When processing car bodies and other surfaces that require high-quality coatings, conventional brushes, rollers, compact cans of paint are not used. A layer of material, the quality of which is comparable to the factory, can only be applied using an airbrush. In the presence of a pistol-type handle, this tool is also called a spray gun. To work effectively with a complex pneumatic tool, you need to adjust it. Competent adjustment of a pneumatic spray gun is the key to successful work of a painter.
Spray gun design
Most sprayers are pneumatic. Accordingly, a compressor is required for their operation. Air passes through a hole in the pistol grip, is regulated by a valve, bypasses several chambers and enters the annular head. The paint and varnish composition comes out of the tank if the trigger of the spray gun is pressed with a certain force. The first phase of pressing opens the way for air, the second for paint.
After leaving the head, the coloring composition is sprayed with an air stream to a mist consistency. Air from additional holes forms an elongated ellipse on the treated surface, resembling a torch. This technology allows you to quickly paint large areas. Painters who know how to set up a pneumatic spray gun can adjust the diameters of the ellipse, turning it into a circle if necessary. At the same time, they observe the quality of the coating, do not allow streaks and poorly treated areas.
Spray gun design elements:
- compressed air intake
- 3 regulators,
- paint container,
- removable spray head
- nozzle (nozzle).
Using a needle, determine the load of paint. The nozzle is used to transfer the material to the head for subsequent spraying.
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Modern spray guns usually have 3 adjustment devices:
- A valve for determining the area and geometry of the spray jet is located on top or on the side of the body.
- The regulator of its course is located coaxially to a needle.
- Closer to the fitting is a valve that makes it possible to regulate the air pressure.
For the effective functioning of the sprayer, it is necessary that the supply volume of the coloring composition and the air pressure are in harmony with each other. In this case, the paint is distributed evenly and in the right amount. As a result of spraying, a regular geometric figure is obtained — an ellipse or a circle, no eights and streaks.
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Spray gun setup: basic steps
To determine the air pressure in the fitting, the pressure gauge readings are needed. It is advisable to take them not from the device installed on the compressor. The best option is to connect a pressure gauge directly to the nozzle of the sprayer. Algorithm for further actions:
- Turn off the air regulator to the end.
- Unscrew the needle to the end. We bait a twisted lamb. We press the trigger to the end. We twist the regulator until it stops.
- We open the torch regulator to the full.
- We arrange the horns of the head horizontally. This is the standard position, giving a vertical flame.
- We prepare the paint and start testing.
This is the algorithm at the initial stage, before testing. In the process of checking the spraying of the material, adjustments have to be made. Read on how to properly set up a pneumatic spray gun, taking into account the main nuances of its operation.
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Regulating inlet pressure
Manufacturers in the documentation indicate the maximum number of atmospheres at the inlet to the air gun. The optimum pressure for painting should be lower, usually in the range of 3-4 atmospheres for conventional sprayers. If you want to adjust the spray gun of the hvlp or lvlp series, then set the pressure gauge to 1.5-2.5 atm. Approximately this pressure should be at the inlet to the sprayer, but it is often measured with an instrument that is several meters away.
This happens when there is a hose and filters between the pneumatic tool and the pressure gauge. In order for the spray gun to work for a long time and with high quality, it is necessary to ensure the supply of fresh air to the nozzle. To do this, it is filtered. One of the recommended air supply schemes includes a chain: pressure gauge — oil separator — adapter — hose — adapter — fitting.
In this case, the pressure will be lost at 4 intermediate points. The filter «eats» from 0.3-0.5 atmospheres, a 10-meter hose — about 0.6 atmospheres. The best setting option is when the pressure gauge is screwed directly to the spray gun. In this case, there are no intermediaries that take part of the pressure.
The pressure is checked as follows:
- Set the air valve to the maximum open position.
- Watch the readings of the pressure gauge by launching air into the atomizer by pressing the trigger. If the pressure is too high, tighten the regulator to the desired level.
