1. The roll material is in the same state as a scar. Cause: foreign matter peeling off, caused by foreign matter on the surface or inside of the steel plate.
2. The corners of the coil are damaged. Cause: The corners (20-30mm) are deformed or crushed due to uneven stress.
3. The roll material is bulging. Cause: The roller slips, foreign matter enters the back of the coil, and the foreign matter disappears when it falls.
4. Roll traces. Cause: foreign matter adheres to the roller, causing obvious groove marks on the surface.
5. Surface scratches. Cause: It is caused by the surface of the roller or foreign material.
6. The edges of the metal stamping parts are irregularly damaged. Cause: It is caused by poor material beyond the rules.