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ball mill question


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#1 MadMat

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Posted 21 April 2017 - 12:08 PM

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?



#2 lloyd

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Posted 21 April 2017 - 12:43 PM

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.

 

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#3 MadMat

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Posted 21 April 2017 - 12:46 PM

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 by MadMat, 21 April 2017 - 12:56 PM.


#4 lloyd

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Posted 21 April 2017 - 01:02 PM

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.

 

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Edited by lloyd, 21 April 2017 - 01:04 PM.

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#5 MadMat

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Posted 21 April 2017 - 01:16 PM

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 by MadMat, 21 April 2017 - 01:18 PM.


#6 lloyd

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Posted 21 April 2017 - 01:35 PM

Speed_Calculations.jpg


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#7 MadMat

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Posted 21 April 2017 - 01:43 PM

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 :wacko:



#8 lloyd

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Posted 21 April 2017 - 01:56 PM

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

 

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#9 Tino777

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Posted 11 May 2017 - 04:05 AM

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.
 
 
And for steel balls to grind:
 
 
To use only those with a diameter of 12.7 mm (1/2") or more.
 
:)


#10 lloyd

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Posted 11 May 2017 - 05:37 AM

C'mon, Tino!  Give it up!

 

Lloyd


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#11 calebkessinger

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Posted 11 May 2017 - 08:14 AM

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.woodysroc...ll_Milling.html


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#12 starxplor

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Posted 11 May 2017 - 09:24 PM

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.woodysroc...ll_Milling.html

 

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



#13 calebkessinger

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Posted 12 May 2017 - 09:19 AM

:D

 

Thanks!


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#14 lloyd

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Posted 12 May 2017 - 09:54 AM

Caleb,

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

 

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#15 clarkie752

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Posted 12 May 2017 - 10:03 AM

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. 😉
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#16 OldMarine

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Posted 12 May 2017 - 10:19 AM

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!  :D


Come on! Name one other hobby in which you cheer as your money and hard work go up in smoke!

#17 calebkessinger

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Posted 12 May 2017 - 12:45 PM

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. 


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#18 OldMarine

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Posted 12 May 2017 - 01:15 PM

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.


Come on! Name one other hobby in which you cheer as your money and hard work go up in smoke!

#19 PeteyPyro

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Posted 20 August 2017 - 10:13 AM

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.

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#20 lloyd

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Posted 20 August 2017 - 10:34 AM

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.

 

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