The team used the extremely bright X-rays to take super-fast video and images of a 3D printing process called laser power bed fusion, in which lasers melt and fuse metal powders. The lasers, which scan each layer of powder to fuse metal where it is needed creates the finished product from the ground up. Until now, manufacturers and researchers did not know much about how the laser drills into the metal, producing cavities called “Vapor depressions,” but they assumed the type of metal powder or strength of the laser were to blame. As a result, manufacturers have been using a trial-and-error approach with different types of metals and lasers in an effort to reduce the defects. During laser powder bed fusion, a 3D printer “Drills” a hole into the metal. Under perfect conditions, the melt pool shape is shallow and semicircular, called the ”Conduction mode.” But during the actual printing process, the laser, often moving slowly, changes the melt pool shape to something like a keyhole: round and large on top, with a narrow spike at the bottom. The research shows that keyholes form when the laser power density is high enough to boil the metal.
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