## Innovations in Metal 3D Printing

A team of Rice University students has developed a cold spray metal 3D printing device that relies on pressure and velocity rather than temperature to create a metal part. Their work could help expand the repertoire of metal additive manufacturing techniques, bringing down cost and enhancing the quality of making or repairing one-off complex metal parts.

Team AeroForge members—Eli Case, Julianna Dickman, Garrett French, Galio Guo, Douglas Hebda, Grant Samara, Davis Thames, and Aasha Zinke—used the device to successfully deposit copper, demonstrating the viability and potential of their prototype. The project won an Excellence in Capstone Engineering Award and first place in the Willy Revolution Award for Outstanding Innovation at the annual Huff OEDK Engineering Design Showcase, which took place on April 11 at the Ion.

“We’re very excited and very relieved,” Dickman said. “We spent many late nights in the Oshman Engineering Design Kitchen, and it feels very rewarding to get recognized for our work,”

Guo said that when the team did not win its category award, he thought it was not going to win anything.

“Then we won the first award, and I was really happy, and when we won the second award, I was really, really happy,” Guo said.

Team AeroForge’s project is also the recipient of this year’s Hershel M. Rich Invention Award, presented to Rice engineering students or faculty members for “original invention development.”

“Traditional metal 3D printers generally use a laser to melt metal powder into a particular shape, but melting can really impact the properties of your product,” Zinke said. “Cold spray technology, which has been used for coatings, uses velocity instead of heat, basically accelerating metal particles so fast that they adhere to and deform onto a substrate. The system that we’ve designed aims to accomplish that in a 3D printing capacity.”

Applications for the device include the manufacture and repair of metal parts with a complex structure, such as components used in industrial assembly lines or in vehicles or aircraft. Industries that rely on metal components, like automotive, oil and gas, and defense, can incur significant losses as a result of supply chain disruptions, so the team hopes its device can provide a viable, low-cost alternative for making or repairing parts on demand.

Thames, who first pitched the idea for the project to a teammate almost a year prior to the start of the senior design class, explained the advantages of using the cold spray metal 3D printer over welding.

“Typically, with repairs, you can only remove material as you reshape a metal part,” Thames said. “But with this process, you can add material and then machine it back down. With welding, for instance, varying melting temperatures may result in uneven material properties. We don’t have that issue with this device.”

The device consists of a gas tank that feeds high-pressure nitrogen gas into the system; controls that regulate valves and monitor pressure and temperature; a pressure vessel that heats the gas to 450 Celsius (842 Fahrenheit); a powder feeder designed to dispense metal powder into a nozzle at a precise rate; and a custom nozzle.