponenter i säkerhetskritiska flyg- och rymdtillämpningar en betydande utmaning på grund av komplexiteten hos processerna. Denna komplexitet kan leda till tillverkningsvariationer som i sin tur kan resultera i defekter i de tillverkade strukturerna. Därför är framsteg inom automation genom utvecklingen av lösningar för övervakning och styrning under processens gång ett nödvändigt steg för att uppnå tillräcklig pålitlighet och repeterbarhet.

Denna avhandling presenterar en utveckling av multisensorövervakning och styrning av Directed Energy Deposition (DED) med en laservärmekälla (LB). DED-LB är en avancerad teknik som möjliggör tillverkning av storskaliga metallkomponenter nära den slutliga formen. I detta arbete har lösningar undersökts för övervakning av DED-LB med tillsatspulver och tråd. För fallet med tillsatstråd kan denna kompletteras med resistiv förvärmning (så kallad hotwire), vilket ger möjlighet att ytterligare finjustera värmetillförseln och förbättra smältprocessen. För övervakningsändamål undersöktes tre olika in-situtekniker för processens stabilitet och varians. Maskinseende och elektriska givare användes för DED-LB med tillsatstråd (DED-LB/w), medan optisk spektroskopi användes för övervakning både av processen med tillsatspulver (DEDLB/p) samt med tråd. Ett multisensorsystem baserat på de tre teknologierna testades för DED-LB/w. Det kamerabaserade systemet gav tydliga indikationer på avvikelser från nominella processförhållanden.

Spännings-och strömgivarnas signaler korrelerade med förändringar i processparametrar och återspeglade tydligt metallöverföringen. Spektrometersystemet indikerade förändringar relaterade till värmeöverföringen. Dessutom möjliggjorde analysen av erhållna spektra en detektering av förluster av viktiga legeringselement under DED-LB/p.

Slutsatsen från resultaten understryker behovet av multisensorövervakning, eftersom det inte bara möjliggör detektering och skattning av processförändringar utan även en bättre förståelse av deras grundorsaker. Den presenterade ansatsen är ett viktigt bidrag i utvecklingen av ett framtida robust och feltolerant automatiskt styrsystem.

Abstract [en]

In recent years, an extensive effort has been made to leap European aviation towards more sustainable transportation. Conventional manufacturing methods used in aerospace industry require significant amounts of raw materials, whose extraction, processing, and utilization have adverse environmental impacts. Thus, there is a strong motivation to develop novel, more material efficient fabrication methods. Additive Manufacturing (AM), also known as 3D-printing, offers the advantage of manufacturing near-net-shape structures by adding material only where it is needed, minimizing waste, and improving material efficiency. However, introducing AM fabricated structures as components in safety-critical aerospace systems poses a significant challenge due to the inherent complexity of AM processes. This complexity can result in variations that may lead to defects or inconsistencies in the fabricated structures. Thus, increasing automation by developing in-process monitoring, and control solutions is the vital step to reach the necessary reliability and repeatability.

This thesis presents development towards multi-sensor monitoring and control of Directed Energy Deposition (DED) using a Laser Beam (LB). DED-LB is an advanced technology that allows to manufacture large-scale, near-net-shape metallic parts. In this work, in-process monitoring solutions for DED-LB with feedstock powder and wire were investigated. The set-up of the latter was complemented by resistive pre-heating of the feedstock wire (hot-wire) which provided means of fine-tuning the heat input and improving metal fusion. Formonitoring purposes, three different in-situ techniques were investigated to monitor process stability and variability. Machine vision and electrical sensing were utilized during DED-LB with feedstock wire (DED-LB/w) depositions,while optical emission spectroscopy was used for monitoring processes with feedstock powder (DED-LB/p) as well as wire. A multi-sensorsystem based on the three sensing technologies was tested during DED-LB/w depositions. The vision system gave clear indications of variations from nominal conditions. Voltage and current sensors indications correlated to changes in process parameters and reflected well the metal transfer (liquid bridge) condition.The spectrometer system indicated well changes related to heat input. In addition, analysis of obtained spectra allowed to detect losses of vital alloying element during DED-LB/p. The main conclusion from the results underlines the need for simultaneous multi-sensor monitoring as it allows not only to detect and estimate process changes but also to better interpret their root causes. Such setup will positively enable a future robust, fault tolerant control system.

