While 3D printing with plastic has come a long way in the last 10 years, there is still a mechanical weakness to plastic parts developed in this way that researchers are trying to solve.
|Researchers at Texas A&M University and industrial 3D-printing technology provider Essentium have developed technology to weld adjacent 3D printed layers more effectively to boost the reliability of the final product, they said. (Image source: Essentium)|
Scientists at Texas A&M University think they have now solved this problem, which stems from the imperfect bonding between the individual printed layers that make up the printed object.
The researchers, working with scientists from the company Essentium Inc., have incorporated nanotechnology into standard 3D plastic printing that can help bind these layers together in a stronger way.
Specifically, the team, led by Micah Green, associate professor in the university’s Department of Chemical Engineering, integrated plasma science and carbon nanotube technology into the process, which welds adjacent printed layers more effectively in a way that boosts the overall mechanical stability of the final product.
“Finding a way to remedy the inadequate bonding between printed layers has been an ongoing quest in the 3D printing field,” Green said in a press statement. “We have now developed … technology that can bolster welding between these layers all while printing the 3D part.”
Green’s team worked with C. Brandon Sweeney, a former Texas A&M materials science and engineering student in his laboratory who is now the head of research and development and co-founder of Essentium, which develops industrial-scale 3D-printing technology.
The most common 3D printing process for plastics is called extrusion printing, or fused-deposition modeling, which works by squeezing molten plastic out of a nozzle that prints objects layer by layer. They fuse together in the cooling process to create the final part.
Researchers have discovered in tests that parts developed this way are weaker than those made by injection molding, a process in which melted plastics, once cooled, take the shape of a mold into which melted plastic is poured.
To strengthen the bonds in extrusion-printed parts, scientists need to use additional heating. However, this also has its drawbacks.
“If you put something in an oven, it’s going to heat everything, so a 3D-printed part can warp and melt, losing its shape,” Green explained in a press statement. “What we really needed was some way to heat only the interfaces between printed layers and not the whole part.”
To accomplish this, researchers coated the surface of each layer of the printed part with carbon nanotubes, a versatile material comprised of carbon particles that heat in response to electrical currents.
The Microwave Effect
The idea behind their method is similar to how microwaves heat food; they can heat the carbon nanotube coatings using electric currents, which will bond the printed layers together.
One challenge to this idea, however, was that the electrical currents had to bridge a tiny gap of air that exist between the printhead and the 3D part, Green noted. While one option to do this would be to use metal electrodes that directly touch the printed part, this idea could create unintended and unwanted damage.
Green’s team turned to mechanical engineers to help them solve this problem, working with David Staack, an associate professor in the Texas A&M’s Department of Mechanical Engineering.
Staack’s team came up with the idea to generate a beam of charged air particles, or plasma, that could transport an electrical charge to the surface of the printed part, researchers said. In this way, electric currents can pass through the printed part, thus heating the nanotubes and bonding the layers together more effectively.
Researchers published a paper on their work in the journal Nano Letters.
To test their technology, researchers added carbon nanotubes as well as the plasma-based transport technology to conventional 3D printers. They found that the strength of 3D printed parts using their new technology was on par with injection-molded parts, achieving a longtime goal of plastic 3D printing.
“With our technology, users can now print a custom part, like an individually tailored prosthetic, and this heat-treated part will be much stronger than before,” Green said in a press statement.
Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York City. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.