Pneumatic spray guns are generall available as high-pressure and low-pressure spray guns according to air consumption. Usually, we use 0.2Mpa to judge whether the spray gun is a high-pressure or a low-pressure model.
High-pressure spray gun: effective air pressure is about 0.4-0.5Mpa, it is the air pressure range of general pneumatic spray guns. It’s a relative term to low pressure guns. The main feature is its strong atomization ability. It’s able to quickly spray over products in different industries at large area which will greatly improve our work efficiency. But the big weakness is high rate consumption of coating.
Low-pressure spray gun: As the name tells, it’s able to atomize the paint well under low air pressure condition. The shinning point is there’s no bounce back paint due to high pressure, thus the paint will not run away so much and finally increased the paint rate.
In order to understand well of the spray gun working principle, we will explain three of the common signs on spray gun – CYL/CAP/FAN. All spray guns are functional based the three piping configuration, so what are their functions?
- CYL: the switch of spray gun, control the needle on/off through magenetic valve, paint will be discharged when air in, and vice versa.
- CAP: atomization control by the air pressure regulator. When the paint flow is increased, it is necessary to increase the atomization air pressure.
- FAN: Atomized paint width or fan-shape size adjustment.
Firstly we open CLY valve to set the air pressure between 0.3Mpa-0.5Mpa with stable air pressure supply. Then set the CAP air pressure according to the size of the existing flow, until the spray gun atomization is uniform and fine, the atomization now is conical. Finally, adjust the FAN air pressure for a appropriate width.
Why does the paint flow gradually decrease for automatic spray gun?
This happens in many scenarios where automatic spraying equipment is used. Is the spray gun broken, or the paint system lack of supply? Actually such phenomenons are rare in production case.
The main reason we found is because we selected an incorrect size gun nozzle. So what is the relationship between the problem and spray gun nozzle size? In fact, most of us will face this situation because we adjusted very small flow rate, the gap between the needle and the spray gun nozzle is very close, thus the force of the piston spring is relatively big. If the air pressure is slightly weakened or the flow is divided, the needle will reset and close spray gun.
So how to solve it? That is to select a smaller or compatible nozzle size. Because when we adjust the flow rate to obtain a smaller flow on big size nozzle, while the equipment can’t make it work within a limit all the time, so it will not achieve good results, that’s why spray gun have various sizes nozzle. When small flow rate required, a smaller size spray gun nozzle should be selected. The vice versa.
Therefore, in the process of integrating with spray equipment, we must fully understand the production process and specific requirements, then choose the best configuration on spraying device.
It should be noted here that whether it is the air or paint tube, it is better to have a larger main pipe to ensure the paint or gas volume is sufficient.
