#### Ball Mills an overview ScienceDirect Topics

where d is the maximum size of feed mm ; σ is compression strength MPa ; E is modulus of elasticity MPa ; ρb is density of material of balls kg/m 3 ; D is inner diameter of the mill body m Generally a maximum allowed ball size is situated in the range from D /18 to D/ The degree of filling the mill with balls also influences productivity of the mill and milling efficiency