Reposted from 3Ders.org July 30, 2014
3D printing has dramatically expanded in the last several years. 3D printer has been used to create all kinds of things, from gadgets and accessories to implantable medical devices. 3D printing technique for fabricating metal alloys have also been available for more than a decade. But for making spacecraft, engineers need custom parts with the properties of multiple metals.
Now, researchers at NASA’s Jet Propulsion Laboratory in Pasadena, California, are implementing a 3D printing process that transitions from one metal or alloy to another in a single object.
Since 2010 JPL scientists have been developing and improving techniques to combine parts made of different materials. But Why would you need to make a machine part like this? For example you want a metal object to be 3D printed in one piece with different properties. One side could have a high melting temperature and the other a low density, or one side could be magnetic and the other not. Of course, you could separately make both halves of the object from their respective metals and then weld them together. But the weld itself may be brittle, so that your new object might fall apart under stress. That’s not a good idea if you are constructing an interplanetary spacecraft, for example, which cannot be fixed once it is deployed.
Schematic of the laser deposition
Working together with researchers from JPL, the California Institute of Technology, Pasadena, and Pennsylvania State University, University Park, JPL scientists have developed a new 3D printing process to tackle this issue.
“We’re taking a standard 3-D printing process and combining the ability to change the metal powder that the part is being built with on the fly,” said Douglas Hofmann, a researcher in material science and metallurgy at JPL, and visiting associate at Caltech. “You can constantly be changing the composition of the material.”
Rather than adding layers from bottom to top, as in the other 3D printing technology, Hofmann and his colleagues deposit layers of metal on a rotating rod, thus transitioning metals from the inside out. Here laser deposition (LD) – a laser melts metal powder to create the layers – is used to fabricate multifunctional metal alloys. Using the technique in combination with rotational deposition enables fabrication of compositional gradients radially from the center of a sample. The strategically graded composition will alter their mechanical and physical properties.
After removal of 1.5 mm of surface layer, a fully dense gradient rod is obtained.
Although gradient alloys have been created in the past in research and development settings, this is the first time these composite materials have been used in making objects, such as a mount for a mirror (see image below), said John Paul Borgonia, a JPL mechanical engineer.
This is a prototype of a mirror mount that scientists made using a new 3-D printing technique. The part at the top near the glass mirror is made of a metal with low thermal expansion, so that it won’t shrink in space as much as most metals do. Using this kind of metal therefore prevents stress in the epoxy adhesive between the mirror and the metal. The bottom part of this mount is stainless steel, and could be connected to a stainless steel component of a spacecraft. Image credit: NASA-JPL/Caltech
“You can have a continuous transition from alloy to alloy to alloy, and you can study a wide range of potential alloys,” said R. Peter Dillon, a technologist at JPL. “We think it’s going to change materials research in the future.”
The new process could have practical applications in future space missions, auto industry and the commercial aerospace industry, Hofmann said. The work was funded by NASA.