Modular Box Design Eases Silicone Mold-Making

Resin casting is a fantastic way to produce highly detailed parts in a wide variety of colors and properties, and while the process isn’t complicated, it does require a certain amount of care and setup. Most molds are made by putting a part into a custom-made disposable box and pouring silicone over it, but [Foaly] was finding the process of making and re-making those boxes a bit less optimized than it could be. That led to this design for a re-usable, modular, adjustable mold box that makes the workflow for small parts considerably more efficient.

The walls of the adjustable box are four identical 3D-printed parts with captive magnets, and the base of the box is a piece of laser-cut steel sheet upon which the magnetic walls attach. The positioning and polarity of the magnets are such that the box can be assembled in a variety of sizes, and multiple walls can be stacked to make a taller mold. To aid cleanup and help prevent contamination that might interfere with curing, the inner surfaces of each piece are coated in Kapton tape.

The result is a modular box that can be used and re-used, and doesn’t slow down the process of creating and iterating on mold designs. The system as designed is intended for small parts, but [Foaly] feels there is (probably) no reason it can’t be scaled up to some degree. Interested? The design files are available from the project’s GitHub repository, and if you need to brush up a bit on how resin casting works, you can read all about it here.

Mold-Making Masterclass In Minutes

Making silicone molds seems easy, but there are a lot of missteps to be made along the way that can mean the difference between a great, reusable mold, and one that’s a sad waste of silicone. If you’re helpless to know the difference, then check out [Eric Strebel]’s 9-minute masterclass teaser video on making a two-part mold for resin casting, which is also embedded below.

Even if you already know how to do this, there’s probably a good tip in here somewhere. One of them being that you should always pour your silicone from one place and let it coat the piece being copied. Otherwise, there might be lines on the mold. Another tip is for DIY mold release made from petroleum jelly thinned with naphtha.

Our favorite tip has to do with the way [Eric] makes this a reusable two-part mold, which is more akin to injection molding. To pour silicone for the second part and get it to separately nicely, [Eric] uses sprues made out of resin rods that were cast inside of drinking straw molds. These he chamfers against a belt sander to minimize the contact with the cast part, which makes them a snap to break off. [Eric] says this is just the beginning, and there are more videos to come that will break down the steps.

There’s more than one way to make a mold, especially for casting in metal. We’ve seen everything from 3D-printed molds to kinetic sand.

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Hackaday Podcast 070: Memory Bump, Strontium Rain, Sentient Solder Smoke, And Botting Browsers

Hackaday editors Elliot Williams and Mike Szczys bubble sort a sample set of amazing hacks from the past week. Who has even used the smart chip from an old credit card as a functional component in their own circuit? This guy. There’s something scientifically devious about the way solder smoke heat-seeks to your nostrils. There’s more than one way to strip 16-bit audio down to five. And those nuclear tests from the 40s, 50s, and 60s? Those are still affecting how science takes measurements of all sorts of things in the world.

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download (60 MB or so.)

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Pumping Concrete

Due to social distancing, gym rats throughout the world are turning everyday objects into exercise equipment to keep up the routine without actually hitting the gym. A particularly pleasing version of this are these concrete dumbbells whipped up by the unfortunately named hacker [ShitnamiTidalWave].

If you happen to have half a bag of concrete — quick set or otherwise — out in the shed you can follow the lead on this one. But even if you’re not the kind of person who has “arm day” on your calendar (most of us here in the Hackaday bunker do not) this hack is still worth your time. Mold making is one of the uber-useful skills you should have in your hacker toolkit and [ShitnamiTidalWave] has done both an excellent job of building a mold, and of explaining the process.

Raw material for this one couldn’t be easier; each mold is made out of plywood, 2×4 stud, and nails, along with handles made of 3/4″ PVC pipe. The studs were ripped down and used to create the 45 degree chamfers at each edge. Mold-making veterans will tell you that release agent is a must and in this case rubbing the insides of the molds with wax made it a snap to pry the wooden forms off of the set concrete.

