Coating defects caused by incomplete grinding, irregular or grinding scratches, sandpaper grains, and the failure of the top coat to cover.

Reason:

(1) The technical condition of the grinding tool is poor or the operation is not serious.

(2) The quality of the sandpaper is poor, and there is a phenomenon of falling sand.

(3) No module is used when grinding the plane, and the local force is too strong.

(4) The quality of the ground surface was not checked after grinding.

Prevention:

(1) Make sure that the grinding tools are in good technical condition and operate carefully. Use high-quality sandpaper. Before using new sandpaper, sandpapers should be sanded with each other to eliminate the phenomenon of sand loss.

(2) Grinding blocks should be used when grinding the plane, and attention should be paid to the grinding direction.

(3) After grinding, the grinding quality should be checked. For example, after watering after wet grinding, check the grinding quality with the help of water grinding reflection.