Ball Milling FAQ

[Peret]

Motor speed controller

 

http://cgi.ebay.com/...=item3efe24aaf3

 

Would this work for adjusting the speed on a ball mill?? Decent price!

 

Steve

It depends on the motor, but I would say probably not. A router would use a motor like an electric drill, shunt wound with brushes. Every mill I've ever seen, home made or not, uses an induction motor. These don't play very well with inexpensive triac speed controllers because they're only designed to work over a small range of speeds.

[dagabu]

I bought a 10A variac for foam cutting and use it for other AC motors as well, it works very well and there are some on eBay for under $100.00.

[moondogman]

I know I saw a ball mill made with conveyor rollers and parts somwhere...... and now I cant find it. Anyone out there have a link to that one??

 

Steve

[moondogman]

Is this whacha yall mean by ball milling.....

 

This is what I got after aobut 24hrs with Kno3 I forgot to shut it off before I went to bed last night.

 

Steve

[moondogman]

I have a question that may show my ignorance, and I have lots of it.

 

Why dont we fill the ball mill jars with an inert gas when we are milling??

Would this prevent a possible explosion or can a reaction start just between the Kno3 and charcoal without O2?? Heck can a spark even occur in an O2 free enviroment?? I figured if adding a gas was safer we would all be doing it already.

 

Steve

[Mumbles]

The reaction provides it's own oxygen, so no back filling with an inert gas would not prevent an explosion, etc. Most inert gases are pretty dry, so that may actually increase the static risk.

[dagabu]

KNO3 is an oxidizer, ergo it creates oxygen as it burns. Inert gasses are wasted on oxidizers, the materials in question would need to depend on oxygen for combustion.

[moondogman]

Thanks Guys thats what I thought.

 

Steve

[oldguy]

I am a newbie.

But, with a grain of salt, you can take it from me.

This ball mill media is fantastic.

Magnesia Stabilized Zirconia grinding media mills twice as fast as equivalently-sized alumina media with only 1/2 the media weight loss and only 1/3 the wear (weight loss) of the grinding jar, with accompanying reduced batch contamination. Available in radius end cylinders, with length equal to their outside diameters.

 

Features:

• 1.6 times denser than high alumina

• Hard, non-porous surface, chip resistant, easily cleaned.

• Non-conductive, non-magnetic, excellent resistance to mechanical and thermal shock

Specifications:

1/4" Radius end cylinder.................. 485 PCs/lb

3/8" Radius end cylinder.................. 150 PCs/lb

1/2" Radius end cylinder.................... 65 PCs/lb

3/4" Radius end cylinder ....................50 pcs/lb

 

 

NOTE: With a specific gravity of 3.42, the charging factor of Burundum (pounds of media to be used per gallon of total jar capacity to give a 50% vol. Media charge) is approximately 9 lbs/gallon.

 

[oldguy]

 

Do you-all think this motor will run tandem 12 X 14 inch PVC jars.

Set up like this.

 

3/4 inch stainless rod rollers with pillow block bearings.

Will also include an adjustable swing arm idler to adjust belt tension.

Edited March 25, 2011 by oldguy

[dagabu]

I suggest 1" shaft so that you can fit rubber hose over them for grip and sound proofing. 3/4" shaft still has enough flex to wear the jar unevenly. 1/3 hp ought to move the jars fine but there is no cooling for the motor so it may cut out from time to time if it overheats. A TEFC motor is definitely the way to go with ball mills.

[Mumbles]

I don't know how big of a deal it is, but it's recommended that the driven roller "lift" the jar, not turn it down. With that configuration, you'd be lifting one and turning the other down.

 

The easiest way around this is to run the two jars side by side instead of on different sets of rollers. To prevent roller bending, some people like to place the motor and thus the pullys in the middle.

[oldguy]

I suggest 1" shaft so that you can fit rubber hose over them for grip and sound proofing. 3/4" shaft still has enough flex to wear the jar unevenly. 1/3 hp ought to move the jars fine but there is no cooling for the motor so it may cut out from time to time if it overheats. A TEFC motor is definitely the way to go with ball mills.

