When polishing the painting assembly line, the main items to be noted are:

1. The sanding material should be selected strictly according to the process requirements, dry sanding putty with 80#～120# water sandpaper; wet sanding with 240#～320# water sandpaper for middle coating; wet sanding with 360#, 400#～ 600# water sandpaper, it is required that no traces of sandpaper remain. At the same time, the quality of water-resistant sandpaper should be checked before sanding, and there should be no mechanical impurities (coarse sand particles) to prevent scratches on the coating film. When the water-resistant sandpaper is to be torn apart for use, it should be moistened with water first, and then torn or folded for use;

2. Pay attention to the directionality of polishing, not to grind randomly in all directions, and not to press too tightly during polishing. In order to improve the flatness of the surface to be polished, a cork or rubber abrasive block can be placed on the sandpaper during manual polishing. Cork abrasive block is suitable for polishing putty in middle coating occasions; rubber abrasive block is suitable for middle coating or topcoat;

3. During the polishing process, the polishing dust should be removed continuously, after wet polishing, thoroughly rinse with deionized water and blow dry to make the coated surface dry;

4. The coating should be dry before polishing, otherwise the sandpaper will stick to the polishing, which will affect the polishing quality.

Because polishing is generally performed manually, sometimes with the help of pneumatic tools or some simple instruments, the labor intensity of polishing is high, and efforts are being made to eliminate this work in the industrial coating of flow production.