The Die Is Cast!

March 1, 2023 by Jenny List 31 Comments

We all know the basics of how metal casting works, a metal is heated up to melting point and the resulting liquid metal is poured into a mold. When the metal sets, it assumes the shape of the mold. It’s a straightforward way to reliably replicate a metal item many times over, and the basics are the same whether the metal is a low-temperature alloy in a silicone mould or a crucible of molten steel poured into a sand mould.

The mould is black sand in a cast iron box, and the pattern piece is half submerged in it — A sand mould being formed around a pattern. Lukas Stavek, CC BY-SA 3.0 .

What we all understood as casting in our conversation was sand casting. Sand is packed around a pattern of the piece to be cast, and then the pattern is removed leaving a cavity in its shape which becomes the mould. There are refinements to this process and the mould is frequently formed in two halves, but it’s something that’s even practical to do in a hackerspace level setting.

A refinement of sand casting is so-called lost-wax casting, in which a hollow wax model of the piece to be cast is packed around with sand, and ~~when the metal is poured onto the top of it the wax melts~~ and the wax is melted out before pouring the metal in to take its place. A variation on this appears here from time to time, so-called lost-PLA casting, where the wax model is replaced with a PLA 3D print.

Injection Molding For Metals

Diagram of a die casting machine — A die casting machine. Ahmed elbhje, Public domain.

Where our confusion crept in was with die casting. We could recognise a die-cast piece, but just what is die-casting, and how is a die-casting made? The answer there lies in mass-production, because a snag with sand casting is that a sand mould can be labour intensive to produce. Much better to come up with a quick-turnaround process that re-uses the same mould over and over, and save all that time!

Enter the die-casting, to metalwork what injection moulding is to polymers. The die is a mould made out of metal, usually with liquid cooling, and the casting is done not by pouring but by forcing the molten metal into the mould under pressure. The whole process becomes much quicker, meaning that it can become a piece of process machinery spitting out castings rather than a labour-intensive individual task. The metals used for die-casting are the lower temperature ones such as aluminium, zinc, and their alloys, but you will find die-castings in all conceivable places.

It’s obvious that Hackaday editors are not experienced foundrymen even if some of us grew up around metalwork, but we know that among our readers lie genuine experts in all sorts of fields. If that’s you and you operate a die-casting machine, please take a moment to tell us about it, we really would like to know more!

Header: Constantin Meunier, Public domain.

Cast Metal From Prints To Solidify Childhood Memories

June 1, 2020 by Kristina Panos 32 Comments

As far as the hacker’s toolbox goes, the 3D printer is way up there in terms of utility. Sure, it takes time to learn the ins and outs of designing, slicing, and extruding, but after that, the world is pretty much your additive oyster. Follow those design dreams, or use it to replace the things that break. The icing on the cake? You can chase those dreams into other materials, because 3D prints can be used to cast metal.

[RetroTech Journal] wanted to fry up some rosette cookies, a Scandinavian delight from his youth that look a lot like fancy, personal funnel cakes. They’re made with special aluminium irons that shape the dough while it fries, as opposed to the jumbled chaos that is funnel cake.

Rosette irons come in a few traditional shapes, but once you get tired of those, it’s up to you to cast them in aluminium. And how would you go about doing that? By creating a firmly-packed sand mold using a mounted 3D print.

In the endlessly entertaining video after the break, [RetroTech Journal] takes you through the entire process from CAD to cookies. It has everything you could possibly want: LEGO stop-motion, claymation, a little bit of cooking, and a whole lot of knowledge. We can’t wait to see what comes next.

We’ve seen quite a few sand casting projects over the years, but this lathe is among the most useful.

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Watch A Sand-Cast Slingshot Made, From Start To Finish

December 18, 2019 by Donald Papp 13 Comments

Sand-casting metal parts is a technique that has been around for a very long time, but it can be educational to see the process from start to finish. That’s exactly what [Frederico] shows us with his sand-cast slingshot of his own design, and it’s not bad for what he says is a first try!

First, [Frederico] makes a two-part green sand mold of the slingshot body. Green sand is a sand and clay mix, and is only green in the sense that it is wet or “raw” and not further processed. After the mold is made, it’s time to melt aluminum in the propane-powered furnace, and the molten aluminum is then poured into the mold.

After cooling, [Frederico] breaks up the sand to reveal the rough cast object. There is post-processing to do in the form of sprues to cut and some flashing around the seams to remove, but overall it looks to have turned out well. You can watch the whole process in the video, embedded below.

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Fire Extinguisher Ball Mill Destined To Grind Kitty Litter

March 2, 2018 by Dan Maloney 15 Comments

Nothing says hack like a tool quickly assembled from a few scrap-heap parts. For [Turbo Conquering Mega Eagle], his junkyard finds were a fire extinguisher, an old office fan, and a few scraps of plywood; the result was a quick and easy ball mill.

