We’ve really owed one of these for a long time, and couldn’t decide whether to call it a “roundup” or an “update.” Well, the technology enables entirely new things, so why not new words? We’re going to try to do one of these once a month.
We’ve been getting pretty deeply immersed in the technology, while not really informing all of you what we’ve been doing and learning. This post is all technical, not legalistic or political.
Some places to learn more
One of the best sources for information and updates on 3D printing of plastic gun parts remains the Defcad forums. Another great resource, although far from gun-centric, is the GrabCAD forum. Some time spent on GranCAD will open your eyes about some of the capabilities.
Finally, there are trade publications. The trade magazine Modern Machine Shop has an Additive Manufacturing supplement every other month, featuring several in-depth stories and a fascinating set of ads. The magazine Desktop Engineering often has 3DP content. And a new online newsletter from New Equipment Digest, 3D Printing 360º, has more links than you can practically read, but you’ll want to try. Another online newsletter we haven’t had time to dig into is 3D Printing Industry. As we said, we’ve spent little time with it but it looks good. There’s a lot of information out there: take a deep breath, pick up the fire hose, and try to take a sip.
Doing the Impossible with Additive Manufacturing
We’ve said before that additive manufacturing comes into its own by enabling designs that were not possilble with traditional subtractive manufacturing. Additive is not going to replace subtractive, which has centuries of experience bringing it to a high state of optimization. But it’s going to enable new things and open new doors to us all. This is very well illustrated by a recent contest held by General Electric. GE wondered if they could crowdsource the redesign of a jet engine bracket. The bracket, made of a machined titanium forging, weighed over 2 kg, and GE would like to reduce the weight by 30% — something any manufacturer would tell you is an ambitious goal. But the 667 entries placed on GrabCAD by contest entrants did the impossible — most of them weighed much less. Nine of the ten finalists, including the ultimate winner, passed physical testing after manufacture by DMLS. The 10 finalists were all around or under 400 grams, and the winner cut the weight of the engine bracket by 84%. Impossible! But real.
(A commenter suggests that the winning part could have been designed by FEA — maybe — and made by casting — if he thinks so, he’s mistaken about the capabilities and limitations of metal casting).
GE hasn’t stopped with one lightweight bracket. It’s now running a second contest for additive manufacturers, and the 10 winners of Phase 1 (who’ve received prize money, a little funding for Phase 2, and materials) are competing for the up-to-three winners of Phase 3: which gets them a $50k prize and the chance to work together with GE going forward. The 10 Phase 1 winners have shown they can (per GE):
Create parts that
- Are made from high density, high atomic number metals, such as refractory metals and/or their alloys
- Have wall thicknesses down to 150 microns, with tolerances ±15 microns
- Precisely position walls 1mm apart, with tolerances ±25 microns
- Exhibit consistent, parallel walls, with little or no warpage across entire part
- Have a high density factor – as close as possible to the density of the bulk material
- Are able to withstand conditions that exert up to 80g’s of acceleration
Yes, that’s a pretty big deal. And if you’re thinking what we’re thinking, you’re thinking, “Not only suitable for firearms, maybe overkill for firearms. Or maybe… revolutionary for firearms.”
Technical advances are coming faster than expected
Additive manufacturing is advancing at the very high rate customary for new technologies, like computers in the 1980s or airplanes in the 1910s.
Additive is quickly finding a place in manufacturing by producing sacrificial patterns for lost-foam casting and in speeding the production of tooling, if not being used for products themselves.
One of the growth areas: figuring out new ways to employ this technology. Laser sintering is widely used to make new parts, but it can also be used to repair old ones. It’s in use already to fix worn or broken injection-molding or die-casting dies or to modify them: “rejuvenation and repurposing” of costly, complex tooling that would otherwise be scrap. A vendor shows a similar example: An injection-molding insert with a broken prong has a new one built up, saving an expensive tool.
“Rejuvenation and repurposing” sounds like something a gunsmith would welcome. Imagine the capability to undo the hackwork of Bubba the Gunsmith! It’s coming.
Until recently, of course, additive manufacturing was limited to ABS or PLA plastic resins, but laser sintering and direct laser melting has made it possible for metal parts, like that GE engine bracket, to be made additively. Those technologies have required industrial-sized, -priced, and -power-using machinery that puts them out of the reach of the home user or the small shop (and has created a whole new market for rapid prototyping service bureaus).
