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Ball mill construction


AlexPyro66

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Hello guys this is my first tutorial in this forum.I hope you like it any criticism is accepted.

First a few wards about ball mill.Ball mill is one of the most important tools in the pyro hobby.It is used for grinding course chemicals into fine powders and making black powder.Ball mills can be bought or custom made to your needs i believe the second option is better because you will be able to construct it with cheaper materials,as i did, and fit it to your needs.

MATERIALS:

  • motor (must be able to work for big periods of time under small temperatures and dont spark)
  • Pulleys
  • Axle (I used an aluminium rod)
  • Ball bearings (that fits the axle)
  • Belts (to drive the pulleys)
  • Table (big and stable to fit all the above
  • Ball mill jar

Some photos of the constuction

 

The motor is 1/2hp 0.37kW 1380rpm

 

post-14147-0-02555000-1421175967_thumb.jpg

post-14147-0-87269400-1421175844_thumb.jpg

 

A 4in pulley that has been presed in the 20mm axle

 

post-14147-0-88161000-1421176113_thumb.jpg

 

A 2in pulley for the motor

 

post-14147-0-33239200-1421176259_thumb.jpg

 

The axle

 

post-14147-0-82138900-1421176438_thumb.jpg

 

Ball bearings

 

post-14147-0-08292100-1421176060_thumb.jpg

 

Table (temporary solution)

 

post-14147-0-27520200-1421176553_thumb.jpg

 

Ball mill jar

 

post-14147-0-74426200-1421176966_thumb.jpg

 

And the ball mill in it's position(not finished yet)

 

post-14147-0-99877900-1421177074_thumb.jpg

 

 

 

Now its time to make the bill:

  1. 90€ the motor
  2. 15€ the pulleys
  3. 10€ the ball bearings
  4. 5€ tha axle
  5. 15€ the jar

I havent calculate the belt and the two wheels I need for the other side of the axle.

 

This is it guys I hope you find it useful.Suggestions are welcome.

Thank you

 

 

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It's possible that your 4" pulley could work loose since it is pressed on. Suggest drilling a hole through the pulley bushing while in correct position on the main drive shaft and installing a split pin so it can not slip in the future.

 

Looks like you are off to a nice start on your mill. :D

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You may also need some rubber tubing to go over the drive shaft, or rubber coating on the jar. Metal on plastic doesn't usually provide enough friction for good spinning.

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Looks like a 6L jar, depending on the media type and axle length/diameter you might get a bit of deflection with an aluminium axle. A 50% charge using lead media will be over 50lb ;)

Edited by Col
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Please mention speed reduction (RPM) method for motor you are using.
  • Like 2
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Assuming no losses and the shafts end up at 3/4" od (with the help of some rubber radiator hose), the jar will turn at 66.38rpm which is right in the ball park for 1/2" media.

Motor: 1380rpm, motor pulley 2", shaft pulley 4",shaft od : 3/4", drum od: 7.75" (198mm)

 

edit: just noticed the 20mm axle diameter, so assuming its 1" od with the hose its going to be running a little faster than ideal (89rpm)

Edited by Col
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Yes Col the jar is 6L.If i just tape the axle with elecrical tape it will be ok?Now i only have to cast 20kg of lead media :D if they are cylinders will it be a problem?And i have to start thinking about a soundproof box

Edited by AlexPyro66
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I dont think tape will hold up to the weight without being shredded. Rubber radiator hose is the best bet, I used it with the same 3.6L and 6L jars before i switched to using the kart tyre jars. Taming the noise will probably take a bit of work, those hard hdpe jars with lead media are mega loud even 100ft + away :)

I used lead balls but cylinders would work, 20kg which equates to about 1500 x 1/2" lead should be around the right amount.

Edited by Col
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  • 2 months later...

Hi everyone!

 

I'm not going to open a new thread on ball mills, since there are already a lot of them. I'm in the process of making a ball mill and I would like to hear your opinions/suggestions on it, since this is my first ball mill ever. I'm now going to present the details of it, although I'm almost halfway through the process of making it.

