3D printed jet engines, prosthetic limbs, and car engines.

06 March 2015

The state of the art of personal 3D printing is still in a state of flux. Mostly, we're still limited to variants of low-melting point plastics and we're still figuring out new and creative ways of making more complex shapes that are self-supporting to some extent. What isn't getting a whole lot of press right now are some industrial applications of this technology, some of which date back a good decade.

For example, a research team consisting of personnel from Monash University in Australia, the Commonwealth Scientific and Industrial Research Organisation, and Deakin University recently unveiled the world's first 3D printed jet engine. They started the project with the design for an older model gas turbine jet engine, which are nothing to sneeze at anyway and reverse engineered it. Each major component was scanned, probably with a laser, and the data was used to work up a mesh that was then sliced into layers that the 3D printer could lay down successively. A certain amount of geometric jockeying was most assuredly involved in getting each piece positioned optimally for fabrication. The 3D printer used to build the components was based upon selective laser sintering and used alloy dust as its feedstock; each layer laid down was approximately 0.05 mm thick, or about 1/30 the width of a line drawn with a #2 pencil (remember those?) Two copies of each part were fabricated, a process that, all in all took about a year to accomplish. As far as I know the jet engines haven't been spun up yet but are on display. Frankly, they're not sure they'll work as-is so they're going back to the drawing board and double checking their work to make sure that the fruits of their labors won't suddenly turn into so much shrapnel if they're fired up.

In 2002 one Nicolas Huchet lost his right hand at the wrist in an an accident at work. Sounds like a pretty simple way to set up a story that's about to take a hairpin turn into unexpected territory, doesn't it? He eventually acquired a myoelectric prosthesis but soon ran into its functional limits insofar as using and teaching DAW software. In October of 2012 Huchet stepped into a fablab and began a project of epic proportions, designing and building his own prosthetic hand. From the moment he saw his first 3D printer the spark was lit. Add to the volatile mix an Arduino or two and what appears to be a few components from the InMoov project to interface the servomotors and by February of 2013 Huchet and a few hackers from the fablab had finished a prototype prosthetic hand. The superstructure, joints, and phalanges of the hand were run off on a 3D printer and appear to have been assembled using off-the-shelf hardware, like screws and bolts. High test fishing line was used in lieu of tendons for actuating the digits; I've no idea what kind of motors are doing the heavy lifting but their power requirements interest me. Costing something like $250us to construct in total, the open source unit is actuated by picking up and interpreting electrical impulses from the muscles in Huchet's forearm and is nearly (if not just as) functional as a commercial prosthetic limb costing over 300 times as much. Rather than trying to achieve an "opera hand," or as close to normal as possible appearance, Huchet and company seem to have gone for the cyberpunk "high-tech wires and chrome" look. A bunch of talented hackers built that arm and there's no two ways about it.

Incidentally, if anyone out there is interested in getting involved in the open source prosthetics movement I strongly recommend getting in touch with the E-Nabling the Future community.

For quite a few years the automotive industry has been using very sophisticated 3D printers to manufacture engines for cars because they're more efficient to produce that way and tend to be somewhat more sturdy. Having been a Toyota owner for a decade, I can vouch for their sturdiness: They run very quietly, almost silently right up until they're about to die, and then they go out with a bang that the entire neighborhood hears. However, getting back to the story at hand, 3D hacker and mechanical engineer Eric Harrel decided to see if he could reverse engineer a Toyota 4 cylinder 22RE engine and make printable meshes from it to build his own engine. The 22RE has 80 distinct components that fit together with very tight tolerances (as one would expect of a 21st century engine) so the entire design project required around 60 hours from start to finish to engineer each component, including scaling them to 35% of normal so they could be run off in his 'printer (modulo a handful of springs, fasteners, and bearings that had to be purchased or fashioned some other way). Fabbing each of those components took another 72 hours in total. I don't know how long it took to finish and assemble the scaled down engine but my wild guess would put it around another 72 hours in total. At the end, though, the pistons drive, the valves work, and the driveshaft turns. The greyprints are available on Thingiverse for download if you've got a mind to try it yourself.

If 3D printers are toys, they're fabulously capable toys.