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elementcollector1
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[*] posted on 23-10-2012 at 14:58
Ball Mill questions


Before you asked, yes, I did UTFSE. Not much out of it. So, I'll bring the topic up here.

-What grinding media is recommended for grinding aluminum foil, and where can one obtain this media (preferably some sort of OTC)?

-What is the best size for the media?

-Can the ball mill (In this case, a Lortone 3A rock tumbler with rubber barrel and such) be run in the outside (it's winter now! :D) to cool off the aluminum?

-What is a good test to prove the aluminum is usable?




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Funkerman23
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[*] posted on 23-10-2012 at 15:46


OK here you want NON SPARKING media. I am sure you already know why a powdered metal would require such. Hardened lead antimony can work as well as some ceramic media( although I myself worry about the media becoming useless from"loading up" with the aluminum) Both are available from United nuclear. Home making the lead balls can be done however they will have to be cast( and alloyed) then finished to be come proper balls. I do not now or ever recommend using a tumbler outside given the material you are milling. In the winter I have had a lot of issues with static and this could ignite the powder if not accounted for. there is a formula ( when I find it I will post here) for the best size of media but the peed of the mill's spinning is critical here( again I will post the formula when I find my notes) the grinding balls need to be spun fast enough for them to "fall' in the tumbler. Here again the material being milled presents a problem: you cannot really mill it without watching or monitoring it. some have build computer systems to do so. Your end use is needed here as that will tell what other steps are needed. the aluminum will, inevitably, oxidise when ground so if this is a problem the best I can suggest is to have a static free inert gas pumped or sealed in the milling chamber to prevent this. But overall without knowing what the final use of the product is it will be hard to recommend anything in greater detail. Please be careful in any event. the data above is easily found elsewhere on the web and under no circumstances am I liable for what is or is not done with the data above.

[Edited on 23-10-2012 by Funkerman23]
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[*] posted on 23-10-2012 at 16:06


There really is a lot of information available. I suggest you try tweaking your search terms a little.
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elementcollector1
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[*] posted on 23-10-2012 at 16:11


How does winter create static?
Final use of the product: Good 'ol thermite! But I need fine powder.




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elementcollector1
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[*] posted on 23-10-2012 at 16:54


Oh! I was fishing a soup can out of the recycling today, and a thought struck me: Would the ball mill powder stuff faster if I used a steel barrel instead of a rubber one? It would be harder, giving the media more impact against the aluminum.



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hyfalcon
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[*] posted on 23-10-2012 at 17:42


Steel=sparks, sparks and aluminum especially finely powdered aluminum is a mixture for disaster.
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elementcollector1
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[*] posted on 23-10-2012 at 18:25


Lead and steel too? Darn.
...PVC?




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[*] posted on 23-10-2012 at 18:45


Quote: Originally posted by elementcollector1  
How does winter create static?
Final use of the product: Good 'ol thermite! But I need fine powder.
Winter typically has a lot of dry cold air. With drier air the resistance changes and the chance of sparking is higher. Not guaranteed to spark but still more likely. as for cooling the crum: a good drum design will have a general max amount of grinding media and metal that can be accommodated. Usually the drum is large enough to cool itself with it's surface area and still spin fast enough to effectively grind. Again once I find my notes I will PM & post the proper formulas and rules of thumb. Bear in mind to get good at milling will require some experimentation. All the theory in the world still doesn't stop Murphy from dropping a wrench in the works. I am sure you are familiar with the scaling process? Slowly and incrementally build up until you have a sufficient amount of experience & knowledge of the processes. Safety is still the most important thing here. Be careful.

[Edited on 24-10-2012 by Funkerman23]
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[*] posted on 23-10-2012 at 18:48


Quote: Originally posted by elementcollector1  
Lead and steel too? Darn.
...PVC?
Lead usually won't spark in a ball mill( it would take quite a lot of abuse & extraordinary circumstances for it to become a possibility). when hardened with antimony it is a rather good choice for your needs, assuming a negligible amount of lead is acceptable. Mind the usual hazards with lead & such.
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hyfalcon
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[*] posted on 23-10-2012 at 19:56


I've got some old Linotype lead that I use when it must be lead. I mostly use various sized and shape of alumina media for most of my ball mill grinding needs.
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elementcollector1
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[*] posted on 23-10-2012 at 20:11


Quote: Originally posted by Funkerman23  
Quote: Originally posted by elementcollector1  
Lead and steel too? Darn.
...PVC?
Lead usually won't spark in a ball mill( it would take quite a lot of abuse & extraordinary circumstances for it to become a possibility). when hardened with antimony it is a rather good choice for your needs, assuming a negligible amount of lead is acceptable. Mind the usual hazards with lead & such.


So...Are you saying a steel tumbler would work with lead media? I'm a bit confused.




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[*] posted on 23-10-2012 at 20:20


Quote: Originally posted by elementcollector1  
Quote: Originally posted by Funkerman23  
Quote: Originally posted by elementcollector1  
Lead and steel too? Darn.
...PVC?
Lead usually won't spark in a ball mill( it would take quite a lot of abuse & extraordinary circumstances for it to become a possibility). when hardened with antimony it is a rather good choice for your needs, assuming a negligible amount of lead is acceptable. Mind the usual hazards with lead & such.


So...Are you saying a steel tumbler would work with lead media? I'm a bit confused.
steel isn't a safe option here but some have managed to get away with it before.I myself do not use steel for milling metals. I would much rather wait for the grind to complete than rush it and risk harm. there is the idea of running a wet grind( IE grinding the metal in say mineral oil than washing& drying with hexane) but I do not know enough about it. what I meant was that the media itself won't spark. pardon that.

