this post was submitted on 21 Sep 2023
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[–] themeatbridge@lemmy.world 44 points 1 year ago (4 children)

I don't trust a 3d printed gun, why would I trust a 3d printed car? But if I could make a car myself, I definitely would, even if I had to pirate the designs.

[–] rockSlayer@lemmy.world 31 points 1 year ago (2 children)

3d printed firearms have transformed into a whole cottage industry with all sorts of variations. The ones that are safest are essentially just stocks capable of holding the parts of a firearm. The ones that are completely 3d printed are still pretty sketchy and illegal to sell

[–] Zron@lemmy.world 21 points 1 year ago (2 children)

Any firearm that you, a private citizen, manufacture, is illegal to sell.

You are not a licensed firearm distributor.

But, at least in most of the US, it is perfectly legal to manufacture them for your own use. You just can’t sell them.

[–] nBodyProblem@lemmy.world 8 points 1 year ago (1 children)

You can sell homemade firearms you made for personal use and later decided to get rid of.

You cannot manufacture them for the purpose of sale, however.

[–] Tar_alcaran@lemmy.world 4 points 1 year ago (2 children)

That sounds like a pretty massive loophole...

[–] nBodyProblem@lemmy.world 2 points 1 year ago

Why? What’s wrong with selling a gun you have made at home? It’s still subject to applicable law on private party transfers just like any other firearm.

[–] BearOfaTime@lemm.ee 1 points 1 year ago

IIRC, it depends on state law too. Some states permit local sales, feds would stomp on you if you sold to a non-resident.

Probably best to avoid the selling part altogether. Ruby Ridge and all that.

[–] rockSlayer@lemmy.world 3 points 1 year ago (1 children)

that's true. I should have specified that a lot of the purchasable (fully and unquestionably in the right) stuff just sell CAD files for 3d printed parts, or print the parts for you. The more questionable ones sell ghost gun kits

[–] ArcaneSlime@lemmy.dbzer0.com 2 points 1 year ago* (last edited 1 year ago)

It is illegal for them to print the guns for you (unless they have their FFL; and Manufacturers license; and they NICs check you, and engrave a serial number, company name, and location of manufacture in accordance with ATF rules.) And the "ghost gun kits" are 80% complete lowers, which you have to mill the remaining bits yourself or else it is subject to all the above rules as well.

They can sell the .stl files though, or freely offer them.

[–] nBodyProblem@lemmy.world 14 points 1 year ago* (last edited 1 year ago) (1 children)

The thing people forget is that 3d printing doesn’t just enable the direct manufacturing of parts, it also enables the manufacturing of tooling for parts that would never have been manufacturable at home otherwise.

For example, you can rifle a metal tube and form a chamber using electro etching and printed tooling. Or, you can make tooling to make magazine springs

The key point to be made here is that a fully plastic gun is sketchy but 3d printing has absolutely transformed the ability to make reliable and effective firearms at home without any off the shelf firearm parts

The same type of thing is happening in the car hobbyist world. We aren’t printing cars but people are using prints to make molds, form sheet metal, align parts for weldments and manufacture low stress plastic parts like intake manifolds.

[–] themeatbridge@lemmy.world 3 points 1 year ago (1 children)

reliable

Out of everything you said, this is the only thing that I disagree with, but it's the only thing that matters. I mentioned 3d printed guns because, if you don't use off the shelf parts, you really don't have any way of knowing how many rounds you can put through it before it explodes in your hand. Was there a tiny defect in your print? A misalignment or some debris in the print material? You're right that boring your chambers from stock is safer, but that doesn't make it safe. And that's a firearm you can inspect after each round.

A car has many critical components under the hood, especially when you use an internal combustion engine. That's a bunch of tiny explosions every second, and even setting that aside, you have the transmission, the brakes, the steering, the windshield, the stereo, any one of those could fail and kill you (or make life not worth living, in the case of that last one).

3D printing will continue to evolve and improve, but it will be a long time before I trust it enough to download a car.

[–] nBodyProblem@lemmy.world 2 points 1 year ago* (last edited 1 year ago)

I mentioned 3d printed guns because, if you don't use off the shelf parts, you really don't have any way of knowing how many rounds you can put through it before it explodes in your hand.

I mean. Ya kinda do. A broken receiver isn’t going to make the gun explode in your hand, it’s just going to cease being functional.

Was there a tiny defect in your print? A misalignment or some debris in the print material?

More importantly, the issue with small defects is sidestepped by good engineering and process control. Your statement applies to almost every sort of manufacturing. All materials have internal defects and a range of potential material properties. You account for this by applying a safety factor so that the design stresses are well below the nominal material properties. For a material with higher uncertainty on the properties you simply apply a higher safety factor

That’s why many 3d printed guns look like bricks when an injection molded receiver would be much more sleek in comparison.

A car has many critical components under the hood, especially when you use an internal combustion engine. That's a bunch of tiny explosions every second, and even setting that aside, you have the transmission, the brakes, the steering, the windshield, the stereo, any one of those could fail and kill you (or make life not worth living, in the case of that last one).

Home built cars have been a thing pretty much since the start of the automobile. People who home-build cars don’t typically build their own drivetrain. It’s just not worth the effort when donor engines from wrecked cars can be had cheaply and easily.

Usually the DIY fabrication work involves building the chassis, suspension components, body panels, etc. As I pointed out, you wouldn’t just print the chassis. You’d use printed parts as jigs to align the welds, build mold for composite pieces, etc.

Nobody is going to be printing a complete car in the conceivable future, but 3d printing can absolutely help you build a good and reliable car from conventional materials with greatly reduced effort and tooling costs.

[–] FuglyDuck@lemmy.world 2 points 1 year ago

3d printing has come a long way, both in materials and quality. especially as you step away from FDM or resin printers. I certainly wouldn't trust a rando facebook marketplace printer who bought a creality to make a quick buck... but I would trust my own prints- mostly because I know what the materials are, and know I'll check for good print quality. reality is, though, that about the most you can print right now is a half baked golf cart chasis. if you want it to be safe... you're going to have to add a lot to it, and at that point, you might as well just buy a damn car or something.

[–] Honytawk@lemmy.zip 2 points 1 year ago

Most dashboards in cars are already 3d printed.