The Principle, Selection and Adjustment of Automatic Spray Gun

1. The principle of auto spray gun

There is a pneumatic piston mechanism inside the auto spray gun. A stainless steel spray needle is installed above the piston, and a set of high tension springs are installed behind the piston. When the compressed air stops supplying, the spring will push the piston and the spray needle forward. At the same time, the spray needle and the nozzle are closely matched with high precision to block the passage of the liquid. On the contrary, when the compressed air starts to supply, the pressure of the compressed air pushes the piston away, so that a gap is formed between the spray needle and the nozzle for the liquid to be ejected. The sprayed liquid immediately contacts with the air for atomization to produce atomization effect.

2. The selection of auto spray gun

The choice of spray gun should be noted that the primer mainly plays the role of filling in the coating and increasing the thickness of the coating, so the particle size of the primer is larger, the viscosity is larger, and the specific gravity is larger. The spray gun for primer should have a large diameter nozzle, and the paint storage tank below should be larger.

For spraying the topcoat, the requirements for the degree of atomization are high, and the spray gun with a small diameter and good atomization is often used. The nozzles of the commonly used spray guns have different diameters, such as 0.6mm, 0.8mm, 1.0mm, 1.2mm, 1.3mm, 1.5mm, 1.6mm, 1.8mm, 2.0mm, 2.2mm, 2.5mm and other models.

It can be selected according to the paint to be sprayed and the size of the object to be sprayed. For example: the diameter of 2.0-2.5mm is often used to spray primers with coarse particle size and high viscosity or large-area spraying; the diameter of 1.0mm-1.8mm is mainly used for spraying. To spray topcoat; diameter 0.6-1.3mm, mainly used for spraying small parts or handicrafts.

3. Adjustment of auto spray gun

The adjustment of the auto spray gun mainly refers to the adjustment of the air volume and the air output. These are two major interrelated factors. If the air output is too small, it is not easy to atomize the paint liquid, so that the paint liquid spills in a drop shape, which will make the application uneven. The size of the paint output corresponds to the size of the air output. Before spraying, it is necessary to adjust the appropriate air output and the corresponding paint output, so that the paint liquid is well atomized and sprayed evenly on the surface.

To adjust the auto spray gun, you need to listen first (listen to the sound of the air flow to know the size of the air flow), and secondly look at it (see the degree of atomization of the paint liquid at the nozzle of the spray gun and the size of the fan-shaped area).

Several important parameters of the auto spray gun are as follows:

1. Air pressure: The air pressure for spraying is generally (0.4Mpa-0.6Mpa);

2. Spray width: the width of spraying on the working surface is about 10cm;

3. Spraying distance: When spraying, the distance between the gun nozzle and the object to be sprayed is 15cm-20cm;

4. Moving speed: The moving speed of the spray gun is generally 30cm-60cm/s;

5. Overlap range: the overlap range of each gun during spraying is 1/2-1/3 (except for crack paint);

6. Spraying angle: The angle between the gun nozzle and the sprayed object is generally 90°.