Cheryl Cross, the digital media specialist at the University of North Carolina at Greensboro (UNCG), has seen students use the school’s 3D printers for a multitude of interesting projects ranging from game pieces to a wheelchair for a dog.
“The most exciting things in 3D printing now are probably the biomedical things like tissue printing and surgical implants and the micro- and nanoscale printing,” said Cross. “Which of course we don’t do here, but hopefully when people learn how to [use these 3D printers] they’re learning the theory of how to do that, and it can carry over into something like that if it was something they wanted to get into in the future.”
She explained that there are many different types of 3D printing. The oldest, called stereolithography (SLA), was invented as far back as 1984 and uses an ultraviolet laser to solidify a light-sensitive resin one layer at a time.
Fused deposition modeling (FDM) is the most common type of 3D printing, found in homes, offices and the UNCG library. FDM works similarly to a hot glue gun—a plastic wire called a filament is fed into the machine, where it is heated and deposited onto the print bed to build up a structure layer by layer.
The nozzle, where the heated filament comes out, moves on a grid system that can be likened to an arcade claw machine. The print bed, where the 3D printed structure rests, moves very slightly downward as each new layer is deposited.
“On these printers, [the layers] are either 0.1, 0.2 or 0.3 millimeters,” said Cross. “So they’re very small, but that’s actually large in comparison to what you can do with some other types of 3D printers…”
Most FDM 3D printers are able to reach temperatures of up to 530 degrees Fahrenheit, but the exact temperature needed depends on the type of filament being used. If the filament is overheated and becomes too soft, the structure will sag. On the other hand, if it isn’t soft enough it may clog the printer.
“We have the ABS [acrylonitrile butadiene styrene], which is like Lego-type plastic, or PLA [polylactic acid], which is a plant starch-based plastic,” said Cross. “There are also specialty filaments that are like PLA, but it has wood dust in it so it will print out like wood. Same thing with metal—you print out something that will have a high metallic content, and you can polish it.”
Expensive nylon alloys are often used in prosthetics because the final structures have both toughness and a smooth surface. To combat this expense, however, a non-profit organization called the Helping Hand Project (HHP) uses alternate materials to provide children with high-quality prosthetic devices at no cost to them.
“…There are professionally manufactured prosthetics on the market already,” said Rachel Hodges, a UNCG student and member of the HHP. “[But] prosthetics are very expensive. Since children continually grow, it is not feasible for families to afford new prosthetics every time they outgrow it. HHP supplies children with prosthetic-like devices for free to help alleviate the financial burden for families.”
The idea for HHP originated in 2014 when a family in need of a prosthetic hand contacted the biomedical engineering department at UNC Chapel Hill. After using open-source hand designs to 3D print the prosthetic, student Jeff Powell formed the HHP to help other families struggling with the same problems.
“We are currently working to design a hand for a child who outgrew the prosthetic another chapter made for him approximately two years ago,” said Hodges. “While we are awaiting his most recent measurements, we are using his old measurements to develop a rough model of the hand he will need.”
The process begins with open-source designs found on websites such as Thingiverse, which can then be modified based on each individual child’s condition. Unique features such as missing digits, angles and protrusions are all design challenges that the engineers must overcome before anything can be physically printed.
“When printing the hands, we use PLA filament,” said Chris Cotter, founder of the HHP group at UNCG. “This material is very durable and non-toxic, which is important in case the child chews on the device [or breaks it]…. After printing, the hand requires assembly. We use affordable materials such as fishing line, adhesive foam, and Velcro. This helps us to be able to make them quickly and inexpensively.”
Today, HHP chapters exist at multiple universities, including North Carolina State University and UNC Charlotte. For those interested in learning more about the HHP, the Digital Media Commons will host an interest meeting on Tuesday, Feb. 26 from 5 p.m. to 6 p.m. as they prepare to start a new chapter at UNCG. Undergraduate and graduate students from all departments are welcome.