Robert “Red” Jensen of NASA Armstrong Flight Research Center’s Subscale Aircraft Research Laboratory, had an engineering problem. An instrumentation data cube that was to be installed in a small glider being constructed for preliminary flight tests of a Towed Glider Air Launch Concept needed a new case to accommodate changes in how the electronics were put together.
His solution? Jensen used a 3-D modeling program installed on his computer to help him merge elements of three separate drawings into a single design. He also made modifications so the data cube would fit in its intended position in the glider’s center fuselage.
Manufacturing the part would also involve some new high-tech software and equipment at the NASA field center.
In the past, Jensen would have sent the designs for the towed glider data cube to NASA Armstrong’s Experimental Fabrication Branch to make the part. However, thanks to the foresight of center engineers, he had another option – just print it via the additive manufacturing process with the center’s recently acquired high-resolution 3-D printer, and then install it in the aircraft after quality assurance inspection and approval.
“It creates good parts without my having to rely on someone else to do it,” Jensen said. “I need a lot of one-of-a-kind parts here. I don’t have to burden the Fabrication Shop every time I want to make a proof-of-concept part, and I don’t have to fear wasting materials to do it,” he said.
NASA Armstrong’s Chief Technologist David Voracek had been asked by several young engineers at the center to pursue purchase of a high-resolution 3-D printer. Voracek agreed and tapped the center’s innovation fund – available for technology development – for the purchase late last year.
“This is a good tool for engineers, technicians and mechanics to prototype a part, or make a part for use in their technology development,” Voracek said.
NASA Armstrong already had 3-D printers, but none capable of the high resolution of the new printer that can rapidly process prototype parts. Although data cubes are traditionally fabricated out of lightweight metal, such as aluminum, the 3-D printer makes its parts out of stable, high-performance plastic.
It all begins when a part designed from a 3-D modeling program is loaded into the printer. Most parts are created in less than an hour, although that varies by complexity, Jensen explained. The printer creates a black base and builds up the part layer-by-layer to a size as large as a bowling ball.
One example of that was a clamp used to keep the pitot-static boom that acquires real-time flight data attached to the nose of an aircraft. Former lab technician Lesli Monforton designed the one-of-a-kind clamp, but Jensen needed three. NASA Armstrong engineers reverse-engineered the clamp and Jensen was able to create a working prototype.
Another example is a tiny part called a control-position transducer coupler that is only a quarter inch long. It has a hollow center to attach measurement devices called string pots and is created with the 3-D printer to a tolerance of about 15 thousandths of an inch, Jensen explained. The coupler is attached to aircraft control surfaces and helps measuring devices deliver high-precision flight or structural loads data in real time.
When multiple parts need to be printed at the same time, the machine’s software can determine the best configuration for arranging the parts to maximize the material used to create them, he said.
Instead of loading paper like a computer’s inkjet or laser printer, this 3-D additive manufacturing printer is loaded with cartridges that melt and dispense the plastic material as it builds the part layer by layer. The black material used for the base also settles in areas that simulate its mounting.
For example, if a screw goes into the part, the part would be one color and the black material fills in where the screw would go, Jensen explained. Once the part comes out of the printer and the tray where it was created, it is placed in an acid bath. The process melts the black base material, leaving a pristine part ready for use, or a good prototype to examine.
The subscale glider for which the parts were designed and printed is a proof-of-concept model intended to demonstrate an approach to launching small satellites into orbit from a rocket carried by an unpowered glider towed to launch altitude by a powered aircraft. If successful, the concept could significantly reduce the cost and improve the efficiency of sending satellites to orbit.
One or more of Jensen’s parts for the twin-fuselage glider is often “cooking” inside the printer, including the data cube, cable tie clamps, wire loom holders, data storage boxes, servos and linkage covers to help with the aircraft’s aerodynamics, he explained. In addition to a relatively quick fabrication, the plastic material has the added benefit of cutting four to six ounces of weight from the aircraft, he added. That’s no light accomplishment, as weight is at a premium for this small glider.
When Jensen sends parts to the NASA Armstrong machine shop for finishing, it is with confidence.
“The printer is a blessing because we can check the fit and function of the part before we send it to the machine shop,” Jensen explained. “It adds a capability and an opportunity to draw, print and see how a part works.”