 

The Jar - is made of a section of HDPE pipe. The pipe has an OD of 200 mm (8 inch) and an ID of 176 mm (7 inch), giving a wall thickness of 12 mm. Length of the pipe is 200 mm, therefore a total inner volume of roughly 4800 cc (4.8 Litres). The ends are made of 2 mm thick steel sheeting. The bottom end is secured with 8 dry-wall-type screws and sealed with silicone caulking. The top end is detachable and is secured to the pipe with 8 6 mm screws (the screws are screwed in the wall of the pipe). The top cover will be sealed with a rubber gasket running the circumference of the top part of the pipe. The reason behind using metal ends is that when the mill is done I will use 2 metallic/graphite brushes touching the ends to collect static electricity and ground it. The pipe will be covered with a piece of tyre tube or other rubber strips/rings to ensure grip on the drive shaft.

 

The motor - is an old washing machine motor. I don't have any specs for it, but I tried it and it is very powerful - I cannot stop it with my hand, no matter what I do... I don't know the RPM of the motor, but when the mill is ready I will play with different pulley dimensions to get the optimal RPM of the jar (which I calculated to be approx. 69 RPM).

 

The drive shaft - is made of steel, and the active portion of it (the part in contact with the jar) is 30 mm in diameter. I have covered it with bicycle tube for better grip, although I don't think it will stand up very well to wear (the media will be very heavy). One thing that I don't know is what best placement to choose for the drive shaft, i.e. should it be "pushing the jar down" or "pulling it up" - because pulling the jar would mean that the weight of the media is on top of it, giving better traction, but at the same time the jar could go over the shaft and fall outside of the mill frame. Maybe a guiding wheel would help keeping the jar in place. Another problem would be the distance between the drive shaft and the idle shaft - what do you guys think?

 

The media is the hardest part. I plan on using two sets of media, one made of steel (a mix of round and conical media salvaged from different types of bearings) and one made of lead (which I will cast later, as I approach the final of the construction). The steel media mix is around 20 mm in diameter (15 and 20 mm balls + 16 and 22 mm conical media), whereas the lead media will all be 20 mm diameter balls/cylinders - I will cast the media in paper tubes from 20 mm fireworks cakes; the lead cylinders, which will be 20 mm diameter by 20 mm long, will get spherical over time. The reason behind 2 sets of media is that I intend to mill inert materials (Charcoal, Sulfur, KNO3, etc.) separately with the steel media and I will mill "live" mixtures (BP, star comps) using the lead, non sparking, media. This way I would shorten the time that live mixtures are being milled (thus giving it less chances of accidents), since I would grind the components separately. This would also give me the advantage that the inert components (fuels, oxidisers, binders, etc.) will be ground a lot faster, given the much higher hardness of steel media.

 

These are my plans for this ball mill. I may have omitted to tell you various aspects of the construction that might help you to better understand what I want to do so please ask for more details if necessary. Whatever flaws you see in my design, please let me know, so that I can correct before it's too late.

Edited by ropyro
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Take the lower bearing as drive shaft an let the barrel run into the direction of the 2nd roller (so pushing it up).

Also you should aim for two different jars, one for bp, nitrate, charcoal and sulfur, the other one for oxidzers like chlorate, perc, or non pottasium nitrate.

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Hi,

 

Thanks for the advices.

 

I have attached a sketch of the 2 possible ways of doing it. Which one do you talk about, from the sketch?

post-82-0-53497100-1426933380_thumb.png

 

I've given it some thought also, about having 2 jars, one for chlorate/perchlorate and one for nitrate. For the moment I'm only doing nitrate based comps. After the ball mill proves to be sucessfull, I will make another jar with the same dimensions, for chlorates.

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From what i've been told, pushing towards the next roller is the way to go. Pushing away supposedly lets the jar slip more.

Never did any testing, so cant confirm or deny.

B!

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Thanks for your reply!

The thing that worries me about this approach (mode "A" in the sketch I attached) would be the fact that when the drive roller pushes the underside of the jar toward the idle roller, most of the media will be grouped over the idle roller. Therefore increasing the down-force on the idle roller; which leaves only a small weight pressing on the drive roller. And that could cause slippage at the drive roller.

