Portable Lightweight Foundry

[Makercise] is getting ready for Maker Faire. One of the things he’d really like to do is some casting demonstrations. However, he has no desire to take his expensive and heavy electric kiln based foundry to Maker Faire. So, he made his own.

He got into metal casting during his excellent work on his Gingery lathe series. He started off by modeling his plan in Fusion 360. He’d use a 16qt cook pot turned upside down as the body for his foundry. The top would be lined with ceramic fiber insulation and the lid made out of foundry cement. He uses a Reil style burner, which he also modeled as an exercise. This design is light and even better, allows him to lift the top of foundry off, leaving the crucible completely exposed for easy removal.

All went well with the first iteration. He moved the handles from the top to the bottom of the pot and filled it with insulation. He built legs for the lid and made a nice refractory cement bowl on the bottom. However, when he fired it up the bowl completely cracked along with his crucible. The bowl from design flaw, the crucible from age.

A bit put off, but determined to continue, he moved forward in a different direction. The ceramic insulation was doing so well for the top of the foundry that he decided to get rid of the cement altogether and line the bottom with it as well. The lid, however, would be pretty bad for this, so he purchased another pot and cut the top portion of it off, giving him a steel bowl that matched the top.

The foundry fires up and has worked well through multiple pours. He made some interesting objects to hopefully sell at Makerfaire and to test the demonstrations he has planned. The final foundry weighs in at a mere 15lbs not including the fuel cylinder, which is pretty dang light. Video after the break.

21 thoughts on “Portable Lightweight Foundry

  1. I made something very similar to use as a portable pottery kiln. I used a 5 gallon steel bucket – the stainless pot is a good idea, as the (non-stainless) bucket starts to rust quickly.

    The Reil burner is great – that’s what I use as well. Steel legs for supporting the burner are a good idea. I used a stack of wood scraps, which I do not recommend.

    I also used a sheet of cement board to protect our patio from dropped ceramic pieces. I don’t know if it would be adequate/safe for casting, but it seems to work well for our purposes. Legs for the kiln/forge are a good idea.

    I couldn’t tell how he held the fiber blanket against the walls of the pot, but these ceramic buttons work well: http://www.axner.com/ceramic-fiber-washer.aspx

    A few pictures of our setup are on this page: http://lanahobbs.com/about.html

      1. Thanks! The kiln, reduction bucket, and burner all fit in a large plastic bin, which helps for transporting without making a mess.

        Good question about preheat. I think the main reason we didn’t preheat with the pot in the kiln is that was how my wife was taught the raku process. I think we also wanted to get the kiln to a stable temperature, and didn’t want to risk overshooting with the pot in it. Also, clays that are good for raku are by nature more resistant to thermal shock.

  2. Great video but, perhaps I’m a woose, because I really don’t think that is a smart way to work with a hole saw safely. So near your soft a squishy bits, surely it is better to secure things with straps and have the work piece down lower because it is better to cut a hole in your lower leg than it is to eviscerate yourself?

    1. There have been cases where a cold empty tank has been opened, therefore allowing air into the tank. So more safety devices have been installed to reduce the likelihood of ignition in the hose(s). Usually not necessary for propane but is common practice for acetylene tank connections.

      1. Propane isn’t inherently unstable like acetylene is, either. Propane needs a proper oxygen mix to detonate. Gaseous acetylene will detonate with only a sufficient thermal or mechanical shock.

        1. I was actually thinking about a HHO generator, which is also scary https://www.youtube.com/watch?v=gdy5_nitn7I

          So no there is no need because propane is not inherently unstable, and it is not premixed with an oxidizer.

          I was thinking about the very last second when the tank is almost fully empty, but I guess that any heat source would be extinguished before there was a chance of a flashback.

          1. The tank will run out of pressure to run anything way before there’s any danger of it having a flammable mixture inside.

            Commercially / industrially, propane and butane bottles don’t have arresters. In large fixed installations & filling stations (automotive LPG for example) they do use that stuff, but they are super-cautious.

  3. Mesh style reinforcing grid (1 inch or 2 inch) also makes a very good surround if ceramic blanket is used inside.
    It’s very light and easy to lift, the reduced amount of metal makes heat easier to manage.
    The blanket can be ‘sewn’ on with links of nichrome etc.
    This style is used a lot in portable Raku kilns.

  4. Had a chance to see him and his Gingery lathe at the Makers Fair yesterday, his work looks great.
    We talked about a similar furnace I made several years ago. Instead of using propane,I used a heating element from electric hotplates I picked up for a couple dollars at a Goodwill store. No need to cut a big hole in the top cover. Drilled some small holes in the sides and top of the pot, and used some nichrome wire to hold the blanket in place. Drilled holes in the bottom pan and fed the wires to the heating element through ceramic tubes held in place with high temp silicone on the outside.. Heating elements lasted about 8 to 10 heats before they had to be replaced. Still a lot cheaper than refilling the propane tank had been. Very easy to use, just plug it into an outside power outlet, also much easier to store, just roll the cord up and stick in the furnace.

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