Hammermill

Not to be confused with a trip hammer.

For the record label, see Hammermill Records.

Hammermill for milling grain

A hammermill is a machine whose purpose is to shred or crush aggregate material into smaller pieces. These machines have many sorts of applications in many industries, including:

• Ethanol plants (corn)
• A farm machine, which mills grain into coarse flour to be fed to livestock
• Fluff pulp production
• Fruit juice production
• Grinding used shipping pallets for mulch
• Milling grain
• Sawmills, size reduction of trim scrap and planer shavings into boiler fuel or mulch

Desktop hammer mill used for preparing growth media in a life sciences laboratory

• Shredding paper
• Shredding scrap automobiles (see automotive shredder residue)
• Shredding yard and garden waste for composting
• Crushing large rocks
• In waste management

High speed industrial hammermill for waste fragmentation

Slow speed horizontal pallet grinder

Operation

The basic principle is straightforward. A hammermill is essentially a steel drum containing a vertical or horizontal rotating shaft or drum on which hammers are mounted. The hammers are free to swing on the ends of the cross, or fixed to the central rotor. The rotor is spun at a high speed inside the drum while material is fed into a feed hopper. The material is impacted by the hammer bars and is thereby shredded and expelled through screens in the drum of a selected size.

Hammer mill apple shredder for juicing.

The hammermill can be used as a primary, secondary, or tertiary crusher. A major disadvantage of the hammermill is the tremendous amount of wear (linings must constantly be replaced).

Small grain hammermills can be operated on household current. Large automobile shredders can use one or more 2000 horsepower (1.5 MW) diesel engines to power the hammermill.

The Screenless hammer mill uses air flow to separate small particles from larger ones. It is designed to be more reliable, and is also claimed to be much cheaper and more energy efficient than regular hammermills.

See also

• Blade grinder
• Trip hammer, which may be housed in a mill usually known as a forge, but which was historically occasionally described as a "hammermill".