Lost Foam Casting In Action

Even though not all of us will do it, many of us are interested in the art of casting metal. It remains a process that’s not out of reach, though, especially for metals such as aluminium whose melting points are reachable with a gas flame. The video below the break takes us through the aluminium casting process by showing us the lost-foam casting of a cylinder head for a BSA Bantam motorcycle.

The foam pattern is CNC milled to shape, and the leftover foam swarf is removed with a hot wire. The pattern is coated with a refractory coating of gypsum slurry, and the whole is set up in a tub packed with sand. We get the impression that the escaping gasses make this a tricky pour without an extra sprue, and indeed, they rate it as not perfect. The cooling fins on the final head are a little ragged, so it won’t be the part that goes on a bike, but we can see with a bit of refining, this process could deliver very good results.

For this pour, they use a gas furnace, but we’ve seen it done with a microwave oven. Usually, you are losing wax, not foam, but the idea is the same.

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How To Cast Silicone Bike Bits

It’s a sad fact of owning older machinery, that no matter how much care is lavished upon your pride and joy, the inexorable march of time takes its toll upon some of the parts. [Jason Scatena] knows this only too well, he’s got a 1976 Honda CJ360 twin, and the rubber bushes that secure its side panels are perished. New ones are hard to come by at a sensible price, so he set about casting his own in silicone.

Naturally this story is of particular interest to owners of old motorcycles, but the techniques should be worth a read to anyone, as we see how he refined his 3D printed mold design and then how he used mica powder to give the clear silicone its black colour. The final buses certainly look the part especially when fitted to the bike frame, and we hope they’ll keep those Honda side panels in place for decades to come. Where this is being written there’s a CB400F in storage, for which we’ll have to remember this project when it’s time to reactivate it.

If fettling old bikes is your thing then we hope you’re in good company here, however we’re unsure that many of you will have restored the parts bin for an entire marque.

More Microwave Metal Casting

If you think you can’t do investment casting because you don’t have a safe place to melt metal, think again. Metal casting in the kitchen is possible, as demonstrated by this over-the-top bathroom hook repair using a microwave forge.

Now, just because it’s possible doesn’t mean it’s advisable. There are a lot better ways to fix something as mundane as a broken bathroom hook, as [Denny] readily admits in the video below. But he’s been at the whole kitchen forging thing since building his microwave oven forge, which uses a special but easily constructed ceramic heat chamber to hold a silicon carbide crucible. So casting a replacement hook from brass seemed like a nice exercise.

The casting process starts with a 3D-printed model of the missing peg, which gets accessories such as a pouring sprue and a thread-forming screw attached to it with cheese wax. This goes into a 3D-printed mold which is filled with a refractory investment mix of plaster and sand. The green mold is put in an air fryer to dry, then wrapped in aluminum foil to protect it while the PLA is baked out in the microwave. Scrap brass gets its turn in the microwave before being poured into the mold, which is sitting in [Denny]’s vacuum casting rig.

The whole thing is over in seconds, and the results are pretty impressive. The vacuum rig ensures metal fills the mold evenly without voids or gaps. The brass even fills in around the screw, leaving a perfect internal thread. A little polishing and the peg is ready for bathroom duty. Overly complicated? Perhaps, but [Denny] clearly benefits from the practice jobs like this offer, and the look is pretty cool too. Still, we’d probably want to do this in the garage rather than the kitchen.
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Retrotechtacular: The Master Hands Of The Early Automotive Industry

When motion pictures came along as a major medium in the 1920s or so, it didn’t take long for corporations to recognize their power and start producing promotional pieces. A lot of them are of the “march of progress” genre, featuring swarms of workers happy in their labors and creating the future with their bare hands. If we’re being honest, a lot of it is hard to watch, but “Master Hands,” which shows the creation of cars in the 1930s, is somehow more palatable, mostly because it’s mercifully free of the flowery narration that usually accompanies such flicks.

