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Ball Mill

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Ball Mill

Unread postAuthor: zeigs spud » Mon Dec 08, 2008 10:29 pm

I made a ball mill outta my sis's broken kid slushy maker. the chamber is abour 5 inches wide, 6 or 7 deep but it prolly rotates about 20-30 times a minute. how fast do i need to make this go? and the only media i have are marbles which dont seem to work (grinding aluminum pop can scraps) im wondering wht i could use as media tht i dont have to buy.
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Unread postAuthor: Lentamentalisk » Mon Dec 08, 2008 10:47 pm

LOL!!!
You got this all wrong! A ball mill is not for grinding! A ball mill is for crushing black powder, and mixing it completely.

If you want to grind something, you need a grinder.

Also, if you are trying to end up with aluminum, don't use aluminum cans, because they have a plastic coating on the inside.
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Unread postAuthor: Daltonultra » Tue Dec 09, 2008 1:34 am

If you want powdered aluminum and don't wish to, or can't, buy it, you need a grinder. The real problem is keeping it from just going everywhere. The easiest way to do that is to grind it under water.

All you need is an angle or bench grinder, something to make a splash shield out of, and a pan the right depth to cover the bottom third of the grinding wheel.

Your splash shield should cover the top two-thirds of the wheel. The pan of water should be deep enough to cover the lower third, plus a little of the shield. Find an aluminum piece, like the intake of a car, and grind away. The water will keep the dust from flying away. When you've reduced the aluminum scrap to nothing, simply pour the water through an old hanky or bedsheet. You'll have a small amount of grit in it from the wheel wearing away, but that shouldn't hurt anything.
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Unread postAuthor: zeigs spud » Tue Dec 09, 2008 12:32 pm

ugh wow crap....
so what exactly does a ball mill do then? i thoght it just slowly punded stuff into powder?
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Unread postAuthor: zeigs spud » Tue Dec 09, 2008 12:33 pm

A ball mill is a type of grinder used to grind materials into extremely fine powder for use in paints, pyrotechnics, and ceramics.


strait off wiki..
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Unread postAuthor: SpudFarm » Tue Dec 09, 2008 12:41 pm

a ball mill is used to grind chemicals with friction and kinetic energy, one ball slides over (example) the potassium nitrate crystal grinding it into finer powder. when one has slipped ofer another one comes falling and does the same thing.

it is widely used where you need a finer dust of something. the thing it grinds is crystals so pop cans wont be damaged ever.

the best media you can ask for is lead for flammable chemicals and steel for harder non flammable chemicals.
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Unread postAuthor: john bunsenburner » Tue Dec 09, 2008 2:39 pm

Some people say they got very good results with a coffee grinder and aluminium foil. Once you have a powder you could try to grind it in your ball mill, I would use heavy steel ball bearings though! Just out of interest, what are you planing to use the Al powde for? It is really only used in pyrotechnical mixtures(disscussing these would be against the rules). My guess is you want to make flash powder, if so, watch out, it can get very dangerous, I do not recomend making it and what ever happens Do not ball mill it
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Unread postAuthor: iPaintball » Tue Dec 09, 2008 3:18 pm

Alright, I suggest you read up on your pyrotechnics before you and try and make the aluminum powder. Since you most likely plan on making flash powder with this stuff, be careful. That stuff deflagrates at around 2.2km/s so don't blow your hands off.
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Unread postAuthor: john bunsenburner » Tue Dec 09, 2008 3:58 pm

I personally suggest you find some one whith alot of knolage about pyrotechincs, this is a very dangerous thing and a "little mistake" is ussually fatal. In a case like this, I woudl not rely on the internet, just as I would nor look up "how to rock climb" on google, and then just go nd try it. Ask some one with knolage if you must do this, or, the best thign to do: Let it be. I will not disscus any pyrotechinics on here and i highly doubt you will find any one here to help you.
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Unread postAuthor: psycix » Tue Dec 09, 2008 4:21 pm

A ball mill is useful to grind powders to finer powders. (higher meshes)
If you want to create aluminium powder, I suggest sanding off a block of aluminium (from a hard drive or pencil sharper) and collecting the powder.
Then you can mill the powder further to an usable mesh, but you will need to use hard grinding media. Steel with some sort of coating or maybe a type of ceramic media would be best.

Marbles are BAD media. They are too low of density. Are too soft for grinding aluminium and they may give off tiny shards of glass.
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Re: Ball Mill

Unread postAuthor: jimmy101 » Tue Dec 09, 2008 5:51 pm

zeigs spud wrote:how fast do i need to make this go?

Ball mills can't be run too fast or the balls are just plastered against the cylinder's wall by centrifical force and don't do anything.

Rock grinders are ball mills that are used to polish instead of pulverize. They actually do both but they polish much quicker than they pulverize. The stones themselves are generally the "balls", though often a powdered polish is added.

Ball mills won't usually work on anything with the softness of most metals. Like others have said, they are generally used for pulverizing crystaline materials which have essentially zero ability to deform. Most metals will deform enough to absorb most of the impact of the balls. Instead of breaking the metal up into smaller pieces you just hammer it into varying shapes.
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Unread postAuthor: zeigs spud » Tue Dec 09, 2008 6:20 pm

thanks for the info.
im not making flashpowder but for the sake of it, lets just say i collect aluminum powder lol.

idk where to get my grinding media and ill put some lifters in my mill so the balls can fall more regularly.
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Unread postAuthor: iknowmy3tables » Tue Dec 09, 2008 6:33 pm

bench grinders!, sanding! no no no, manually grinding alluminum is too freaking tedious, a bench grinder will grind it to fast and produce sparks of aluminum oxide, when the alluinum is already burned/oxidized it's no longer good.

take some aluminum foil, and cut it up into a zillion pieces with scissors, then put it in a blender or coffee grinder, then you put this stuff in a ball mill
http://www.metacafe.com/watch/1050854/p ... um_powder/
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Unread postAuthor: zeigs spud » Tue Dec 09, 2008 8:13 pm

yay thanks!!! wht if my mom wont let me use the blender for such purposuses haha?
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Unread postAuthor: jimmy101 » Wed Dec 10, 2008 1:48 pm

iknowmy3tables wrote:bench grinders!, sanding! no no no, manually grinding alluminum is too freaking tedious, a bench grinder will grind it to fast and produce sparks of aluminum oxide, when the alluinum is already burned/oxidized it's no longer good.

That's an excellent point. The dust from grinding Al in air isn't Al, it is Al<sub>2</sub>O<sub>3</sub>. Or, most of it will be within a farily short time after grinding.

Al corrodes very fast, indeed it corrodes faster than iron does. For a fine dust the majority of the Al will be the oxide surface coat. That's why it is usually made under water or some other (preferably non-flammable) liquid.

I'll leave it to others to explain how Al can corrode faster and easier than iron (and all types of steels) but Al is often used because of it's "corrosion resistance".
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