The process conditions of high-voltage electrostatic spraying have an important impact on the appearance and quality of the coating film formed by powder coating spraying, so the appropriate process conditions should be selected according to the specific conditions of the workpiece. Important process parameters mainly include the following items.
The electrostatic field voltage applied between the Spray Gun and the workpiece has an important influence on the adsorption of powder on the workpiece, because the electric field force between the nozzle and the workpiece is the main driving force of powder coating, which determines the powder coating rate. Within a certain range, as the voltage increases, the amount of powder attached to the workpiece also increases, but when the voltage exceeds 90kV, the amount of powder attached will decrease with the increase of voltage, and the spraying voltage is too high, which will make the powder The coating is broken down and affects the quality of the coating, so the voltage should be controlled between 60~80kV, too low will cause the coating to be too thin. The electrical performance of the Spray Gun system is different depending on the age, so after a period of use, it is necessary to increase the electrostatic voltage appropriately to ensure the required coating thickness.
The distance from the nozzle of the Spray Gun to the surface of the workpiece is called the spraying distance. When the applied electrostatic field voltage is constant, the electric field strength will decrease with the increase of the spraying distance, and the reduction of the electric field strength will reduce the deposition efficiency of the powder. , The thickness of the powder layer is reduced, so the size of the spraying distance directly affects the thickness of the powder layer absorbed by the workpiece and the deposition efficiency. Generally, the spraying distance is preferably controlled between 150~300mm. Under the premise of ensuring the thickness of the coating, it is better for the Spray Gun to be a little farther away from the workpiece, which is conducive to the uniform distribution of the coating.
Refers to the air pressure of the powder delivery pipe in the powder feeder. Within a certain range, as the powder supply air pressure increases, the air thrust on the powder coating increases, which is conducive to its adsorption on the workpiece, but the powder supply pressure exceeds 0.05MPa Finally, too much thrust of the air is not conducive to the adsorption of powder on the workpiece, and the sedimentation efficiency will be reduced, so the air pressure of the powder supply should be controlled below 0.05MPa.
It refers to the amount of powder coating sprayed from the nozzle of the Spray Gun within a unit of time. The thickness of the powder layer and the deposition efficiency are directly proportional to the amount of powder sprayed within a certain range. But with the increase of powder spraying amount, its influence on deposition efficiency decreases gradually. Therefore, the amount of powder spraying should also be controlled within a certain range, generally 100~200g/min is more appropriate.