What is the basic principle of friction electrostatic spraying method?

Flocking Machine Manufacturers

1. Basic principles. The friction electrostatic spraying method is researched and invented by the Swedes on the basis of electrostatic spraying method. Unlike the high-voltage electrostatic spraying method, it does not require a high-voltage electrostatic generator, and the electrification of the powder and the electrostatic field are generated by friction. When the powder is transported by purified compressed air through a friction spray gun made of strong electric negative material, it will rub against the inner wall of the gun and become positively charged; after the charged powder is sprayed out of the muzzle, a space electric field is formed, which is determined by the intensity of the electric field. Due to the charge density of the powder and the geometry of the electric field; the charged powder is mainly sprayed to various parts of the workpiece under the air flow, and adheres well to the surface of the workpiece, thereby forming a dense coating, which will form a film after curing.

2. Main features. There is no external electric field in the friction electrostatic spraying method, which can effectively overcome the Faraday shielding effect that is easily produced by the high-voltage electrostatic spraying method, so that the powder electrostatic spraying method can also be applied to workpieces with more complex geometric shapes. At the same time, because the friction gun is used, no high-voltage electrostatic generator is needed, which saves equipment investment and eliminates the hidden dangers of spark discharge, dust combustion and explosion caused by short circuit. At the same time, there is no metal electrode in the spray gun, no electrode powder accumulation, and the gun body is easy to operate. In the friction electrostatic spraying, the reverse ionization phenomenon only occurs within 10-20s after the spray gun is started, which can increase the powder rate of the spraying. There is no breakdown of the counter ion current when spraying thick films, ensuring the quality of the coating film.

But due to friction charging, the service life of the spray gun is short, and the powder charge is not sufficient. The friction charging effect on the powder variety and the requirements for air source and environment are relatively strict, which limits its application range.

3. Construction technology. The state of powder frictional charging is the main factor that affects the powder deposition efficiency and the quality of the film. Therefore, around this factor, certain requirements are put forward on the following points in the process:

　　 1) The electrification of the friction gun.

　　 2) Purification of powder supply air pressure and air flow.

　　3) The charging performance, dryness and particle size of the powder.

　　4) The amount of powder spraying.

　　5) Spraying distance.

　　6) Humidity and cleanliness of the construction environment.

To obtain good spraying quality, the above-mentioned optimal process conditions must be formulated comprehensively.

4. Main equipment and process flow. Compared with the high-voltage electrostatic spraying method, the equipment just does not need a high-voltage electrostatic generator, the spray gun is a friction spray gun, and the inner wall of the powder pipeline also needs to be attached with an electric negative friction material to increase the powder friction charge; other equipment and process flow are similar.