KINGSLEY FIELD, Ore. – For years, structural maintainers have emerged as artisans of sorts, creating parts by hand, meticulously shaping them from custom wood forms and delicate hand-tool work.
Gently tapping away with a small hammer, slowly giving shape to a sheet of aircraft-grade aluminum so it will slide into the tight confines of an F-15 fuselage with an expected tolerance of .005 of an inch.
This is necessary because of the thousands upon thousands of parts that make up an F-15C. Many of them don't exist in the supply system any longer—they haven't for decades.
"It's a 50-50 shot when you need a part that it's out there," said Master Sgt. Paul Allen, a structural maintenance technician at the 173rd Fighter Wing.
One such part is a fairing rib; a semi-circular part originally stamped from a sheet of aluminum with three-dimensional relief. It's a part that sustains damage in refueling operations when the boom cracks into the aircraft—a somewhat common occurrence—creating an ongoing demand for fairing ribs.
Allen and his structural maintenance co-workers make new ones. First, they cover the part with tape, then carefully cut away a section to give them a rough pattern for the new part, and then trace that part on a new piece of metal. Once traced, they cut it from the sheet with hand tools and file it to match or as close as they can get. Allen says it's really not possible to get to .005 of an inch this way—the acceptable tolerance for this part.
Now, this flat piece of metal needs to be formed and so they carefully hammer it to shape around a mold. First, they tried a hard plaster cast, but it cracked when they hammered the sheet metal against it. They got it done, though, as they have for years now—27 man-hours later.
Today, emerging technology can shorten that process to seven hours.
It begins with a better way to assess the parts' exact dimensions—enter a brand-new scanning arm with a mounted camera and an attached computer, which can map a piece perfectly, rendering it in three dimensions. A mold is created using the same software and printed using the brand-new 3-D printer located not five feet away, and this printed part takes the place of that wood mold.
"We're definitely using innovation to save time and money," says shop supervisor Master Sgt. Joshua Fuhrer. "If you think about carving a tool from wood, that's something that goes back to the 1950s, now we are printing parts in a matter of hours and that's cutting edge."
And this mold is solid. Printed from a carbon filament proves vastly more durable than a wood mold.
The team relies on that strength to utilize another piece of time-saving technology, a "smash-box." It's something drill-status Airman Tech. Sgt. Michael Jordan brings to the shop from his experience at Rogue Aerospace Engineering, the company he runs specializing in helicopter repair and part fabrication when he's not wearing the uniform on drill weekends.
The "smash-box" is a reinforced steel box lined with a thick rubber mat and closed with a reinforced "lid" made of steel. The rubber used is a very high durometer and does not easily deform, and it's challenging to make an indentation in it even with, for example, a screwdriver. But when placed in a 100-ton press, that same rubber flows around the mold in a nearly fluid state and that shapes the accompanying part perfectly—every time.
"Being able to reproduce the parts and get the same outcome every time is very valuable," says Jordan. "For the Air Force, not just the F-15 fleet."
He says it represents value to the Air Force because once a part is printed and mapped, those files can be transferred to another unit when they need to replace the same part.
Allen envisions a time near at hand when units will share these files frequently, creating a platform within the community of Air Force structural maintenance capitalizing on the initial effort being "crowd-sourced" across the fleet and beyond. He says he doesn't see a reason why it should be confined to a career field or service and thinks it may likely be beneficial to the whole of the Department of Defense.