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Atomization principle: Air Duster Gun generally uses compressed air pressure of 0.3Mpa-0.6Mpa to flow through the air nozzle of the spray gun at a high flow rate to form a partial vacuum around the nozzle. The paint is sucked into the vacuum space by the compressed air, and the paint is atomized into The fine droplets are coated on the surface of the part to be coated to form a continuous coating film.
Main features: simple structure, convenient operation, easy color change, can adjust the size of the spray fan surface according to the geometry of the workpiece to be coated, and the atomization effect is good. However, the air spray paint mist is easy to rebound and scatter, polluting the operating environment, and the paint utilization rate is only 25%-35%. For air spraying, the paint is mixed and contacted with compressed air, and dust, oil, and water filtering devices must be installed on the air source to ensure the quality of the coating film.
Introduction to spraying methods
1. Air spraying
(1) Principle of atomization
Air spraying generally uses compressed air at a working pressure of 0.3Mpa-0.6Mpa to flow through the air nozzle of the spray gun at a high flow rate to form a partial vacuum around the nozzle. The paint is sucked into the vacuum space by the compressed air, and the paint is atomized into fine droplets. Coated on the surface of the coated part to form a continuous coating film.
(2) Features and applications
The main features of air spraying are simple structure, convenient operation, easy color change, the size of the spray fan surface can be adjusted according to the geometry of the workpiece to be coated, and the atomization effect is good. However, the air spray paint mist is easy to rebound and scatter, polluting the operating environment, and the paint utilization rate is only 15%-30%. The air sprayed paint is mixed and contacted with compressed air, and the air source must be equipped with a dust, oil and water filter device to clean the compressed air to ensure the quality of the coating film.
The working pressure of the air source of air spraying is relatively low, and it is difficult to atomize high-viscosity coatings. It is generally suitable for the spraying of decorative low-viscosity coatings.
In today's coating industry, air spray guns are the most used, especially products that require high film quality, such as high-end cars and high-end furniture, all use air spraying or air electrostatic spraying.
(3) Classification of air spraying
1. According to the feeding method
1), siphon type
The siphon spray gun is a widely used air spray gun. The lower end of the spray gun is equipped with a paint cup, and compressed air flows through the nozzle of the spray gun at a high speed, and a partial vacuum is generated around it. The paint in the paint cup is sucked into the nozzle and atomized into paint droplets.
The capacity of the paint cup is usually 600mL-1000mL, which is selected according to the amount of spraying, and the spray gun can be sprayed with compressed air. The nozzle of the spray gun should not be vertically upward or downward to prevent the paint from leaking from the vent of the paint cup.
2), gravity type
The gravity spray gun is used for small workpieces and paint touch-ups. The upper part of it is attached to a paint cup, which is delivered to the spray gun by the weight of the paint. According to the position of the paint cup relative to the axis of the spray gun, it is divided into center and side types. In spraying construction, the central type restricts the tilting position of the spray gun; the side type can use different positions while the paint cup remains vertical. The paint cup of the gravity spray gun generally has a small capacity, 400-600 mL.
The gravity spray gun is easy to change colors and clean consumes fewer materials, and is suitable for color spraying processes with frequent color changes and two-component coatings with fast curing speed.
3), pressure type
The pressure spray gun delivers paint to the spray gun through pressure. The spray gun itself does not come with a paint cup, and the spray gun is light in weight and can be sprayed at any position and angle. It is suitable for workpiece gap type, continuous spraying or coating line use, the spraying efficiency is improved, and the coating film quality is good.
Pressure spray paint delivery devices are divided into two categories: pressure barrels and pneumatic double diaphragm pumps.
The pressure barrel is a cylindrical pressure vessel, generally made of stainless steel or carbon steel. The lid is equipped with a pressure regulating valve, pressure gauge, and safety valve. The pressure of the input compressed air can be adjusted to achieve the pressure of the output paint. Some pressure tanks are also equipped with pneumatic agitators. Commonly used pressure tanks have a capacity of 10L, 20L, 40L, 60L, etc. The pressure tank is simple in structure, easy to maintain, and the paint output pressure is relatively stable. The disadvantage is that it is inconvenient to clean and change colors.
The pneumatic double diaphragm pump uses compressed air as power, and the air pressure acts on the inner side of the diaphragm through a reversing mechanism, and the outer side of the diaphragm and the pump body together form a paint chamber with a variable volume. When the volume of the paint chamber on the left increases from small to large, a partial vacuum is generated. The lower one-way valve opens and the upper one-way valve closes. The paint in the paint bucket enters the left paint chamber under atmospheric pressure, and the volume of the right paint chamber changes from large to small. The lower one-way valve is closed, the paint generates pressure, and the upper one-way valve is opened to discharge the pump body.
There are two coating chambers on both sides of the double diaphragm pump. When the volume of one is changed from small to large, the volume of the other is changed from large to small. Therefore, each reciprocation of the double diaphragm pump has two paint suction and discharge, so that the output efficiency of the pump is improved, and the output is relatively stable. Since the ratio of the input pressure of the compressed air to the output pressure of the paint is 1:1, the output pressure of the paint can be changed by adjusting the input pressure of the compressed air.
The little knowledge about air spraying is shared here today, and it will be updated in the future. If you need air spraying, welcome to visit our company!
