inlay nichrome in aluminum/bronze casting?

Hi everybody. I'm doing some 3d printing with Mark Ganter at the University of Washington and am happy jump into the mix here at reprap.

This question isn't directly related to printing, though. I'm taking a foundry class in the art department and will be casting bronze and/or aluminum. Once I've made my objects, I want them to be able to get hot. But I want the heating mechanism to be hidden.

My first question is: what do you think will happen if I try to inlay nichrome wire into an aluminum cast? a bronze cast? Aluminum, which is preferable to me aesthetically for this project, has melting point is 660 C, so the pour will probably be a little hotter than that. Bronze is about 1000 C I think. I've read that nichrome can be used up to about 1100 C in theory. So maybe the wire will be ok? Being gradually brought up to temp is a little different than having gobs of molten metal poured over it all of a sudden. Kanthal wire is a higher temperature alternative. But could any freaky stuff happen, like metals in the wire reacting with the pour and corrupting the wire? Kanthal is an alloy of Iron, Aluminum, and Chromium.

A concern with using this approach is that then my final part becomes electrically charged when the nichrome is on. Since one of the ideas I'm toying with deals with dropping water droplets on it and creating steam, this could be a problem. Maybe I can coat the wire with something electrically insulating but not heat insulating before I inlay it.

I should say that I'm mostly thinking about heating water or oil, so the temperature I'd need to heat the nichrome to would be ~300 F / 150 C, I'm guessing .

Another option might be to make a hole in my part big enough to insert a resistor later, a-la nophead.

I appreciate the help,
Josh

Dunno if the nichrome will melt at the bronze's pour temperature, but ... all that metal surrounding that resistive wire is going to short out the wire. The electrons will just go winging out into the bulk of the metal, rather than through the nichrome.

Another option might be to make a hole in my part big enough to insert a resistor later, a-la nophead.

This sounds like it will work.

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Hmmph. Yeah. I'm trying to think of of something to insulate it electrically, and ceramic wrap comes to mind. The problem when searching for electrically insulating materials that can withstand the high heat of the pour is, those materials are going to insulate the heat of the wire. Maybe this would keep it from heating up my part, maybe if I heat the wire to like 600 F with cerawrap the part could still get to like 300 F.

The resistor might work for the idea I have in mind at the moment. Still, it seems like if I could figure out how to use resistance wire with a pour, it could open up doors to a lot of other 3d forms.

The part I want to heat at the moment is a test tube/burett clamp (pic attatched).

Yeah. I'm trying to think of of something to insulate it electrically, and ceramic wrap comes to mind.

I was going to say "Oh, just use ceramic-shell (as in the ceramic-shell process for bronze casting)." but you'll need to bake the water out of it before you pour the bronze or you'll get some fun steam explosions.

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-Sebastien, RepRap.org library gnome.

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Remember, you're all RepRap developers (once you've joined the super-secret developer mailing list), and the wiki, RepRap.org, [reprap.org] is for everyone and everything!

remember that silicone can be used as a mold for casting low temp metals as long as it is fully cured

here is a sheet that shows various mold types of silicon

[alumilite.com]

I think this company also sells powdered metal materials.

there are some other issues to consider if you are embedding wire in aluminum. rate of expansion of material, amount of oxide growth, and thermal stress.

sounds interesting. i would need to agree that the best method currently is use a spec well designed part like a resistor, that is somewhat tolerant at high temp. at least you can look at a sheet of paper and say, hey i know how the part should perform. not that it does so.

... we use nicro-wires, that are coated with a vowen glass-tube - this could withstand the temperature of molten aluminium ...

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this may be helpful:

[en.wikipedia.org]
melt temp 660c
Thermal expansion .000023 per degree Celsius,

[en.wikipedia.org]
melt temp 1400c
Thermal expansion .000014 per degree celcius.

[en.wikipedia.org]
melt temp 950
Thermal expansion .000018 per degree Celsius,



more reading, actual stuff:
[psec.uchicago.edu]

now you know i can use wiki and google. just like anyone else....