Introducing New Production Methods Saves the Air Force Time and Money > Air Force Materiel Command > Article Display

The 448th Supply Chain Management Wing, part of the Air Force Sustainment Center, has a new additive manufacturing approach to solving an old problem, sourcing hard-to-acquire parts for legacy aircraft.

By digitally recreating the mold used to create castings, instead of building the part from scratch, the Strategic Alternate Sourcing Program office can work with suppliers to produce parts faster while saving money of the Air Force.

“We’re trying to find ways to get the low-quantity parts faster,” said Loren Lutz, Air Force Lifecycle Management’s chief propulsion engineer. “We support a significant number of older platforms and we’re going to continue to support them for a long time. We need to figure out how to get the parts we need. Whatever we can do technically to make that possible, and then work with our partners on the supply chain side to be able to go and buy them, is really valuable.

Additive manufacturing has been a specialty of Tinker Air Force Base’s Reverse Engineering and Critical Tooling Lab, known as REACT, for several years. However, the size and complexity of some parts do not lend themselves to current 3D printing methods where the part is built from scratch. Even if the part were to be recreated using this method, the part would undergo lengthy airworthiness tests before being cleared to fly.

This is the case of the rear gearbox casing of a TF33 turbojet. Made from magnesium, the case was originally produced by casting – pouring molten metal into a mold and then milling the part to produce a final product. The mold used to create the part is also known as a hard tool and is usually made from high tensile steel.

Variants of the TF33 powered aircraft such as the B-52H Stratofortress, E-3 Sentry and E-8 JSTARS. As these legacy aircraft continue to fly, parts that weren’t meant to wear out need to be replaced.

“If we haven’t bought this part for 20 or 30 years, we no longer have the hard tooling; original equipment manufacturers, vendors, they don’t have it,” said Randolph Harris, OTA program manager for the 429th Supply Chain Management Squadron. “That’s why it takes 900 days or more to get these parts because they’re going to spend the first 18-24 months recreating the hard tooling.”

Adding to the problem is the fact that many parts will only be needed in small numbers, leading many suppliers to choose not to “bid” on a contract.

The Pathfinder project to address these issues began in 2019, exploring the use of additive manufacturing to address the challenges of securing molded parts.

Using the real part as a guide, new digital molds were created. Compared to the original, the parts obtained are precise to a thousandth of a millimetre. Even the embossed lettering on an oil inlet port is identical.

The time it took to develop the new process and build a prototype was actually shorter than the production time the gearbox housing would have taken had it been produced using traditional methods.

“What we really get out of this process is the full drawing package of how you do the part,” Lutz said. “It’s the foundry drawing, the manufacturing drawing and the final drawing of the part; that’s all you would need to make the part, which is a deeper level of knowledge than we have on our parts that show up at OEMs.

With the digital plans in hand, a sand mold to cast the piece was created. The sand mold is destroyed during the crafting process, but can be easily recreated the next time a part is needed. What normally took over 900 days can now be done in 30-60 days.

“We used additive manufacturing in this process, but we don’t have to do a configuration control board, we don’t have to do airworthiness, unless the engineer tells me otherwise, because this part is produced exactly like the part we have already installed,” said Harris. “What we did differently was that Renaissance Services, Inc. developed the process and we removed the hard tooling, manufacturing the mold additively.”

Because the Air Force owns the resulting intellectual property, it can be outsourced to other vendors for production rather than being tied to a single manufacturer. The part could also be manufactured in-house, which would make the situation much more competitive with a high potential for savings.

The castings are where the project began, but it won’t be where it ends. One of the main missions of the SASPO office is to match the needs of the Air Force with suppliers who can help maintain the fleet.