Adjustment and repair of the paint gun at various faults

To achieve consistent atomization of different types of paint and varnish materials (paintwork), primers, liquid putties, protective compositions, and impregnations, painters utilize paint guns, also known as painting devices. These devices can vary not only in their design but also in their operational principles, which directly influence the quality of the coating being applied.

The device and the principle of operation of the paint sprayer

Electric and pneumatic paint sprayers with various tank configurations are commonly used in both domestic and professional settings. These devices may also feature a built-in or attached pressure gauge to the handle.

Electric paint sprayer

An electric paint sprayer is composed of a housing, either made of plastic or aluminum, that contains various components (depicted in the diagram below).

1. An electromagnet that operates in pulse mode and attracts the bar.
2. An oscillating bar that is attracted by the magnet and pushes the piston forward.
3. A paint supply regulator that limits the movement of the oscillating bar.
4. A nozzle that atomizes paint or other substances.
5. A cylinder that serves as the pump housing and allows the piston to move.
6. A valve that opens and closes the paint supply.
7. A suction tube for drawing in paint, which may have a filter at the end.
8. A piston spring that returns the piston (along with the bar) to its original position after forward movement.
9. A piston that sucks in and pushes out the paintwork through the atomizer.

On the unit, there is also a button to supply power and a connection for the tank.

The sprayer operates based on the following principle. When the trigger is pressed, the electromagnet (1) is activated with short bursts of energy. The electromagnet attracts and then releases the bar (2). The range of motion for the bar and, subsequently, the piston, is adjusted using the screw (3). The bar pushes against the piston rod (9), initiating its movement. The back-and-forth motion of the piston allows it to draw paint from the tank and propel it towards the valve (6). As the piston moves forward, the valve opens, allowing the paint to flow through the nozzle (4) and be atomized. When the piston moves in the opposite direction, prompted by the expanding spring (8), the valve closes, and the paint is suctioned out of the tank through the tube (7). This process is then repeated.

Attention! Electric paint sprayers additionally come with models featuring a separate compressor. When it comes to these models, the construction of the paint sprayer is slightly altered, while the functioning principle of the paint gun is comparable to that of a pneumatic paint sprayer.

Pneumatic paint sprayer

The device operates using compressed air supplied by the compressor. Here is a diagram (in cross-section) showing the device’s structure.

The pneumatic sprayer consists of several key components (as depicted in the diagram above).

1. Spray head with a nozzle. Both the nozzle in the spray gun and the air head are detachable parts. They can have different exit hole diameters, which are selected based on the viscosity of the composition being sprayed.
2. Paint tank. It can be made of plastic or metal and can be located either at the top or bottom of the tool.
3. The body of the paint sprayer. This serves as the foundation where all the elements of the device are mounted.
4. Locking screw. This adjusts the paint supply intensity by limiting or increasing the mobility of the locking needle. Some paint sprayer models also come equipped with an air regulator.
5. Handle. This is designed for comfortable grip and control of the tool.
6. Gasket. It functions as a seal in the mechanism that controls the movement of the needle.
7. Trigger. Activates the needle lock.
8. Needle lock. Controls the opening and closing of the nozzle orifice.

The operation of the pneumatic spray gun is as follows. When the trigger is lightly pressed, the air valve opens and air starts flowing through a separate channel into the air head. Applying more pressure on the lever causes the needle to retract, thus opening the nozzle and allowing paint to flow out. The paint mixes with the airflow in the air head, creating small particles and forming an aerosol spray.

To facilitate work with a paint sprayer, it is recommended to use a special wall holder.

The paint sprayer stand is extensively used by painters, and it can be easily crafted by themselves.

Nuances of the design of paint sprayers with a different type of tank

The previous section discussed the design of a paint sprayer with a top tank and how it operates. To clarify, the method of delivering paint to the tool’s body needs to be addressed. As the paint tank is positioned at the top of the device, it naturally flows down to the locking needle under the force of gravity.

In contrast, a paint sprayer with a lower tank has the tank positioned differently. In this case, paint is drawn into the sprayer through a vacuum created by the airflow inside the device. Once again, the operation of this sprayer is identical to the one with a top tank.

