The principle of roller coating is similar to roller coating. Both are to transfer the paint to the surface of the coated workpiece by rolling the paint-absorbed roller (or roller) on the surface. However, the roller coating is divided into the same direction roller coating machine (sequential radial coating machine) and reverse pro-coating machine (reverse roller coating machine) by mechanical rolling. The direction of the paint roller is the same as that of the workpiece to be coated, which is the same direction roller coater. Conversely, if the rotation direction of the paint roller is opposite to the forward direction of the workpiece being processed, it is a reverse roller coater. As shown in Figure 23.
The supply roll (l) is a chrome-plated steel roll. The paint roller (2) is in close contact with the surface of the workpiece to be coated so as to transfer the material to the surface of the workpiece. It wraps a layer of solvent-resistant rubber on the steel surface. The backing roller (3) supports the super-feeding effect of the workpiece. Its surface is only covered with ordinary rubber. (5) in the co-rotating roller coater is a scraper, which can turn over excess feeding material. By adjusting the gap between the roller and the workpiece, the thickness of the paint film can be controlled. The roller coating machine is divided into two structures: one painting and two sides painting at the same time.
The mechanical roller coating method is generally used in continuous automatic production, and the production efficiency is high.
Factors affecting roller coating include: the gap between the feed roller and the coating roller, the feed speed of the workpiece, the viscosity of the coating, the pressure of the coating roller on the workpiece, and the leveling of the coating. In addition, the roller rubber will swell and be damaged after long-term contact with organic solvents, so it needs to be checked frequently and replaced in time.
In production, the same-direction roller coater is mainly used for hole filling, leveling and coloring of plates and plate components. However, it is not suitable to install the topcoat, because the topcoat has relatively high requirements for decorative corners. Varnish, color paint, hole-filling paint, leveling paint, and primer are all available for roller coating, but they require good leveling and are not easy to dry when the roller is running. The coating with low viscosity and good leveling property is suitable for thinner coatings, and it can be coated with 10-20 microns each time. Pay special attention to the pressure of the paint on the workpiece. If the pressure is too high, part of the paint will be extruded from both sides of the plate, causing defects such as thick edges.
The reverse roller coater is widely used for the coating of metal plates, plywood, cardboard, leather, plastic film, etc., and is sometimes used together with printing.
The disadvantage of this coating method is that the equipment investment is large, and the paint roller will be damaged at the cut of the metal plate section when working at home. The pre-coating materials developed in recent years now include colored steel plates, organic-coated steel plates and various decorative plates, which not only overcome the above shortcomings, but also save labor and materials, and improve work efficiency.
