Size Reduction Equipment

Pulverizers & Cage Mill Crushers

What is a Cage Mill and How Does it Work?

Invented by Nathan P. Stedman, a cage mill is an internally fed impactor that crushes grinds or pulverizes many different materials to specified degrees of fineness.

Early cage mill crushers were used principally to crush materials that were not particularly abrasive – corn, salt, coal, clay kaolin. By 1900, Nathan Stedman had built more than 100 cage mills. After its invention, numerous applications were discovered and soon cage mills were used for crushing chemicals, clay and fertilizer materials. It wasn’t until the 1930s that the true value of cage mills as an agricultural limestone crusher, a size reduction mill and beneficiation was realized. Cage mills can be configured in two, four, and six row designs, each with their own unique crushing applications.

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What Industries Use Them?

• Agricultural Industry: Common applications include crushing fertilizer, animal feed, and distilled dry grains (DDG & DDGS)
• Brick & Clay Industry: Applications and materials for this industry include shale, roof tile, and commercial & residential brick
• Energy Industry: Reduce the size of materials such as coal and corn
• Aggregate Industry:  Common materials that cage mills can finely crush include limestone, gypsum, shells, sandstone and more

Click here for a comprehensive overview of Cage Mill principles

Stedman’s range of multi-cage mills and pulverizer machines includes the H-Series, F-Series for sticky, high moisture and Y-Series designed for less abrasive material applications. In general, the larger the cage mill, the larger the feed size it will accept and the greater capacity it will produce. Capacity also depends on upon the speed at which the mill is operated, the feed size and its specific gravity, and the size of the desired product. Cage mills work by reducing the material they are fed to predetermined smaller sizes by striking repeatedly with cage pins and throwing the particles at high speed against each other, against the cage mill housing and against the other pins.

Single Row Cage Mills

Single-row mills, although normally classified as secondary crushers, are designed for heavy-duty crushing, frequently of hard and highly abrasive materials, although their versatility makes them valuable for the reduction of many kinds of materials. They are particularly useful in the beneficiation of sand and gravel and in the upgrading and crushing of all kinds of aggregates, ores and coal.

Multi-Row Cage Mills

Multi-row mills normally consist of an even number of cages: two, four or six. The cages are arranged concentrically, with each cage spinning in the opposite direction from that of the cage adjacent to it. A multi-row cage mill employs multiple stages of selective impact reduction. The material to be reduced is fed into the center of the innermost cage, where it is struck by the massive spinning pins and distributed 360 degrees around the cage. Centrifugal force and the impact of the pins causes the material, now reduced to smaller pieces, to pass through the cage into the pins of the next cage, which is spinning in the opposite direction. The farther away from the center cage the particles travel, the more their impact velocity is increased. 

Stedman Machine Cage Mills