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Set the size of the torch
To adjust the spray gun torch lvlp or hvlp, you need to turn the knob that is responsible for its geometry. Turns of the lamb change the amount of air passing through the holes located on the horns of the atomizer head. When the valve is fully open, the maximum amount of air flow is achieved, providing a torch in the form of a regular elongated oval. As the lamb is screwed on, the airflow decreases, the ellipse turns into a circle. With the regulator fully closed, we get a torch in the form of a round spot.
Turning the knob all the way out is a step towards maximum staining speed. However, with this approach, the edges of the torch may turn out to be dry, and a slight overrun of the material is possible. To avoid this, it is worth unscrewing the lamb completely, and then twist it back a little.
The second extreme is working with a twisted regulator and a round torch. This option is relevant if you need to paint a small detail. At the same time, together with a decrease in the torch, it is necessary to reduce the volume of sprayed material. If this is not done, there will be too high concentration of paint in a limited area, which will lead to streaks.
You can also adjust the angle of the torch by changing the position of the spray head. Standard option — the horns are set horizontally, the oval is vertical. With the vertical orientation of the horns, a horizontal ellipse is obtained. They paint less often, it is exposed when it is necessary to process narrow vertical details.
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We select the diameter of the nozzle
The speed of painting depends on the diameter of the spray gun nozzle. For thick paints and varnishes, a nozzle with a wide opening is installed and vice versa. If you need to set up a pneumatic spray gun for varnish or acrylic enamel, then the value recommended by the paintwork manufacturer is usually 1.4-1.5 mm. For the rest of the materials, something like this:
- local painting — 1.2 mm;
- base enamels — 1.3 mm for light formulations, 1.4 mm for dark ones;
- primary soils — about 1.3-1.5 mm;
- thick-layer primers-fillers with increased viscosity — 1.6-2 mm;
- putties of liquid consistency — 2.5-3 mm.
Not only the speed of painting depends on the diameter of the nozzle: the choice of nozzle is reflected in the consumption of material and the thickness of the layer.
When choosing a nozzle diameter, it is also worth considering the temperature and humidity at which staining will be performed. If you have to paint in the heat, you can try to take a nozzle with a diameter of 1 mm more. For wet weather, a nozzle with a smaller diameter is suitable, for dry weather — with a large one.
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Adjusting the ink supply
After adjusting the air supply and the torch, it remains to adjust the amount of incoming paint. To do this, we twist the lamb until it stops, after which we release the clamp a couple of turns. Do not immediately release the regulator to the full, as this can cause drips. In some cases, it is more rational to “add gas” gradually, observing the thickness of the film that forms on the surface of the part to be painted.
The position of the needle depends on the position of the ink supply regulator. When unscrewing the lamb, it moves away from the spray head. As the distance between the needle and the head increases, the amount of paint ejected from the spray gun when the trigger is pressed increases. Accordingly, the area of the torch increases. An example of the dependence of the torch width on the volume of material consumed by the tool:
Material consumption, ml/min
|Torch width, mm|
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How to test the spray gun setting?
For testing, we take a sheet of drawing paper, fix it in a vertical position, and proceed to check the spray gun. The distance to the sheet of paper should be about 15 cm for HVLP/LVLP paint guns and 20-25 cm for more powerful conventional machines. We open the paint supply for a maximum of a second, evaluate the shape of the spot. By adjusting the valves, we try to obtain a uniform layer of material of the correct geometry.
In the technical documentation for sprayers, it is usually recommended to open all the regulators to the end. If you start testing after such manipulations, you can get a dumbbell-shaped silhouette on the Whatman paper. In this case, reduce the pressure using the air regulator.
If you need to paint a small detail with a round torch, you need to screw on its regulator and reduce the pressure that has grown after screwing on the top lamb.
The setting gives a good result if two conditions are met: the coloring composition is of proper quality and consistency, the device does not belong to little-known Chinese brands. Setting up a budget spray gun for painting as expected is a task that is difficult for a beginner to handle. Even experienced craftsmen find it difficult to manage the no name technique. When buying a sprayer, it is better to focus on brands from Germany, Poland and other European countries.
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