Grinding - Ball Mills
Short flash video at bottom of page showing batch ball mill grinding in lab.
The point where the mill becomes a centrifuge is called the "Critical Speed", and ball mills usually operate at 65% to 75% of the critical speed.
Ball Mills are generally used to grind material 1/4 inch and finer, down to the particle size of 20 to 75 microns. To achieve a reasonable efficiency with ball mills, they must be operated in a closed system, with oversize material continuously being recirculated back into the mill to be reduced. Various classifiers, such as screens, spiral classifiers, cyclones and air classifiers are used for classifying the discharge from ball mills.
This formula calculates the critical speed of any ball mill. Most ball mills operate most efficiently between 65% and 75% of their critical speed.
Photo of a 10 Ft diameter by 32 Ft long ball mill in a Cement Plant.
Photo of a series of ball mills in a Copper Plant, grinding the ore for flotation.
Image of cut away ball mill, showing material flow through typical ball mill.
Flash viedo of Jar Drive and Batch Ball Mill grinding ore for testing
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