How to choose a spray gun - pneumatic or electric
Despite the apparent simplicity of the device, it is quite difficult to decide how to choose a spray gun. Not so long ago, this task was a little easier, because only pneumatic devices were present on the market, but now electric ones have also been added - with their advantages and disadvantages. To make the right choice between them, you need to know their device, operating principle, scope and clearly imagine for what purposes they will be purchased.
Content:
- The device and principle of operation of a pneumatic spray gun
- The choice of a pneumatic spray gun
- How to choose a compressor for a spray gun
- Electric spray guns - how to determine the type of device
- What parameters of electric spray guns should be considered when choosing
- In which case is it worth buying a pneumatic, and in which electric spray gun
The device and principle of operation of a pneumatic spray gun
The very name of this type of spray guns involves the use of compressed air during their operation, therefore, the compressor (mainly with an electric motor) with a receiver will necessarily be present in the design of the entire device. The spray gun itself is a spray nozzle in the form of a gun, on top or bottom of which a paint tank is attached. The receiver and spray are connected by a rubber flexible hose, through which air is supplied under pressure. Also, paint is supplied to the spray gun, which is broken by a stream of compressed air into the smallest particles and blown by it from the nozzle of the gun. Its shape is made in such a way that the flow of air and paint is not direct, but forms a so-called torch, diverging at a certain angle to the sides.
1. Trigger.
2. Paint feed channels.
3. Nozzle.
4. Air ducts.
5. Air head.
6. Tank.
7. Hook for hanging.
8. Torch size adjuster.
9. Paint control knob.
10. Air regulator.
11. Lever.
12. Hose fitting.
For such a device to work without failures, its components must be made of high-quality materials and precisely matched to each other. All this affects the final price, so pneumatic spray guns are mostly used by professionals.
The choice of a pneumatic spray gun
There is a lot of debate about what to choose first of all - a spray gun or a compressor. You can give different arguments, but it will be most correct, depending on the planned types of work, to choose a spray gun, and already select the suitable compressor for it.
Paint spray technology supported by spray gun
The spray gun can be equipped with one of three paint application technologies that differ in working pressure and the amount of air required for this to be supplied by the compressor. The technology used is directly displayed in the abbreviations of the names of spray guns - HP, HVLP, LVLP. Each of them in its own way copes with the main drawback of pneumatic spray guns - the formation of "colorful fog". It appears due to too strong grinding of paint particles, which become very light, and along the way from the nozzle of the gun to the surface to be painted, they are simply braked by air and remain in it in the form of a suspension.
1 HP (High Pressure) - high pressure.
This technology is used in devices of a low price range. She has a lot of drawbacks, due to which she is used less and less and is gradually fading into the background, but with a limited budget, such spray guns are still in demand.The main advantage of such devices is the quick painting of surfaces due to the large air flow, but their disadvantages are also associated with it:
- A high percentage of paint that does not fall onto the surface to be painted is about 50-55%, and this is a significant overspending of paints and varnishes, plus high air pollution. We often have to buy paint and change respirators with protective suits - a mandatory attribute in such works.
- High air pressure requires the skills to use such equipment - if you bring the nozzle of the gun too close to the surface to be painted, then the air flow will simply inflate the paint that has already been applied, but has not yet hardened.
- Although the spray gun, using HP technology, has a budget cost, the need for high pressure and high air flow require a sufficiently powerful compressor.
If you do not pay attention to the issue of economy, then high-pressure spray guns are inexpensive and versatile devices that can be used in the vast majority of types of paintwork.
2 HVLP (High Volume - Low Pressure) - large air volume, low pressure.
The nozzle of the gun of such a spray gun is designed in such a way as to lower the high pressure from the compressor at the outlet. Accordingly, the paint, although it flies out at a lower speed, but in a larger quantity per unit of time.
Since the air flow is lower, this allows you to keep the gun closer to the surface to be painted, which gets more paint, due to which the loss of paint materials is reduced - the transfer coefficient can be over 65%.
Such devices are noticeably more expensive than high-pressure spray guns, but saving paint over 15% allows them to quickly pay for themselves.
3 LVLP (Low Volume - Low Pressure) - low air volume, low pressure.
Premium devices, with a transfer coefficient of paintwork materials up to 80%. This technology does not require the presence of a high-pressure air inlet at the gun; accordingly, a powerful compressor is also not needed - enough to produce about 200 liters per minute.
It would seem that with a lower air pressure, the speed of operation should drop, but this does not happen due to the higher transfer coefficient. The quality of painting under these conditions only increases, since less control is required on the distance from the gun to the surface to be painted.
Although LVLP spray guns are the most expensive, they are indispensable devices when working with premium coatings. Even if the paint savings increase by only 5-10% compared with HVLP, with regular use, the purchase will quickly pay off.
