Mechanism have demonstrated that stresses of varied nature are required to achieve size reduction. Mainly there is 4 modes of stress is applied in reducing the size of particle.
- Cutting: The material is cut by means of a sharp blades. Mainly fibrous or waxy solid are reduced by this process. Ex: is Cutter mill
- Compression: In this type of mode the material are compress or crushed by the help of rollers by the application of pressure. Ex is roller mill.
- Impact: In this mode the hammer or bars at the high speed. When a lump of material strikes the rotating hammers, the material splits apart. By the continues of this mode reducing the particle size. Impact also occurs when moving particles strike against a stationary surface. Ex: hammer mill.
- Attrition: In this modes the breakdown of particle by rubbing action, when particles are rubbing between two surfaces. attrition is helpful for fine grinding. Ex: fluid energy mill.