Effects of lifter bars on the ball motion and aluminum foil milling in tumbler ball mill

Effects of lifter bars on the ball motion during ball milling and characteristics of aluminum flake powders prepared by the ball milling of aluminum foil scraps were studied. When rotation speed of milling jar without lifter bar is below 75% of critical revolutions per minute (rpm), balls slide in the jar. As rotation speed of milling jar increases up to 93% and 140%, the mode of balls motion changes to cascading and cataracting type, respectively. By setting even one lifter bar in the jar, balls move as cascading mode and cataracting mode at 37% and 56% of critical rpm, respectively. As number of lifter bars increases, the necessary rotation speeds of milling jar for cascading mode and cataracting mode decrease drastically. The aluminum foils scrap was milled in the milling jar with four lifter bars and without lifter bar under the rotation speeds of jar corresponding to cascading and cataracting modes. That result shows that it is possible to achieve same quality of milled fine powder by using lifter bars even under the significantly lower rotation speeds of jar. (C) 2002 Elsevier Science B.V. All rights reserved.