The diameter of the nozzle of a pneumatic spray gun
Depending on the density of the paint, its viscosity and grain size, nozzles with an outlet diameter from 0.8 to 7 mm can be used. Also, this size depends on the size of the part to be painted - for example, in the ship repair area or in car building, the ability of the airbrush to apply paint in a single pass over a large area comes to the fore.
Many manufacturers make spray guns with replaceable nozzles, but completely monolithic tips for one size are not uncommon - the same professional devices for painting ships are unlikely to need additional nozzles for nozzles.
The nozzle diameter of professional devices is selected depending on the colors with which you most often have to work, and the size of the painted parts. For domestic needs, nozzles with nozzles with a diameter of about 1.5 mm are most often needed - they are suitable for the vast majority of varieties of paints and varnishes, representing a reasonable compromise between speed and quality of painting.
As a result, if a set of additional nozzles does not particularly affect the price, then refusing to expand the functionality is stupid, otherwise you should already estimate how much they will be in demand.
Paint tank
A mandatory detail of the entire structure, which can not always be remembered when choosing a spray gun, although the convenience of work depends on the material from which it is made or the location:
1 Plastic or metal.
Here it is necessary to take into account such nuances as the weight of the tank and its transparency. The first one determines how much faster the hand will get tired during long-term work, and the second one controls the level of remaining paint. According to these indicators, plastic containers are unambiguously leading and sellers note that they account for a larger percentage of sales.
However, metal also has its own buyer - sometimes the strength requirements outweigh the rest.
2 Top or bottom location.
When the tank is on top, the paint is fed into the gun by gravity, and at the lower location it is absorbed due to the air supplied from the compressor. Placing the tank on top or bottom does not give any improvement in the quality of painting, so only the usability will affect the choice between them.
When the container is fixed on top, the spray gun will have a slightly better weight distribution, but during breaks in work you will have to think where to put it.
When the tank is located below, it forms its own stand, plus, if you often paint the walls near the ceiling, or a surface with a similar configuration, then the airbrush can be raised higher.
Availability of adjustments
Each manufacturer can equip spray guns with various adjustments, the presence and quantity of which are not regulated by anything.
It is mandatory to set the needle stroke control, which determines the amount of paint supplied. Limiters of the amount of air supplied, settings for the shape and size of the paint torch, as well as additional adjustments that can affect the painting process in different ways, depending on the materials used, can also be set.
How to choose a compressor for a spray gun
If the characteristics of the spray gun determine the quality of the paint in a lot, then everything else depends on the compressor: whether the gun will receive the required amount of air with the right pressure and how long it can work without stopping.
Receiver volume
The main task of this device is to equalize the outgoing air flow (the pump delivers it with jerks) and accumulate the necessary pressure. There is a directly proportional relationship - the larger the receiver volume, the more stable the air flow and the longer the compressor engine will rest until the pressure drops. On the other hand, a large receiver will gain the desired pressure longer.
A receiver with a volume of 25-50 liters is quite suitable for using spray guns at home - this is the golden mean between compactness, performance and the frequency of switching on during continuous operation - this amount will be enough even for professional painters.
A larger receiver volume - 100-500 liters - may be needed only to ensure the operation of production lines.
If you have doubts about the correct choice or just need a reserve for the future, then you should pay attention to the presence of a connector for connecting an additional receiver - they are often installed in case of need to increase the working volume.
Engine power
The vast majority of budget and semi-professional compressors are equipped with electric motors with a capacity of about 1.3 kW - with a receiver volume of up to 50 liters this is more than enough to maintain a working pressure of up to 6 bar. At the same time, in the store you can see two identical engines, but on one the power is 1.3 kW, and on the other all 1.8 or 2 kW. Of course, it is tempting to think that a more powerful engine is better - it pumps air faster, just more reliable, and the seller is likely to say the same thing. But here it must be understood that theoretically it is possible, due to the quality of the winding, to increase the engine power, but basically, the more powerful it is, the larger its size.
To check the veracity of the seller’s words, just look at the pumps of these compressors - if they are the same size, with almost 100% probability this indicates the marketing delights of the manufacturer. The fact is that power has nothing to do with the speed of air injection - it all depends solely on the size of the piston and the number of revolutions of the engine shaft per minute. If the pumps (pistons) are the same, then a significant increase in speed is required to significantly increase the speed of air injection. Even if the seller insists on a version about the super engine model, it must be remembered that a large number of revolutions is proportionally to the rapid wear of the bearings and piston group.
In an extreme case, a full-scale experiment will put all the points on the “i” - you just need to bleed the air from the receivers, detect the time of their filling, and then decide whether the overpayment of the promised benefits is worth it.
