Thread: 3-D Printers
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Old February 27, 2013, 09:57 PM   #37
barnbwt
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Join Date: May 17, 2012
Posts: 680
Quote:
I'm unfamiliar with the terms RP or FCG. Have no idea.
Forgive my TLAs (three letter acronyms):
RP-Rapid Prototyping
(subtypes; FDM=melted plastic addition; SLA=UV laser cured epoxy resin)
FCG-Fire Control Group (trigger, sear, disconnector,hammer, safety, their pivots, and housing)
CYA-cover your...we all know this one already

Quote:
IRCC? Does that mean you haven't seen it? You haven't seen it work?
Of course I haven't . Like many things we "hear" about, I heard about it and passed it along. It was on Thingiverse (now purged of gun stuff ) and, yes, mostly served as a "concept" of what a 100% mag looks like. However, it worked well enough the designer exluded it from his file release as a CYA so he wouldn't end up in the papers if some killer used his magazine. (Not very trusting of the gun-owning public, is he?)

The current RP designs are facsimilies of older metallic forms, and are therfore doomed to failure. But plastic has a modulus and yield point, therefore a functioning spring can be made. Yes, it will be huge (and short lived) compared to a steel leaf spring. But that's not the point of the guy's excercise. It's a working spring, a working follower, and a working mag-body with feed lips. They don't work well yet, but the concept is sound, the design will improve, and the current issues and shortcomings will be addressed. That's innovation. I can already see someone trying to epoxy some fiberglass tape to the spring to make it truly functional.

Quote:
And that spinning thing doesn't have anywhere near the close tolerances needed in a working gun.

Upper portion of an Eiffel Tower model made on the Form 1 . Though they may not be ready for all firearms applications just yet (though I still think that will change soon), makers of table-top game pieces are on notice

The Form 1 printer by Formlabs is spec'ed at 10 microns for accuracy--tight enough for a finish as smooth as injection moulding. Tight enough that the similiarly-made (SLA) AR lower made by Distributed Defense that's shot 600 rounds (so far with no wear) needed no thread-chasing on the formed threaded holes.

Tolerance aside, the thing that spinning toy impresses me the most with is that there is no other way to make it. (I also saw in a still-photo that the spheres aren't loose; each layer rotates on pin-bushings mounted on the next layer.) Just think of all the new design possibilities that open up when you can form additively like this! Intricate, high-tolerance details suddenly become as easy/cheap to make as a planar face!

Back in school, professors/students were constantly printing assembled mechanisms (gears and stuff for optics gimbals they were designing, if memory serves). My rockets design class even used a FDM-formed dowel to mould the inner combustion chamber cavity of our solid fuel plug*. The star-shaped piece was stout enough to be pushed out of a 6" long block of adhered wax/polymer mixture by a press. The stuff's plenty tough, but the layers are bonded to each other very weakly, making it bad for tension. SLA is much better for that.

Quote:
Printed guns are currently fiction. Maybe someday, in fact I'd invest money in a company that I thought could do it. But no one has done it yet.
That's true, but it's not fair to claim it can't be done until it finally is, either. Honestly, I really hope no one does make a poly-gun until this current ban-storm passes, because many folks get real reactionary when ordinary citizens are empowered to do stuff for themselves. I'm saving up for a Form 1 because I want to invest in a small, new, American company that I think has the potential to market a prototyper that can actually do some things, and will only get better with development. And at a price point that approaches affordable for many people. And because I think it has a place in producing (even now) functional parts for firearms and tons of other uses (like 922r compliance parts for my obscure-as-all-get-out Stgw57 build).

TCB

*nifty engine test videos; ignition at the minute mark for both
Engine test 1
Engine test 2
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