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Author: Subject: High temp conductive material for mounting cartridge heaters
RogueRose
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[*] posted on 14-2-2019 at 13:07
High temp conductive material for mounting cartridge heaters


I got some cartridge heaters (6 40-50watt 12v) that I'm planning on installing in a aluminum billet/heating block. These are pretty high density heaters, they get past red hot when not in contact with anything, probably very near 1,700 - 2000F (has a stainless casing).

The thing with these high density heaters is they need a very tight fitting mounting hole which is tough to produce with the accuracy supposedly required. I'm wondering if adding something like a heat paste (similar to cpu heatsink paste) could be used. I'd prefer not to use a paste, other than making it with water/alcohol/solvent etc (will evaporate when heated so it doesn't turn into glue).

I'm considering using something like graphite powder or maybe even Al or Cu powder? Would CuO or Cu2O be thermally conductive?

I was considering trying to make some very find copper powder with electrolysis - I think I accidentally made this when trying to make CuSO4 long ago. It was a brown foamy/slimy looking substance that appeared on one of the electrodes.

I also have some copper compound that I think is left from making some copper salt (I think CuSO4) that appeared on the wire while washing off any remaining acid (with tap water). It is a brown/red super fine powder that often appears on the surface of copper after being in acid - it comes off when shaking the copper wire in a bottle w/o wire so the wire abrades it off - then adding water to collect the powder at the bottom. The compound looks like something like bronzing makeup powder.

The only other thing I can think of is getting fine aluminum some way, I have no powdered Al. IDK if it can be made via electrolysis or simply grinding between 2 steel plates maybe?

I figured I'd combine one of the powders with a solvent or water then brush/paint the cartridge with it and insert in the mounting hole.

Any suggestions on the powder/compound or how to make it?
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Twospoons
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[*] posted on 14-2-2019 at 13:16


I think graphite would be your best best. Not only is it good thermally, it will also act as a lubricant and anti-seize, in case to blow a heater and have to replace it. Al is notoriously 'sticky'. You should still make your hole as tight as possible (that sounds terrible). I don't know the particulars of your setup - is it possible to drill the hole then slit the side and add a compression screw to take up the tolerance?
What temperature are you heating your billet to?




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VSEPR_VOID
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[*] posted on 14-2-2019 at 14:43


copper power will not last long and will oxidize. I would recommend aluminium powder or graphite. Graphite could be a fire hazard at those temps, or burn during the first use.



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RogueRose
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[*] posted on 14-2-2019 at 17:03


Quote: Originally posted by VSEPR_VOID  
copper power will not last long and will oxidize. I would recommend aluminium powder or graphite. Graphite could be a fire hazard at those temps, or burn during the first use.


I don't think the unit will get above 1000F, the heaters can get a lot hotter but only when no heat is being pulled away from it. The heaters will be in contact with Al, so it will wick the heat away quickly. I'll probably put a thermocouple on the unit and have it turn off the power over a certain temp, I don't want the Al to melt, but I doubt there will be enough wattage to do this unless it was very well insulated.

The reason I thought graphite would be good is because it is used in crucibles, so I thought there wouldn't be a problem with the heat. Also, I can't see much air getting into the hole to oxidize the carbon. I guess I'll have to see.
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draculic acid69
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[*] posted on 16-2-2019 at 02:16


Nux vomica from nuxs channel on YouTube and here on the forum is the guy to talk to probably if you watch his videos you'll see his equipment that I think he makes himself is like what you're talking about.
https://m.youtube.com/watch?v=IAN5MPXR3iE is a good start

[Edited on 16-2-2019 by draculic acid69]
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[*] posted on 16-2-2019 at 06:32


I've used this sort of cartridge in 3-D printers up to about 400C in the print head. I've used "rope seal adhesive" thats used to secure the glass fibre seals on the doors of log/multifuel burners - it's basically just sodium silicate and is rated upto 1250C.
Another alternative would be to slightly overdrill your holes and have a slit in the side that you can close with a screw.
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