# My ball mill



## kjavanb123 (May 15, 2014)

All,

After reading posts related to ball mill, I finally decided to get in the action and build one. This is a copy from design by samuel-a.

The mill diameter is 21cm(8.26 in), the polly or is it puly that decrease the rpm is 25cm (9.84 in), and the polly attached to washing machine motor is 4cm(1.57 in). The motor has 2 speeds, 450rpm and 3000 rpm, I set it to 450rpm, then attach it to the polly, but it did not produce the speed and the balls just stay down the bucket, so I switched to 3000rpm, and still did not move that much, is there any formula to what types of balls to use and how many?






Thanks
Kevin


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## Anonymous (May 15, 2014)

Slower speeds work best for ball mills. It's not about whizzing round fast. It's a calculated process rather than blunt force and trauma.

You have to ensure the ball weight and diameter is calculated correctly to match the housing and the relevant speed of rotation because the idea is to use the balls to break up the material between them as opposed to crushing it against the walls of the cylinder.


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## samuel-a (May 15, 2014)

Kevin,

You need to find more information about critical speed for ball mill.
there's ton of info out there, here a good one thoguh:
https://www.sagmilling.com/tools_millspeed

Have you masured the actual RPM you are running?
As rule of thumb, a ball mill should run arond 80% of critical to do the job. For your diameter, roughly 70-80 RPM is needed.
The smaller the drum's (inner) diameter the higher the RPM needed.


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## Smack (May 15, 2014)

It's a pulley that the belt runs on. Mine is 15" diameter and it's rpm is about 80, as you add material the dynamics will change a bit. The media as it's called I use is 1" carbon steel balls.


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## GotTheBug (May 15, 2014)

Do you have fins inside the barrel to pick up the material and drop everything? Or just trying to rely on the spin to mix it all together?


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## kjavanb123 (May 16, 2014)

All,

Thanks so much for your comments, I have the media the steel balls 8cm (3.1in). But since I used plastic bucket as my mill, there were not enough friction so those heavy steel balls just stayed, I calculated the rpm by just warching and clocking it, around 120 rpm, so tommorow I have the pulley of size 30cm (11.8").
I think I have to replace the mill with a steel drum instead of plastic bucket, and use smaller ball sizes.

Regards
Kevin


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## GotTheBug (May 16, 2014)

An old water heater tank, the inner tank, might be ideal for what you are trying to build.


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## Smack (May 17, 2014)

The thicker the walls the better, thin=more noise and less durable. Mine is either 5/16" thick or 3/8" and when I run it I put a Gaylord box with lid over it. May want to give it solitary in it's own padded room.


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## kjavanb123 (May 19, 2014)

All,

Finally I put together the ball mill, using this water heater tank, varity size balls, and speed I counted to be 80rpm, but after watching couple if videos online I realized I need more balls than this 10 pieces, I am also using 0.5" balls. 




And closer look inside



Best regards
Kevin


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## butcher (May 20, 2014)

Kevin it is looking good.

Is the drum just being moved on the rods (without friction loses) will the roller rods or drum have a rubber coating or something to keep the roller bar rods in good friction contact with the drum, besides just the weight of the drum on the moving roller rods?


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## kjavanb123 (May 20, 2014)

Butcher,

I had to make some modification to optimize the ball mill, and it finally worked, it is a great feeling. I had used tapes for coating but did not produce friction to spin the metallic mill, so I used a plastic tank I have at the shop, filled it with 10 2.5cm and another 10 3cm balls, and had to expand the distance between two rods so the plastic container touches the rod at the middle section along with the weight of materials inside, it got a good friction, and speed was 85rpm.


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## GotTheBug (May 20, 2014)

Kevin, I've used old fan belts, automotive type, glued to the drive axle to get enough friction to turn the tumbler. My smaller version ended up being a tumbler for brass casings out of an old pickle jar and a drive from a dead, smaller bandsaw. The rubber makes the world go round...


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## kjavanb123 (May 21, 2014)

GotTheBug,

As you can see from the picture below, I cut a 2.5cm PVC pipe and covered part of the rods with them, they fit nicely. It is working great as I tested it with some incinerated ICs, today. Here are some pictures,

The feed in materials, incinerated ICs,



Inside the mill, rolling,



After 40 minutes,



I am going to try to leach the ashes using sodium cyanide, and use filter press to remove the cyanide from the ashes.

Regards,
Kevin


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## Smack (May 21, 2014)

Mine has 3/4" ID rubber hose over the shafts, same type of drive on mine.


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