The experiments were conducted at the TOMCAT beamline of the Swiss Light Source at PSI, with the miniaturized LPBF printer developed in the group of Dr. To facilitate the measurement of the width and depth of the melt pool in X-ray images, the Image Analysis Hub of the EPFL Center for Imaging developed an approach that makes it easier to visualize small changes associated with the liquid metal and a tool for annotating the melt pool geometry.ĭetecting These Defects Using SoundIn a joint venture with the Paul Scherrer Institute (PSI) and the Swiss Federal Laboratories for Materials Science and Technology (Empa), the EPFL team formulated an experimental design that melded operando X-ray imaging experiments with acoustic emission measurements. During unstable keyhole regimes, when the molten powder pool delves deeper than intended, it can create pockets of porosity, culminating in structural flaws in the end product. These instances, termed "inter-regime instabilities", can sometimes prompt shifts between two melting methods, known as "conduction" and "keyhole" regimes. Occasionally, due to variables such as the laser's angle or the presence of specific geometrical attributes of the powder or of the part, the process might falter. When the laser interacts with the metal powder, creating what is known as a melt pool, it fluctuates between liquid, vapor, and solid phases. Nevertheless, this promising method isn't devoid of challenges. This technique enables the crafting of bespoke, complex parts like lattice structures or distinct geometries, with minimal excess. The laser moves across this layer, melting specific patterns based on a digital blueprint. Rather than melted plastic, it employs a fine layer of microscopic metal powder, which can vary in size from the thickness of a human hair to a fine grain of salt (15–100 μm). Think of LPBF as the metallic version of a conventional 3D printer, but with an added degree of sophistication. Essentially, it uses a high-intensity laser to meticulously melt minuscule metal powders, creating layer upon layer to produce detailed 3D metallic constructs. How Does LPBF Manufacturing Work?LPBF is a cutting-edge method that's reshaping metal manufacturing. Subscribe to Technology Networks’ daily newsletter, delivering breaking science news straight to your inbox every day. Milad Hamidi Nasab, remarked, "The synergy of synchrotron X-ray imaging with acoustic recording provides real-time insight into the LPBF process, facilitating the detection of defects that could jeopardize product integrity." In an era where industries continuously strive for efficiency, precision, and waste reduction, these innovations not only result in significant cost savings but also boost the dependability and security of manufactured products. This research is of paramount importance to the industrial sector as it introduces a groundbreaking, yet cost-effective solution to monitor and improve the quality of products made through Laser Powder Bed Fusion (LPBF). Our research not only confirms its relevance but also underscores its advantage over traditional methods." Professor Roland Logé, the head of the laboratory, stated, "There's been an ongoing debate regarding the viability and effectiveness of acoustic monitoring for laser-based additive manufacturing. Professor Roland Logé, Head of the Laboratory of Thermomechanical Metallurgy Our research not only confirms its relevance but also underscores its advantage over traditional methods. There's been an ongoing debate regarding the viability and effectiveness of acoustic monitoring for laser-based additive manufacturing. However, researchers at the Laboratory of Thermomechanical Metallurgy ( LMTM) at EPFL's School of Engineering have successfully challenged this assumption. But what if it were possible to detect defects in real time based on the differences in the sound the printer makes during a flawless print and one with irregularities? Up until now, the prospect of detecting these defects this way was deemed unreliable. They often either overlook defects or misinterpret them, making precision manufacturing elusive and barring the technique from essential industries like aeronautics and automotive manufacturing. Traditional monitoring methods, such as thermal imaging and machine learning algorithms, have shown significant limitations. The progression of laser additive manufacturing - which involves 3D printing of metallic objects using powders and lasers - has often been hindered by unexpected defects.
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