Mill Speed - Critical Speed In most cases, the ideal mill speed will have the media tumbling from the top of the pile (the shoulder) to the bottom (the toe) with many impacts along the way The ideal mill speed is usually somewhere between 55% to 75% of critical speed...

Mill Critical Speed Determination The "Critical Speed" for a grinding mill is defined as the rotational speed where centrifugal forces equal gravitational forces at the mill shell's inside surface This is the rotational speed where balls will not fall away from the mill's shell Enter the mill diameter inside the shell (excluding liners)...

Ball Mill Critical Speed Ball mills have been successfully run at speeds between 60 and 90 percent of critical speed, but most mills operate at speeds between 65 and 79 percent of critical speed Rod mills speed should be limited to a maximum of 70% of critical speed and preferably should be in the 60 to 68 percent critical speed range Pebble....

The formula to calculate critical speed is given below N c = 42305 /sqt(D-d) N c = critical speed of the mill D = mill diameter specified in meters d = diameter of the ball In practice Ball Mills are driven at a speed of 50-90% of the critical speed, the factor being influenced by economic consideration...

Calculations: The critical speed of ball mill is given by, where R = radius of ball mill; r = radius of ball For R = 1000 mm and r = 50 mm, nc = 307 rpm But the mill is operated at a speed of 15 rpm Therefore, the mill is operated at 100 x 15/307 = 4886 % of critical speed...

The present work is significant variation B values with fraction of mill critical speed later y values to decrease for higher from 85% of mill critical speed values for grinding of ,...

For instance, if your jar had in inside diameter of 90 mm and your milling media was 127 mm diameter lead balls, the optimum rotation would be 98 RPM Optimum RPM= 65 x Critical speed (cascading action of the media stops) Critical speed = 26545/sqrt (Jar ID - Media OD) with dimensions in inch...

How can the answer be improved?...

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...