When selecting the spray gun, factors such as the size of the spraying object, the variety of coating and the quality registration standard of spraying shall be considered. If the object to be coated is large, the spray gun with large diameter shall be selected, so that the paint output is large and the speed is fast. When the spraying quality requirements are high, the paint spray gun with good atomization of paint nozzle shall be selected. On the contrary, due to large objects and low quality requirements, the selection of spray gun with good atomization will affect the efficiency. When the amount of paint is small, the area of spraying objects is small, and there are many color types, the use of a large spray gun will cause waste and can not improve the quality. At this time, the gravity spray gun should be selected, because the spray gun has less paint loading capacity, convenient color change, and saves diluent when cleaning the paint pot.

The larger the diameter of the spray gun, the greater the air pressure required, the more paint sprayed, and the higher the consistency of the paint required. The caliber of the spray gun is matched with the air hole of the air cap of the spray gun nozzle. The air cap is divided into multi hole type and few hole type. The porous air cap has large air consumption, good atomization performance and good coating quality; The air cap with few holes has small air consumption, but poor atomization ability. It is suitable for spraying objects with low quality requirements.

The atomization degree of spraying coating is closely related to the diameter of spray gun, the viscosity of coating, the exhaust air volume of air outlet hole and the arrangement angle P, etc. Therefore, the caliber of spray gun nozzle and the number of air outlet holes should be selected according to different varieties of coatings, and the viscosity of coatings should be adjusted.