Lasers, 3D printers aid prosthetics

A cutting-edge 3D printer, called a laser metal sintering machine, is aiding the development of robotic fingers, hands and arms for amputees at the University of Colorado Anschutz Medical Center.

The metal printer is allowing Richard Weir, research associate professor-bioengineering, to build better prosthetics, including joints and robotic articulations, right in his laboratory.

The technology, which was funded through a grant from the Veterans Administration, uses a three-dimensional image to methodically laser-sinter beads of metal powder into solid metal to build complex, small 3D metal constructions. The printer “may actually enable us to build more complicated devices because we have this very sophisticated tool,” Weir said.

He also uses a high-quality plastic rapid prototype machine that will print 3D as well.
Every component of the hand is designed in CAD, and then Weir and his team build prototypes out of plastic to see what works and what doesn’t.

The 3D printing in plastic is “very powerful. It allows us to implement very quickly the 3D computer CAD models we constructed. It tells us very quickly what the object is going to look like for scale,” Weir said. “A lot of work we do … a lot is very small. Working in computer CAD, it is very easy to work on a screen that is 2 feet by 1 foot large, but the parts are only 3 or 4 millimeters across. You lose the idea of the scale of the thing you are working in.”

By being able to print concepts three-dimensionally, it is very “grounding and helps you visualize and see how things will be assembled and tests whether things can be assembled,” Weir said.

After the kinks are worked out in the plastic model, the next step is to test the structure, forces and strength of the materials that will actually be used in construction of the hand, including titanium, nickel, magnesium and cobalt. Enter the laser metal sintering machine, which was purchased for the lab early in 2013 but has only been utilized in the past couple of months.

Most of the 3D prototypes printed on the laser metal sintering machine are made of powdered steel. Because it is powdered metal, the machine only uses what it needs to make the parts, Weir said. Everything else drops back into the reservoir to be used at a later time.

In traditional machining, you start with a block of material and carve away anything that isn’t needed. There’s a lot of waste.

“We’re not throwing away stuff we don’t use. There is not a lot of waste. But the upfront cost on the machine is not insubstantial,” Weir said.

He hopes that his lab will get to the point where it can produce small runs of parts for custom prosthetics. The metal printer will never be used for mass production of prosthetic arms or hands, but the university could get to the point where it makes up to 25 hands at a time.

He added that some of the things it can manufacture with the 3D printer can’t be made any other way. “That’s the kind of area where we see its real strengths,” he said.

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