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 Post subject: Aluminum Collection for Casting Small Parts
PostPosted: Fri Jul 24, 2009 3:41 pm 
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Hey, at our last meeting we discussed the process of collecting and melting aluminum to use for casting small parts.

I go through a LOT of aluminum each month, but do not necessarily want to keep it in storage. Is anyone here able to collect and store aluminum for future use by TC Maker?

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 Post subject: Re: Aluminum Collection for Casting Small Parts
PostPosted: Sun Jul 26, 2009 3:35 pm 
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Eh, I'll do it. I've been planning on salvaging from work to start building up a store anyway.

Besides, my garage already pretty much looks like Fred Sanford's yard.

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 Post subject: Re: Aluminum Collection for Casting Small Parts
PostPosted: Sun Jul 26, 2009 9:08 pm 
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If cans can be crushed, bagged, and transferred to me on wednesday meeting nights, I'm sure they could be hidden in the attic space above the garage until they're needed

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 Post subject: Re: Aluminum Collection for Casting Small Parts
PostPosted: Sat Aug 08, 2009 11:46 am 
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how do skim the dross off when melting aluminum cans? any techniques?

awhile ago i tried melting cans for the first time. i had lots of crud and couldn't skim it. i think part of my problem was i didn't have enough fuel and maybe the temp wasn't hot enough. the aluminum stuck to my improvised skimmer. i tried removing the aluminum from the skimmer by wiping it in molding sand but that just made things worse.

anyways, i couldn't pour the aluminum out of the soup can. after it cooled i peeled off the soup can. all i have to show for my effort is a chunk of aluminum with a bunch of crap embedded into it. not worth re-melting. i was just trying to make ingots.


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 Post subject: Re: Aluminum Collection for Casting Small Parts
PostPosted: Sat Aug 08, 2009 3:50 pm 
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bobble wrote:
how do skim the dross off when melting aluminum cans? any techniques?

awhile ago i tried melting cans for the first time. i had lots of crud and couldn't skim it. i think part of my problem was i didn't have enough fuel and maybe the temp wasn't hot enough. the aluminum stuck to my improvised skimmer. i tried removing the aluminum from the skimmer by wiping it in molding sand but that just made things worse.

anyways, i couldn't pour the aluminum out of the soup can. after it cooled i peeled off the soup can. all i have to show for my effort is a chunk of aluminum with a bunch of crap embedded into it. not worth re-melting. i was just trying to make ingots.
Bobble, thanks for sharing. At some point I'm sure our group will give this a go as well.

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 Post subject: Re: Aluminum Collection for Casting Small Parts
PostPosted: Sat Aug 08, 2009 7:56 pm 
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bobble wrote:
how do skim the dross off when melting aluminum cans? any techniques?

awhile ago i tried melting cans for the first time. i had lots of crud and couldn't skim it. i think part of my problem was i didn't have enough fuel and maybe the temp wasn't hot enough. the aluminum stuck to my improvised skimmer. i tried removing the aluminum from the skimmer by wiping it in molding sand but that just made things worse.

anyways, i couldn't pour the aluminum out of the soup can. after it cooled i peeled off the soup can. all i have to show for my effort is a chunk of aluminum with a bunch of crap embedded into it. not worth re-melting. i was just trying to make ingots.


I'm just guessing but what you used to melt the cans had an open top exposed to air. What I see looks like you had way to much oxidization. Aluminum loves to oxidize and once you get it instead of 1280F you are looking at 3700F to melt it. So some tips.

Melt under a hood. (Let the combustion byproducts take care of the O2.)
Don't skim. Just like on an aluminum cookie sheet the oxide layer protects the rest.
Once the melt has started push the can down blow the surface. Its going to create some oxide give it as little chance as possible.

The Inks and organics are long since gone once you see that scum.

Aluminum melts at 1280F but is almost always poured (even for ingots) at 1350-1375.

Hope that helps a little. I've never done a melt at home.


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 Post subject: Re: Aluminum Collection for Casting Small Parts
PostPosted: Sat Aug 08, 2009 8:16 pm 
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Judeling wrote:
I'm just guessing but what you used to melt the cans had an open top exposed to air. What I see looks like you had way to much oxidization. Aluminum loves to oxidize and once you get it instead of 1280F you are looking at 3700F to melt it. So some tips.

Melt under a hood. (Let the combustion byproducts take care of the O2.)
Don't skim. Just like on an aluminum cookie sheet the oxide layer protects the rest.
Once the melt has started push the can down blow the surface. Its going to create some oxide give it as little chance as possible.

The Inks and organics are long since gone once you see that scum.

Aluminum melts at 1280F but is almost always poured (even for ingots) at 1350-1375.

Hope that helps a little. I've never done a melt at home.


the picture is my crude set up. i kind of got the idea this other site.

i didn't want to invest alot of time and money in building a foundry. i just used a popcorn can to hold the coals. when i started, i had the coals almost to the top of the soup can. it didn't take long for them to burn down.

i thought most people had to skim aluminum cans because of the inks and varnishes. most sites say its not worth the hassle and to cash in the cans and buy aluminum from casted parts. i dunno... just wanna get medieval and melt crap. if i like it, then i'll invest more time into it.

maybe i'll put some fire bricks on top to retain the heat.


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 Post subject: Re: Aluminum Collection for Casting Small Parts
PostPosted: Sat Aug 08, 2009 8:56 pm 
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Your setup works. Just not well enough to get a lot of aluminum out of cans. Melting thicker pieces would have worked a lot better.

The Inks and varnishes have mostly gone up in smoke long before the aluminum melts.

I'd do two things to try and increase your yield. First I would put a little taper at the top of the soup can. Just sniping the top and folding it in a little will trap those organic burn offs (ink, varnishes) and reduce to oxygen.

Next after you have add all you are going to I'd inject a lot more air into the system for several minutes. A last minute blast will raise the temp a lot just before the pour. The blower probably isn't enough for this if you have a compressor that would be perfect.

Industrial recycle operation generate between 2%-30% of dross (the stuff you skim). Cans are in the 10-30% rate. So 30 cans should get you 0.7 - 0.9 lb


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 Post subject: Re: Aluminum Collection for Casting Small Parts
PostPosted: Sun Aug 09, 2009 9:00 am 
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I've seen the dross skimmed with a stainless steel ladle.

I'm guessing the melted aluminum needs to be hotter than hell to get to the point where the surface tension is low enough, but I don't know that.

Google does, though...

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 Post subject: Re: Aluminum Collection for Casting Small Parts
PostPosted: Sun Aug 09, 2009 12:05 pm 
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Mike the real problem with cans is not the dross it is the surface area.

Cans present some unique problems. First cans are one of the purest forms of aluminum used today. Because the objective is lightness very little alloying occurs for cans. Cans have a huge surface area for their weight. Again because the goal is lightness.

Aluminum loves to oxide, the oxidization process for Al is measured in picoseconds. There is a reason that Flash powder is Al based. While we are not making enough at a time right now, Al also needs to go through a degassing phase as it will create lots of hydrogen when it pulls the O2 out of the airborne water vapor.

Any skimmer should not deform at AL melt temp so it should be thick. Also it should be near the melt temp before you start skimming.


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