ball mill question

[MadMat]

I recently made a larger "barrel" for my ball mill. The first load was just charcoal so I could be close by and check things out. I noticed that because of the extra load the motor gets rather hot after about a hafl hour. I use a sealed DC motor and power it with a 6/12 volt 2/6 amp battery charger. The various settings on the charger give me a small amount of control on the speed of the mill. I figure I could break up the run time (1/2 hour on 15 minutes off ect). Now, I can't see any problems with this as long as the total run time is added up, but I figure I would differ to someone with more expertise. Would breaking up the run time require more total time or any other problems?

[lloyd]

I don't see that as a problem. I would recommend checking the speed, though. If it's running below the optimum speed, it will take longer (total).

 

You're only dissipating 72 watts(max) in that motor. That's just NOT enough power for anything larger than about 4" i.d. jar-size.

 

Lloyd

[MadMat]

I didn't make the jar bigger in diameter but rather longer and you hit it on the head it's 4" diameter. My RPMs are running about 67.

My mill is home made. Now don't laugh, but it is belt driven, straight from a pulley on the motor to the od of the jar and the jar runs on casters. I have always intended to buy/make something better, but it has served me well for a large number of batches now and best of all, it cost me less the $20 to make.

Edited April 21, 2017 by MadMat

[lloyd]

Oh, I wouldn't laugh. I applaud folks who apply the principles to make affordable stuff.

 

But your RPMS are WAY LOW for optimum milling times. A 4" jar should be turning about 90rpm. (92). TRY increasing your motor pulley diameter by 40%, and see what happens. If it stalls, then you'll have to reduce it again. But if it doesn't, you'll speed-up your milling significantly.

 

Lloyd

Edited April 21, 2017 by lloyd

[MadMat]

I can switch up the power and get around 88 (I've been running it at 12v 2A setting). I must have made a math error, because I thought approx 70 was the "sweet spot" for the speed on a 4" dia.

Edited April 21, 2017 by MadMat

[lloyd]

http://www.pyrobin.com/files/Speed_Calculations.jpg

[MadMat]

Yep, thats the formula I used.... recalculated and hmmm old age brain fart?? and to think I went as far as a semester of calculus in college

[lloyd]

Heh! We ALL do! That's why I made the chart... I 'forget', sometimes.

 

Lloyd

[Tino777]

If you are dealing with coarse materials and want to produce fine powders for making paint or pyrotechnic powders,

Then you need grinders.

Depending on the size of the material you may need:

1) Graters.

These can be used to scrape materials in large pieces such as coal, wood or plastic; Generally tender, because metal is preferred "fusion granulation".

Fusion granulation is a process in which a molten metal is poured into a perforated vessel, forming drops that then solidify in small grains.

Gratings are therefore used to reduce the material from large pieces to small pieces.

2) Centrifugal rotary blade grinders.

These are the most used and of great reliability, such as kitchen blender with ice-breaker blades, ideal for grinding coal or metal powders, to produce impalpable powder particles with particles below 200 microns.

3) Gravitational grinders.More known by the term "ball milling machine", they use the force of gravity and the friction to pulverize materials (which must be dry). They can also produce micro-particles with particles of a few micrometers. Ideal for producing micropulver for paints or pyrotechnic applications.

http://www.stainlesstumblingmedia.com/relo...s/tumblers.html
http://www.pyrosupplies.com/shop/page/cate...2b43075aaf.html

And for steel balls to grind:

http://simplybearings.co.uk/shop

To use only those with a diameter of 12.7 mm (1/2") or more.

[lloyd]

C'mon, Tino! Give it up!

 

Lloyd

[calebkessinger]

I'd just get all that stuff from Woody's. That guy has a better price on em. Stainless balls, lead, mills, screens.

http://www.woodysrocks.com/store/c15/Ball_Milling.html

[starxplor]

I'd just get all that stuff from Woody's. That guy has a better price on em. Stainless balls, lead, mills, screens.

http://www.woodysrocks.com/store/c15/Ball_Milling.html

 

And Caleb...Woody's has great customer service too!

[calebkessinger]

 

Thanks!

[lloyd]

Caleb,

If you're looking for a "custom design", I understand that Woody's shop also makes 1-offs for folks.