Concrete has a tendency to crack as it cures so if you’re casting large pieces like this touch-sensitive concrete countertop you might want to throw in some fiber reinforcement to the mix. If you’re keen on seeing some of the more impressive mold-making skills at work, check out how metal parts are cast from 3D-printed molds and how a master duplicates parts using silicone molds.

[via r/DIY]

Giant LEDs, Ruby Lasers, Hologram Displays, And Other Cool Stuff Seen At Maker Faire Rome

Hackers from all over Europe descended upon Rome last weekend for the Maker Faire that calls itself the “European Edition”. This three-day event is one of the largest Maker Faires in the world — they had 27,000 school students from all over Italy and Europe attend on Friday alone.

This was held at Fiera Roma, a gigantic conference complex two train stops south of the Rome airport — kind of in the middle of nowhere. I was told anecdotally that this is the largest event the complex hosts but have no data to back up that claim. One thing’s for certain, three days just wasn’t enough for me to enjoy everything at the show. There was a huge concentration of really talented hardware hackers on hand, many who you’ll recognize as creators of awesome projects regularly seen around Hackaday.

Here’s a whirlwind tour of some of my favorites. On that list are a POV holographic display, giant cast-resin LEDs, an optical-pump ruby laser built out of parts from AliExpress, blinky goodness in cube-form, and the Italian audience’s appreciation for science lectures (in this case space-related). Let’s take a look.

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Hackaday Podcast Ep16: 3D Printing With Steel, Molding With Expanded Foam, QUIP-Package Parts, And Aged Solder

Join editors Elliot Williams and Mike Szczys to recap the week in hardware hacking. This episode looks at microfluidics using Shrinky Dinks, expanding foam to build airplane wings, the insidious effect of time on component solder points, and Airsoft BBs used in 3D printing. Finishing out the episode we have an interview with two brothers who started up a successful business in the Shenzhen electronics markets.

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download (67.6 MB of audio splendor)

Places to follow Hackaday podcasts:

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Incredible Atari 800XL Case Restoration

If you’ve been hanging around Hackaday for a while, you know that a large portion of the stuff we publish goes above and beyond what most people would consider a reasonable level of time and effort. One could argue that’s sort of the point: the easy way out is rarely the most exciting and interesting route you can take. We, and by extension our readers, are drawn to the projects that someone has really put their heart and soul into. If the person who created the thing wasn’t passionate about it, why should we be?

That being said, on occasion, even we are left in awe about the lengths some people will go to. A perfect example of this is the absolutely insane amount of time and effort [Drygol] has put into restoring an Atari 800XL that looked like it was run over by a truck. Through trial, error, and a bunch of polyester resin, he’s recreated whole sections of the Atari’s case that were missing.

To start the process, [Drygol] used metal rods to bridge the areas where the plastic was completely gone. By heating the rods with a torch and pushing them into the Atari’s case, he was able to create a firm base to work from. Additional rods were then soldered to these and bent, recreating the shape of the original case. With the “skeleton” of the repair in palce, the next step was filling it in.

[Drygol] borrowed an intact Atari 800XL case from a friend, and used that to create a mold of the missing sections from his own case. Most of his rear panel was missing, so it took some experimentation to create such a large mold. In the end he used silicone and a custom built tray that the case could sit in vertically, but he does mention that he never quite solved the problem of degassing the silicone. The mold still worked, but bubbles caused imperfections which needed to be filled in manually during the finishing process.

Using his silicone mold and the same tray, he was then able to pour polyester resin over the wire frame. This got him most of the way to rebuilding the case, but there was still plenty of filler and sanding required before the surface finish started to look half-way decent. When he got towards the very end of the finishing process, he used a mold he created of the case surface texture to roughen up the smooth areas left over from the filling process. Add a bit of custom spray paint, and the end result looks absolutely phenomenal considering the condition it was in originally.

We were already impressed by the work he put in during the first stages of the restoration, but this case repair is really on a whole new level. Between this and the incredible instructional videos [Eric Strebel] has been putting out, we’re really gaining a whole new respect for the power of polyester.

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