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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Moldy Rechargeable Batteries

What’s worse than coming in from the workbench for a sandwich only to discover that the bread has molded? That red bread mold–Neurospora crassa–can transform manganese into a mineral composite that may improve rechargeable batteries, according to a recent paper in Current Biology.

Researchers used the carbonized fungal biomass-mineral composite in both lithium ion cells and supercapacitors. The same team earlier showed how fungi could stabilize toxic lead and uranium. Mold, of course, is a type of fungus that grows in multi-cellular filaments. Apparently, the fungal filaments that form are ideal for electrochemical use of manganese oxide. Early tests showed batteries using the new material had excellent stability and exceeded 90% capacity after 200 discharge cycles.

The team plans to continue the use of fungus in various metallurgical contexts, including recovering scarce metal elements. This is probably good news for [Kyle]. This is quite an organic contrast to the usual news about graphene batteries.

Image: Qianwei Li and Geoffrey Michael Gadd

[Bil’s] Quest for a Lost Finger: Episode I

A little over a year ago I had a semi-gruesome accident; I stepped off of a ladder and I caught my wedding ring on a nail head. It literally stripped the finger off the bone. This was in spite of me being a safety-freak and having lived a whole second life doing emergency medicine and working in trauma centers and the like. I do have trauma center mentality which means, among other things, that I know you can’t wind the clock back.

hand9A few seconds make an incredible differences in people’s lives. Knowing that it couldn’t be undone, I stayed relaxed and in the end I have to say I had a good time that day as I worked my way through the system (I ended  up in a Philadelphia trauma center with a nearby hand specialist) as I was usually the funniest guy in the room. Truth be told they ask incredibly straight questions like”are you right handed?”  “Well I am NOW”.

So now I could really use a bit of a body hack, having seen the X-Finger on Hackaday long before I knew that I would one day work with them, I was hoping that we could get one to work for me. In speaking with a couple of the mechanical engineers on the Hackaday staff we decided to get [James Hobson] and [Rich Bremer] involved and that the best way to do it was to get a casting of my injured hand out to them.

 

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Injection Molding With Hot Glue

Injection molding is simply forcing a melted thermoplastic into a mold of some sort, letting it cool, and then prying the mold apart to get to the finished piece. Hot glue guns are basically handheld thermoplastic extruders, so when [scorch] dug up some old injection molds he had sitting around, it didn’t take long to put two and two together.

Injection molds aren’t something any normal person has sitting around, but a few years ago [scorch] found two books published by Gingery, the same people who have published instructions on how to build a metalshop from scrap. [scorch] created his molds on a small CNC mill – a Sieg X3 – and his initial experiments with injection molded plastic were fairly successful, even if the molds were made from self-cast billets.

After molding a few hot glue LEGO parts with his equipment, [scorch] had a look around the Internet and noticed this was nothing new. One company even sells a hot glue gun-based injection molding kit using polyethylene glue sticks. Their demo video (seen below) seems much more complicated than [scorch]’s efforts, so  we’ll say he came out ahead on this one.

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Retrotechtacular: The Magic of Making Cars in the ’30s

retrotechtacular-manufacturing-chevrolet

We usually shy away from calling things ‘magic’ in our features because, you know… science. But in the case of this Chevrolet manufacturing reel from 1936 the presentation is nothing short of an industrialized version of The Sorcerer’s Apprentice. Well, not in the sense of mischief, but in that there is almost no explanation and the way the footage is laced together you get the strong feeling that, at the time, this type of industrialization was magic; a modern marvel. The techniques and skills of each worked passed down from a master to an apprentice but virtually unknown to the general public.

The clip, which is also embedded below, starts off in the machine shop where mold makers are getting ready to go into assembly line production. From there it’s off to the foundry for part casting and then into the stamping plant where white-hot (perhaps red-hot, but black and white film) metal is shaped by man-mangling presses. The image above follows the cast, stamped, and machined parts onto the assembly line. We like seeing a room full of pistons being QA checked by hand using a width gauge and micrometer.  The film continues through to the finished vehicle and we think you’ll agree there’s more than enough voyeuristic video here to overcome that lack of narration.

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Fail of the Week: Silicone Molding That Won’t Cure

fotw-uncured-silicone

Mold making is a hacking skill we see pop up around here from time to time. But rarely do we hear about problems in the process, and they must happen. Here’s proof. This Fail of the Week focuses on [Michael’s] unfortunate experience with failed mold making due to uncured silicone around the master mold. It’s worse than it may sound, since he lost about a pound of silicone to the fail, and we’re unsure of whether he can even use the master again (how do you clean uncured silicone off of something?). Not to mention the time lost from setting up the pour and waiting 20 hours for it to cure.

Soon after the issue presented itself [Michael] started researching to see what had gone awry and noticed that the master should have been sealed with acrylic lacquer. This gave him the opportunity to test several different finishes before making a run at the full mold once again. He picked up a variety of the paint products he could find locally, used them to coat some scraps, and globbed on some silicone to see which worked the best.  He found a couple of different primers worked well, as did both glossy and matte acrylic coatings.

If you’ve never had a reason for mold making before, keep it in mind. You’d be surprised what kind of factory-production-type things can be pulled off by 3D printing a master, and casting a silicone mold of it.


2013-09-05-Hackaday-Fail-tips-tileFail of the Week is a Hackaday column which runs every Wednesday. Help keep the fun rolling by writing about your past failures and sending us a link to the story — or sending in links to fail write ups you find in your Internet travels.

Fabricate Your Own 7-Segment Displays

diy-seven-segment-displays

We see more and more projects that use custom molds and casting materials. The latest is this custom seven segment display which [Ray74] put together. The idea of making your own LED displays couldn’t be much easier than this — everything but the LEDs and wire is available at the craft store.

He started by making models of each segment out of pink erasers. The lower left image of the vignette above shows the eraser segments super glued to some poster board. The decimal is a pencil eraser, with a fence of wood to contain the molding material. Amazing Mold Putty was mixed and pressed into place resulting in the mold shown in the upper right.

From there, [Ray] cast the clear epoxy three times. Once dried the clear pieces were sanded, which will shape them up physically but also serves to diffuse the light. They were then placed inside of another mold form and an epoxy pour — this time doped with black enamel paint — finishes the 7-segment module. The final step is to glue the LEDs on the back side and wire them up.

This definitely trumps the build which Hackaday Alum [Kevin Dady] pulled off using hot glue sticks as light pipes.