ARNOLD AIR FORCE BASE, Tenn. – When a decades-old part could no longer be purchased, the Plant Operations and Maintenance team at the Arnold Engineering Development Complex Engine Test Facility at Arnold Air Force Base coordinated with members of the Condition Based Maintenance group, or CBM, to determine how best to recreate the piece.
The most economical solution was determined to be 3D printing the part, a circuit breaker handle used to supply a 20 horsepower, 480-volt alternating current motor to the lube oil system, which directly supports two of the process air compressors for C-Plant.
“The piece is a component of the equipment that feeds air to the compressors for all of ETF,” explained Ronald Reagan, electrical engineer for Plant Operations and Maintenance at Arnold. “It is part of the Lube Oil System that serves two of the air compressors that provide process air for engine testing.”
The handle is a plastic composite that contains a spring loaded locking mechanism that prevents the circuit breaker from operating when it is locked out for plant maintenance activities.
“The piece is from the late 1970s, and from age and use, it broke,” Reagan said.
Paul Kurtz, an intern with the Test Operations and Sustainment contractor National Aerospace Solutions, was tasked with working with the CBM group in 3D printing a new circuit breaker handle.
“The interns are not here for a long time and we wanted to give Paul something he could follow through on,” he said. “We thought this was an area in which he could explore the use of 3D printing. This was a perfect opportunity.”
In Kurtz’ report on the project, he detailed his process, which began with getting guidance from Matthew Breuhl, the CBM subject matter expert for the 3D printer.
“The software used on the CBM laptop for 3D printing is called CURA,” Kurtz said in a report. “The program is responsible for processing a 3D Object File into many layers that can be printed on top of one another to form the whole object. This process is referred to as slicing.”
In order to generate a 3D Object File, Kurtz used AutoCAD software to develop a 3D model of the breaker handle. He made a hand drawing of the handle, noting detailed measurements before beginning the digital model.
“Getting familiar with the AutoCAD software took some time, but eventually I became familiar enough with the program’s features that I could generate an accurate model rather quickly,” Kurtz wrote in his report. “I created the model to the exact scale from the measurements I had taken off the broken handle.”
Kurtz deviated from the original for the 3D printed version in an effort to bolster the strength of the handle.
“The only modifications I made were to completely fill the center section as a solid instead of maintaining the ribbed structure the original piece had,” he said. “In addition, I altered the joints between the rounded end sections and the center rectangular section. I changed it from a straight intersection to a rounded fillet with a 0.3-inch radius connection.”
Using nylon as the material, a new breaker handle was successfully fabricated using the 3D printer, and Reagan believes that it is likely a better piece than the original.
“I think it is sturdier and will definitely last a few years,” he said. “This project was a big success, and it shows that with 3D printing, we can replace certain parts that we can no longer buy and these parts can be as fully functional as the original.”
Reagan mentioned that whether the handle project succeeded or failed, the Operations and Maintenance group is continually looking to strengthen their working relationship with the CBM group. He feels the project succeeded in both areas.
“We want to enhance our process of working with them, in the event we run into something similar in the future, or even find other opportunities to apply new technology to our work” he said.