Eliminating fractures in 3D printed parts

Article By : Vivek Nanda

A new technique microwaves carbon nanotubes sandwiched between 3D printed layers to weld them together and make parts to up to 275% stronger.

Brandon Sweeney, a doctoral student in the Department of Materials Science and Engineering at Texas A&M University has developed a method to make 3D printed parts 275% stronger and immediately useful in real-world applications. Sweeney, together with his advisor Dr. Micah Green applied traditional welding concepts and a carbon nanotube composite filament to bond the submillimetre layers in a 3D printed part together with focused microwaves.

Sweeney began working with 3D printed materials while employed at the Army Research Laboratory at the Aberdeen Proving Grounds in Maryland. “I was able to see the amazing potential of the technology, such as the way it sped up our manufacturing times and enabled our CAD designs to come to life in a matter of hours,” Sweeney said. “Unfortunately, we always knew those parts were not really strong enough to survive in a real-world application.”

Fracturing limits 3D printing use

3D printed objects comprise thin layers of materials, usually plastics, deposited on top of each other to form a desired shape. The layers are prone to fracturing. You don't want that in, say, a medical device.

“I knew that nearly the entire industry was facing this problem,” Sweeney said. “Currently, prototype parts can be 3D printed to see if something will fit in a certain design, but they cannot actually be used for a purpose beyond that.”

Figure 1: Sweeney and Blake Tiepel working in the lab.

Sweeney, Green and Dr. Mohammad Saed, assistant professor in the Electrical and Computer Engineering Department at Texas Tech, crafted an idea to use carbon nanotubes in 3D printed parts, coupled with microwave energy to weld the layers of parts together.

“The basic idea is that a 3D part cannot simply be stuck into an oven to weld it together because it is plastic and will melt,” Sweeney said. Since the layers making up the 3D printed parts are so tiny, special materials have to be used to control where the heat hits and bonds the layers together.

“What we do is take 3D printer filament and put a thin layer of our material, a carbon nanotube composite, on the outside,” Sweeney said. “When you print the parts out, that thin layer gets embedded at the interfaces of all the plastic strands. Then we stick it in a microwave—we use a bit more of a sophisticated microwave oven in this research—and monitor the temperature with an infrared camera.”

The technology is patent-pending and licensed to a local company in College Station, Essentium Materials. The materials are produced in-house, where they have also designed a new 3D printer technology to incorporate the electromagnetic welding process into the 3D printer itself. While the part is being printed, they are welding it at the same time. They are currently in beta mode, but this has the potential to be on industrial and consumer 3D printers where strong parts are needed.

“If you're an engineer and if you actually care about the mechanical properties of what you're making, then this ideally would be on every printer in that category,” Sweeney said.

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