Professor Stuart Williams of Cranfield and the Ti alloy spar.
Cranfield University (this is kind of the RAF’s engineering academy, and probably where Q went to where he learned how to make all the cool stuff for Bond has) has built a large titanium spar section using a process called Wire Arc Additive Manufacturing that is proprietary to Cranfield. It was the largest metal part made by additive manufacturing in the UK at the time. They warn that it will be a while before such a spar takes to the air, but the RAF is already flying non-structural parts like radio covers and PTO shaft guards, experimentally, on its Tornado GR4 fleet. In the long term, this would let field maintainers stock raw materials and digital files instead of large quantities of low-demand finished parts.
Certain laser sintering patents are set to expire this year, making a great reduction in cost very likely. But it remains an industrial technology, not a workbench one. For now.
The coming consumer-grade, metallic 3D Printer
The MTU Low Cost Open Source 3D Metal Printer at work
IEEE Access, a peer reviewed journal, has accepted for publication a paper by four Michigan Technological University materials scientists, engineers and designers and led by Joshua Pearce of the same university’s departments of Materials Science & Engineering and Electrical & Computer Engineering with a first proof-of-concept consumer-grade metal 3D printer. The press release is here; the paper here: A Low-Cost Open-Source Metal 3-D Printer.
The MTU printer is completely open source and they have published the instructions and bills of materials as well as the paper. It cost less than $2,000 (in fact, their materials cost was $1,192.93), and works by using an inexpensive MIG welder — by far the costliest component — to deposit metal.
The machine has only been tested with steel at this time.
The principal limitation at this time is that the machine cannot deposit a voxel smaller than the diameter of the welding rod. It also can’t bridge sufficiently to make parts with horizontal (relative to the machine) holes, so all holes must be vertical if they are to be printed-in.
Pearce has written a book, now in press, about building open-source lab hardware, and he and his MTU Open Sustainability Technology Research Team, alone and with other scholars, have written extensively on additive manufacturing, including a thought-provoking study on the economics of 3D Printing, and articles on creating plastic filament for common 3D printers from recycled bottles.
Meanwhile, the gun guys keep moving forward
There are constantly new designs on the DEFCAD forums and elsewhere online. While some of the files in places like GRABCAD are clearly rubbish, others have serious potential. And everyone in the industry is at least looking at additive for prototyping and tooling manufacture. Meanwhile, the guys who are working with cheap consumer, open-source RepRaps and similar printers keep expanding the envelope and making things like the rimfire pepperbox illustrated here. The relative impracticality of their initial designs, like the relative impracticality of Cody Wilson’s Liberator, should not be overestimated. One is reminded of Ben Franklin’s supposed retort to a woman who asked him what use the Montgolfier brothers’ hot-air balloon was. “What use, madam, is a newborn baby?”
Who’s using this technology now?
The two most important sectors are rapid prototyping and aerospace/defense. Rapid prototyping is a natural for additive, because many iterations of a part may take place before it’s released for series production. And aerospace/defense is a natural because weight and performance may be more important than cost; aerospace MRO organizations, though, are finding cost benefits in distributed additive manufacturing of updated parts and wear parts: the maintenance customer pulls the print (the solid file) from the net and builds it locally.
A third area where Additive is extremely useful is tool production, and one final one is reverse engineering. When you think, “3D printer,” don’t forget that, “3D scanners” — coordinate measuring machines — are improving at a similar, breakneck pace, and those improvements include increased precision and speed at one end of the market, and reduced cost at the low end (MakerBot already offers a low-cost consumer 3D scanner, the Digitizer).
Reverse engineering is often thought of as an espionage technique (governmental and corporate espionage alike), but its most common use in industry seems to be to recover lost drawings or to update drawings and 3D models to match as-produced parts. And the same 3D model that allows you to print a part also allows you to submit the part to FEA (this is how the Army weighed its own redesign of the M9 locking block against Beretta’s to lay the locking-block ear fracture problem to rest — although they didn’t print parts).
That’s who’s using the technology now, but future users are more widespread and eclectic — and probably include you. Recent research at Michigan Tech and by EADS (parent of Airbus Industrie) has documented that home manufacture of some items using a 3D printer can be more economical and more environmentally safe than the current centralized-manufacture-fractal-distribution supply chain is.
So the question you need to be asking yourself is: where will we put the printer?