Bohai Steel Structure Co., Ltd.

Bohai Steel Structure Co., Ltd.
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    Spray gun operation points

    author:Bohai Steel Structure Co., Ltd.

    【Font size: big medium smail

    time:2019-08-20 14:38:48

    When using the spray gun for painting, what are the operating specifications and points, Bohai Steel Structure for you to explain

    (1) master the angle of the spray gun and the member being sprayed. In order to facilitate the operation, the operator should stand in one step or T-step. During the movement of the spray gun, whether it is a horizontal spray or a vertical spray, keep the spray gun at 90° from the work surface when moving up and down or left and right. And move at the same distance and stable speed as the surface, otherwise the paint film may be uneven. Never bend the wrist or elbow by an arc. Otherwise, the paint film of the coated component may be uneven, the sag may appear in the thick part, the exposed bottom may appear in the thin part, and some of the paint mist is lost in the air. The spray gun is allowed to swing in a small area only when it is sprayed in a small area, because the film is required to be thin at both sides in the middle.   

    (2) Master the distance between the nozzle and the member to be coated. The paint spray distance of the car is preferably 150-200mm (can be operated according to the process conditions provided by the paint supplier). If the spraying distance is small, it is easy to cause sag, wrinkle and uneven spraying; the spraying distance is large, the utilization rate of the coating is low, and the coating particles are also in the air for a long time. For the paint, the paint mist may arrive. When the surface of the workpiece is too thick, its leveling is affected, and orange peel and particles are produced. The normal spray distance should match the gun air pressure, the fan';s fan adjustment, and the type of paint.   

    (3) Master the spray pressure. Choosing the right spray pressure is related to a number of factors, such as the type of paint, the type of diluent (fast, slow), and the viscosity after dilution. The liquid material is atomized as much as possible during the spraying operation, and at the same time, the solvent contained in the liquid material is required to evaporate as little as possible. Generally, the air pressure is adjusted to ~, or it can be adjusted by spraying. It is necessary to develop good habits that strictly follow the construction parameters provided by the paint manufacturer';s product specification in order to achieve the desired results. A suitable spray pressure can achieve the proper spray, emission rate and minimum spray rate requirements. If the pressure is too low, the atomization may not be good. The paint is sprayed onto the surface of the component like rain, which is prone to sag, pinhole, and foaming. Excessive pressure may cause excessive evaporation, and in severe cases, a so-called dry spray phenomenon may occur.   

    (4) master the fog shape. It is important to measure the fog shape on the cover paper before spraying. It is a comprehensive measurement of the distance and pressure of the spray gun. During the test, the nozzle is separated from the wall by about one hand when the palm is opened, and the trigger is pulled to the end and then released immediately. The sprayed paint leaves a slender shape on the test paper. The uniformity of the paint distribution within the mist is then tested. Loosen the air cap ring and turn the air cap so that the air cap angle is in the vertical position. At this time, the air cap produces a fog shape that is moving horizontally. Spray again, this time hold the trigger until the paint begins to flow down (this is the submerged fog). Check the length of the sag of each section. If the adjustments are correct, the lengths of the sags are approximately equal. If the spray is too wide or the air pressure is too low, the sag is in a separate shape. The mist control valve can be tightened half a turn, or Increase the air pressure and alternate the two adjustments until the sag length is even. If the middle of the sag is short, the lacquered valve should be tightened until the sag length is even.   

    (5) Master the speed of the gun movement. The speed of movement of the spray gun is related to the drying rate of the paint, the ambient temperature, and the viscosity of the paint. The moving speed is approximately 0.3/s. If the moving speed is too fast, the paint film will be rough and dull, and the paint film will have poor leveling property; if the movement is too slow, the paint film will be too thick and sag. Therefore, the speed must be the same, otherwise the film thickness is uneven. Never allow the spray gun to stop during the spraying process, otherwise it will cause sag. Using a slower drying coating, the moving speed can be appropriately increased from 0.4 to 0.8 to /s.   

    (6) Master the spraying method and route. Spraying methods include a vertical overlap method, a horizontal overlap method, and a vertical and horizontal alternate spray method. The spraying route should be from high to low, left to right, and from top to bottom, first and second. The gun should be moved steadily according to the planned stroke. When the    reaches the end of the one-way stroke, release the trigger, then pull the trigger and start spraying in the opposite direction. Closing the gun at the end of the stroke avoids sagging and minimizes flying paint. Difficult to spray parts, such as corners or edges, must be sprayed first, to face the part to be sprayed, so that the corners or edges of each side are half painted. The distance between the guns is closer than the normal distance, and all edges and corners are sprayed before spraying the horizontal surface. The vertical panel usually starts from the uppermost end of the plate and the nozzle is flush with the upper edge. The stroke of the second unidirectional movement of the spray gun is opposite to that of the first time. The nozzle is flush with the lower edge of the first stroke, and the upper half of the mist overlaps with the lower half of the first mist, and the overlap width should be second. The layer overlaps the previous layer by approximately 1/3 or 1/2. The lower half is sprayed on the unsprayed area and should be mixed with the “wet edge” of the previous sprayed part. The overlap of the spray start is selected to avoid double coating and sagging. Allow a few minutes of flash-dry time between the coatings.

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