May_June_2022_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A Y / J U N E 2 0 2 2 6 4 3D PRINTSHOP SOFTWARE REDUCES HEAT BUILDUP IN PRINTERS New software developed at the University of Michigan reduces harmful heat buildup in laser powder bed fusion printers. The printers use a laser to fuse layers of powdered metal or plastic together. But the laser’s heat can build up in the delicate parts being printed, causing deformation and other defects. Called SmartScan, the software demonstrated a 41% improvement in heat distribution and a 47% reduction in deformations in a recent study. It’s also likely to speed the manufacturing process in two ways: by reducing the need for printers to slow down to help with cooling, and by significantly reducing heat-caused defects that must be corrected after printing. “This problem gets even more serious for parts with really thin features,” says Chinedum Okwudire, U-M associate professor of mechanical engineering. “The heat doesn’t have a lot of room to spread, so you need to be smart about how you move the laser around, otherwise your part will deform in really weird ways.” The researchers plan to further improve the software by factoring the fusing of metal or plastic powder into their thermal modeling, as well as enabling active updating of a scan sequence during printing based on real-time observed temperature measurements using an infrared camera. umich.edu. LIQUID METAL MICROGEL INKS FOR ‘SMART’ CLOTHES Researchers are developing an electrically conductive ink made of liquid metal droplets that can be printed onto a variety of fabrics. The team from Zhejiang University in China believe this is a cost-effective way to print intricate, flexible, and durable circuits that can monitor posture, communicate with smart devices, and manage body temperature. Conventional electronics are rigid and unable to withstand the twisting and stretching motions that clothing undergoes during typical daily activities. Because of their fluid nature and excellent conductivity, gallium-based liquid metals (LMs) are promising ma- terials for flexible electronics. However, LMs don’t stick well to fabrics, and their large surface tension causes them to ball up during 3D printing, rather than form continuous circuits. Yong He and colleagues wanted to develop a new type of conductive ink that could be 3D printed directly onto clothing in complex patterns. To make their ink, the researchers mixed LM and alginate, a polymer derived from algae. Stirring the solution and removing the excess liquid resulted in LM microdroplets coated with an alginate microgel shell. The ink was very thick until it was squeezed through a nozzle for 3D printing, which broke hydrogen bonds in the microgel andmade it more fluid. After the ink reached the fabric surface, the hydrogen bonds reformed, causing the printed pattern to maintain its shape. The team 3D printed the new ink onto a variety of surfaces, including paper, polyester fabrics, nonwoven fabrics, and acrylic-based tape. Although the printed patterns were not initially conductive, the researchers activated them by stretching, pressing, or freezing, which ruptured the dried alginate networks to connect the LM microdroplets. After activation, the printed circuits had excellent electrical conductivity and strain sensing properties. In addition, applying a small voltage to the ends of the circuit caused it to heat up, even in very cold temperatures. www. zju.edu.cn/english. In a paper published by Florida State University, researchers describe how to improve 3D printing by teaching machines to learn from each other. The researchers connected different printers on a cloud platform, and then had the machines share data about accurate processing, which decreased the time needed to prepare and calibrate them. eng.famu.fsu.edu. BRIEF Thermal-model-based software directs printer lasers to reduce warpage. Courtesy of University of Michigan. Interconnected 3D printers collaborate to share data to achieve ‘group intelligence.’ Courtesy of M. Wallheiser/FAMU-FSU Engineering.

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