Extrusion-based 3-D printers typically generate temperatures of about 200 degrees Celsius to soften their thermopolymer filaments. That is not a huge power draw, but the printer might need additional energy to keep its build chamber heated—this helps keep objects from distorting or curling as the bottom layers dry under the newly deposited ones, says Lonnie Love, a senior research scientist at Oak Ridge National Laboratory’s Measurement Science and Systems Engineering Division. If the build chamber is not heated, another option is to use a heated build platform—like a hot plate—to keep the lower layers from cooling too quickly. Love knows a thing or two about 3-D printing—he is principal developer on Oak Ridge’s project to develop a 3-D printed robotic prosthetic hand.
Higher-grade plastic 3-D printers require lots of heat—often supplied by a power-hungry laser—to liquefy feed polymers and build denser, more durable plastic objects. Extrusion-based systems make lower-quality plastic items by softening polymers so they flow through the printhead more like toothpaste. Installing lasers on the ISS is likely impractical because power usage would be a concern, says Joseph Beaman, a University of Texas at Austin mechanical engineering professor and pioneer in additive manufacturing techniques such as 3-D printing. “As efficient as 3-D printers are in not wasting materials, they are not terribly energy efficient,” he adds.
Although Snyder says he cannot go into detail about the power requirements of his company’s printer, he points out that devices operating in the ISS Glovebox are limited to about 200 watts. The Made in Space machine operates “nominally” within that requirement, he adds.
NASA’s interest in 3-D printing makes a lot of sense, and Made in Space’s extrusion-based approach seems rational, given the size and power constraints imposed by the ISS, Love says.
Moving space-based 3-D printing to more industrial levels that would enable ISS crew to replace sturdier, more sophisticated parts is beyond the scope of the current experiment. Three-dimensional printers that build items out of titanium and other metal powders would be great for repairing or replacing more critical components on the space station but are an even bigger stretch for a microgravity environment, Beaman says. “You don’t want those powders flying around, although maybe you might be able use an electrostatic system to keep nonconducting powders down in the build chamber,” he adds.
Challenges aside, “I think [3-D printing on the ISS] actually will work,” Beaman says. “The question is how useful it will be, but it’s certainly worth trying out.”
Love agrees, particularly if and when astronauts move beyond the space station: “Rather than sending all of the materials needed to a particular location, you just send a printer, and you make what you need using what’s available locally,” he says. “It sounds way out there, but technically it’s feasible.”