### 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 kgm 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 D24 The degree of filling the mill with balls also influences productivity of the mill and milling efficiency