In order to obtain the effect of uniform coating thickness, excellent appearance and durability, the operator needs to spray correctly and master the correct spraying technology. Among them, the correct overlap and sequence of the spray patterns have an important impact on the quality of the repair coating.
The overlap width of the spray pattern should be kept consistent during repair coating. If the overlap width is not consistent, streaks and spots will occur due to uneven film thickness. Generally, the overlap degree of spraying should be 1/2 of the effective spray pattern width, at least More than 1/4. When it is required to obtain a more uniform coating, the second coat should cross the previous paint (if the first coat is sprayed horizontally, the second coat should be sprayed vertically and cross at right angles). Spraying can be divided into single-film and double-film coatings. The double-layer spraying sprayed twice can establish a thick coating with good leveling and gloss, and will not form a rough film of dry spraying.
At present, the "wet-on-wet" spraying process has been widely used in repair spraying. It is a double-coat spraying process. After spraying the first coat of paint, let it dry for a certain period of time, then spray the second coat of paint, and then dry it together. And baked in the process. At present, this process is also widely used in the process of spraying synthetic resin primer or topcoat. This can make the dry film thickness of one spraying more than 40µm, reduce the number of drying times, thereby saving energy and improving the bonding force.
Drying time refers to the time necessary to allow solvents to evaporate in order to obtain good film appearance and performance between each coat of paint or before drying. Proper drying time can avoid spray defects caused by excess solvent left in the coating.
When repainting the whole vehicle, it is necessary to design the spraying sequence in advance to reduce dry spraying (flying paint atmosphere falls back to the painted surface) and dry overlapping joints, so as to make the operation coherent and reduce unnecessary movement. The operation sequence of spraying is: blow off the dust on the whole vehicle with air before the car enters the spray booth, close the door of the spray booth tightly after the car enters the spray booth, then wipe the whole vehicle with a cloth, and blow the air off when starting to spray. The atomization pressure of the Spray Gun is reduced to 0.14MPa, and the atomization pattern is adjusted into a circle. Generally, spray the hard-to-reach parts such as the trunk, the edge gap of the engine cover and the door switch handle, and then start spraying from the roof of the car, and then spray the trunk cover and sides. In a spray booth where the air flows from top to bottom, the roof and pillars should be sprayed first, and then spray along the body from the open door. In the spray booth with one inlet and one outlet ventilated at both ends, the front of the car should face the air inlet side, and the body should be sprayed in the spraying sequence from front to back.
According to the size of the area to be repaired, it is divided into two types: point type and plate type repair spraying. The use of plate repair is to use the method of expanding the repair area to cover up the uneven color tone of the repair paint and the original paint. However, when it is unreasonable, uneconomical or still unable to cover up the color difference, spot repair spraying can be used. When spraying, the Spray Gun sprays the topcoat in a reciprocating motion from the center to the outside, so that each layer is slightly superimposed on the surface. On the previous coat, the spraying range should be wide, the paint output should be small, and the air pressure should be low. After removing the surrounding cover, after the topcoat layer is dry, it is polished and polished.
冯文;李正超;向旭东 - 《东方汽轮机》