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Application of machine vision for the detection of powder bed defects in additive manufacturing processes

Korzeniowski Marcin, Małachawska Aleksandra, Wiatrzyk Marta

Materials Science Poland

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2023

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Vol. 41, No. 1

214--226

EN

The quality of the powder layers in the 3D printing process is extremely important and directly corresponds to the quality of the structures made with this technology. Therefore, it is essential to control it. It can be made in-line with a vision system combined with image processing algorithms, which can significantly improve control of the process and help with the adjustment of powder spreading systems, especially in case of difficult-to-feed powders like magnetic ones – e.g., Fe-based metallic glass powder – Fe56.04Co13.45Nb5.5B25. In this work, two algorithms – machine learning – Support Vector Machines (SVM), deep learning – Convolutional Neural Networks (CNN) – were evaluated for their ability to detect and classify the enumerated anomalies based on powder layer images. The SVM algorithm makes it possible to efficiently and quickly analyze the powder-spreading process. CNN, however, appears to be a more promising choice for the developed application, as they alleviate the need for complex image operations.

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Experimental Investigation on an Algorithm for Testing the Quality of Powder Distribution During 3D Printing Process

Korzeniowski Marcin, Małachowska Aleksandra, Biały Mateusz, Kanczewska Maria, Tkaczyk Michał, Grajczyk Krzysztof

Advances in Science and Technology. Research Journal

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2023

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Vol. 17, no 5

289--301

EN

Metal 3D printing is a modern manufacturing process that allows the production of geometrically complex structures from metallic powders of varying chemical composition. This paper shows the results of testing the powder feeding and distribution system of the developed 3D printer. The device using the SLM method (Selected Laser Melting) was developed by research team of WroclawTech and used in this investigation. The powder feeding and distribution system was tested using a vision system integrated into the printer control system. Thousands of tests performed made it possible to identify the reasons corresponding to incorrect powder distribution on the working field. In addition, a quality control algorithm was developed and implemented in the MatLab environment. Algorithms based on image analysis automatically identifies powder distributed in an unacceptable way. An 88% accuracy rate was achieved for identifying defects in all images within a dataset of 600 pictures, classified into following categories OK and NOK consisting of: recoater streaking, recoater hopping, super-elevation. The strength of the algorithm developed lies in its utilization of variations in shades of gray, rather than solely relying on the actual gray values. This approach grants the algorithm a certain degree of adaptability to changing lighting conditions.

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Application possibilities of scanning acoustic microscopy in the assessment of explosive welding

Korzeniowski Marcin, Białobrzeska Beata, Lewandowska Anna

Materials Science Poland

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2022

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Vol. 40, No. 3

93--111

EN

The last two decades have brought stable and impressive development accompanied by the industry acceptance of the use of high energy techniques based on energy obtained from explosive detonation energy. Such manufacturing processes are not only commercially viable, but also allow complex product shapes and unique combinations of metal sheets in terms of materials to be obtained; they enable the creation of composites which cannot be obtained by other conventional methods. Plated sheets are composed of a base material and a thinner plating material layer. An essential aspect in the validation of explosive welding is the quality control of joints made using this technology. The basic control methods are destructive tests – mainly metallographic, which reveal the microstructure at the connection boundary. Non-destructive tests, used in industrial practice, are classical, normalised ultrasonic tests of welding joints, conducted in accordance with ISO 17640:2017 and ISO 11666:2018 standards. Due to the relatively low thickness of the explosion-tested layers (2 mm and 3 mm single layers), which is the object of this study, assessing them using widely available ultrasonic techniques is limited. According to current scientific studies, the application of the scanning acoustic microscopy (SAM) is a prospective non-destructive method allowing for the qualitative and quantitative assessment of the continuity of the metallic connection on the contact surface of two materials. This paper presents the results of research on the quality of clads, welded explosively using a non-destructive research technique, namely SAM, verified with metallographic tests.

4

Hybrid welding of metal-polymer composites with a non-conducting polymer layer

Kustroń Paweł, Korzeniowski Marcin, Piwowarczyk Tomasz, Sokołowski Paweł

Biuletyn Instytutu Spawalnictwa w Gliwicach

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2021

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Vol. 65, No. 4

33--40

EN

Metal-polymer composites (MPCs) are becoming increasingly popular primarily because of their high strength-to-weight ratio. Metal-polymer composites consist of three layers, i.e. two external metallic sheets (linings) and the core made of plastic. The presence of the internal plastic layer makes MPCs impossible to join using conventional welding processes, which significantly limits their usability. One of the solutions to the problem involves the use of hybrid methods, e.g. ultrasonic method-aided resistance welding. The research work discussed in the article involved the development of a prototype test rig and a technology enabling the joining of the Litecor® composite with steel DP600. The joining process consisted of two stages. The first stage involved the removal of the non-conducting layer of polymer from the welding area and the making of an appropriate electric contact for resistance welding. The second stage was the classical resistance spot welding process. The development of the concept posed a challenge as it was necessary to develop an appropriate acoustic waveguide for high-power ultrasonic waves which, at the same time, could transfer loads in the form of electrode force as well as provide appropriate electric and thermal conductivity without compromising acoustic parameters during the welding process. The development of the test rig was followed by the performance of numerous tests aimed to identify the appropriate window of process parameters. Test joints were subjected to macrographic, strength, ultrasonic and topographic tests.

