Roller coating —pre painted galvanized steel coil
Roller coating is the most widely used process. The cleaned steel sheet enters the painting room after surface pretreatment and drying. The liquid paint is drawn by the draw roller of the roller coater, and the paint is applied to the upper and lower surfaces of the sheet through the coating roller. The steel strip coated with wet paint Enters the curing furnace for heating and baking so that the solvent is completely volatilized and the coating is cured. The solvent-containing waste gas is discharged and sent to the incinerator for treatment. After the coating is cured, the strip is cooled by quenching water and dried with hot air.
The roll coating method is suitable for coating flat metal plates, especially for the high-speed coating of metal coils. Roller coating has fast coating speed, high production efficiency, simultaneous coating on both sides, and coating utilization rate close to 100%. However, roller coating is only suitable for flat coating, not for protrusions of other shapes, because the roller coating machine adopts a uniform coating circulation conveying.
The recycling system requires a large amount of paint, which is unsuitable for multi-variety and small batch production. The paint is transferred to the surface of the coated object in the form of a wet film on the surface of the coating roller. The solvent volatilizes quickly, and the viscosity of the paint is easy to change during the roller coating process. If the process conditions are not properly controlled, the coating film is prone to roll marks.
The roll coating process is usually limited by the thickness of one coating film of the roll coater and the capacity of the baking curing oven. If the product requires a large coating film thickness, multiple coating and baking curing are required. Therefore, in order to meet the requirements of different coating thicknesses, the roller coating process has one coat and one bake, two coats, and two bakes, or even three coats and three bakes. At present, the widely used roller coating process is double coating and double bake type.