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Carderock Engineers Help Marines Soar

By By Justin Hodge, Naval Surface Warfare Center, Carderock Division Public Affairs | NSWC Carderock Division | Aug. 15, 2018


A team of engineers from Naval Surface Warfare Center (NSWC), Carderock Division; Naval Sea Systems Command (NAVSEA) headquarters; NSWC Philadelphia Division; and Military Sealift Command (MSC) proved that being in the right place at the right time is vital to the mission of the fleet.

While participating in an annual Navy exercise in the Republic of Korea in April, Sam Pratt, a mechanical engineer with Carderock’s Additive Manufacturing Project Office, didn’t expect he would soon be working with a team of Marines, Sailors and naval engineers seeking a solution to what could have been a costly fix for a redlined F-35 airframe.

The week prior, Pratt was aboard USS Wasp (LHD-1) analyzing how 3-D printers performed in shipboard conditions, while also training Marines of the Combat Logistics Battalion 31 (CLB-31), on Solidworks — a computer-aided design tool — when he was notified by the maintenance platoon officer that they were having issues with a replacement part for a landing gear door.

“I was with the maintenance platoon in South Korea training Marines from CLB-31 on the processes of drafting a design and how to apply it to printed items,” Pratt said. “I was told they were having issues with printing a part needed to get the F-35 operational again. Their officer suggested teaming up to see what we could come up with as a whole, which turned out to be a great opportunity for collaboration.”

Pratt said once they realized the issues they were facing it was fairly easy to find a solution.

“The Marines designed the part before I arrived, but were having sizing issues,” Pratt said. “The 3-D printer they had bought was a machine used primarily by hobbyists, which wasn’t ideal for this type of project, but they were also using a free software tool called Blender, which is more typically used for special effects work to design movie and game characters. The software tool isn’t really built for the types of accurate measurements needed for engineering since it is focused on artistic designs. I thought about how to design the part so it would fit and function properly.”

The part in question was a small landing gear component that mounts on the landing gear door; as the landing gear door closes it presses the landing gear into the latch.

Pratt said it is good that the Marines were able to fix the issue when they did, in turn saving the fleet from incurring a hefty expense.

“It doesn’t affect the landing gear or function of the plane directly, but eventually after continuous wear, the landing gear could begin to develop a rattle,” Pratt said. “You can’t buy the piece separate from the landing gear door which is a cost of $70,000. By having the capabilities to print in the field, we were able to replicate the part for a cost of roughly 9 cents."

The original part was plastic; the part that was manufactured by Carderock team was made of a material called Polyethylene Terephthalate Glycol (PETG).

To complete the task, Marines were able to take advantage of a new process for a field manufactured part which can be applied to a vehicle.

The deputy commandant for aviation in the Marine Corps worked on a policy for parts authorized to be installed on an aircraft that are not critical. Pratt was previously involved in this work, but it wasn’t broadly known yet inside the Marine Corps.

The policy was just two days old when the group encountered their issue with producing a replacement part for the aircraft.

Pratt said the opportunity to work with the group on the tools and software was the most exciting part, but what ultimately allowed them to be successful was the policy.

“The biggest impact Carderock had for being out there was the policy for installing printed parts on vehicles,” Pratt said. “On ground vehicles the policies are pretty straight forward. If it is not a critical part that will break the vehicle, then try to print an adequate replacement part for it. Aircrafts by nature are a lot more restrictive. There are airworthiness concerns, so when trying to print a part, you really have to know that the part is good so you don’t put your pilots and flight crews in danger.”

Pratt believes this type of capability will be used more and more in the field since it offers the ability to get a vehicle back online that might otherwise take days or weeks to fix.

“We will see additive manufacturing used more often to make replacement parts,” Pratt said. “There are already about 85-90 parts currently approved to print for ground vehicles, so it is as easy as going online, downloading the file and printing the part.”

Marine Systems Command (MSC) maintains and approves each part submitted through the portal, Marine Maker, which houses the documents and specifications necessary to print a new part.

Many of the parts approved for printing are brackets, covers, caps and items that tend to gradually become a problem over time, while others might be application specific tooling, like a wrench.

Pratt said in the field, the material selection is limited to five plastics ranging from stiff and brittle to tough and flexible that are easier for printers to handle, but there are a number of other materials currently being researched.

“We are working on getting more material capabilities out to the field, in particular the ability to print metal,” Pratt said. “We can use it in a laboratory setting, but the machines aren’t ready for the field yet. They are fragile, the materials are dangerous and its generally challenging. Once this is possible it opens up a huge opportunity to print functional parts for vehicles.”

Before returning stateside, Pratt and the group collaborated on a handful of other vehicle parts enabling the Marines to hone their skills and become more efficient in their processes.