 

Okay 1 inch shaft is what I will use.

I have this near unused motor and a few others on hand, so they are free.

I would prefer a TEFC motor, but don't have a free one.

 

I will mount a small fan on the stand next to the motor to keep it cool.

[oldguy]

I don't know how big of a deal it is, but it's recommended that the driven roller "lift" the jar, not turn it down. With that configuration, you'd be lifting one and turning the other down.

 

The easiest way around this is to run the two jars side by side instead of on different sets of rollers. To prevent roller bending, some people like to place the motor and thus the pullys in the middle.

 

I had thought about the fact with this design one jar would turn up & the other down. But, in talking with a few folks that had reversible motors & had run them both ways. The difference in milling efficacy was under 10% between the 2. At least that’s what they say.

 

That difference is minimal enough it matters not, except to allow 10% more milling time on any jar turning down. Which is good enough for me. I am trying to keep the design as “toilet flush” simple & idiot proof as possible. Plus, use what I have on hand, to minimize cost.

 

Break to go mock up & measure things

 

The mock up on the table saw stand (minus the saw & motor) I intended to use is slightly to small for 2 big jars side by side. I have a couple other stands & they are to small too. So, I guess I will build one to suit. Since I am going to build a stand. You are right. I will use longer shafts so I can run 2 jars in tandem both terming up.

 

Since the shafts will be about 36 inches long, I will simply mount a pillow block bearing at their centers. Which will stabilize the shafts & keep the jars apart.

At least thats the plan at this stage.

 

 

I don't want to order the pillow block bearings & shafts until I am positive how this will all go togather.

Decisions, & more decisions…..LOL

 

 

[Bonny]

I had thought about the fact with this design one jar would turn up & the other down. But, in talking with a few folks that had reversible motors & had run them both ways. The difference in milling efficacy was under 10% between the 2. At least that’s what they say.

 

The turning up/down, AFAIK was more to prevent the jar slipping than for efficiency. I use a reversible motor and it seems to work fne either way.

[pyrochris732]

does anyone think it would be a problem to mix media sizes in a milling jar? I have one nice layer of 5/8" brass rod cut but I need another 2-3 foot bar to cut up to have enough media. I think I would like to do 1/2" diameter bar this time.

 

The jar is 6 lbs. i already went through a 4 foot brass bar and it only covers one layer of the jar

Edited March 26, 2011 by pyrochris732

[jermain]

Anyone know where i could buy a decent ball mill from in the UK?

 

Thanks

[Bonny]

does anyone think it would be a problem to mix media sizes in a milling jar? I have one nice layer of 5/8" brass rod cut but I need another 2-3 foot bar to cut up to have enough media. I think I would like to do 1/2" diameter bar this time.

 

The jar is 6 lbs. i already went through a 4 foot brass bar and it only covers one layer of the jar

 

My (brass) media is all different sizes (and shapes)...works just fine. Maybe not the most optimum, but like I said, it works just fine.

[oldguy]

Bonny.....LOL, so long as it works, it does. Thats what counts.

 

Along the lines of what works.

 

 

 

How would this 1/2 HP TEFC motor work for driving a BM, with two 12X14 or 12X16 inch jars (about 40 lbs per jar or 80 lbs total).

Everyone says TEFC is the way to go, so I went shopping.

 

$150 for a motor, $50 more for pillow block bearings & $50 more for 1 inch SS shafts.

$200 so far not counting stand, pulleys, belt, jars & media.

 

Ebay has some fairly good looking 35 to 40 lb rigs for about $300.

[oldguy]

Anyone know where i could buy a decent ball mill from in the UK?

 

Thanks

 

http://cgi.ebay.co.u...=item41581965e8

[moondogman]

Hello all especially math wizards

 

Ok Im attempting to do the engineering on my ball mill speed. Here is what I have or plan on.... 1725 rpm motor with a 2in pully (smallest i found for a 5/8 shaft) 1 in stainless tube for the rollers that will be covered with rubber tubing that would make them about 1.5 inches. Daves 1 gal jar 6 inch diameter jar + wall thickness and wall thickness of the fittings that makes it close to 7 inches diameter which would be 21.99 circumference 1.5 goes into 21.99 14.66 times so roughly 14.66 revolutions of the shaft to turn the jar one time. 60 rpm is about optimal so that is 879.6rpm I would want at the rollers ????????????????? The handy dandy rpm caclulator says the driven pully should be 3.98 inches.

