635 replies to this topic

[marble]

Other buyers dropped out, second chance offer

[marble]

Got my mill, must say im rather impressed. The barrel is made out of 1cm polycarbonate and thats prrtty much impossible to break or scratch. The barrel spins perfectly, very close to optimal speed

[crystal palace fireworks]

Got my mill, must say im rather impressed. The barrel is made out of 1cm polycarbonate and thats prrtty much impossible to break or scratch. The barrel spins perfectly, very close to optimal speed

Marble, out of interest, what is the optimal speed for ball milling?

[marble]

There is a formula.

285.45 dived by square root of jar ID minus media outside diameter

[TheExplosionist]

What thickness of polycarbonate would work for a 300mm diameter decagonal barrel?
In addition, what difference would increasing the diameter to say 350mm have on the efficiency and the smallest possible particle size? (assuming the speed is the same and the hardness of any materials is not a limiting factor)

Edited by TheExplosionist, 08 October 2007 - 02:31 PM.

[dr thrust]

ho man, just stick with a barrel and 12mm brass rod and make life easy for yourself it turns every thing to talc like powder the secret is not to overload, saying that though atomised ally takes about 12-14 hours to get a good flake, and now my question! whats ferro ti like to mill ive seen some but its 5-20mm

Edited by chris m, 16 October 2007 - 08:52 PM.

[Andrew]

There is a formula.

285.45 dived by square root of jar ID minus media outside diameter

ID and OD in what unit??????

[BrightStar]

There is a formula.
285.45 dived by square root of jar ID minus media outside diameter

Almost, but not quite... 265.5 / SQRT (jar id " - milling media diameter ") gives you the critical speed in RPM

The critical speed is where your media starts to stick to the walls and so is less efficient in milling.

The optimum milling speed = critical speed * 65% to 75%

So, given an Inoxia 4" jar with their 0.8" media, the critical speed is 148 RPM and the optimum milling speed is 96 RPM to 111 RPM.

Hope this helps

Edited by BrightStar, 16 October 2007 - 09:34 PM.

[x-Ammo-Nx-x]

I`m intending to make a mill from my desk fan and I`m trying to choose a good drum to use as the tumbler. My first thought was a Cillit Bang tub which would be ideal

but would it be advisable to use plastic as I`m concerned about a build up of static.
Also I heard copper coins can be used as milling media.

Edited by x-Ammo-Nx-x, 18 October 2007 - 08:08 AM.

[marble]

plastic is fine, i don't like using copper. Use brass or lead.

[cooperman435]

Yeah stick to the lead as its safer, quicker and much more economical on time and energy.

your jar really wants to be tougher than a cillit bang tub though.

[Jerronimo]

Buy yourself a length of 13cm or 10cm diameter thick walled PVC pipe, and a pair of endcaps.
Cut the tube to the length you desire and glue one endcap to the end of the tube with PVC cement.
The other endcap can be used as a ''lid''

Cheap, available everywhere and lasts for a very,very long time.

[sasman]

I have bought a couple of Ball mil jars from inoxia ..I am having problems with the media just slipping and not churning in the jar?.. i know you can use lifter bars to help this .. is there any easy way of adding lifter bars..
I added some perspex strips to the inside of my large jars.. but it was a lot of hassle and i cant clean the jars properly..I recently milled some charcoal streamer comp for a a total of 24 hours... and i have noticed that i can get the same effect from using my hexagonal barrel ..in just a few hours.. the hexagonal barrel is far better.I am hoping some one can give me an easy way of adding lifter bars ??

Thanks

[pyrotrev]

Rob - do you know what kind of plastic the jars are made of? it's struck me that with some kind of jig and the application of a little heat it should be possible to add some flat spots to any jar made of thermoplastic, producing a hexagonal/octagonal profile and increasing the lifting. Alternatively if you're using PVC tube for the jars it should be quite easy to glue some bits of PVC extrusion to the inside - I know you can get jars for the Beach rock tumbler like this. Alternatively upping the speed should help the slipping.

Edited by pyrotrev, 18 October 2007 - 10:58 PM.

[cooperman435]

slipping I found can be a result of slow rpms. simply speeding the mill up can cure it completely.