1) Contains a large number of critical material particles close to the separation point. That is, the size of the crushed stone is the same as the size of the mesh of the screen. During the screening process, the particles are stuck in the mesh and cannot be smoothly screened to cause plugging, which is called critical plugging.

2) There are many materials having a shape of a plurality of contact points for the mesh holes.

3) The flaky particles have more materials. Due to the reason of crushing or stone itself, there are more flakes in the stone material, and the flake materials in the screening cannot be smoothly sieved by themselves, and the flake materials are interwoven into a mesh shape, which hinders the screening of other materials to cause plugging.

4) The wire diameter of the sieve is too thick.

5) The sieving material has high moisture content and contains viscous substances such as mud sand. Because the stone contains more mud, or the stone requires water washing, the fine stone material is bonded to the group by the water, on the one hand, the stone is bonded to the sieve surface, and the soil is difficult to be sieved, causing the hole to be blocked.