L to R: Naseem Jibrin, Benjamin Ennis, Brandon Ennis and Michael Winn (UTC)
A small consultancy in Chattanooga, Tennessee is helping the U.S. Navy turn explosives into custom shapes using commercial 3D printing techniques. The staff of E&G Associates – engineers Benjamin Ennis, Brandon Ennis, Nasseem Jibrin and Michael Winn, all graduates of the University of Tennessee – are working on ways to use an off-the-shelf Hewlett Packard 3D printer to create shaped charges.
HP’s ink-and-thermoplastic powder bed fusion printers have been on the market since 2016, making them a relatively recent arrival (compared with more established 3D printing technologies like material extrusion or laser sintering). Hewlett Packard advertises them for low-cost, rapid prototyping and short-run parts manufacturing.
“The printer spreads the nylon powder and then prints on that flat layer of powder with the ink. Then the printer passes a heat lamp back and forth to make the dark areas melt. And that’s how you get your parts,” Jibrin told UTC’s alumni magazine. “The process is repeated in three steps. Spread a layer, ink the specific selected areas and fuse with heat lamps. You do that over and over again until you build a part.”
HP’s printers are not marketed for bomb-making, but with some careful R&D and a $150,000 federal grant from the Small Business Innovation Research program, the E&G team thinks that the platform can be adapted for military applications. The group is testing nylon powder infused with explosive material, polymer additives and printer ink to create its 3D explosive charges.
E&G doesn’t have a blast chamber on site to test out the final product, but it has an agreement with the Missouri University of Science and Technology’s engineering department, which has all the equipment needed to detonate samples and study the results. “We’ll test in a chamber that’s basically a giant metal tube. It’s about eight feet high with inch-thick walls,” said Benjamin Ennis.
E&G’s shaped-charge research is not the Navy’s first foray into 3D printing. Last year, the Oak Ridge National Laboratory worked with Surface Warfare Center Carderock to make a 30-foot submarine printed entirely of thermoplastic resin. The prototype was similar in size and function to the covert infiltration mini-subs used by the Navy SEALs, but Oak Ridge built its model much more quickly, and at a fraction of the normal construction cost.