Place, publisher, year, edition, pages
Trollhättan: University West , 2023. , p. 62
Series
Licentiate Thesis: University West ; 41
Keywords [en]
Directed Energy Deposition, Laser Beam, in-situ monitoring, multisensor, resistive pre-heating
Keywords [sv]
Directed Energy Deposition, laserstråle, in-situ övervakning, multisensor, resistiv förvärmning
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
URN: urn:nbn:se:hv:diva-20864ISBN: 978-91-89325-50-0 (print)ISBN: 978-91-89325-49-4 (electronic)OAI: oai:DiVA.org:hv-20864DiVA, id: diva2:1807393
Presentation
2023-11-09, J111, Gustava Melins gata, Trollhättan, 10:00
Opponent
Supervisors
Note

Paper 3 is under acception but included in this thesis with CC BY-license.

Available from: 2023-11-09 Created: 2023-10-26 Last updated: 2024-01-15Bibliographically approved
List of papers
1. Hot-Wire Laser-Directed Energy Deposition: Process Characteristics and Benefits of Resistive Pre-Heating of the Feedstock Wire
Open this publication in new window or tab >>Hot-Wire Laser-Directed Energy Deposition: Process Characteristics and Benefits of Resistive Pre-Heating of the Feedstock Wire
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2021 (English)In: Metals, ISSN 2075-4701, Vol. 11, no 4, p. 1-25Article in journal (Refereed) Published
Abstract [en]

This study investigates the influence of resistive pre-heating of the feedstock wire (here called hot-wire) on the stability of laser-directed energy deposition of Duplex stainless steel. Data acquired online during depositions as well as metallographic investigations revealed the process characteristic and its stability window. The online data, such as electrical signals in the pre-heating circuit and images captured from side-view of the process interaction zone gave insight on the metal transfer between the molten wire and the melt pool. The results show that the characteristics of the process, like laser-wire and wire-melt pool interaction, vary depending on the level of the wire pre-heating. In addition, application of two independent energy sources, laser beam and electrical power, allows fine-tuning of the heat input and increases penetration depth, with little influence on the height and width of the beads. This allows for better process stability as well as elimination of lack of fusion defects. Electrical signals measured in the hot-wire circuit indicate the process stability such that the resistive pre-heating can be used for in-process monitoring. The conclusion is that the resistive pre-heating gives additional means for controlling the stability and the heat input of the laser-directed energy deposition.

Place, publisher, year, edition, pages
MDPI, 2021
Keywords
laser-directed energy deposition with wire, laser–metal deposition with wire, hot-wire, resistive pre-heating, in-process monitoring
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-16428 (URN)10.3390/met11040634 (DOI)000643283500001 ()2-s2.0-85104042477 (Scopus ID)
Funder
Vinnova, 2019-02752
Note

Finansiärer:Stiftelsen för Kunskaps- och KompetensutvecklingProjektnummer: 20160281, 20170060

Available from: 2021-04-14 Created: 2021-04-14 Last updated: 2023-10-26
2. In-process spectroscopic detection of chromium loss during Directed Energy Deposition of alloy 718
Open this publication in new window or tab >>In-process spectroscopic detection of chromium loss during Directed Energy Deposition of alloy 718
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2020 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 186, article id 108317Article in journal (Refereed) Published
Abstract [en]

In this work, a fast optical spectrometer was used to monitor the Directed Energy Deposition (DED) process, during the deposition of Alloy 718 samples with different laser power, thus different energy inputs into the material. Spectroscopic measurements revealed the presence of excited Cr I atoms in the plasma plume. The presence was more apparent for the samples characterized by higher energy input. The Cr depletion from these samples was confirmed by lower Cr content detected by Energy-Dispersive X-ray Spectroscopy (EDS) analysis. The samples were also characterized by higher oxidation and high-temperature corrosion rates in comparison to the samples produced with low energy input. These results prove the applicability of an optical emission spectroscopic system for monitoring DED to identify process conditions leading to compositional changes and variation in the quality of the built material.

Keywords
Spectroscopic system, Additive manufacturing, Directed energy deposition, Cr depletion, High-temperature corrosion
National Category
Metallurgy and Metallic Materials
Research subject
ENGINEERING, Manufacturing and materials engineering; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14733 (URN)10.1016/j.matdes.2019.108317 (DOI)000505221700047 ()2-s2.0-85075265930 (Scopus ID)
Available from: 2019-11-28 Created: 2019-11-28 Last updated: 2023-10-26Bibliographically approved

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Kisielewicz, Agnieszka

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