How to Size a Ball Mill Design Calculator Formula15/05/2015· A Total Apparent Volumetric Charge Filling including balls and excess slurry on top of the ball charge plus the interstitial voids in between the balls expressed as a percentage of the net internal mill volume inside liners B Overflow Discharge Mills operating at low ball fillings slurry may accumulate on top of the ball charge causing the Total Charge Filling Level to be