Process principle of powder electrostatic spraying

The power supply for powder electrostatic spraying is supplied by a high-voltage electrostatic generator. Connect to the electrostatic spray gun via the high-voltage cable. The spray gun is connected with the air source at the same time, and is connected with the powder supply pipe and the powder supply. A powder is mixed with the air flow in the powder supply and is sent into the spray gun. The high voltage generated by the high-voltage electrostatic generator is connected to the inside or front end of the spray gun. The powder particles in the powder-air mixture are charged inside the spray gun or at the outlet of the spray gun (determined by the structure of the spray gun). The powder particles fly to the grounded workpiece to be coated under the action of the electrostatic field. Therefore, it can not only be sprayed on the front of the workpiece, but also can be coated on the back of the workpiece. The powder adheres to the coated object. When the thickness exceeds a certain thickness, the same-same repulsion will occur, and the later powder will not be easy to adsorb to make it reach a uniform film thickness. The powder is generally negatively charged, and the voltage is between 30 kV and 100 kV. After spraying, the powder layer is melted, leveled, and solidified in the curing furnace to form a uniform film layer.

Powder electrostatic spraying equipment consists of the following equipment: high-voltage electrostatic generator, electrostatic spray gun, powder supply, powder spraying room, powder recovery device (with mechanical ventilation), compressed air and oil-water separator, etc. For easy operation, another console can be added.

In order to make the powder water electrostatic spraying to form a thin and uniform coating, the following process parameters should be referred to.

The output voltage of the high-voltage electrostatic generator should be 80-100 kV. In order to improve the enveloping effect of the electrostatic field force, the output voltage can be increased to 20-110 kV. The pressure of compressed air supplied to the spray gun should be 1.5 kg/cm². The powder output from the powder feeder through the spray gun is generally 3-18 kg/hour. The distance between the end of the electrostatic powder spray gun and the workpiece is about 200 mm. In order to ensure that the powder coating is not contaminated, the oil-water separation requirement of the compressed air oil-water separator is that the air dew point temperature should be below -3 degrees Celsius. Some powder coatings require the temperature of the compressed air to transport the powder to be 10 degrees Celsius.