The efficiency and cost-effectiveness of three-dimensional printing is revolutionizing the fabrication of O&P devices, but plastics have limited strength and durability. Direct metal laser sintering machines, which can print metal parts in three dimensions, present a solution.
Richard Weir, PhD, a leading researcher in the development of upper extremity prostheses, recently received a three-dimensional metal printer through a capital equipment grant from the Department of Veterans Affairs. The machine, which Weir estimates is one of only a few dozen in the United States and the second to be used in a university setting, is housed in Weir’s lab at the Children’s Hospital Colorado.
“It will change the way that we think about fabrication,” Weir, who is also an associate research professor of bioengineering at the University of Colorado Denver and the national director of research and development for Advanced Arm Dynamics, told O&P Business News.
Typically used in the fabrication of devices in the medical and aeronautical industries, Weir first saw direct metal laser sintering technology being used to make pediatric titanium cranial plates.
“I had seen it before a number of years ago and had always had it in the back of my mind as something that would be a truly revolutionary way to make things,” Weir said.
The fabrication process
According to Weir, direct metal laser sintering has the potential to transform the fabrication process for O&P devices.
“Things like medical applications are one place that we see that this machine may be of use because we have the ability to build one-off things that are custom designed for an individual,” Weir said. “With this machine, we have the ability to make anthropomorphic shapes that are customized to an individual, which is something that tends to be hard to draw or send as a set of drawings to a machine shop.”
Direct metal laser sintering uses computer aided designs to create three-dimensional products through the process of sintering metal powder with a high powered laser. Inside the machine, a build plate acts as the base of the part that is being fabricated. Metal powder is swept onto the build plate, and the powder is then sintered, or melted, with the laser. The build plate then drops about 20 microns and another layer of metal is swept onto the plate.
“You basically repeat this process over and over again, stepping down and sweeping a layer of powder and sintering with the laser in 20-micron steps until you grow the part,” Weir said. “At the end of this process, you have to clean away all of the powder that was not sintered, and you are left with a sintered shape that is bonded to the build plate.”
The entire process takes approximately 10 hours to 14 hours, and Weir typically works with maraging steel.
“We will set something up in the evening and come back in the morning and hopefully everything has gone smoothly and there have been no problems overnight,” Weir said. “We are still learning how to make sure there are no problems.”
According to Weir, there is still a lot to learn about this technology in order to determine the best way to utilize laser sintering fabrication.
“We have to figure out when it is an advantage to send the parts out to be fabricated using conventional processes vs. when we can just use this machine to build them,” Weir said. “The way the process might work is that we draw our stuff in CAD, print it out in plastic first on a 3-D plastic prototyper and make sure everything fits and works as we thought, iterate the design if it doesn’t, and then send it to this machine and just print it out in metal.”
Weir also acknowledged that working with metal will present new challenges when compared with other three-dimensional fabrication techniques.
“We are familiar with 3-D fabrication because we already have plastic 3-D fabricators,” Weir said. “So we are going to have to figure out what the issues are going to be when we print in steel vs. plastic. And the most immediately-obvious difference is the amount of post-machining will be different.”
Unlike printing in three-dimensional plastic, where the parts are ready to use almost immediately after they are printed, the metal parts will require some work because the part must be removed from the build plate with a saw and then cleaned with a grinder or sander before it will be ready for use.
“It’s not just a print and go type thing,” Weir said. “There’s a post-processing step, and we have to establish what makes the most sense there.”
Once they have more experience with the technology, Weir and his colleagues hope to experiment with different fabrication techniques and apply this technology to the fabrication of prosthetic devices.
“We are looking at maybe the ability to scan in a residual or sound limb and be able to print out a form of a hand in 1-mm steel skin, and work with that to cast new concepts or prosthetics limbs,” Weir said. — by Megan Gilbride
Disclosure: Weir received funding through a capital equipment grant from the Department of Veterans Affairs.