[Edited on 24-10-2012 by Funkerman23]

[Edited on 24-10-2012 by Funkerman23]
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hyfalcon
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[*] posted on 24-10-2012 at 01:43


Here's my mill. I use 6" PVC for the mill jar.

Ball Mill smrezied.JPG - 156kB
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Eliteforum
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[*] posted on 25-10-2012 at 10:07


Why not order some Al powder off ebay? It'll probably be cheaper in the long run than your electricity bill would be from making your own. Also, almost all Al foil is an alloy, so impure.



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elementcollector1
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[*] posted on 25-10-2012 at 10:43


Because if I make enough Al foil per run, and the Al foil is usable, I think it will be better off for me.
The alloy is 95% Al, at least. Reynolds comes with a layer of polyethylene on top, making it almost useless.

I'm going to try to fit a PVC barrel inside the main barrel, so the mill runs the same way but now with PVC. (For 4x the cleansing power!)




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franklyn
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[*] posted on 25-10-2012 at 10:54


Found this _
http://www.harborfreight.com/3-lb-rotary-rock-tumbler-67631....
http://www.harborfreight.com/dual-drum-rotary-rock-tumbler-6...
http://www.amazon.com/Diameter-Chrome-Steel-Bearing-Balls/dp...
From here _
http://www.sciencemadness.org/talk/viewthread.php?tid=14884&...

.
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elementcollector1
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[*] posted on 25-10-2012 at 11:14


@franklyn: Thanks a ton for that third one! :D
I don't quite know where to get stearic acid OTC, though... Is it necessary for a better aluminum powder?




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[*] posted on 25-10-2012 at 11:24


Palm stearic acid.

http://www.texasnaturalsupply.com/Palm-Stearic-Acid-p/pmsd-c...

Add .5%-5%, you'll have to experiment a little to get the right percentage with the aluminum you are using. After you've reduced it to the level of fineness you want, in an inert atmosphere, you heat your aluminum and stearic acid till it carbonizes. Needless to say you don't want any oxygen around during this process.
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[*] posted on 27-10-2012 at 08:44


UKGE Limited – www.ukge.com
UKGE USA – www.ukge.com/usa/
UKGE Canada - www.ukge.com/canada/
UKGE Ireland – www.ukge.eu/en/
UKGE Australia – www.ukge.com/australia/
UKGE New Zealand – www.ukge.com/NZ/
Deposits Magazine – www.depositsmag.com




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[*] posted on 28-10-2012 at 07:09


Carbon steel balls in a ball mill - they can be a royal PITA to keep from hopelessly corroding. After milling, the balls need to be cleaned, generally washed. No problems there, but getting them dry and preventing corrosion at the same time is very difficult. And you cannot wipe them down with oil because that would contaminate the next mill job.

I'll never use steel balls again unless they are stainless, preferably 316, and these are very expensive.
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[*] posted on 11-11-2012 at 11:28


I have heard of people purging the container with Ar to decrease chances of combustion. If you dont have Ar can you just breath into it (filling it with CO2) for a while to get the same effect?
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elementcollector1
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[*] posted on 11-11-2012 at 13:32


Quote: Originally posted by weschem  
I have heard of people purging the container with Ar to decrease chances of combustion. If you dont have Ar can you just breath into it (filling it with CO2) for a while to get the same effect?


...No. There's also lots of water vapor in your breath, and tons of contaminants.




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[*] posted on 11-11-2012 at 15:25


Quote:
If you dont have Ar can you just breath into it (filling it with CO2) for a while to get the same effect?


Exhaled air typically still contains 13-16 % oxygen (and only 4-5% CO2).





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[*] posted on 12-11-2012 at 09:56


I actually don't see what the problem would be with using steel balls. I would definitely agree that sparking of the balls is an inexcusable hazard when milling, say, black powder because the mixture contains its own oxygen and fuel and thus an ignition source would cause the whole thing to explode. When milling aluminum, however, the only oxygen is in the small amount of air inside the mill, which actually ends up oxidising the aluminum anyway as the foil is broken up and fresh metal is exposed to the air.

Fresh aluminum actually spontaneously reacts with air to form a thin coating of oxide (this is called passivation) and thus the sparking of the steel balls is really not an issue. The only real hazard is that all the oxygen inside the jar will be used up and when you open the jar all of the non -passivated aluminum will react at once and cause the aluminum to burn because of the very high energy released in a short amount of time.

Let's say that your jar is 10cm in diameter and 15cm in length and is half full of air, then divide by 1000 to conver to L.
-Volume of mill = pi*h*(d/2)^2 = 1.178L
Divide by 2 because the container is only half air and multiply by 0.21 because air is only 21% oxygen:
-Volume of oxygen= 0.124L
Divide by 22.4 to find moles of oxygen because there are 22.4L in 1 mol at STP:
-moles of oxygen gas: 0.0055mol
Find grams of aluminum by multiplying by 4/3 to find mol Al and then by 27.0 to find grams:
Grams of Al: 0.20g

As you can see the amount of aluminum that can even burn in the closed atmosphere of the ball mill is very low. You should be fine to use steel milling media. Just make sure they are clean and free of rust. Of course lead media can still be used, but steel balls are harder and will result in faster milling.

(Edit): You can also add a small amount of charcoal at the start of the milling run to coat the aluminum and decrease the amount of passivation. Fery fine aluminum used in pyrotechnics is coated this way.

[Edited on 12-11-2012 by Erbium_Iodine_Carbon]
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[*] posted on 12-11-2012 at 21:35


How fine of a mesh size can be attained?
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