Moreover, there has been a recent emergence of vacuum containers in the paint spraying equipment market. These innovative cans are being effectively utilized as an alternative to traditional spray cans. The vacuum tank is a solid cylindrical container with a aperture at the base, wherein a flexible cup with a cover is inserted. The container is additionally labeled with a gauge, allowing for easy determination of the quantity of paint.

Vacuum tanks have the benefit of enabling the sprayer to operate in all orientations. Irrespective of whether the device is inverted or upright, the dye can still enter the gun thanks to the vacuum created within the flexible cup. The cup undergoes deformation, ensuring that the dye is fully expelled.

Adjusting the parameters of the spray gun before work

When examining the structure of a contemporary paint sprayer, it is possible to identify two or three adjustment screws. The initial regulator may be positioned either at the top or on the side of the device, as is evident in SATA sprayers (refer to the image below). This particular component plays a role in determining the shape and dimensions of the spray pattern.

The second screw provides the opportunity to modify the scope of needle motion, thus controlling the quantity of paint being sprayed into the nozzle. Certain paint sprayer variants are equipped with a third regulator, which enables adjusting the air supply to the tool.

The adjustment of the sprayer entails establishing an accurate material-to-air balance. By fine-tuning the optimal ratio, one can attain the desired shape of the aerosol spray, ensuring a uniform dispersion of the substance onto the treated surface.

Adjusting the inlet pressure of the atomizer

Important: The manufacturer specifies the inlet pressure parameter in the technical documentation of the device and it is standardized.

For optimal performance, it is recommended to set the inlet pressure using a regulator that has a built-in pressure gauge. This regulator should be connected to the sprayer handle. This is important because pressure losses in the water supply can be significant, reaching up to 1 bar or even more. The length and configuration of the supply duct can also affect pressure loss. Additionally, any filters, moisture separators, and oil separators installed can impact this parameter.

Tip! It is advisable, especially for beginners, to install the regulator as close as possible to the sprayer handle. This will enable precise adjustment of the device.

With regulator and pressure gauge

It’s a simple task to adjust the top tank sprayer when you have the regulator and pressure gauge installed:

• Begin by fully unscrewing the air supply adjusting screw (1) (refer to the diagram below);

• First, untwist the torch’s shape and size adjuster (2);
• Once the screws are untwisted, proceed to press the trigger (3), which will activate the air supply;
• Finally, adjust the pressure gauge (4) to the recommended value by rotating the pressure regulator.

With electronic pressure gauge

There are a few paint sprayers that can be considered "advanced" because they come with an electronic pressure gauge already integrated into their design.

It’s even simpler to adjust a sprayer with a built-in electronic pressure gauge (see figure below).

1. Fully open the torch control.
2. Squeeze the trigger.
3. Referencing the gauge, adjust the air regulator until the inlet pressure matches the recommended pressure level.

With pressure gauge without regulator

To properly set the sprayer, check if the handle has a pressure gauge and lacks a regulator. Follow the steps shown in the figure below.

1. Set the air regulator to its highest setting.
2. Adjust the flare regulator to its maximum level.
3. Afterward, depress the trigger to deliver air to the gun.
4. Manage the pressure by utilizing the pressure reducer or filter group attached to the compressor outlet and monitor the pressure gauge.

Without pressure gauge

If your sprayer doesn’t have a pressure gauge, you can still roughly adjust it by using the compressor reducer and considering the pressure losses in the line.

Tip! When adjusting the device, keep in mind that a filter, if it’s in good condition and not clogged, can reduce the pressure by 0.3-0.5 atm, not to mention a clogged element. Additionally, about 0.6 atm is "lost" in the air hose if it has an internal diameter of 9 mm and a length of 10 meters.

To adjust the spray gun for painting without a measuring device, you can use the following method (refer to the figure below).

1. Turn on the air supply for the paint sprayer.
2. Adjust the regulator responsible for the torch width.
3. Activate the trigger to release the air supply.
4. Utilize the reducer at the outlet of the compressor to set the pressure, accounting for pressure loss in the pipelines. Specifically, ensure that the pressure gauge reads 0.6 bar higher than the recommended pressure when using a 10 m long hose with a 9 mm internal diameter. For a more precise calculation, consider the presence of filters between the sprayer and the compressor.

