Spraying method is one of the most important methods in the construction of water-based coatings. By coating the surface of the object by spraying, a thin and uniform coating film can be obtained. For different geometric shapes, there are small holes, gaps and irregularities, and the coating can be used. Uniform distribution; this method is faster and more effective than painting for large objects. However, there are some operational skills to be mastered by spraying:
First, adjust the viscosity of the paint to a suitable spray with clean water and measure it with a viscous meter. The appropriate viscosity is generally 20 seconds to 30 seconds. If there is no viscometer at one time, visual method can be used: stir the paint with a rod (iron rod or wooden stick) and pick it up to a height of 20 cm to stop and observe. If the paint liquid is continuous in a short time (several seconds), It is too thick; if it is off the edge of the barrel, it is too thin. When staying at a height of 20 cm, the paint liquid is in a straight line, and the instantaneous flow is turned into a downward drop. This viscosity is suitable.
Second, the air pressure is preferably controlled at 0.3 to 0.4 MPa (3 to 4 kgf/cm2). If the pressure is too small, the spray liquid will be atomized, and the surface will form pitting. If the pressure is too large, it will sag and the paint mist will be too large, which will waste materials and affect the health of the operator.
Third, the distance between the nozzle and the object surface is generally 300 mm to 400 mm. When it is too close, the paint film is easy to sag; the paint mist is not uniform too far, the pitting is easy to occur, and the nozzle is far away from the object surface, and the paint mist is scattered on the way to cause waste. The specific size of the distance should be adjusted according to the type of paint, viscosity and pressure. Slow drying paint spraying distance can be a little farther, quick drying paint spraying distance can be closer; when the viscosity is thick, it can be closer, when the viscosity is thin, the distance can be farther; when the air pressure is large, the distance can be farther, the pressure can be closer; the so-called near A little further is a small adjustment between 10 mm and 50 mm. If it exceeds this range, it is difficult to obtain an ideal paint film.
Fourth, the spray gun can be moved up and down, left and right, preferably at a speed of 10 to 12 m / min. The nozzle should be sprayed flat on the surface to minimize the oblique spray. When spraying to both ends of the object, the hand of the trigger of the spray gun should be quickly loosened to reduce the paint fog, because the two ends of the object often need to be sprayed twice or more, which is the most likely place for sag.
Fifth, when spraying, the next one should hold 1/3 or 1/4 of the previous one, so that there will be no leakage. When spraying quick-drying paint, it is necessary to spray it in sequence, and the refilling effect is usually not ideal.
Sixth, when spraying in an open space, pay attention to the wind direction (not suitable for operation in high winds). The operator should stand in the downwind direction to prevent the paint mist from being blown onto the sprayed paint film to create an unsightly grainy surface.
Seventh, the order of spraying is: first difficult and then easy, first and then outside. After the height is high, the small area is small, so that it will not cause the spray paint spray to spray on the sprayed paint film, destroying the sprayed paint film.
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