The key equipment of electrostatic spraying is high-voltage electrostatic controller, high-voltage electrostatic generator and Spray Gun, and some generators are set in the electrostatic Spray Gun. According to its atomization principle, electrostatic Spray Guns mainly include centrifugal force electrostatic atomization, air electrostatic atomization and hydraulic electrostatic atomization (see Figure 2_2_13).
(1) Centrifugal electrostatic spraying
Centrifugal force electrostatic spraying generally makes the paint form an initial phase quotient under the action of 2000~4000r/min centrifugal force and carries a negative charge on the tip of the muzzle, and is further fully atomized under the repulsion of the same-sex charge. There are two kinds of methods for generating centrifugal force: disc type and rotary cup type.
1. Disc electrostatic spraying
Since the disc electrostatic spraying is electrostatically sprayed in the "a" type spray booth, it is also called a electrostatic spraying. The rotation speed of the rotary disc is generally about 4000r/min, and there are also rotary discs with a maximum speed of 60,000r/min. At such a high rotational speed, the paint has a considerable degree of atomization. Since the direction of the centrifugal force of the rotating disc is the same as that of the electric field force (same plane), the paint mist of the disc electrostatic and electrospraying is less scattered, and the adhesion efficiency is very high. When working, the turntable moves back and forth up and down, so that all the workpieces on the hanger are evenly coated with paint film up and down. The front and back of the workpiece can be evenly coated by the rotation of the hanger or double-a electrostatic spraying. n Electrostatic spraying is very suitable for painting medium and small pieces, and has high painting efficiency.
2. Rotary cup electrostatic spraying
The mouth of the rotary cup is sharp, and it has a high electron density as a discharge electrode, which makes the coating easy to charge. The rotational speed of the rotary cup is generally above 2000r/min, and the high-speed rotary cup can reach 60,000r/min. Since the direction of the centrifugal force of the rotary cup is perpendicular to the direction of the electric field force, the spray pattern formed is ring-shaped, and the scattered paint mist is more than that of the disc type. , the hollow figure will cause uneven coating thickness for complex workpieces. Two measures are usually taken to improve it. One is to set an auxiliary corona electrode to compress the spray toward the center; the other is to set an air ring behind the rotary cup to adjust Spray the image frame and suppress the spraying of paint mist.
(2) Air atomization electrostatic spraying
For portable electrostatic Spray Guns, due to the low voltage applied, the atomization of the paint needs to be guaranteed by compressed air. Impulse and diffusion effects, the paint utilization rate of this electrostatic spraying is lower than that of the high centrifugal type, but higher than that of air spraying, and is suitable for spraying of workpieces with more complex shapes.
(3) Hydraulic atomization electrostatic spraying
This method is a combination of high-pressure spraying and electrostatic spraying. Due to the high pressure (about 10MPa) applied to the paint, the paint is sprayed from the gun at a high speed; the charge rate of the paint liquid is poor, and the atomization effect is also poor, so this method The effect of electrostatic spraying is not as good as that of air electrostatic spraying, but it is suitable for spraying complex shapes of workpieces, and the spraying amount of paint is large, the coating film is thick, and the coating efficiency is high. If high-voltage electrostatic spraying is combined with heating spraying, that is, high-voltage heating electrostatic spraying Spraying, at this time, the heating temperature of the paint is about 40°C, and the paint pressure is about 5Mpa. Because the paint pressure is greatly reduced, the charge rate of the paint is improved, the effect of electrostatic spraying is improved, and the coating film has better appearance quality. High-voltage electrostatic spraying Another form of air-assisted high-voltage electrostatic spraying is air-assisted high-voltage electrostatic spraying. The auxiliary air can suppress the scattering of paint mist, improve the utilization rate of paint, and improve the atomization effect.
