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Some castings

Posted: 2008-08-30 11:08am
by Korto
First a couple of axes
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Just doodling, really...
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Was meant to be a war-pick, but legally iffy, so it's a sculpture with the socket where the handle was meant to go filled in.
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Double the Fist!
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A sacrificial dagger
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And my favourite piece. Not sure whether to call it Dark Froggy or Evil Kermit. That shit on its eye (your right) seems to be just a trick of light and bad camera angle; there's nothing actually there.
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Finally, something out of aluminium
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Posted: 2008-09-07 02:52am
by Falkenhorst
Please show some pics of your furnace.

Posted: 2008-09-07 04:10am
by loomer
Damn it, stop making me want to get into forging.

Posted: 2008-09-07 06:44pm
by Falkenhorst
Hey Loomer, did you see my thread on here a couple months ago where I was melting down aluminum in a 55 gallon drum? I went and built a pouring device to set the pot in and then I fabricated some ingot molds. I can get some more pics if you want to see em. I have video too.

Posted: 2008-09-07 09:43pm
by loomer
I did, yes, and that'd be pretty cool.

Posted: 2008-09-09 11:51am
by Korto
You asketh, you geteth

Since I work at the TAFE foundry, I use their furnaces. I plan one day to make one of my own, but at present having them pay for the gas suits me just fine.
Anyway, this is our little furnace, used for melting copper alloys (brass and bronze), as well as being a general workhorse (pewter, lead, and whatever else they bring in with a melting point copper or less)
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And our big furnace, used for aluminium. Image

Since I was there with a camera, I decided to make a day of it.
Here's two other views of the foundry,
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In the first, you can see the sand mill, for mixing green sand, and in the second you can see our old induction furnace. Anyone knowledgeable in the field of induction furnaces will notice that this one was built sometime in the early 15th century (a good trick, as they hadn't discovered electricity yet), and is of course powered by rats running on treadmills. Unfortunately a few years ago our rats died (give them a break, over 500 years is a long lifespan for a rat) and new rats will apparently cost tens of thousands of dollars (presumably for a very large block of cheese). So I'm stuck with this bloody thing taking up space in my bloody foundry.

Anyway

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Inside the small furnace - just a refractory cement cylinder, in the upper right quadrant you can see the exhaust hole to the far right (higher in the furnace), and a gas hole lower down.

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Removing a pot of brass from the furnace, and cleaning off the dross.
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Making a Casting (Note - This isn't how the pieces above were made. Most of those are lost wax castings, while this is a green sand casting)
First, get your stuff together Image
You can see the bottom half of a box, the pattern (that anvil-looking thing), and a wheelbarrow full of green-sand (the black stuff)
Green-sand is a mix of sand, clay, graphite, and water. I'll tell you why it's called green when its self-evidently black, later.

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As there's no 'flat back' to the pattern, a box half has to be lightly filled with sand, and then the pattern pressed into it to the half-way mark, in order to hold the pattern correctly to start making the mould

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The other box half is then placed over the top, and sand firmly packed in around the pattern. The white stuff you can see in the left picture is Parting power (typically chalk). Green-sand sticks together because it's damp. That's fine, except you don't want the two box halves to stick together, or you'll rip the mould apart when you try to remove your pattern (this is generally considered a bad thing in foundry circles). The parting powder sucks up the moisture on the surface and thereby creates surface dryness. And why is it called green-sand? Because it's damp (think green wood).

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Final packing down for the half.
You then turn the whole thing over, remove the bottom box (which only has loose sand), empty out the loose sand, replace the box, and repack the sand again, this time properly. No pictures. It's exactly the same as the last bit, including the parting powder.
You then cut in your pour hole, and a riser hole (you see there a thin-sided metal pipe. It can be pushed in and will cut out a section of sand)

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Split the boxes and remove the pattern. Ooops, damage! Those black areas around the pattern is where sand has broken loose and will have to be repaired. (Quick repair job ensued)
Finally, the finished mould, with pourer-cup (powdered for contrast against the black, for ease of seeing it. Sometimes it can be hard to see when you have a brightly glowing pot of metal.)

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The aluminium furnace is emptied (as you can see, one of us is still capable of bending his knees); and the mould is poured (unfortunately, this picture didn't come out).

The finished casting. Image

Posted: 2008-09-10 05:02am
by Superman
Do those pics remind anyone else of Freddy Kreuger's basement?

Nice work. What do you do with those castings when you finish?

Posted: 2008-09-10 11:22pm
by Falkenhorst
I haven't forgotten that I said I would post some pictures, but I'm real busy with my job this time of year. Korto, maybe you could help me out a little though. I assume your furnaces are gas fired; what type of gas do you burn? I have an old forge furnace I got from a junk man and I rigged up an electric leaf blower to it but I am trying to figure out what kind of regulator I should have and whether to run it on Natural Gas or Propane. I'll post some pictures of it soon, but it's not my main project right now. The next thing I'm planning to do is build a wood flask to do some casting.

Posted: 2008-09-11 10:05am
by Korto
Superman wrote:Nice work. What do you do with those castings when you finish?
I'm supposed to be trying to sell them. Except for that anvil thing I just made, which is decoration for a fence I'm supposed to be putting up.

Falkenhorst, the furnaces run on natural gas, but just because that's the gas supplied here. As far as I know, propane should work just fine. Propane apparently has 20% more energy, and a 1990C flame v LNG's 1790C (quick google search), so litre for litre presumably propane is better. If I were you, I would make the decision based on price, and what's convenient (particularly if one is on tap).

Should be posting a few more pieces in some days time. I'm going through all the stuff I've had lying around part-finished, and trying to finish them off.

Posted: 2008-09-15 08:14am
by Korto
Here we go. I'm trying out the name "River plates" for these things, as when I make them I try to visualise water streaming around stones. Not too sure about the name. Then again, pick a name, stick to it, and sooner or later it'll sound just fine.
They're actually bracers, to go around the arm (or will be, once I attach a leather backing).
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I'm considering the idea of making flat tiles the same way, and covering a small table with them.