They call it Selective Inhibition Sintering, or SIS, and according to a group of researchers at the University of Southern California, it will serve as the basis for consumer 3D printers capable of creating high-performance metal parts on a desktop budget.
Developed by a team at the Center for Rapid Automated Fabrication Technologies, the idea is built around technology used in low-cost inkjet printers, but here's the rub; unlike the standard approach to metal powder sintering – fusing ground metal materials via a combination of heat and pressure – SIS turns the idea on its head by preventing the sintering process in defined regions of the base powder layers.
"This technology uses a fundamentally new approach to 3D printing, one that could expand the reach of metal printing," says Hod Lipson, PhD and a Professor at Cornell University's Sibley School of Mechanical and Aerospace Engineering.
Current additive manufacturing devices for metals are largely based on three technologies which use lasers, electron beams or inkjet-like deposition. They're all high performance machines and generally start with a price tag anywhere from $100,000 all the way up to over $1,000,000.
The SIS method, developed by the team of USC researchers led by Dr. Behrokh Khoshnevis, works by preventing powder layers from being sintered by treating the specific regions outside the working boundaries of the part with a sintering inhibitor. According to Khoshnevis, such AM devices could have a price point under $5,000.
The USC solution to the metal printing process utilizes a commercially-available piezoelectric printhead to deposit a liquid inhibitor chemical solution where required, and after all layers have been completed, the entire part is bulk sintered in a sintering furnace. As that process takes place, the inhibitor along the boundary of the object decomposes into particles meant to impede the sintering process, thus preventing those regions from fusing and allowing technicians to remove the boundary sections, revealing the completed object. The researchers refer to the object being held within a "sacrificial mold," and that means SIS-made parts remain uncontaminated by any of the binder or resulting residue.
The inhibitor solution, composed of sucrose dissolved in water and an organic surfactant, was used to create bronze parts like a crescent wrench which was fabricated and manually assembled from four total pieces.
The work on the SIS-metal process was funded by grants from the National Science Foundation at the CRAFT laboratories located at the University of Southern California.