Sanding is a very important job in paint construction. Grinding is also called sanding, splitting mill and machine grinding. It is sanding the surface of wood products with abrasive materials such as wood sandpaper, water sandpaper, iron sand, pumice stone and fine stone powder to smooth the surface and remove the wood. The dust particles and air bubbles on the surface of the film and the surface of the film are roughened by sanding. The main functions are decontamination, leveling, complementary color, polishing, and rough surface (improving the adhesion of the coating). Grinding methods include dry grinding, water grinding, oil grinding, wax grinding and toothpaste polishing. Dry grinding is divided into rough grinding, flat grinding and fine grinding. The coarse grinding is generally used to remove the wood wool, scars, glue marks and pencil marks of the wood blank during the pretreatment. The flat grinding is usually wrapped in small wood. The block or hard rubber sand cloth and sandpaper are used to polish the large plane, so that the leveling effect is better. Fine grinding is generally used in the middle layer treatment of the putty, the upper seal paint, the color matching and the complementary color. The sanding requires carefulness. The water mill is sanded with water sandpaper (or soapy water). Water mill can reduce wear scars, improve the smoothness of the coating, and save labor and sandpaper. The sandpaper commonly used in construction is wood sandpaper, water sandpaper, iron sand skin, and the like. Generally, the partially filled putty sanding should be applied to the 1st or 1st wood sandpaper; the full-scraping putty and primer layer should be coated with No. 0 sandpaper, and the middle layer of the paint film can be made with the finer No. 00 sandpaper. Some paint films are dry-ground with sandpaper. Friction and heat will cause the paint film to soften and damage the film. At this time, wet grinding with water sandpaper is required. Before wet grinding, first soak the water sandpaper in water, then wrap it on the outside of the neatly folded cloth, and then sand it on the paint film, so that the water sandpaper is wrapped on the outside of the cloth, which can be enlarged. The area of sanding is also used for force. In order to improve work efficiency, electric sanders can also be used in large-area sanding construction, generally in the form of disc, vibrating, belt and drum.