Rod mills and ball mills both belong to the category of cylindrical grinding equipment and are widely used in mineral processing, building materials, and chemical industries. However, there are significant structural differences between the two. Firstly, in terms of grinding media, rod mills use long cylindrical steel rods as grinding bodies, while ball mills use steel balls. This difference in media directly affects the design of the internal structure of the cylinder. The cylinder of a rod mill is usually longer, with a length-to-diameter ratio generally greater than 1.5, to ensure that the steel rods remain parallel during rotation and reduce entanglement; while the cylinder of a ball mill is relatively shorter, with a length-to-diameter ratio mostly between 1 and 1.5, which is more suitable for the free rolling and impact of steel balls.

Secondly, the liner structure also differs. Rod mills often use corrugated or stepped liners to increase the height of the steel rods' fall and prevent them from sliding; ball mills commonly use bar-shaped, corrugated, or small-wave liners to enhance the lifting and impact effect of the steel balls. Furthermore, the discharge end of a rod mill often uses an overflow or open-type structure to facilitate control of product particle size and prevent over-grinding; while ball mills can be equipped with grate plates according to process requirements to achieve forced discharge and improve processing capacity.

Finally, in terms of the transmission and support systems, although they are basically similar, the longer cylinder and greater weight of the rod mill require higher load-bearing capacity for the main bearings and foundation structure. Overall, the rod mill structure focuses more on uniform grinding and particle size control, while the ball mill is geared towards efficient crushing and fine grinding. These structural differences stem from their different working principles and application requirements.