If the sprayer is from an unknown manufacturer

In some situations, it may happen that there are no instructions available for a particular device or it is not possible to determine the manufacturer in order to find out the required pressure for the sprayer. Determining the input pressure for such an unknown tool can only be done through experience.

1. The first step is to select a standard viscosity paint and pour it into the tank.
2. Next, you will need to unscrew all the regulators on the tool and use the adjustment screw on the pressure gauge to "experiment" with the pressure. The goal is to achieve a value at which a uniform imprint of the spray pattern appears on the painted surface. The tool should be held at a distance of 15 cm from the surface that has been prepared for testing.
3. Once you have achieved the desired outcome, set the inlet pressure to a fixed value. This will serve as the operating pressure for the device.

Important! It is important to note that lower-end, lesser-known paint sprayers typically require a higher air consumption rate, exceeding 200 liters per minute. As a result, not all compressors are capable of supplying such tools with the required amount of compressed air, which can have an impact on the quality of the painting results.

Size of the spraying torch

The efficiency of coating with a paint sprayer greatly relies on the condition of the nozzle, and this is no secret. The size of the nozzle plays a significant role in ensuring an even application of the coating with minimal passes. When dealing with small parts or hard-to-reach areas, a smaller nozzle size may be required.

Adjusting the size of the nozzle is a simple task. By turning the screw towards the "+" sign, the width of the nozzle increases. Conversely, moving the knob towards the "-" sign reduces the atomization area.

Hint! Typically, you want the adjustment screw to be fully open in most situations.

Paint supply

When it comes to regular repairs, applying coatings, and body painting, it is advisable to open the material regulator all the way. Typically, this would entail making 3-4 complete turns of the adjusting screw. Additionally, it is important to fully retract the nozzle after pulling the trigger.

Nozzle size

The size of the nozzle is crucial when it comes to configuring the paint sprayer. It is chosen based on the thickness of the substance that is going to be sprayed. The following table can be utilized to easily identify the appropriate nozzle size for various coatings.

The main faults of the spray gun

Although the paint sprayer has a straightforward structure, it is still susceptible to malfunctions. You can easily count the number of common breakdowns that the paint gun frequently experiences.

The gun does not paint

This occurs in the following scenarios.

1. When the air pressure in the system drops to a critically low level, the issue arises. To resolve the problem, it is necessary to make adjustments to the compressor.
2. Another situation that can lead to this problem is when the paint supply is interrupted due to blockage of the needle and nozzle. In such cases, the sprayer needs to be taken apart and the aforementioned components cleaned.
3. If the needle or nozzle is found to be damaged, it will be necessary to replace these parts to rectify the issue.

Sprayer spits

The issue of spitting paint when using a paint sprayer can be attributed to several possible faults.

1. One possible cause is that the air head of the sprayer may not be tightened properly. It is important to ensure that this part is securely tightened.
2. Another potential issue could be that the viscosity of the paint does not match the air pressure. It is crucial to achieve a suitable pressure-viscosity ratio for optimal performance.
3. If the paint being used is too thick, it may result in spitting. In such cases, it is necessary to prepare a paint mixture with a less thick consistency.
4. A clogged breather plug on the paint tank can also lead to spitting. To resolve this, the plug should be removed and the hole in it thoroughly cleaned.
5. Lastly, if the pressure in the receiver falls below the required level, it can cause the paint sprayer to spit. To rectify this, adjust the compressor settings to ensure that the lower pressure threshold matches the operating characteristics of the spray gun.

The torch is moving to the side

If the atomized paint torch moves away from the gun, there are several possible causes:

1. The side openings of the air head may be clogged. In this case, the air head should be removed and cleaned thoroughly.
2. It is also possible that the side ports of the air head have been damaged. If this is the case, the damaged part will need to be replaced.

Flare spot misalignment

There are several possible causes for this issue:

1. The problem may be due to a clogged nozzle. To fix the paint sprayer, you need to remove the nozzle and clean the hole.
2. Another possibility is that the nozzle itself is damaged and needs to be replaced.
3. The air head, specifically the center hole, could also be clogged. In this case, you should remove the air head, rinse it, and clean out any blockages.
4. If the center hole of the air head is damaged, you will need to replace this part.