Air pressure
A pressure switch is installed on each receiver, at which the necessary values are set at which the engine turns on and off. In compressors used for paint work, most often the lower bar is 6 bar, and the upper bar is 8. This means that when the receiver is less than 6 bar, the engine turns on and pumps air until the pressure rises to 8 bar. The need for more pressure arises only when using compressors in production.
Performance
As in the case of engine power, there were some marketing frills here, so you need to pay special attention to this parameter. The fact is that there are two types of compressor performance - the amount of air that it pumps into the receiver from the environment and the volume blown out by the gun.
Manufacturers, not crooked, indicate in the characteristics the amount of air that the pump drives through itself, silent about the inevitable loss in compression, which reaches 35%. Accordingly, in order to get a real figure, you need to multiply the passport by 65% (* 0.65). Those. if the characteristics of the compressor indicate the capacity of 200 liters per minute, then the spray gun from them will receive 200 * 0.65 = 130 l / min. You also need to consider a certain margin, to which manufacturers of spray guns recommend allocating about 15%. For example, a spray gun needs 200 l / min, then the calculations will look like this: (200: 0.65) + 15% ≈ 307.7 + 46.15 ≈ 355 l / min.
If you take a compressor with lower performance, either the gun does not have enough pressure and you have to make long pauses in the work to pump air, or the engine will work almost without interruptions, which will accelerate its wear without the right to warranty repair.
As a result, compressor performance is one of the most important characteristics and it must be selected with a margin, taking into account, besides the operation of the spray gun itself, the possibility of connecting additional equipment.
Additional compressor components
Some of the additional functions must be present without fail, and the availability of others depends on the manufacturer. The first include a safety valve that will bleed off excess air when the pressure switch fails, and a circuit breaker that will turn off the engine when it is overloaded.
Additionally, the compressor can be equipped with a pressure regulator, pressure gauge and air filters. Since the mass of the engine with the receiver is large enough, you need to look at the presence of wheels and overall ergonomics - how convenient it will be to move the compressor from place to place.
As a result, the choice of compressor comes down to a number of simple calculations, but you need to perform them correctly - otherwise you can get a device that does not meet expectations.
Electric spray guns - how to determine the type of device
The types of electric spray guns are quite different from each other according to the principle of action and the form factor, therefore, you can decide which spray gun to choose only if the front of work for which it will be used is known exactly.
Airless electric spray guns
Structurally, an electric airless spray gun consists of a nozzle, a valve, a cylinder, an electromagnet, an oscillating bar and a piston. The principle of operation is as follows: an oscillating bar pushes the piston forward, and it returns back under the influence of a spring, when the piston moves backward, a rarefied space is formed in front of it, where the paint is sucked in, and when moving forward, the paint is pushed out through the nozzle. Since a large number of oscillations and strokes of the piston occur per second, a continuous supply of paint is created.
1. Suction tube.
2. Valve.
3. Nozzle.
4. Cylinder.
5. Electromagnet.
6. Oscillating level.
7. Adjusting screw.
8. Piston.
9. Piston spring
When using this technology, it is impossible to get sufficiently small droplets of paint - even the budget pneumatic airbrush wins by a large margin in this parameter. The advantages of an airless spray gun in its overall compactness, unpretentiousness and relatively low cost, which makes it a good helper in everyday conditions.
The principle of operation of an airless spray gun allows you to get a torch of the correct form with clear outlines and use even high-viscosity paints and varnishes for work.
The characteristics of airless devices determine their scope: for any work in the home and when it is impossible or impractical to use pneumatic spray guns, for example, when applying viscous compositions.
Aerial electric spray guns
Such devices are difficult to unambiguously attribute to pneumatic or electric - rather, it is a hybrid that has taken all the best sides from both varieties of spray guns. This is a standard design that works on the principle of pumping pressure into a container of paint, which then passes through the tube and is sprayed through the nozzle of the gun.
From a pneumatic spray gun, here is taken the method of applying paints and varnishes, which are broken by a stream of air and applied as thin as possible. However, there is a mini compressor precisely designed for the gun. A big plus of such devices is the possibility of using one spray gun in turn for different types of paints and varnishes.
The disadvantages of airborne electric spray guns are the same as pneumatic ones - the appearance of colorful fog during operation, with corresponding limitations.
Such devices are divided into spray guns with built-in compressor and remote. Spray guns with an integrated compressor have a small size and low price, but are suitable for performing only those jobs where high quality coating is not required.
Devices with an external compressor are more expensive, but they are more convenient in operation, since the supercharger is located separately and is connected to the gun through a hose. Such devices provide a fairly uniform flow of paint and have a number of adjustments, which allows to achieve good hiding power and quality of painting.