“Master Hands” was produced in 1936 and focuses on the incredibly labor-intensive process of turning out cars, which appear to be the Chevrolet Master Deluxe, likely the 1937 model year thanks to its independent front suspension. The film is set at General Motors’ Flint Assembly plant in Flint, Michigan, and shows the entire manufacturing process from start to finish. And by start, we mean start; the film begins with the meticulous work of master toolmakers creating the dies and molds needed for forging and casting every part of the car. The mold makers and foundrymen come next, lighting their massive furnaces and packing the countless sand molds needed for casting parts. Gigantic presses stamp out everything from wheels to frame rails to body panels, before everything comes together at the end of the line in a delicate ballet of steel and men.

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Making A Concrete Sign

While paging through the feed a few days ago our attention was caught by something a little away from the ordinary in Hackaday terms, a DIY video about creating cast concrete signage from [Proper DIY] which we’ve placed below the break. A deceptively easy-looking mould-making process has a few tricks that  will make the difference between a hard-wearing sign that lasts for years, and a lump of concrete.

So, to make a cast concrete sign, you throw together a mould with some letters, and chuck in some concrete? Not so fast, because the key appears to be preparation, and ensuring that there are no 90-degree corners on the mould parts. The letters are carefully shaped and sealed with varnish before being attached to the mould with silicone adhesive, and all the corners are beveled. Finally a light oil is used as a release agent, and hefty vibration takes care of any air bubbles.

The result is a set of signs, but we can see these techniques finding uses outside signage. For example, how about casting using a 3D printed mould?

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Nuke Your Own Uranium Glass Castings In The Microwave

Fair warning: if you’re going to try to mold uranium glass in a microwave kiln, you might want to not later use the oven for preparing food. Just a thought.

A little spicy…

Granted, uranium glass isn’t as dangerous as it might sound. Especially considering its creepy green glow, which almost seems to be somehow self-powered. The uranium glass used by [gigabecquerel] for this project is only about 1% U3O8, and isn’t really that radioactive. But radioactive or not, melting glass inside a microwave can be problematic, and appropriate precautions should be taken. This would include making the raw material for the project, called frit, which was accomplished by smacking a few bits of uranium glass with a hammer. We’d recommend a respirator and some good ventilation for this step.

The powdered uranium glass then goes into a graphite-coated plaster mold, which was made from a silicone mold, which in turn came from a 3D print. The charged mold then goes into a microwave kiln, which is essentially an insulating chamber that contains a silicon carbide crucible inside a standard microwave oven. Although it seems like [gigabecquerel] used a commercially available kiln, we recently saw a DIY metal-melting microwave forge that would probably do the trick.

The actual casting process is pretty simple — it’s really just ten minutes in the microwave on high until the frit gets hot enough to liquefy and flow into the mold. The results were pretty good; the glass medallion picked up the detail in the mold, but also the crack that developed in the plaster. [gigabecquerel] thinks that a mold milled from solid graphite would work better, but he doesn’t have the facilities for that. If anyone tries this out, we’d love to hear about it.

1000 Aluminium Cans Cast Into A Guitar

Aluminium cans are all around us, and are one of readily recyclable. While you can turn them into more cans, [Burls Art] had other ideas. Instead, he turned roughly 1000 cans into a custom aluminium guitar.

Both the body and neck of the electric guitar are made out of aluminium. It’s an impressive effort, as manufacturing a usable neck requires care to end up with something actually playable when you’re done with it.

Producing the guitar started with a big propane furnace to melt all the cans down so they could be cast into parts for the guitar. 38 lbs of cans went into the project, and were first dried out before being placed into the furnace for safety reasons. Aluminium cans aren’t made of the best alloy for casting, but you can use them in a pinch. The cans were first melted down and formed into ingots to be later used for producing the neck and body.

[Burls Art] then built sand casting molds for his parts with a material called Petrobond. Wood plugs were used to form the sand into the desired shape. The neck casting came out remarkably well, and was finished with a grinder, hacksaw, and sandpaper to get it to the right shape and install the frets. The body proved more difficult, with its multiple cavities, but it came together after a second attempt at casting.

Fully kitted out with pickups and hardware, the finished product looks great, and weighs 12.3 pounds. It sounds remarkably like a regular electric guitar, too. It does pick up fingerprints easily, and does have some voids in the casting, but overall, it’s a solid effort for an all-cast guitar.

We’ve seen some other great casting projects over the years before, too. Video after the break.

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