What is the difference between impact crusher and hammer mill?

Both impact crushers and hammer mills are used for breaking down materials, but they function in different ways and are suitable for different types of materials and applications:

1. Design and Operation:

   • Impact Crusher: It utilizes impact force to crush materials. The materials are fed into a chamber containing a high-speed rotor with bars or hammers, and the material is thrown against impact plates or breaker plates. This results in the material breaking along its natural fracture lines, producing a more uniform product.
   • Hammer Mill: Uses swinging hammers attached to a rotating shaft to crush the material by impact. The material is fed into a chamber where the rotating hammers beat it against a screen or grinding plate. The material must be small enough to pass through the screen to be discharged.

2. Applications:

   • Impact Crusher: Typically used for primary and secondary crushing of medium-hard to very hard materials, such as limestone, gravel, granite, basalt, and concrete, among others. It's widely used in industries like mining, construction, and recycling.
   • Hammer Mill: More suited for smaller, softer materials. It is often used in the agricultural industry for grinding grains and in the production of ethanol. It can also be used for crushing less abrasive materials such as coal and limestone.

3. Output Size and Shape:

   • Impact Crusher: Produces a more cubical product and the size can be more easily controlled by varying the speed of the rotor and the distance between the impact bars and impact plates.
   • Hammer Mill: Generally produces a coarser grind and can have more irregular particle sizes due to the nature of the hammering process.

4. Cost and Maintenance:

   • Impact Crusher: Generally higher initial cost but lower maintenance due to fewer moving parts.
   • Hammer Mill: Typically lower initial cost but may require more frequent maintenance and replacement of hammers and screens due to wear.

Understanding these differences helps in selecting the appropriate equipment for a given application, considering factors such as material properties, desired product size, and capacity needs.