How do cylinder mills grind crushed ore into finer particles?

Cylinder mills grind crushed ore into finer particles through a process of tumbling within a rotating cylindrical container. These mills are mounted with their axis in a substantially horizontal position and are partially filled with grinding bodies, such as iron or steel balls or flint stones. As the container revolves, gravity causes these grinding bodies to tumble, which disintegrates the ore material.1

In addition to traditional cylinder mills, there are specialized variations:

• Autogenous mills: These operate without external grinding bodies, relying instead on the coarser pieces of the ore to grind themselves and the smaller fractions.1
• Semiautogenous mills: These function similarly to autogenous mills but include 5 to 10 percent grinding bodies, typically metal spheres, to assist in the process.1

This stage of comminution is essential for liberating valuable minerals from waste rock, with the final powder fineness determined by the dissemination of the desired mineral. While crushing is generally performed dry, grinding mills can operate under either dry or wet conditions, with wet grinding being the most common practice.2