There’s very little mention of what said ball mill will be for — [TCME] said something about milling bentonite clay, AKA kitty litter — but that’s hardly the point. Having previously fabricated a much smaller version of this ball mill that could chuck up in his lathe, he scaled this one up considerably. The spent fire extinguisher was relieved of the valve and some external bits to create the mill’s drum. Plywood was used for a quick frame to support rollers and to turn a couple of pulleys for the running gear. The fan motor proved barely capable of performing, though, even with the mechanical advantage of the pulleys and an improvised drive belt. The motor just didn’t have the oomph to turn the drum when loaded with ceramic balls, but a quick adjustment to the drive train did the trick. The video below shows the whole build process, which couldn’t have taken much more than a couple of hours.

It looks like a sand casting project may be on deck for [TCME]’s milled bentonite, so we’ll look forward to that. Perhaps his other recent fire extinguisher build will make an appearance in that video too.

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Custom Aluminum Wheels Teach A Thing Or Two About Casting

July 1, 2017 by Dan Maloney 35 Comments

For some mobile projects like small carts or rolling cabinets, your standard casters from Harbor Freight will do just fine. But some projects need big, beefy wheels, and these custom cast aluminum wheels certainly make a statement. Mostly, “Watch your toes!”

To be honest, [Brian Oltrogge]’s wheels are an accessory in search of a project, and won’t be crushing feet anytime soon. He made them just to make them, but we have no beef with that. They’ve got a great look that hearkens back to a time when heavy metal meant something else entirely, and things were made to last. Of course, being cast from aluminum sort of works against that, but there are practical limits to what can be done in the home foundry. [Brian] started with a session of CAD witchcraft followed by machining the cores for his molds. Rather than doing this as lost foam or PLA, he milled the cores from poplar wood. His sand mix is a cut above what we usually see in home-brew sand casting — sodium silicate sand that can be cured with carbon dioxide. All his careful preparation meant the pour went off without a hitch, and the wheels look great.

We’ve featured quite a few metal casting projects recently, some that went well and some that didn’t. [Brian] looks like he knows what he’s doing, and we appreciate the workmanship that he puts on display here.

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Fail Of The Week: Sand Casting Copper

June 7, 2017 by Dan Maloney 90 Comments

There’s trouble in the Kingdom of Random – the smithies of the realm are having trouble sand-casting copper. And while [King Grant] might not be directly asking for help, we think the Hackaday community might have plenty to say about his efforts.

We’ve all seen plenty of sand casting efforts before, including attempts to make otherwise unobtainable engine parts. And “lost foam” casting, where a model of the part is constructed of polystyrene foam that flashes off when the molten metal is poured, is a relatively new twist on the technique that’s been used to good effect on a recent Gingery lathe build. But most backyard foundries work in aluminum, which is apparently much easier to work with than the copper that [Grant Thompson] is working with. Ironically, his first pour worked the best — not perfect, but at least the islands defining the spokes of his decorative piece didn’t break off and float away as they did in every pour shown in the video below. That leads us to think that the greensand is too dry by the second video. Or perhaps the density of copper just makes it more likely for the sand to float. Maybe a cope and drag mold is in order to keep the islands in place and direct the flow of the copper better.

We know there’s a lot of expertise out there, so sound off in the comments about what you think is going on with these pours.

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Custom Engine Parts From A Backyard Foundry

June 23, 2016 by Dan Maloney 40 Comments

Building a car engine can be a labor of love. Making everything perfect in terms of both performance and appearance is part engineering and part artistry. Setting your creation apart from the crowd is important, and what better way to make it your own than by casting your own parts from old beer cans?

[kingkongslie] has been collecting parts for a dune buggy build, apparently using the classic VW Beetle platform as a starting point. The air-cooled engine of a Bug likes to breathe, so [kingkongslie] decided to sand-cast a custom crankcase breather from aluminum.

Casting solid parts is a neat trick but hardly new; we’ve covered the techniques for casting plastic, pewter, and even soap. The complexity of this project comes from the fact that the part needs to be hollow. [kingkongslie] managed this with a core made of play sand and sodium silicate from radiator stop-leak solution hardened with a shot of carbon dioxide. Sure, it looks like a Rice Krispie treat, but a core like that will stand up to the molten aluminum while becoming weak enough to easily remove later. The whole complex mold was assembled, beer cans melted in an impromptu charcoal and hair-dryer foundry, and after one false start, a shiny new custom part emerged from the sand.

We’ve got to hand it to [kingkongslie] – this was a nice piece of work that resulted in a great looking part. But what we love about this is not only all the cool casting techniques that were demonstrated but also the minimalist approach to everything. We can all do stuff like this, and we probably should.

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