 

 

Does any of this seem right??????? I sometimes wish I would have payed attention in math class all those years ago. also does anyone have the actual corcumference of a 1 gallon pvc jar?? I might be a bit more acurate. Im guessing a 4 inch pulley should be about right

 

Steve

[Updup]

Hello all especially math wizards

 

Ok Im attempting to do the engineering on my ball mill speed. Here is what I have or plan on.... 1725 rpm motor with a 2in pully (smallest i found for a 5/8 shaft) 1 in stainless tube for the rollers that will be covered with rubber tubing that would make them about 1.5 inches. Daves 1 gal jar 6 inch diameter jar + wall thickness and wall thickness of the fittings that makes it close to 7 inches diameter which would be 21.99 circumference 1.5 goes into 21.99 14.66 times so roughly 14.66 revolutions of the shaft to turn the jar one time. 60 rpm is about optimal so that is 879.6rpm I would want at the rollers ????????????????? The handy dandy rpm caclulator says the driven pully should be 3.98 inches.

 

 

Does any of this seem right??????? I sometimes wish I would have payed attention in math class all those years ago. also does anyone have the actual corcumference of a 1 gallon pvc jar?? I might be a bit more acurate. Im guessing a 4 inch pulley should be about right

 

Steve

 

You didn't quite finish converting everything into circumfrence.

 

you would want to pi both 7 and 1.5, and then divide the results.

 

We are going to round the 21.991 to 22

1.5 * 3.1459 = 4.71

 

22 / 4.71 = ~4.67

 

so you have a 4.67:1 ratio between shaft and drum, every time you turn the drum, the rod turns 4.67 times.

 

If you want 60 rpm... 60 * 4.67 = 280

 

280 RPM on the shaft, now to finish things up you said you have a 2" pully on the motor yes?

 

1725 / 280 = 6.16 so you want your motor to turn 6.16 times to rotate your shaft once

 

2 * pi = 6.28, so multiply 6.28 by 6.16, divide that by pi, and you have the diameter of the pully that need to be on your shaft

 

Which = *Drum roll* 12.32" Thats a big pully... Anyone care to check my math?

 

EDIT: I suggest you get rid of the 2" pully on your motor, and slip some PVC or other tubing over your motor shaft to get rid of the flat side, then your shaft pully can be a lot smaller... Heres my setup http://www.amateurpyro.com/forums/gallery/image/559-ball-mill/

Edited March 30, 2011 by Updup

[Mumbles]

Updup's math and answer are correct despite using a couple extra steps. (and using pi as a verb )

 

Ratios of the diameters are sufficient.

 

7" OD jar / 1.5" OD roller = 4.67 turns of roller per turn of jar (280 rpm)

 

280rpm * X diameter pully = 1725rpm * 2" diameter pully

 

12.32" pulley.

 

 

Now, the optimal speed in these jars is actually closer to 75rpm, so that more closely corresponds to a 10" pulley. You may have more luck finding them if you refer to them as sheaves instead of pulleys.They're also not cheap. I found the correct size for about $40 at the cheapest.

[moondogman]

Thanks guys the first time I worked it out i came up with close to 12 inches I think 4 sounded alot better just cost wise. Now to look for a 10 inch pulley/ sheave

found one on ebay for about $40 with shipping I need to stop at rural king tomorrow and see what they have.

 

woohoo again found one for 29 including shipping on ebay.

Steve

Edited March 31, 2011 by moondogman

[oldguy]

The ebay seller link below has a very good selection of pulleys @ good prices.

 

http://shop.ebay.com...1.c0.m270.l1313

 

 

EDIT TO ADD:

Would it be any benifit to have both rollers under power?

Rather than one under power & the other free wheeling.

Edited April 2, 2011 by oldguy