The spray gun is a device that uses fast-released liquid or compressed air as power. In the coating industry, such as electrostatic spray guns can be directly used for coatings, mainly for surface spraying treatment of automobiles, furniture, household appliances, etc.
For different types of coatings, three factors are mainly considered when choosing the hole diameter of the matching paint nozzle, namely the viscosity of the coating, the amount of spraying operation and the spraying flow rate of the coating.
(1) Coating viscosity
Fluids with low viscosity have low resistance when flowing, so the nozzle diameter of the spray gun can be smaller and the hydraulic pressure used can be lower. However, the high-viscosity coating has a large flow resistance, so in order to obtain a sufficient flow rate, a large-diameter nozzle and a higher hydraulic pressure must be used. Generally, the diameter of the coating nozzle is between 0.5 and 5.0 mm. The diameter of 0.5 to 0.7 mm is used for spraying easy low-viscosity coatings, such as colorants and shellac, and the diameter of 1.0 to 1.8 mm is used for spraying viscous coatings. For example, nitro degree coating.
(2) Coating flow rate
The larger the amount of coating required, the larger the nozzle diameter, otherwise no more coating can be delivered within the specified time. There are two basic methods to control the spray flow: one is to change the diameter of the nozzle hole, and the other is to change the pressure applied to the coating. Changing the diameter of the nozzle hole is a more convenient method.
For ordinary paint, the liquid at the inlet of the spray gun nozzle should not exceed 0.2 MPa. Too high hydraulic pressure will produce too high spray speed, which will prevent the air nozzle from performing good atomization treatment. Therefore, the largest diameter and lowest hydraulic pressure should be selected to meet the flow requirements.
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