In the "B" mode (drive shaft pulling the underneath surface of the jar away from the idle shaft) the media centre of gravity would be right over the drive shaft. That would increase down-force on the drive shaft and therefore increased grip between the drive shaft and the jar, thus giving less chance to slippage. The problem with this approach is this: the inertia of the media could cause the centre of gravity of the media to go "over" the drive shaft axis, which could cause the jar to be thrown on the other side of the drive shaft. This problem could be addressed by mounting a small wheel to "push the jar back into place" in the event it wants to "escape".

Anyway, once my mill will be ready, I will verify both scenarios. I will use the mill with the steel media and an inert material (I will "mill" some sand to clean the rust from some of the steel balls) and I will watch it (and take a video) carefully to see if any slippage occurs on both modes. I will construct the mill so that the motor position will be easily swapped to reverse the rotation of the drive shaft. After the mill is ready, I will post the video results.

 

However, I have one more question: Which materials are suitable for ball milling with steel media? I mean, "live compositions" are out of the question; also, strong oxidisers (mainly nitrates, chlorates and perchlorates) and metal oxides obviously pose no problem to being milled using steel media; same case for most of the metal salts (chlorides, carbonates, sulphates)

The materials that I'm concerned about are these: charcoal, sulphur and metal sulphides, mixtures of charcoal and sulphur (like the 15:10 - C:S mixture used for BP), metals (aluminium, magnesium and magnalium), over-oxidised and over-fueled mixtures (like, for example, a 15:1 mixture of KNO3 and charcoal, or vice-versa - say 10:2 charcoal:KNO3), some organic compounds (PVC, parlon, benzoates, resins) and also Dextrin/SGRS/other organic binders.

Theoretically, any fuel, when reduced to an air-float state, could mix with the air being present in the mill jar, and if the correct ratio of fuel/air is met it could be ignited by a spark; this could burst open the jar, exposing the rest of the fuel to more oxygen, thus creating a fuel/air "energetic reaction".

Do you think that these concerns of mine are possible, or am I worrying too much?...

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or am I worrying too much?...

 

Thats just not possible.

 

Personally i pretty much just ball mill charcoal, and BP, with lead media, and magnalium, with stainless steel media. Everything you mill, is at some level a risk, take precautions.

B!

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From what i've been told, pushing towards the next roller is the way to go. Pushing away supposedly lets the jar slip more.

Never did any testing, so cant confirm or deny.

B!

 

+1

 

Diagram "A" is the way to go. You want the jar to be sot of "pinched" by the two rollers. I made my ball mill a few months back and had it setup as per diagram "B". It slipped! Fortunately it was not completed when I tested, so I was able to fix it by turning the motor 180deg.

 

It's also helpful to lower the drive roller a bit below the idler (I lowered mine by about 10mm) Doing this means more weight is on the drive roller which helps the jar not slip.

 

I imagine it's probably a rough diagram, but you could consider having the rollers slightly wider spread apart - the jar would be more secure sitting lower and would also give an option for using bigger jars.

 

Cheers.

 

[EDIT] Oh, I only saw this thread starting at post #10 - sorry if this info is a double-up.

Edited by stix
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I simply have the two rollers connected by one belt, saves any slippage and forces the jar to roll.
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This helps me a lot!

It seems that "A" diagram is favoured in general.. I will make the ball mill with this arrangement first and if it shows no slippage, I might even not try the other setup.

 

I'm afraid that I already cannot try to connect the 2 rollers by a belt, since my drive roller is already machined and cut to dimensions that will not allow for a second connecting pulley...

 

The diagrams I made are just for rotation principles only, they are not meant to represent the actual roller spacing in relation to the jar size. But I will take the advice and widen the roller spacing. The jar is 200 mm in diameter. So I think that a 150 mm spacing between the roller-jar contact lines would suffice.

 

Raising the idle roller is an idea that I have already given a thought for increasing weight on the drive roller.

 

......................................................................................................................................................................................................................................................

 

 

 

"Personally i pretty much just ball mill charcoal, and BP, with lead media, and magnalium, with stainless steel media. Everything you mill, is at some level a risk, take precautions."

 

To be honest, I was more concerned about metals being milled with steel media than charcoal...

What reasons are behind you using lead media for charcoal, instead of steel media? Are you afraid of steel for charcoal, or is it simply that charcoal is soft and lead media will suffice in milling it?

