I have two 3d printers and I am currently upgrading their performance so I have a fairly good understanding of them. To help explain it to others, I walk them through the following thought exercise.
Think of a ream of regular printer paper - 500 sheets. Now imagine taking each sheet through a “bath” or soaking of glue. As a last step, while the glue is still wet, lay all of the sheets down on top of each other. When it dries, you will have a fairly solid brick.
Ok, now lets modify this process slightly. Imagine that as each sheet is put down, JUST BEFORE it is put down, the excess of the sheet is cut away. Think of our desired object being a butter knife. The normal ream of paper would be very wastefull to cut down all those individual sheets. So instead, I have a nozzel that extrudes, much like expoxy out a small hole (usually 0.4 or 0.35 mm in size) a tiny ribbon of the glue and paper mix.
At each layer, it prints the outline of the object and then fills in the solid parts by going back and forth and laying down the mix of glue and paper. Then when that layer is done, the head lifts just a tiny fraction (0.1 mm) and then extrudes the next layer.
This is how FDM works. There are other techniques but they tend to be more expensive. You still have the limitations of the material be it plastic, chocolate, wax etc. So if you use plastic, you will have a plastic gun. Usable for support parts but not really a good idea for the barrel. However there are other techniques that would allow you to use steel and construct that barrel.
What are the realistic benefits of 3D technology in your opinion? For instance, will it have more impact on manufacturing or consumers? Speaking as a layman it seems as if no-one knows for sure how this technology will play out.
“However there are other techniques that would allow you to use steel and construct that barrel.”
It is called SLS or laser sintering. I have all of my designed parts made of this process with fiberglass filled nylon. It is far stronger than FDM and is in use on limited production pieces on some of my projects. I do not possess a machine but the price is about half of FDM when using two sources both of which are far less than the “street’ sources like Solid Concepts and the other big players who dominate the marketing side.
SLS is also capable of using different metal powders in the same way to produce weapons that can stand the pressures.
It'd work okay for a gyrojet, or the 40mm high-low pressure chamber system of the 40mm M79/M203 grenade launcher. I know, since in the early 1980s, we were considering a double-barreled, over and under alternative to the Sten gun as a possible item for mass production and airdrop to a potential arming of the Polish resistance Solidarity movement. As it turned out, the actual manufacture of those [and other nifty tools for a potential Polish resistance movement, including an anti-tank version of the Claymore mine, based on the Rockeye cluster bomb munition] was unnecessary, since even the thought of one Soviet *fraternal socialist* country engaged in such acts could well have given the others similar ideas. Would Reagan have done it? Above my pay grade. But the Soviets backed down, and Poland is now one of the few bright spots of relative individual freedom in Europe.
Speaking of the 9mm Sten, I suppose you know that during WWII, some Stens had barrels that were made of a flat rectangular steel plate with 4 grooves milled diagonally across it, which was then bent around a mandrel and fusion-welded at the joint seam and chambered. Nowadays, that'd be done with an Appel-process hammer forging, but even 75 years ago, there were production shortcuts that worked pretty well when the economies of scale were right. Some of those Stens were produced for less than $5,00 each; the 7 magazines that accompanied each gun in its waxed cardboard shipping carton cost more to build than the gun did. And that caused US Army Ordnance to look real hard at the $200 per copy M1928A1 Thompson and $85 per M1A1 versions, and come up with the M3 and M3A1 *grease guns* at circa $18 each instead.