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.
You know the old trope: James Bond is killed but it turns out to be someone else in an incredibly good-looking Sean Connery mask. Mission: Impossible and Scooby Doo regularly had some variation of the theme. But, apparently, truth is stranger than fiction. The CIA has — or at least had — a chief of disguise. A former holder of that office now works for the International Spy Museum and has some very interesting stories about the real masks CIA operatives would use in the field.
According to the video you can see below, the agency enlisted the help of Hollywood — particularly the mask maker from Planet of the Apes — to help them with this project. Of course, in the movies, you can take hours to apply a mask and control how it is lit, how closely the camera examines it, and if something goes wrong you just redo the scene. If you are buying secret plans and your nose falls off, it would probably be hard to explain.
Continue reading “Spy Tech: CIA Masks In Five Minutes Or Less”
For people who work with wheeled robots or RC vehicles, sooner or later one gets interested in making custom tires instead of dealing with whatever is available off the shelf. [concreted0g]’s preferred method is to design and 3D print wheel hubs, then cast some custom silicone tires to fit over them. Of course, the devil is in the details and this process can be a bit messy, so he’s shared useful tips on how to get reliable results with simple materials.
The casting material is cheap silicone caulking from a hardware store, and color can be added with a small amount of cheap acrylic paint. A few drops of glycerin added to the silicone thins it out slightly and helps it flow into a mold better. Mix well (the paint will also serve as a visual indicator of how well it is mixed), then scoop the mixture into the mold while trying to avoid creating air pockets. If your mold is in two pieces, assemble the mold and remove any overflow, then let it sit undisturbed for at least several hours while it cures.
Mounting the resulting tire to a wheel hub can be done with a thin film of super glue, which seems to work perfectly well for small tires and is easy to apply.
The rules are going to be a bit different for big objects. We know that silicone caulking can have difficulty fully curing when it’s applied thickly, especially when sealed into a mold with little to no airflow. In such cases, adding cornstarch (in about a 5:1 ratio of silicone to cornstarch by volume) is all that it takes to cure even thick wads of goop in less than an hour. Stirring cornstarch in tends to introduce more air bubbles into the mixture, but for larger pieces that can be an acceptable tradeoff. Cheap silicone caulking is versatile stuff, one just needs to know what to expect, and take a few steps to deal with the messiness.
Need something tougher? Maybe check out using slices of automotive silicone hose for robot wheels to get something that works just as well, but is a lot more durable.
If you’ve got one of something and you want more, duplicating it with a silicone mold can be a great way to go. This is applicable to 3D printing something you need many copies of, and a whole variety of other usecases. [Eric Strebel] prides himself on his abilities in this area, and has put out a guide to producing very large silicone molds in a simple and reliable manner.
The overarching process is simple, but followed properly, it produces great results. [Eric] starts by building a mold box out of wood, coated in shellac to ensure it doesn’t stick to the silicone. The master part is then stuck to the base, surrounded by a lasercut cardboard strip which acts as a seal and key. Once properly degassed silicone is poured in and cured, the second half can be made. The mold is flipped in the mold box, the seal key removed, and release agent applied to the silicone surfaces. With another pour and cure, the mold is ready for casting new parts.
While simple, if the correct equipment isn’t used or steps skipped, you’ll end up with a useless mold full of air bubbles or surface irregularities. It’s useful to see just what it takes to get a mold of such scale (13″ x 19″!) completed without flaws. We’ve featured [Eric]’s work before, such as his fine detail improvements on the Apple Pencil. Video after the break.
Continue reading “Making Silicone Molds – Big Ones!”
Most of us have a junk drawer, full of spare parts yanked from various places, but also likely stocked with materials we bought for a project but didn’t use completely. Half a gallon of wood glue, a pile of random, scattered resistors, or in [Ken]’s case, closed-cell silicone foam. Wanting to avoid this situation he set about trying to make his own silicone foam and had a great degree of success.
Commercial systems typically rely on a compressed gas of some sort to generate the foam. Ken also wanted to avoid this and kept his process simple by using basic (pun intended) chemistry to generate the bubbles. A mixture of vinegar and baking soda created the gas. After a healthy amount of trial and error using silicone caulk and some thinner to get the mixture correct, he was able to generate a small amount of silicone foam. While there only was a bit of foam, it was plenty for his needs. All without having a stockpile of extra foam or needing to buy any specialized equipment.
We appreciate this project for the ingenuity of taking something relatively simple (an acid-base reaction) and putting it to use in a way we’ve never seen before. While [Ken] doesn’t say directly on the project page what he uses the foam for, perhaps it or a similar type of foam could be used for building walk-along gliders.
Photo via Wikimedia Commons
The border between consumer electronics and DIY projects is getting harder and harder to define. First it was PCBs, which quickly went from homemade to professional with quick-turn services. Then low-cost CAD/CAM packages and high-end fabrication services gave us access to enclosures that were more than black plastic boxes with aluminum covers. Where will it end?
That’s a question [arturo182] begins to answer with this custom-molded silicone keyboard for a handheld device. There’s no formal writeup, but the Twitter thread goes into some detail about the process he used to make the tiny qwerty keypad. The build started by milling a two-part mold from acrylic. Silicone rubber was tinted and degassed before injecting into the mold with a baster. The keys are connected by a thin membrane of silicone, and each has a small nub on the back for actuating a switch.
There’s clearly room for improvement in this proof of concept – tool marks from the milling process mar the finish of the keys slightly, for instance. There may be tips to be had from this article on silicone keyboard refurbishment to improve the process, but overall, we’d say [arturo182] is well on his way here.
Anyone who has delved into DIY wheels knows that they are a trickier than it may seem, especially if the wheels aren’t just for show and need to provide things like decent traction and durability. 3D printers have helped a lot, but they’re not a cure-all.
Check out how [Robert K.] makes wheels from segments of automotive silicone hose, which are constructed with fibers embedded within them for durability and structure. Not only are these hoses easily sourced, but the silicone makes a great wheel surface and the hoses themselves are highly durable. He uses a 3D printed jig to cut a slice of hose that press-fits perfectly onto a 3D printed hub. [Robert] finds that a 28 mm hose pulled over a 35 mm diameter wheel is a perfect fit.
These wheels are for a Beetleweight class combat robot, which are limited to three pounds (1.36 kg) or less. You can see some video of [Robert]’s previous Beetleweight robot named ‘Bourbon’, and we have featured what goes into the even-smaller Antweight class (one pound or less) in the past.