According to the supply method of coating, air spray gun can be divided into suction spray gun, gravity spray gun and pressure spray gun. Suction spray gun and gravity spray gun are commonly used in coating repair.
The compressed air flow of siphon spray gun creates a low pressure area at the air cap to provide siphon effect. The coating in the paint cup enters the siphon pipe and the spray gun upward under the effect of atmospheric pressure, and is atomized at the air cap and ejected from the flow nozzle. The vent hole on the cover of the paint cup must be opened. The paint cup capacity of siphon spray gun is generally one liter or less, and now it is only suitable for low viscosity coatings.
The paint cup of gravity spray gun is located above the spray gun, which can make the coating flow into the spray gun by the gravity and the suction of the nozzle tip. The paint cup of the spray gun does not need a liquid suction pipe because the outlet of the coating is just at the bottom of the paint cup. The vent at the top of the paint cup must be opened. Considering that the overweight of the paint cup and the coating will affect the stability of the spray gun, so the capacity of the paint cup is generally limited to about 600 ml.
The flow nozzle of the spray gun is flush with the end face of the air cap. The coating is pressurized in separate coating cups, tanks or pumps. Under the action of pressure, the coating passes through the flow nozzle and is atomized at the air cap. The pressure spray gun is often used when the coating is too heavy to be siphoned or the spraying operation needs to be completed quickly. This kind of spray gun is suitable for large area operation, and this spraying system is widely used in spray painting workshops of automobile manufacturers.