Unfortunately, I don't have access to antimony metal, so when I will cast my lead media, I won't have the possibility to make a lead/antimony alloy to cast the balls. They will be pure lead balls, which might need longer milling times for charcoal than steel...

Am I really exposing myself to higher risks by milling charcoal with steel media, as opposed to lead media?

Also, what do you think about milling sulphur? Is it more dangerous with steel media than it is with lead?

Edited by ropyro
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To be honest, I was more concerned about metals being milled with steel media than charcoal...

What reasons are behind you using lead media for charcoal, instead of steel media? Are you afraid of steel for charcoal, or is it simply that charcoal is soft and lead media will suffice in milling it?

 

It's more about avoiding a possible contaminant, say for example a nail, or a staple from having something to spark with. It's very unlikely, but once is enough to kill you, if you get unlucky, so i rather be safe. Lead should be plenty hard enough to last a lifetime milling charcoal. Well, more or less. Should it wear enough, it's easy to recast. And the time between those casting parties, should be plenty to get any lead out of your system.

 

 

Unfortunately, I don't have access to antimony metal, so when I will cast my lead media, I won't have the possibility to make a lead/antimony alloy to cast the balls. They will be pure lead balls, which might need longer milling times for charcoal than steel...

 

I never used the steel for charcoal, but i think the heavier lead makes faster work of it then the steel media would. On the topic of lead... If you can find it, just a small amount of wheel weight lead is apparently a huge help towards harder lead. Any lead with arsenic, and antimony supposedly lets the lead harden "more" when quenched. Which is my next suggestion. When casting your media, fill a bucket with water, and put a cloth "funnel" in the water, so that the casted bits can hit the water and start cooling down before they slam in to the bottom of the bucket. I use a mold for casting round fishing weights, so i get a bunch for each casting, and i let them cool, and then dry before cutting of the sprues, and cutting them apart from one and other.

 

 

Am I really exposing myself to higher risks by milling charcoal with steel media, as opposed to lead media?

Also, what do you think about milling sulphur? Is it more dangerous with steel media than it is with lead?

 

I would say "yes" to both questions about the risk factor. Also, in both cases, the risk might not be that great, and none sparking stainless steel media is considered a "safe" media, but if your talking "regular" steel, i'd be staying quite far away. Sadly, now i cant for the life of me find what grade stainless is considered spark resistant / none sparking.

B!

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Thanks for the advices

 

 

I would say "yes" to both questions about the risk factor. Also, in both cases, the risk might not be that great, and none sparking stainless steel media is considered a "safe" media, but if your talking "regular" steel, i'd be staying quite far away. Sadly, now i cant for the life of me find what grade stainless is considered spark resistant / none sparking.

B!

 

Do you think that slightly dampened charcoal/sulphur would increase safety? I'm thinking that being wet, the charcoal particles will not float in the air inside the jar, but rather stay all grouped among the media.

The wetting question also applies to milling BP with lead media. Plus, wetness decreases the static build-up.

One disadvantage of wet material vs. dry material is the fact that dry material doesn't "cake-up" at the ends of the jar. My jar has "squared" ends, not curved. And wet material could gather around the circumferences at the jar ends, and that material would not be milled...

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Do you think that slightly dampened charcoal/sulphur would increase safety? I'm thinking that being wet, the charcoal particles will not float in the air inside the jar, but rather stay all grouped among the media.

 

If you add any significant amount of water, the milling stops, and it all turns in to a solid ball.

Wet ball milling works with heavy stuff, but it slows down the process. In general it's just a bad idea.

B!

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Milling just charcoal is actually pretty hard on lead media. I think you get more self-wear, than you do with milling BP together. The theory I've heard proposed is that the charcoal chunks or powder tend to slip out of the way of the cascading lead, resulting in more lead on lead collisions. Ideally, you'd like the material to absorb all of the energy by being smashed between two balls and never actually allow them to hit one another. The KNO3 and sulfur seem to hold the charcoal in place to allow more efficient grinding.

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  • 2 weeks later...

Hellow everyone. This is my small ball mill ( for 100 gramms of the mix ), took me 2 hours to make and it is working well for more then 4 mounths.

Never cracked even a single bottle. :)

PS: I am from Russia, so sorry if I make some spelling mistakes.

http://www.youtube.com/watch?v=fEYZiOQbuIA

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