Arnold Air Force Base Tunnel 9 Team Adapts to Using 3D Printing

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Since its inception in the factory, additive manufacturing has evolved and flourished at the Arnold Engineering Development Complex Hypervelocity Wind Tunnel 9 in White Oak, Maryland. From plastic platforms to vital elements for tunnel operation, a multitude of components can now be manufactured in-house.

“The success of AM at Tunnel 9 is exciting to say the least,” said Samuel Gigioli, Tunnel 9 System Engineer and Nitrogen Supply. “There is growing interest in plastic prototyping here as more and more people come to me with an interest or need for 3D printing parts. We can spit out parts in hours rather than weeks. Whether it’s a test part or a prototype part, the process further speeds up our operations and can have a huge impact on the success of the Tunnel 9 mission.”

About seven years ago, Tunnel 9 acquired its first 3D printer – a small filament-based device that could be used to quickly produce simple plastic parts. However, the print quality of this ‘hobby’ printer would soon be insufficient.

In 2019, during his first summer working at Tunnel 9, Gigioli was tasked with reviving the printer’s capabilities. This included ordering new parts, filaments and materials for the device. The second round with the printer turned out to be more successful than the first. After its reintroduction, additive manufacturing at Tunnel 9 was mainly used to make plastic mounting platforms, devices, gauges, and things like that.

Building on this progress, Tunnel 9 then acquired two additional 3D printers. One, a resin-based printer, is capable of printing small but highly detailed and strong parts. The other, a dual-filament printer, is capable of consistently printing large, highly detailed parts.

“There were a few prototypes applied to the tunnel,” Gigioli said. “Actually, a very critical aero-optic part was prototyped with our resin printer, but most of the prints are rigs, test fit gauges, or other miscellaneous parts.”

It wasn’t long before Gigioli, now considered the 3D printing “guru” of Tunnel 9, took on a bigger role in the AM efforts, and the projects themselves took on greater prominence.

In February 2020, a research and development project involving the additive manufacturing of refractive metallic material was launched at tunnel 9. Gigioli quickly took charge of this effort, one that aimed to reduce the time and cost of manufacturing certain parts to high temperature used in the tunnel 9. .

“These Tunnel 9 parts endure very cyclical conditions of high pressure and temperature, so the life of these parts is significantly shorter than other tunnel parts,” Gigioli said. “These parts can withstand up to 3,000 degrees Fahrenheit. That’s why refractive metals are chosen, because they are metals that can withstand extreme heat with relatively little warping.

The ongoing AM research and development effort is led by Gigioli, who is responsible for the maintenance of AM materials, devices and printers, and Nicholas Fredrick, chief facilities engineer for Tunnel 9. They work with two teams of sub -contractors, one of which prints the parts and manages the entire manufacturing process from start to finish, and another which supplies the printing powder and analyzes the characteristics of the materials.

Perhaps the most significant achievement of the research and development program to date has been the successful manufacture of a component known as the petal orifice liner. This device, built into the high Mach number tunnel passages, is located between the two split diaphragms that Tunnel 9 uses to act as a high-velocity valve.

The Tunnel 9 team adapts to the use of 3D printing, led by Samuel Gigioli.  From plastic platforms to vital elements for the operation of tunnels.

The AM liner, Gigioli said, outperformed its forged counterpart that has been used for decades in the facility.

“The part is cheaper to manufacture, faster to manufacture and ship, and is more resistant to cyclic thermal loads,” Gigioli said. “The AM process creates very unique microstructures in the material and as a result the structural and thermal properties of the part are different from those of traditional forged metal billets.”

Those involved in AM at Tunnel 9 have already started work on the next 3D printed part to be applied under high Mach number conditions. This component, a particle separator, would act to remove all airborne particles in the gas flow without impeding mass flow through the tunnel.

“We are still waiting for the component to be fully completed, but hope to implement the component in a test program starting around September,” he said.

The success of the 3D printing program at Tunnel 9 sparked conversations among team members about potential future AM projects.

“Those involved in this R&D project and I are excited about what the future holds for the AM,” said Gigioli.

Their efforts so far have not gone unnoticed. Part of the team’s research efforts is to showcase the potential of the AM for the entire Department of Defense. Gigioli said personnel from various DOD components have already chimed in to compliment the success of the Tunnel 9 team and express their amazement at the AM technology or tout its potential.

With the success of the petal AM orifice liner still on his mind, Gigioli said the possibilities of 3D printing could be limitless.

“Imagine if we extend this process to multiple tunnel parts or even entire systems,” he said. “Now some DOD components are interested in printing test models or state-of-the-art models. I hope to continue to lead Tunnel 9 down this path and increase our success with this technology.”


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