As the saying goes: "10 points painter, 3 points in sand", visible grinding in the importance of painting operations. The grinding process has three main functions:
① The substrate is to remove burrs, oil and dust on the surface of the substrate;
② For the surface of the scraped putty, the general surface is rough, and a flat surface needs to be obtained by sanding, so grinding can reduce the roughness of the workpiece surface;
③ Enhance the adhesion of the coating. Before spraying the new paint film, it is generally necessary to polish the old paint film layer after practical work, because the adhesion of the paint on the excessively smooth surface is poor, and the mechanical adhesion of the coating can be enhanced after grinding.
Grinding methods are dry grinding, wet grinding and mechanical grinding three kinds.
① Dry grinding: using sandpaper for grinding. It is suitable for the grinding of hard and brittle paint, and its disadvantage is that a lot of dust will be produced during the operation, affecting environmental health.
② Wet grinding: water sandpaper dipped in water or soapy water polishing. Water grinding can reduce wear marks, improve the smoothness of the coating, and save sandpaper and labor. However, attention should be paid to spraying the lower layer of paint after water grinding, one is to wait until the water grinding layer is completely dry before painting the lower layer of paint, otherwise the paint layer is easy to white. In addition, the substrate with strong water absorption is not suitable for water grinding.
③ Mechanical grinding: large-scale construction, in order to improve work efficiency, mechanical grinding methods can be used, such as electric grinding machine (disc type, vibration type).
There is also a kind of grinding: the painting requirements indicate that it is "light grinding", such as the sealing paint, old paint film recoating, local repair, etc., at this time, finer sandpaper and skilled hands should be used to effectively "light grinding". Otherwise, it will backfire.
When grinding, the grinding material should be selected strictly according to the process requirements, and the sandpaper can generally be selected according to the following rules:
Solid wood white grinding use 180# - 240# sandpaper
For cleats or a primer, choose 220# - 240# sandpaper
The polishing of the primer is made of 320# - 400# sandpaper
