ADVANCED MATERIALS & PROCESSES | APRIL 2025 68 3D PRINTSHOP HIGH-SPEED X-RAYS DETECT KEYHOLE PORES Using synchrotron x-ray imaging, a team from University College London looked at the interaction between laser beam and material during laser powder bed fusion. They were able to see the creation of small keyhole-shaped pores in the component as a result of the vapor generated when the laser melted the metal alloys, and the cause of in- stabilities in the keyhole that leads to defects in 3D printed parts. The researchers performed highspeed synchrotron x-ray imaging of the manufacturing process at the Advanced Photon Source (APS) synchrotron in Chicago. The team then observed the manufacturing process with a magnetic field applied to the metal alloys as the part is formed, which they hypo- thesized might help to stabilize the point at which the laser hits the molten metal, reducing imperfections. This theory proved correct, with an 80% reduction in pore formation in components printed while an appropriate magnetic field was applied. Dr. Xianqiang Fan, first author of the study published in Science, says, “When the laser heats up the metal it becomes liquid, but also produces vapor. This vapor forms a plume that pushes the molten metal apart, forming a J-shaped depression. Surface tension causes ripples in the depression and the bottom of it breaks off, resulting in pores in the finished component. “When we apply a magnetic field to this process, thermoelectric forces cause a fluid flow that helps to stabilize the hole so that it resembles an ‘I’ shape, with no tail to break off when it ripples,” adds Fan. Professor Peter Lee, senior author of the study, notes that “in this study we’ve been able to watch the manufacturing process in unprecedented detail by capturing images over 100,000 times a second, both with and without magnets, to show that thermoelectric forces can be used to reduce keyhole porosity significantly. In real terms, this means that we have the knowledge we need to create higher-quality 3D printed components that will last much longer and expand use into new safety critical applications, from aerospace to Formula 1.” doi.org/10.1126/science.ado8554. PRINTING TECHNIQUE FOR CERAMICS MINIMIZES SHRINKAGE A new technique called aerosol jet 3D nanoprinting (3D-AJP), allows researchers to print highly complex structures with the favorable properties of ceramics. Scientists from Carnegie Mellon University, Pittsburgh, published a study in Advanced Science showing use of the freeform ceramic fabrication method that enables highly complex microscale 3D ceramic architectures—such as micropillars, spirals, and lattices—with minimal shrinkage and no auxiliary support. While existing 3D printing techniques have opened doors for ceramics fabrication, oftentimes severe shrinkage or defects are observed during post- printing processing due to the removal of additives from the ink that were needed to support the material during printing. 3D-AJP does not rely on additives in the ink and therefore sees only a 2 to 6% shrinkage rate, so manufacturers can feel confident that the structure they want is the structure they’ll print. To ensure this, the research team performed a detailed manufacturability study to identify the CAD programs needed to produce the final shape. Additionally, the team demonstrated 3D-AJP’s unique ability to print two ceramic materials in one single structure, which allows for advanced applications. “Using these structures, we can detect breast cancer markers, sepsis, and other biomolecules from a blood sample in just 20 seconds,” says Rahul Panat, professor at Carnegie Mellon University. This application, which is an extension of past research in which Panat’s group developed a metal biosensor to detect COVID-19 in just ten seconds, is advantageous, because compared to metal, ceramic sensors can be manufactured nearly five times faster. doi.org/10.1002/advs.202405334. Reducing the number of defects in 3D printed pieces like this handlebar assembly would enable them to be made significantly lighter, adding a winning edge. Courtesy of Prof. I. Todd, University of Sheffield, U.K. 3D-AJP shows near-zero shrinkage. Courtesy of Advanced Science.
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