Glue Your Sumo Robot to The Mat With Custom Sticky Tires

Mini Sumo seems like one of those hobbies that starts out innocently enough, and ends up with a special room in the house dedicated to it. One day you’re excitedly opening up your first Basic Stamp kit, and the next you’re milling out mini molds on a mini lathe to make mini extra sticky tires.

[Dave] started out trying to find a part from the local big box store that was just a little bigger than the wheel he wanted to rubberize. He set the wheel inside a plumbing cap and poured the urethane in. It worked, but it required a lot of time with a sharp knife to carve away the excess rubber.

In the meantime he acquired a Sherline Mini Mill and Lathe. With the new tools available to him, he made a new mold out of a bit of purple UHMW and some acrylic. This one produced much nicer results. Using a syringe he squeezed resin into the mold through a hole in the acrylic. Much less cleanup was needed.

He later applied these methods to smaller, wider wheels as his mini sumo addiction took a stronger hold on his life.

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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Hacker Straightens Own Teeth

So you say your wonky smile has you feeling a bit self-conscious? And that your parents didn’t sock away a king’s ransom for orthodontia? Well, if you have access to some fairly common fab-lab tools, and you have the guts to experiment on yourself, why not try hacking your smile with DIY braces?

First of all: just – don’t. Really. But if you’re curious about how [Amos Dudley] open-sourced his face, this is one to sink your teeth into. A little research showed [Amos] how conventional “invisible” braces work: a 3D model is made of your mouth, each tooth is isolated in the model, and a route from the current position to the desired position is plotted. Clear plastic trays that exert forces on the teeth are then 3D printed, and after a few months of nudging teeth around, you’ve got a new smile. [Amos] replicated this hideously expensive process by creating a cast of his teeth, laser scanning it, manipulating the teeth in 3D modeling software, and 3D printing a series of intermediate choppers. The prints were used to vacuum mold clear plastic trays, and with a little Dremel action they were ready to wear. After 16 weeks of night and day wear, the results are pretty amazing – a nicely aligned smile, and whiter teeth to boot, since the braces make great whitening trays.

Considering how badly this could have turned out, we’ve got to hand it to [Amos] for having the guts to try this. And maybe he’s onto something – after all, we’ve advocated for preemptive 3D scanning of our bodies recently, and what [Amos] did with this hack is a step beyond that.

[LupusMechanicus], thanks for the tip!

Machine Shop Soaps Are Good, Clean Learning Fun

At first glance, it’s easy to dismiss the creation of custom bath soaps as far outside the usual Hackaday subject matter, and we fully expect a torrent of “not a hack” derision in the comments. But to be able to build something from nothing, a hacker needs to be able to learn something from nothing, and there is plenty to learn from this hack.

On the face of it, [Gord] is just making kitschy custom bath soaps for branding and promotion. Cool soaps, to be sure, and the drop or two of motor oil and cutting fluid added to each batch give them a little machine shop flair. [Gord] experimented with different dyes and additives over multiple batches to come up with a soap that looked like machined aluminum; it turns out, though, that adding actual aluminum to a mixture containing lye is not a good idea. Inadvertent chemical reactions excepted, [Gord]’s soaps and custom wrappers came out great.

So where’s the hack? In stepping way outside his comfort zone of machining and metalwork, [Gord] exposed himself to new materials, new techniques, and new failure modes. He taught himself the basics of mold making and casting, how to deal with ultra-soft materials, the chemistry of the soap-making process, working out packaging and labeling issues, and how to deal with the problems that come from scaling up from prototype to production. It may have been “just soap”, but hacks favor the prepared mind.

Fail of the Week: Not All Mold Releases Release All Molds.

I’m writing a series of articles on resin casting as an extension to my experiences with the instructions found in the wonderful Guerrilla Guide. However, mistakes were made. Having run out of my usual mold release I went to a back-up jar that was lying around from a casting project long, long ago in a workshop far, far away.

GLUE
Never much for readin’ the nutrition facts myself.

I’m refining a technique of making a mold the quick and dirty way. Everything was going well, the sprues looked good and the master released from the silicone. It was time to do the second half of the mold. As usual I applied a generous amount of mold release. Since it was the first time this mold was to be used I went ahead and did all the proper steps. Rubbing off the dried release and applying a few more coats just to be sure.

I was completely unaware that I was applying mold release designed for urethane molds only. In other words I thoroughly covered my silicone mold in silicone bonding agents. I remained unaware until trying to separate the halves of the mold and found them thoroughly joined. After going through the stages of grief I finally figured out where it all went wrong.

Oh well. I’m ordering some of my regular pick, Stoner A324, and that should do the trick. There’s also Mann- Ease Release 200. While having probably the best name a release agent can have, it doesn’t work as well and needs approximately 100 years to dry. After this setback I’d rather just, grudgingly, learn my lesson and order the correct thing.

I wonder if the smooth-on description can say URETHANE RUBBER a few more times.
Oh. Yes I see. Urethane… Urethane…

So now that we know the right way to fix this is to order the right product, is there a hack to get around it? Does anyone have a homebrew trick for release agent that can be used in a pinch? Leave your comments below.

An Introduction to Casting With Nuka Cola

There’s less than a month until the next Star Wars is released, and consequently a few weeks until amateur propmakers and cosplayers go insane fabricating their own lightsabers with lightsaber cross guards and rolling robots. Until then, Fallout is pretty cool and [Bill] is here to give us an introduction to prop making with one of the defining objects of this post-apocalyptic universe. He created a real life copy of a Nuka Cola bottle and created a great introduction to resin casting in the process.

As with all proper part making endeavours, this project began with getting reasonably accurate models of the object to be copied. In Fallout, we’re lucky enough to have a way to look at a specific object while zooming and spinning around it, giving [Bill] the basic shape. The size was rather easy as well: all bottlecaps are the same size, so [Bill] just scaled the model to that.

With the model created and the part printed out, assembled, and finished, it was time to create the mold. [Bill] used a two-part silicone mold for the basic shape. The actual casting was done by rolling around a little resin on the inside of the mold. There’s no need for a solid, bottle-shaped block of resin; bottles are hollow anyway.

There are a few neat tricks [Bill] has up his sleeve, including coating the inside of the mold with aluminum powder and using a vinyl cutter to get the labels and logos exactly right. The finished product turns out great, perfect for leaving in the Wasteland for 200 years until the Sole Survivor stumbles upon it.

Video below.

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3D Printed Eyeglasses, VR Lenses

[Florian] is hyped for Google Cardboard, Oculus Rifts, and other head mounted displays, and with that comes an interest in lenses. [Floian] wanted to know if it was possible to create these lenses with a 3D printer. Why would anyone want to do this when these lenses can be had from dozens of online retailers for a few dollars? The phrase, ‘because I can’ comes to mind.

The starting point for the lens was a CAD model, a 3D printer, and silicone mold material. Clear casting resin fills the mold, cures, and turns into a translucent lens-shaped blob. This is the process of creating all lenses, and by finely sanding, polishing, and buffing this lens with grits ranging from 200 to 7000, this bit of resin slowly takes on an optically clear shine.

Do these lenses work? Yes, and [Florian] managed to build a head mounted display that can hold an iPhone up to his face for viewing 3D images and movies. The next goal is printing prescription glasses, and [Florian] seems very close to achieving that dream.

The last time we saw home lens making was more than a year ago. Is anyone else dabbling in this dark art? Let us know in the comments below and send in a tip if you have a favorite lens hack in mind.