The air Spray Gun does not look difficult in terms of structure and operation, but we also know that the quality of air spray paint depends on the viscosity of the paint, working pressure, the distance between the Spray Gun and the surface to be painted, and the operator's technical proficiency. However, if you want to obtain a smooth, flat, and uniform coating , these correct operation details cannot be ignored. Here are some correct operation methods to share.
① Spray gun preparation First, select the Spray Gun and adjust it to the appropriate working conditions, such as selecting the type of Spray Gun, nozzle diameter, spray pattern, etc. A Spray Gun that delivers a large amount of paint will also have a large spray pattern. The spray pattern can be adjusted from circular to oval through the spray pattern adjustment device. Due to the high efficiency of elliptical coating, it is applied to large objects and assembly line coating. Circular spraying is generally applied to smaller objects and smaller areas.
②The spraying pressure and air pressure are too high, although the atomization is fine, the paint will scatter a lot and the loss will be large. Conversely, if the pressure is insufficient, the spray will become thicker, and the paint film will have defects such as orange peel and pinholes. The pressure should be as low as possible under the required conditions. The degree of atomization is usually judged by observing the dryness and wetness of the wet paint film just sprayed. Too dry indicates excessive atomization, and too wet indicates insufficient atomization, especially when the paint film is a rough surface with pits, it indicates the degree of atomization too bad. Higher viscosity paints use higher pressure, such as putty spraying pressure is generally 0.35MPaj high viscosity paint is 0.25 ~ 0.30MPa; low viscosity paint is 0.1 ~ 0.15MPa.
③The distance between the Spray Gun and the surface of the object to be coated is too close, and the wet paint film is too thick, which is prone to sag and orange peel; The film is uneven, and the gloss is greatly reduced in severe cases. The spraying distance is generally 200~~300mm, the small diameter Spray Gun is 150~~250mm, and the large diameter Spray Gun is 200~300mm.
④ Spray gun operation: The Spray Gun should run at a constant speed and be at right angles to the surface to be coated. The movement of the Spray Gun requires a constant speed, and the speed is generally within 30-60cm/s. When the running speed is lower than 30cm/s, the paint film is too thick and easy to sag. When the running speed is greater than 60cm/s, the paint film is too thin , not easy to level. If the Spray Gun runs in a circular arc or is not perpendicular to the surface of the object being coated, the paint film thickness will be uneven. When switching the gun, it should not face the workpiece, even if the Spray Gun stops for 0.1s, it will cause serious sagging.
⑤ Spray pattern overlap The middle of the spray pattern is thick and the periphery is thin. The edge of the spraying range should be repeated on the edge of the range that has been sprayed before. The circle overlaps 1/2, the ellipse overlaps 1/3, and the flat overlaps 1/4, and the width of the overlap should be consistent. If the width of the boundary is variable and the film thickness is uneven, streaks or spots may occur. When spraying the second coat, it should cross vertically and horizontally with the previous paint film, that is, if the first coat is sprayed horizontally, the second coat should be sprayed vertically.
The spraying sequence is: first the inner surface, then the outer surface, first the secondary surface, then the main surface. The most eye-catching place is sprayed at the end to prevent the coating from spraying and scratching, so as to ensure the appearance of the eye-catching surface. Because when a small amount of paint mist particles are sprayed on the surface of the dried paint film, these paint mist particles cannot be leveled.
⑥Paint preparation The paint should be properly prepared before spraying. The paint in the original bucket needs to be stirred evenly, and the paint needs to be filtered before use. Two-component paint should be mixed evenly and have a pot life of half an hour. Paint viscosity needs to be adjusted with thinner. If the viscosity is too high, the atomization is not good, and the paint film is rough and dull; if it is too thin, it will cause sagging. The more viscous the paint, the less paint will be sprayed. The suitable paint viscosity is 16~~35s (painting - 4 cups), and the spraying viscosity of different paints is also different (see Table 7-2). When loading the paint storage tank, do not overfill it, preferably 2/3, and tighten the elastic knob.
