bubba said:
While you are doing your "reasearch" I am at work, perfoming grinding operations on a daily basis. Both with impact mills, and ball mills. Every tool in the tool box has a job, and is application specific.
Once again, you've missed the point. I spent but a short time researching this subject, and it was done the hard way, from old mining journals. I had no previous knowledge of ball mills, so research was very much a part of what I had to do. Coincidental to my research, the mathematical equation was provided in the same text. The time spent in calculating the proper running speed for my particular ball mill was most likely less time than you waste on an ongoing basis by making a correction of improper speed by adding items that are not needed, increasing maintenance costs as well as operating costs.
I don't understand your mean spirited attack, but for the sake of someone reading this and wanting to know how about mills, I guess I have to stand up to you and defend myself, even though its seems pointless to bicker.
No, you don't have to stand up "and defend yourself". All you have to do is report what you did, and the results you achieved, and do that without making leading statements such as lifters are required. They clearly are not. That's the part you seem to overlook. Just because you corrected an error in running speed by adding lifters doesn't mean everyone must have lifters, which is the point I keep trying to convey to you. All brown dogs do not bite, in other words.
Your carelessly chosen words, most likely a reflection on your inability to see anything but that which you prefer to see, may be the cause of others following in your footsteps, paying no attention to what matters, and too much attention to your "all brown dogs bite" comment.
I had no issues with your claim that you needed lifters. I took exception to your claim that they are a requirement, just as I take exception to your badgering readers because you don't happen to agree with what they do with cats. This isn't a matter of you being in charge, trying to promote your methods, it's a matter of free agency, where readers seek information that they hope will aid them in their quest, one that may or may not make sense to you, but one that they are entitled to pursue to their heart's content. In that regard, no, you do not play well with others. You're too caught up with your own thoughts to understand that others may have a curiosity that must be answered by their own means. It's not for you to determine what they do, just as it's not for me to determine if readers choose to process escrap. I chose not to for my own reasons, but that doesn't mean they must share my thoughts.
Anyway, the basics........big balls make big grinds, small balls make small grinds. simple.
True--and not disputed--although not relevant to the conversation.
Where the lifters come in, and the only place where they make a difference, is in larger feedstock say 1/2" or larger material. Lifters and big balls reduce larger material faster in a big mill, and don't let anyone fool you, Lifters make quicker work of larger feed at ANY speed.
If you run slow enough that they are required, the mill won't turn as many times as it should, so in spite of the lifters, production is slower than if they were not needed. Balls do exactly as they should when they operate at the proper speed, which is lift to the top, where they are dropped to the bottom, hopefully without anything to deflect them from hitting the charge.
You get the illusion that you got increased production because that wasn't happening, but had you increased the speed of the mill, you'd have achieved even better results----more blows per second--more work accomplished. Simple.
Returning to the subject of large balls, what you had to say is counter to logic. Large balls have an even greater chance of hitting a lifter, which, in turn, offers protection to items that fit between the sides of the lifter and the radius of the large ball. The ball does nothing, although the rapid motion of the ball mill keeps presenting the items over and over, so they are eventually crushed. It's called a loss of efficiency. Sure, you get the job done, but what might take 15 minutes may have been accomplished in ten.
A production operation needs a series of mills, to produce a fine grind, say 300, 400, 500 mesh which is required to achieve liberation on many ores, you need small balls. Our finish mill has 1/2" and 3/4" balls only, AND NO LIFTERS,and this is where I agree with harold, on the fine grinds your rpm's must be exact, and lifters actually get in the way.
Funny. You can see the obvious about balls bridging the lifters when the balls are small, but not when they're large? Did you do well in physics? It appears to me you likely did not.
Regardless of ball size, there is an optimum speed at which a ball mill can operate. If the charge is correct, the balls are lifted, in an ongoing basis, to the apex of the upper curve, at which time gravity causes them to fall. It is a perfectly smooth and ongoing motion, where there is maximum efficiency, not interrupted by lifters that alter the process. Under ideal conditions, the balls fall to the shell (for maximum impact), where there are no balls present to deflect the blows. The longer drop, albeit slight, increases velocity of the ball, yielding a greater impact. That's where the charge is critical. When these conditions are correct, maximum crushing is achieved. I don't give a rat's butt if you're running 6" balls or 5/8" balls, that's the way it works.
Do not escalate. This discussion is closed.
Harold
Edit.
There was escalation, which was deleted. This individual has been banned.