PL

Kompozyty metalowo-polimerowe (MPC) zyskują na znaczeniu głównie ze względu na wysoki stosunek wytrzymałości do masy. Składają się one z trzech warstw, tj. dwóch zewnętrznych metalowych arkuszy (okładzin) i rdzenia z tworzywa sztucznego. Obecność wewnętrznej warstwy tworzywa sztucznego sprawia, że nie można ich łączyć za pomocą konwencjonalnych procesów zgrzewania, co znacznie ogranicza zakres ich stosowania. Jednym ze sposobów rozwiązania tego problemu jest zastosowanie metod hybrydowych, np. zgrzewania rezystancyjnego wspomaganego metoda ultradźwiękową. W ramach podjętych badań opracowano prototypowe stanowisko badawcze oraz technologię łączenia kompozytu Litecor® ze stalą DP600. Proces łączenia opierał się na dwóch etapach. W pierwszym istotne jest usunięcie nieprzewodzącej warstwy polimeru ze strefy zgrzewania i stworzenie odpowiedniego styku elektrycznego do zgrzewania oporowego. Etap drugi to klasyczne zgrzewanie rezystancyjne punktowe. Opracowanie tej koncepcji było wyzwaniem ze względu na konieczność zaprojektowania odpowiedniego falowodu akustycznego dla fali ultradźwiękowej dużej mocy, który jednocześnie przeniesie obciążenia w postaci siły docisku elektrod, zapewni odpowiedną przewodność elektryczną i cieplną, a przede wszystkim zachowa swoje parametry akustyczne w trakcie procesu zgrzewania. Po opracowaniu stanowiska badawczego dokonano licznych badań w celu opracowania odpowiednego okna parametrów procesowych. Ponadto wykonane złącza były poddawane niezbędnym badaniom, w tym makrograficznym, wytrzymałościowym, ultradźwiękowym oraz topograficznym

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Possibilities of using scanning acoustic microscopy to analyze incompatibilities in braze welded joints

Piwowarczyk Tomasz, Korzeniowski Marcin, Majewski Dawid

Welding Technology Review

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2019

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R. 91, nr 10

7--15

EN

This article explores the possibilities of using non-destructive ultrasonic techniques to analyze the quality of lapped braze-welded joints. The tests were performed for 4 material groups (DC03+ZE steel and X5CrNi18-19 steel, aluminum alloys AW-5754 and AW-6061, titanium Grade 2 and copper Cu-ETP). As part of the work, additional materials and joint processes and its parameters were selected (TIG, MIG, laser). The quality of joints was monitored using scanning acoustic microscopy. Based on the A-scan and C-scan images, potential joints imperfections were determined. The possibilities of using advanced ultrasonic techniques to analyze the quality of braze joints was assessed.

PL

W artykule analizowano możliwości zastosowania nieniszczących technik ultradźwiękowych do analizy jakości zakładkowych złączy lutospawanych. Badania wykonano dla 4 grup materiałowych (stal DC03+ZE oraz X5CrNi18-19, stopy aluminium AW-5754 oraz AW-6061, tytan Grade 2 oraz miedź Cu-ETP). W ramach pracy dobrano materiały dodatkowe i warunki technologiczne wytwarzania złączy (TIG, MIG, laser). Kontrolowano jakość wykonanych złączy z wykorzystaniem skaningowej mikroskopii akustycznej. Na podstawie obrazów A-skan i C-skan określano potencjalne niezgodności połączeń, Określono możliwość wykorzystania zaawansowanych technik ultradźwiękowych do analizy jakości złączy lutospawanych.

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The effect of the weld pitch on shunting in robotic resistance welding

Sobolewski Sebastian, Korzeniowski Marcin, Piwowarczyk Tomasz

Biuletyn Instytutu Spawalnictwa w Gliwicach

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2019

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Vol. 63, No. 5

33--43

EN

The shunting of welding current during the process of spot resistance welding is a phenomenon which should be taken into consideration both at the design stage of load-bearing structures and during the process of their fabrication. As regards the intensity of shunting, the most important parameter is the distance between neighbouring welds (weld pitch). In spite of technological guidelines concerning the size of the pitch, scientific publications lack information about the correlation between the distance between welds and the size of the weld nugget. The article presents results of individual research aimed to analyse the effect of the pitch size on the diameter of the weld nugget. The welding process was performed using a robotic welding station. Verification (measurements of the weld nugget diameter) was based on advanced ultrasonic testing methods including scanning acoustic microscopy (SAM) and the RSWA (Resistance Spot Weld Analyser) devise provided with a phased-array mosaic transducer.

PL

Bocznikowanie prądu zgrzewania podczas procesu zgrzewania rezystancyjnego punktowego jest istotnym zjawiskiem, które należy uwzględnić zarówno na etapie projektowania ustrojów nośnych, jak również podczas procesu ich wytwarzania. Najistotniejszym parametrem z punktu widzenia intensywności tego zjawiska jest odległość pomiędzy sąsiadującymi zgrzeinami (podziałka zgrzein). Pomimo wytycznych technologicznych dotyczących wielkości podziałki, w literaturze brak jest informacji o zależności pomiędzy odległością pomiędzy zgrzeinami a wielkością jądra zgrzeiny. W artykule przedstawiono wyniki prac własnych, których celem była analiza wpływu wielkości podziałki na średnicę jądra zgrzeiny. Proces zgrzewania przeprowadzono na zrobotyzowanym stanowisku zgrzewalniczym. Do badań weryfikacyjnych (pomiar średnicy jądra) wykorzystano zaawansowane metody badań ultradźwiękowych – skaningową mikroskopię akustyczną (SAM) oraz urządzenie RSWA (Resistance Spot Weld Analyzer) z wieloprzetwornikową głowicą mozaikową.