Ball Mill Project

[Bamboozler]

I journeyed down the path of a ball mill project this fall and am posting a bit about the fun n' games in this post. Thanks goes out to the many related threads/post regarding the topic that helped me with the ideas/calculations/thoughts on the matter. Hope this post helps others looking to strike out on a similar project.

 

 

Started by looking for a suitable TEFC motor to run the show. Came across a new old stock 1/2HP Marathon 56C34F544 (LINK). Specs: 1/2HP, TEFC rated enclosure, 115/208-230V, single phase, thermally protected.

 

 

http://www.pcbwerks.com/pics/mill5.JPG

http://www.pcbwerks.com/pics/mill8.jpg

I know enough of the 3D modeling program Solid Works to be just about dangerous. This was a fairly straight forward and fun project to model up, helps tremendously with visualizing how things go together, length/amount of material needed, where you run into clearance issues etc... The design was to be made with light square tubing, be wheeled around, stored leaning upright if needed. The above is what I came up with. May still make a blast shield enclosure for the top. If anyone wants the solid files to use as a starting point, PM or email me.

 

 

http://www.pcbwerks.com/pics/mill7.JPG

Frame just about done being welded, 1/16" wall mild steel from Online Metals, 10" wheels from Amazon HERE.

 

 

http://www.pcbwerks.com/pics/mill2.JPG

Just about finished being assembled. 1" Pillow block bearings, 1" OD steel intermediate and mill jar drive shafts, 1" heater hose over the drive shafts (I did have a friend mill in a key way for the pulleys on both shafts). The primary drive belt didn't need a tensioner, as you could get the belt plenty tight by pulling and tightening down the motor. Most pulleys were bought from MSC Industrial Supply. Belt length was determined by measuring the distance between the pulleys in Solid Works and using a belt length calculator with the known pulley diameters.

 

 

 

http://www.pcbwerks.com/pics/mill3.jpg

For media I went with brass cylinders of both 1/2" and 5/16" size, figure the cylinder would have more grinding contact surface at any one given point vs. a ball and might be more efficient (shrug). I can't recall the reason for the going with the mixed size media. I remember reading something beneficial here (possibly more efficient when grinding at the airfloat stage due?) and thought it would be worth trying.

 

Bought 72" lengths, sawed and taped them into bundles and cut them into pieces on the band saw. From the first jars of oxidizer, charcoal and comp through through the mill, the mixed media works very well, but I don't have anything other than observation to back it up at this point. Media weight was approximately 35lbs and filled about half of the almost 12" long 6" diameter jar (not including the reducer length).

 

 

 

Mill in action in the link below. I use a WiFi outlet switcher to turn the mill on/off. Set an alarm on your phone for the duration you want to mill, when the alarm goes off hit up the outlet switcher app to turn off the mill.

http://www.pcbwerks.com/pics/mill1.MOV

 

 

 

The mill uses 6" PVC pipe mill jars and were adhesive welded together, 6" cap and 4" to 6" reducer coupling.

 

 

The calculations used that are specific to this mill are listed below (copy/pasted from my notes). When measuring the RPM of the spinning jar I came within a few RPMs of the target, so if there's a boo boo in the work below, it's at least close .

 

Being that the motor RPM was a bit high I had to use an intermediate shaft and secondary reduction pulley to get the final jar speed. In hindsight, if I were to do over, I would probably shoot for a slower 1750RPM (or about) commonly available motor to be able to skip the intermediate shaft and run direct drive from motor to the jar drive shaft. If the 3450 RPM motor were to be direct drive the reduction pulley diameter would be huge. At the time of discovering this I already bought the motor.

 

 

Milling Jar diameter 6.67”*pi: 20.94
Rod diameter with rubber 1.25”*pi: 3.92
20.94 / 3.92: 5.34 ratio between shaft and jar, every turn of the jar, the rod turns 5.34 times.
74RPM target
74 * 5.34 = 395RPM needed on the drive rod w/rubber

2.05” primary motor pulley
3450RPM motor
3450 / 395 = 8.73, so need the motor to spin 8.73 times to rotate the drive rod once

Pulley selection, current pulley set
Primary: 2.05” motor pulley to 7.25” pulley on an intermediate shaft, (7.25 / 2.05 = 3.54 ratio), 3450
RPM / 3.54 = 975 RPM
Secondary: 3.75” pulley on an intermediate shaft to a 8.25” mill drive shaft, (8.25 / 3.75 = 2.2 ratio), 975
RPM / 2.2 = 443 RPM
X RPM * 5.34 ratio = 443 RPM, X = 82 RPM

Ideal pulley selection for 74RPM (different/larger OD jar)
Primary: 2.05” motor pulley to 8.25” pulley on an intermediate shaft, (8.25 / 2.05 = 4.02 ratio), 3450
RPM / 4.02 = 858 RPM
Secondary: 3.75” pulley on an intermediate shaft to a 8.25” mill drive shaft, (8.25 / 3.75 = 2.2 ratio), 858
RPM / 2.2 = 390 RPM
X RPM * 5.34 ratio = 390 RPM, X = 73 RPM

[Richtee]

Looks like plenty of “balls” to that mill. That’s alot of powder.

 

I WOULD fashion a guard for that top drive pully... because if shit can happen, it will

[Bamboozler]

Just wait for the vid with my 55 gallon drum spinning away.. I kid!

 

That's a good call with the belt guard. The thought has crossed my mind, I'm having to make sure the puppies are in the house when running the mill outside. Hate to see a wagging tail near it when on.