The maker posts an answer to a query as to what material was used (from the second link I attached):
Riddle - the material is ABS plastic. Unfortunately, I don't know which specific resin, but it's similar to SABIC MG47 or Stratasys P400. It is not as strong/durable as a composite lower made of glass filled Nylon 66, but I'm seeing what other materials I might be able to use.
MPD142 - I believe I paid about $100 for the spool of material this was printed from (closeout price), and I used perhaps a tihird to half of the spool. The cheaper (yet more finnicky) PA-747 based material used in RepRaps, Makerbots and the other low cost printers exploding onto the market would bring the cost down to perhaps $10 each worth of material. It will only get cheaper.
phurba and cms81586 - my original idea was to sleeve the holes with brass tubing to act as bushings, but the pins fit in quite nicely, so I'm running it as-is for now. The only wear I'm seeing is a little bit of back-and-forth movement on the hammer pin, only perhaps 10 thou. I'll keep running it and see if it wears further, or if that's the extent of the break-in.
Wangstang - I posted the .STL file on Thingiverse: Reinforced AR-15 Lower Receiver by HaveBlue - Thingiverse (external - login to view)
fatkid35 - I don't believe I've seen acetal (Delrin) available in filament form that could be run through a 3D printer, but it is certainly up to the task of serving as a lower when machined (external - login to view)
Wow, I greatly underestimated the interest in this project!
hotdog250j - My printed lower fitted out with a parts kit weighs in at 297g, while my Stag Arms lower fitted out identically is 464g.
Caboose314 - The buffer tube threads are just as they came off the printer - zero tapping required! A buffer tube threaded right in, which made me quite happy (I don't have a buffer tube tap, and they aren't cheap). I didn't have to play with any settings at all - the nice thing about the Stratasys machines is that they hold pretty tight tolerances. Stratasys generally quotes accuracy as +/- 0.005", but my machine has a lot of miles on it and could be approaching +/- 0.010". Holes come out a smidge undersized, but I prefer that to being oversized. I did have to tap the grip screw threads, but I'm tempted to experiment with modeling them into the solid as well.
CFCNC - I love it! Very cool, looks great! You know, with a piston .22 upper (I have no idea if such a beast exists), I'd actually be inclined to give it a try! With crank's printed magazine (external - login to view)
, I've been wondering just how much of an AR could conceivably be printed.
NY_Shooter - Buttstock, pistol grips, forends - a 3D printer would be the ultimate tool for making custom furniture. I can easily imagine your local gunsmith having a 3D printer in a few years - rather than having to find a buttstock of just the right size, or messing with adjustable cheekpieces, you could have rifle furniture custom made to fit perfectly, just like a pair of expensive Italian shoes. Have an injury that makes standard stocks or pistol grips uncomfortable or unusable? There's nothing as ergonomic as something tailored to your specific measurements.
RDTCU - I did notice a little bit of flex on the buffer tower, but unless the material is subjected to its yield stress, it should remain elastic and return to shape when the load is removed (ignoring any possible creep deformation). Even so, I intend to increase the thickness on the buffer tower for the next iteration (whenever that is).
Xanatos903 - I don't think a threaded steel insert would be necessary, just sufficient material thickness around the buffer tower. The really high resolution printers generally use a photopolymer rather than a thermoplastic, so you need to consider the brittleness of the material (the black ABS I used is ever-so-slightly rubbery, so it holds up to shocks quite well).
BM-ARM-DPMS-guns - Stratasys machines (what I printed this on, though mine is quite old) start at just under $10k, but that model only has a 5x5x5 inch work envelope (and is brand new in the market - who knows if it will be successful). At $15k, you're looking at something more like a uPrint (external - login to view)
. If you can swing $45k, then you start getting into the really fun toys (external - login to view)
. Your best bang-for-the-buck is to find a used one - I got mine from Craigslist for a cool grand, if you can believe it! If you're seriously looking for one, drop me a line and I may be able to point you in the direction of a used machine at a good price.
Last edited by Locutus; Jul 27th, 2012 at 12:50 PM..