Making a Gun Without a 3D Printer

Around four years ago the world was up in arms over the first gun to be 3D printed. The hype was largely due to the fact that most people don’t understand how easy it is to build a gun without a 3D printer. To that end, you don’t even need access to metal stock, as [FarmCraft101] shows us with this gun made out of melted aluminum cans.

The build starts off by melting over 200 cans down into metal ingots, and then constructing a mold for the gun’s lower. This is the part that is legally regulated (at least in the US), and all other parts of a gun can be purchased without any special considerations. Once the aluminum is poured into the mold, the rough receiver heads over to the machine shop for finishing.

This build is fascinating, both from a machinist’s and blacksmith’s point-of-view and also as a reality check for how easy it is to build a firearm from scratch provided the correct tools are available. Of course, we don’t need to worry about the world being taken over by hoards of angry machinists wielding unlicensed firearms. There’s a lot of time and effort that goes into these builds and even then they won’t all be of the highest quality. Even the first 3D printed guns only fired a handful of times before becoming unusable, so it seems like any homemade firearm, regardless of manufacturing method, has substantial drawbacks.

Thanks to [Rey] for the tip!

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A Great Way to Make Quick and Easy Knobs

Here’s a great way to quickly and easily make attractive and functional knobs with no tools required. All you need is some casting resin (epoxy would do in a pinch), a silicone mold intended for candy, and some socket head bolts. With the right preparation and a bit of careful placement and attention, smooth and functional knob ends are only minutes away. Embedded below is a short video demonstrating the process.

These may not replace purpose-made knobs for final products, but for prototypes or to use around the shop on jigs, clamps, or furniture they certainly fit the bill. With a layer of adhesive fabric or rubber, they might even make serviceable adjustable feet for low-stress loads.

This technique could be extended to reproducing broken or missing dakaware or bakelite knobs. This, of course, would require an original, unbroken knob and a small silicone mold, but it’s still a project that’s well within the capabilities of the garage-bound hacker.

While we’re on the subject of knobs, don’t forget we’ve seen an excellent method of repairing knobs as well.

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Silicone Molds for Stove-Top Metal Casting

Casting metal parts from 3D-printed plastic or Styrofoam models is all the rage these days, and for good reason — casting is a way to turn one-offs into mass-produced parts. Seems like most of the metal casting projects we feature are aluminum in sand molds, though, so it’s refreshing to see a casting project using silicone molds to cast low-melting point metals.

Don’t get us wrong — sand-cast aluminum is a great method that can even be used to build a lathe from scratch. But not everyone wants to build a foundry and learn the sometimes fussy craft of creating sand molds. [Chris Deprisco] wanted to explore low-melting point bismuth alloys and set about making silicone rubber molds of a 3D-printed Maltese falcon. The bismuth-tin alloy, sold as a substitute for casting lead fishing weights, melts on at 281°F (138°C) and is cool enough for the mold to handle. Initial problems with bubbles in the cast led to a pressure vessel fix, and a dull, grainy surface was fixed by warming the mold before the pour. And unlike sand molds, silicone molds are reusable.

Of course if aluminum is still your material of choice, there’s no need for a complicated foundry. A tuna can, a loaf of bread, and a handful of play sand is all you need to make custom parts.

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Custom Aluminum Wheels Teach a Thing or Two about Casting

For some mobile projects like small carts or rolling cabinets, your standard casters from Harbor Freight will do just fine. But some projects need big, beefy wheels, and these custom cast aluminum wheels certainly make a statement. Mostly, “Watch your toes!”

To be honest, [Brian Oltrogge]’s wheels are an accessory in search of a project, and won’t be crushing feet anytime soon. He made them just to make them, but we have no beef with that. They’ve got a great look that hearkens back to a time when heavy metal meant something else entirely, and things were made to last. Of course, being cast from aluminum sort of works against that, but there are practical limits to what can be done in the home foundry. [Brian] started with a session of CAD witchcraft followed by machining the cores for his molds. Rather than doing this as lost foam or PLA, he milled the cores from poplar wood. His sand mix is a cut above what we usually see in home-brew sand casting — sodium silicate sand that can be cured with carbon dioxide. All his careful preparation meant the pour went off without a hitch, and the wheels look great.

We’ve featured quite a few metal casting projects recently, some that went well and some that didn’t. [Brian] looks like he knows what he’s doing, and we appreciate the workmanship that he puts on display here.

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Fail of the Week: Sand Casting Copper

There’s trouble in the Kingdom of Random – the smithies of the realm are having trouble sand-casting copper. And while [King Grant] might not be directly asking for help, we think the Hackaday community might have plenty to say about his efforts.

We’ve all seen plenty of sand casting efforts before, including attempts to make otherwise unobtainable engine parts. And “lost foam” casting, where a model of the part is constructed of polystyrene foam that flashes off when the molten metal is poured, is a relatively new twist on the technique that’s been used to good effect on a recent Gingery lathe build. But most backyard foundries work in aluminum, which is apparently much easier to work with than the copper that [Grant Thompson] is working with. Ironically, his first pour worked the best — not perfect, but at least the islands defining the spokes of his decorative piece didn’t break off and float away as they did in every pour shown in the video below. That leads us to think that the greensand is too dry by the second video. Or perhaps the density of copper just makes it more likely for the sand to float. Maybe a cope and drag mold is in order to keep the islands in place and direct the flow of the copper better.

We know there’s a lot of expertise out there, so sound off in the comments about what you think is going on with these pours.

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Struggling Robot Made With DIY Soft Limbs

[Jonathan Grizou] is experimenting with robot designs, and recently stumbled upon a neat method for making soft robots. While his first prototype, a starfish like robot, doesn’t exactly “whelm” a person with it’s grace and agility, it proves the concept. Video after the break.

In this robot the frame is soft and the motor provides most of the rigidity for the structure. The soft parts of the frame have hardpoints embedded into them for mounting the motors or joining sections together. The sections are made with 3D printed molds. The molds hold the 3D printed hard points in place. Silicone is poured into the mold and left to cure overnight. The part is then demolded and is ready for use.

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DIY Cast AR-15 Receivers Are More Interesting Than Expected

For some reason the US News media decided on the AR-15 as the poster child of guns that should not be allowed to be made for, or sold to, the consumer. The words still out on the regulation, but, in a very American response, a whole market sprang up around people saying, “Well, then we’ll just make our own AR-15.”

Ordinarily, we wouldn’t cover this sort of thing, but the work [AR-15Mold] is doing is just so dang interesting. They sell a product that enables the home user to cast an AR-15 receiver out of high performance resin. In the process they made a really informative three part video on the casting process.

A lot of people are interested in the product, and having fun with it. In this two part video series, [Liberty Marksman] cast their receivers and test them to destruction. In one video they see how many rounds they can fire out of the gun before it breaks. When it breaks, they excitedly tear down the gun to see where it failed.

It’s quite a bit of fun to watch. Videos after the break.

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