Painting stations
In fact, these are the same manual spray guns, divided into a gun and a paint pump, but large and with characteristics close to professional tools. They are equipped with a powerful electric motor and pump, which are mounted on a separate mobile platform, and painted with a separate spray gun connected to the pump with a high pressure hose. Paint is supplied from the supplied tank or directly from the bucket into which the hose is inserted.
1. Paint supply hose.
2. Piston pump.
3. Airbrush.
4. Lever.
5. Housing with electric motor.
6. Paint suction hose.
7. Drain hose.
8. Pressure adjustment.
9. Legs.
10. Paint intake.
Such a spray gun has a large number of different adjustments, which allows you to configure it to work with any type of paint and apply it on an industrial scale and in various areas of production.
What parameters of electric spray guns should be considered when choosing
Depending on the varieties of the planned work, it is necessary to select the following characteristics of electric spray guns:
Performance
This parameter determines the speed of the entire device - budget models give out about 0.5 l / min, middle-class spray guns - from 0.8 to 1 l / min, and floor painting stations can spend more than 2 l / min.
Type of paint used
Depends on the type of pump that supplies the paintwork. Most electric spray guns are universal, but there are some of them that are designed to work only with water-soluble compounds.
Tank capacity
Since in most manual models the tank is mounted on the gun and during operation it is necessary to keep it on weight, it is seldom when a paint container with a volume of more than 1, maximum 1.5 liters is used. There may not be a tank in the floor painting station - instead there is a place for installing a bucket of paint.
Tank material
Usually it is metal or plastic - most often buyers prefer the second option, since such a tank is lighter and the level of remaining paint is visible through its walls.
Nozzle size
Since the electric spray gun is suitable for work with a large number of coatings, for their various varieties you need a nozzle of your own diameter. For standard enamels, the maximum nozzle size should be selected no more than 1.3 mm, for acrylic compositions - up to 1.6 mm, and a nozzle with a diameter of up to 2.8 mm is suitable for primers.
Gun extension
It helps to paint ceilings and other inaccessible places, which otherwise would have to be reached by stairs.
Hose length
It determines how much you can move away from the compressor, if it is a spray gun with separate blocks or a whole painting station. When purchasing a long hose, you must consider how far the paint can push the pump with the engine.
Availability of adjustments
Manual models often cost the most necessary minimum - setting the amount of paint supplied and the shape of the torch. Models with a remote compressor are closer to professional ones in terms of characteristics: several spraying modes, adjusting the paint pressure at the outlet of the gun, the ability to change the piston speed — they clearly benefit from the number of adjustable parameters.
Housing and accessories material
Although an electric spray gun is a rather complicated device, it is very difficult to find spare parts for it - especially for budget models - therefore, in case of a serious breakdown, it is easier to replace than to repair. When buying, you should once again make sure that it is made of normal plastic, all parts are fitted to each other and there’s nothing to play.
Vibration
The “buzzing gun” during operation can vibrate quite strongly, because of which the hand will get tired faster and the quality of the paint will deteriorate. You can check the vibration level only by comparing the operation of several devices. In parallel, the overall ergonomics and weight distribution of the spray gun will be checked.
In which case is it worth buying a pneumatic, and in which electric spray gun
The main points by which a choice will be made between an electric and a pneumatic spray gun:
Fire safety.
In closed rooms of the paint shop or directly in the paint booth, the use of electrical equipment is prohibited.
Colorful fog.
Here, electrical devices are ahead, but due to the worst quality of painting. If you need an excellent staining result, you will have to put up with colorful fog from a pneumatic spray gun.
Application of viscous paint.
The principle of operation of the electric spray gun allows it to work with most types of paints and varnishes, including those that have a high viscosity. Moreover, often nozzles with a diameter of 1.5 mm or higher are installed on them, which are poorly suited for working with liquid compositions - such paints will flow and be applied unevenly.
Replaceable nozzles and nozzles.
Most often, household electric spray guns have a single nozzle that cannot be replaced. This means that a particular spray gun will work with paints whose viscosity is in a certain range. You will always have to bring the paintwork materials to a certain consistency, otherwise some of them will leak, and others will clog the nozzle.
The quality of painting.
The pneumatic spray gun breaks the paint into as small particles as possible, which allows it to be applied in a thin layer even on surfaces of complex shape. In this regard, electrical devices lose a lot - the paint is not completely broken in them, so the applied layer is much thicker.
Based on the listed properties, it is clear that it is quite difficult to compare pneumatic and electric spray guns - each of them will be good in its place. For home use, where there are no strict requirements for the thickness of the paint layer and other parameters, more compact and versatile electrical devices are better.
For production it is already necessary to choose a pneumatic type spray gun with its high quality of painting. The “division of labor” is also often used, using an electric floor painting station for applying primers, and a pneumatic spray gun for final painting.
