Has anyone ever built a DIY ball mill?

Hello everyone – 

Just curious if anyone has experience building/using a DIY/home-made ball mill, along the lines of  this (links to YouTube video).

I'm currently investigating the subject strictly for small scale production (no more than 10 kg at a time).

Any experience, thoughts, opinions welcome! Thanks. 

I have been thinking about one, but with a different design than the one you linked to. My version would have a U-shaped tub with stirrers that would agitate the balls and chocolate. More or less, it's the same idea as a vertical ball mill, just turned on its side. 

My reason for this is that (if it works) I think you could make a small scale one using a meat mixer. Also, I make a U-shaped conche that could be used for this with by swapping out the conche scrapers for the stirrers.

I think you need to be able to heat it. For the rolling-can design, that's going to be a little more difficult since you can't attach a heating element. You could just heat it with a heat gun, of course, but that's probably not going to be particularly efficient. A ceramic heating element could be better. If it's small enough, too, you could just preheat the whole can, nibs, sugar, etc. in the oven first.

They certainly seem easier and cheaper to make than a stone grinder, which has been on my to do list for a while. I may look more into this

Having now spent a bit of time looking at the concept, it seems that you need to be working with a fat content of 40-50% with a ball mill. Not very useful for creating most chocolate if this is the case.

I know of a few makers using a ball mill to to make 2-ingredient 70% bars, which almost certainly don't have that high a fat content. Where'd you read that?

I read it both on here and CA from a few posters. Unsurprisingly there is very little info outside these sites about it, though most youtube videos do show machines having nibs followed by sugar added (presumably they were not making a 90% chocolate)

However, since I always refuse to take other peoples words for it, I'm going to build a small prototype anyway to handle 1-2kg or so of chocolate, since I want to see how it would handle rolled oats

Another followup question, I'm guessing you can't conch like a melanger in a ball mill because it refines too quickly?

I've not got round to building a prototype yet, I'm still finishing my tempering machine

A 70% 2 ingredient bar would almost certainly be very close to 40% total fat, assuming well fermented beans were in play.

That is true. I'm not sure what I was talking about.    Maybe I just saw 50%, not 40-50%...

updated by @ben-rasmussen: 03/24/17 06:58:55PM

Hello Ben,I've been thinking about this too, and actually I've seen it work in Mexico with a flour mixer. Unfortunately, they rarely ran it more than 30 minutes, so I could not check a longer refining result for taste and texture.

Would you be open to discuss the design? I'm going to purchase a small modified mixer and try this, but I'm not very confident on the modifications yet (RPM, motor power, stirrer design, ball weight/chocolate weight)I've got an engineer helping me but could use chocolatier advice too

Edit: attached the only image I have from the Mexico thing. No balls at that moment, but I think it's what we're talking about.

updated by @victor-marin: 11/07/17 08:40:57PM