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Ball Milling


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I just finished making a direct drive ball mill on the cheap.  I'm milling my first batch of material.  I have stainless steel ball bearings (1/4 ",1/2", and 3/4" dia.) in the drum.  I have no idea about how long it takes to mill material. ( hours vs days?)

  

Right now i have loaded basalt gravel ( 20 mesh) in the mill.  I also have quartz, feldspar, and calcite to mill.  Most of the material is screened to 20 mesh, but some of the granite is a bit larger.

 

Jed

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20 mesh is a good place to start but you are going to have to do trial runs on every new material to find the optimum milling time for the mesh you are looking for.  It could take more than a day or two to get what you want, depending on the speed and loading of the mill.

 

are you able to vary the speed of the mill? This could make a big difference in efficiency.

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Guest JBaymore

I run ceramic balls in the mill. Granite dust to 80 mesh to fines in 6 hours.

 

Look up ball mill operation to understand "critical speed".  It varies by the diameter of the jar and to a degree to the charge.

 

best,

 

...............john

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Any comments from those who used ball mills re the effectiveness of the plastic jar?

 

R

If the balls slide along the jar, they will wear it out. You want to have a pounding motion. Look at Cardew's "Pioneer Pottery book"

I second John. You want porcelain balls or flint stones that you pick up on the beach. I know there is room for joking here, but I am trying to give advice. You also probably want to calcine your flint before grinding.

TJR.

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Guest JBaymore

I think the first thing to do is to throw (or buy) a porcelain jar.  If you make it.... make it thick.... like 1/2" to 5/8".  No glaze inside .

 

The plastic will get torn up fast, I think.

 

Flint pebbles were the "traditional" grinding media.

 

You can make your own round porcelain balls for milling.

 

OR...... you can buy all this stuff.

 

best,

 

...............................john

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The hard part of throwing your own ball mill jar is getting it perfectly round. I found a way to throw a very round ball milling jar.

 

On the base of your giffen grip, with the fingers pulled way out, throw a thick walled cilinder little higher and slightly smaller in diameter than you want to end up with. Get a piece of PVC tubing with an ID the diameter you want the OD of your jar to be and a little bit taller than you want your jar to be. Make sure you cut one end of it very square. I used an 11 inch ID pipe.

 

Slip the pipe over the cylinder you pulled and crank your Giffen grip down on it. Reach into your cylinder and pull it out against the inside wall of the pipe. Then you can reach in and collar the top down to the size of one of those plastic sewage pipe clamps that has a gear clamp around it.

 

Cut the jar with the tube off of the giffen grip and set it aside for a few days, It will shrink away from the plastic tube. It is then easily removed for further drying.

 

Mine turned out perfectly round and could pass for a commercial model.

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I will make porcelain balls. Throwing a large jar with 5/8 in thick wall...will do.… Fired to ^10?

 

I also will be throwing 4 smaller diameter jars/tubes that will fit inside the larger jar, like a rosette. This way, I can mill 4 smaller materials at once.

 

I also have to slow down my RPMs to about 65-70 for the larger jar. The current speed should be OK for the smaller jars, if my calculations for critical speed are right.

 

Second generation mill....on its way.

 

Thanks, jed

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The hard part of throwing your own ball mill jar is getting it perfectly round. I found a way to throw a very round ball milling jar.

 

On the base of your giffen grip, with the fingers pulled way out, throw a thick walled cilinder little higher and slightly smaller in diameter than you want to end up with. Get a piece of PVC tubing with an ID the diameter you want the OD of your jar to be and a little bit taller than you want your jar to be. Make sure you cut one end of it very square. I used an 11 inch ID pipe.

 

Slip the pipe oveer the cylinder you pulled and crank your Giffen grip down on it. Reach into your cylinder and pull it out against the inside wall of the pipe. Then you can reach in and collar the top down to the size of one of those plastic sewage pipe clamps that has a gear clamp around it.

 

Cut the jar with the tube off of the giffen grip and set it aside for a few days, It will shrink away from the plastic tube. It is then easily removed for further drying.

 

Mine turned out perfectly round and could pass for a commercial model.

Great idea.

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Guest JBaymore

The hard part of throwing your own ball mill jar is getting it perfectly round.

 

With the direct drive design it is not as much of an issue. The jar is clamped to the shaft on each end.

 

And I hate to say it, but throwing perfectly round and straight should be doable for a skilled thrower :) .

 

 

 

Fired to cone 9-10 for sure .... higher if you have the claybody and kiln for it.

 

 

best,

 

.......................john 

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Guest JBaymore

Nice job on the ball mill rack to use the wheel drive, Larry. 

 

I was using a home-brew ball mill for probably 30+ years.   A year ago or so I got tired of repairing and cobbling together the old mill.  It had earned its keep anyway.  So I finally broke down and bought the Shimpo Dual unit.  Nice piece of gear.

 

best,

 

.........................john

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What are y'all ball milling and why? I'm always curious about what other potters are doing. 

I had a recent discussion with some others who said ball milling is no longer necessary with

today's material processing. I also remember a workshop where the potter lowered his firing 

temperature by ball milling the glaze for 8 hours. Another potter finds that his ash glaze benefits. 

The price has kept me from getting a ball mill, so I'm intrigued by making one and trying it out.

 

 

Ruth

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Guest JBaymore

Ruth,

 

I use local materials a bit. When used for glazes...... they have to get procesed. Local clay, local granite, local sand, certain wood ash, etc. That is the main use. Also for some ash glazes.

 

best,

 

...............john

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Guest JBaymore

I am really curious as to how long those plastic jars in the video last. For casual use.... probably OK. When I am doing some serious materials grinding to get the stock up.... each charge is 6 to 8 hours..... and the mill is running for days and days on end (mostly at night when I don't have to listen to it :P ).  Even the porcelain wears out eventually.

 

Plus the speed in the video looks all wrong to me for grinding action. I wonder if it is really being all that effective other than as a good mixer. I'd think that the grinding medium would be mainly sticking to the sides of the jar due to centripaedal forces.

 

best,

 

..................john

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one problem with plastic jars, besides wearing out, is that the plastic is smooth so you don't get the grinding action between the balls and the wall. This typically means you have to mill some several times longer than you would with an unglazed ceramic wall.

 

as you can notice on the picture of my ball mill rack on my wheel, there's a gallon glass jar  with glass marbles in it.  this works quite well but be careful not to run it too fast or have too big of rocks  in it.  I got too aggressive once with both speed and rock size.  I cracked the glass jar with a red iron oxide glaze in it. A real mess.

 

Folks who like to use plastic jars find that large PVC tubing with a cap on either end will last forever. But, you're still left with at least overnight milling

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I am really curious as to how long those plastic jars in the video last. For casual use.... probably OK. When I am doing some serious materials grinding to get the stock up.... each charge is 6 to 8 hours..... and the mill is running for days and days on end (mostly at night when I don't have to listen to it :P ).  Even the porcelain wears out eventually.

 

 

 

best,

 

..................john

I just finished 6 hours of basalt (very hard stuff) and 3 hours of granite. The inside of the cooler is pretty scratched up. The lid has taken a big hit and will need to be replaced. I will need to throw a porcelain jar and lid. I was suprised at the wear the lid suffered.

 

End of 2days I have 3 1/2 lbs basalt powder and 10lbs granite powder.

 

Jed

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