 

Lloyd

[clarkie752]

Plus you will not find a faster shipper of your products than woody's. My orders usually get placed on Friday and are at my door step Monday. How's that for speedy shipping. 😉

Adam

[OldMarine]

I've had stuff show up before I paid for it several times. Starting to think he's just sending me things and telling me I must have drunk ordered it!

[calebkessinger]

Oh Drat!

Patrick is on to me!

 

impulse buys are good!

 

I try to be pretty quick on everything Clark. but.. sometimes they have to get in line.

 

 

Back to ball mills. A few of us are looking for parts to make a more economical mill. It's just really hard to do if you want quality. The motor alone on my modified rebel mills costs 150 bucks.

[OldMarine]

I have the aforementioned modified Rebel mill and it is worth every nickle. I bought mine with media and all so all I had to do was load it up and plug it in.

[PeteyPyro]

I have a (dumb?) question, that I believe that someone (like Lloyd) might have the answer to. I have an opportunity to purchase very cheaply, this model of VIBRATORY tumbler. They are normally used for polishing firearm brass while using corn cob grit or walnut shells and Brasso. Why would this type of machine not be suited for use with lead ball media, for the milling of black powder? Any ideas here? I'm rolling this around in my mind (no pun intunded), and trying to visualize the process. I know that it would need to be covered securely, to prevent the composition from getting airborne.

 

to.https://www.google.com/search?q=rock+tumbler&start=40&client=ms-android-hms-tmobile-us&sa=N&biw=360&bih=559&tbs=vw:g,ss:44&tbm=shop&srpd=7859469351576576038&prds=ds:1,num:4,cid:7374819883494657566&ved=0ahUKEwiA7bLHlebVAhUHLmMKHZp2AdA4KBCIcAgx

[lloyd]

Petey,

FWIW, there are vibratory mills suitable for dense media, but one built for brass and walnut hulls won't have the necessary force/power input to properly agitate dense media, unless you were to vastly under-load it.

 

Part of the popularity of ball mills has to do with their relatively low horsepower requirements for a given-size load. They provide a continuous, relatively slow motion. A vibratory mill must stop at the end of each half-stroke and accelerate rapidly in the opposite direction. With a load of lead in there, my suspicion is that it wouldn't vibrate much more than just to be felt with the hand, and that the stroke would be reduced to nearly nothing.

 

Lloyd

[PeteyPyro]

Thanks Lloyd. I didn't account for inertia in the equation.

[MrB]

Dumb ass question... Would you really NEED lead media? We use lead to get the force increase that comes from the higher density, as the media cascades down. But a vibrating unit doesn't really have this cascading thing going for it. A lighter, hard, none-sparking media should work pretty ok?

 

On the other hand, vibrations likes to sort stuff based on density, so it might just end up layering whatever is put in to it, if the differences are to much between composition, and media. (or even between different chems in the composition)

[Baldor]

You still need the inertia of the lead for a vibrating unit. supposedly, you will have the media moving and colliding at higher speeds, but, will it be enough to compensate the decrease in mass? In the end, it all depends of the kinetic energy of the media. From the top of my head, seems that vibrating wastes a lot more power for the same final energy in the media.

[lloyd]

Yeah, but Baldor, in defense of the idea of lighter media, Force = mass * velocity^2... so lighter media could equate to a greater impact force.

 

For instance... take some media of mass 1, and say it could be accelerated to a velocity of 2. That would result in a force of 4 (arbitrary units).

 

Now take media of mass 0.5. A given acceleration should move it at twice the velocity of the first. Force = Mass of 0.5 * velocity(4)^2 = 8 (arbitrary units).

 

I wouldn't rule that out as a vague possibility. But, knowing how those vibratory polishers are driven, I still don't think it would work well, even with ceramic media. 'Real' vibratory mills are strongly motor-driven, not vibrated by 60Hz or 50Hz electromagnetic vibrators, like most of the cheap ones designed for brass-polishing. And it takes a LOT larger motor to run a vibratory mill with the same load as does a ball mill.

 

I'm not criticizing your opinion (which I believe is right), just listing all the physical possibilities.

 

Lloyd

Edited August 20, 2017 by lloyd

[PeteyPyro]

Gee, I wonder what would happen if an ultrasonic mixing vibrator was used, along the lines of an ultrasonic cleaner? Maybe heat would buildup in certain areas, causing ignition? Just another(crazy?)idea.