How to choose a nozzle for airless spraying?

 

When choosing an airless spray paint unit for painting walls and ceilings, the question often arises of how to choose a nozzle for an airless spray gun. Relying on the honesty of the manager and asking him to issue an invoice for a set of nozzles is not quite the right decision.

Usually in such cases, you can get either illiquid or stashed in stock nozzles, which are less likely to be taken. To avoid such troubles, it is advisable to understand a little about the types of nozzle sizes and understand, at least approximately, which nozzles are intended for what.

The paint is supplied to airless spray guns from a special high-pressure pump and sprayed through small-section nozzles. All major manufacturers of airless spray guns and nozzles for them, such as Wagner, Graco or Binks, have nozzles designated by a three-digit number.

For example, take a nozzle with the designation 317, the first digit in the number "3.." indicates the angle of spray paint of 30 degrees, at this angle, you can approximately calculate the width of the ink print, it will be about 15 cm, provided that you adhere to the recommended distance from the spray gun to the surface to be painted (30-35 cm).

The remaining two digits ".17" in the nozzle number indicate the passage section, the hole, the nozzle is 0.017" if you want to understand how much this hole will be in millimeters, then multiply by 25, it will turn out 0.43 mm. The actual paint consumption, the speed of its application, and the viscosity of the sprayed paint depend on the opening of the airless nozzle.

Do not be afraid of the fact that the nozzles are so small. This is normal, because when airless spraying, the device gives from 100-530 bar (depending on the model), so the device will "push" the paint through such a nozzle, in any case, the main thing is that it has enough liters. Let's take another nozzle, well, for example, 219. The first digit "2.." — the angle of the torch is 20 degrees, the width of the torch will give about 10 cm, when maintaining the distance from the spray gun to the painted part. ".19" — the flow section of the nozzle, 0.019" — in millimeters — 0.47 mm.

 Another option is nozzle 415. The first digit "4.." is the angle of the paint torch 40 degrees, the width of the paint print is 20 cm if you maintain the correct distance. ".15" — the opening of the airless nozzle, in millimeters — 0.37 mm So, provided that you maintain the same distance to the surface to be painted, when spraying, for example, GF 021 or PF 115 paint through the nozzle 317, you will get an average width torch at an average application speed. Such a torch can be painted or primed with not very large products, metal beams.

When using nozzle 219, the width of the torch will be narrower than through nozzle 317, the thickness of the application layer will be thicker, and the painter will have to work faster so that there are no drips. But the paint will clog the nozzle less often, and it will not be necessary to clean it often.

Through the 415 nozzle, the torch will be the widest among the above-described nozzles, and due to the small nozzle opening, the application speed is the lowest. This is fraught with more frequent clogging of the nozzle, but the quality of the application will be noticeably better and there will be fewer drips.

All of the above nozzles can be sprayed with GF 021 primer or PF 115 paint, but the speed of spraying, the quality of spraying, and the width of the torch will be different for everyone. Of course, you can take some kind of medium nozzle, and if the part is narrow, bring the spray gun closer to the product, and when painting wide products, take it away. But in this case, the paint may be overspent due to the colorful fog or the surface quality may suffer.

Ideally, you need to have a certain set of nozzles for each painting, so that you can always adjust in place to the paint that needs to be sprayed. Again, the same paint may differ in the viscosity of the jar from the jar. There can be many reasons: different shelf life of paint in different cans, different degrees of dilution (depends on you), or even the ambient temperature-all this affects the spray of paint through the nozzle. Therefore, it is better to have 3-4 different neighboring nozzles in order to quickly adjust in case of something, and not "play" with solvents, the pressure of the paint machine, or constant cleaning of the nozzle.

To find out what kind of spray angle you need, look carefully at your product. If these are narrow beams, take narrow nozzles "1..", "2..", "3..", if the product is a facade of a house, then a wider airless nozzle is needed— "4..", "5..", "6..". To understand which nozzle hole you need, look at the paint passport or call the technologist from the paint seller, he should give his recommendations on how to spray paint. If the technologist, for example, says that the spray nozzles should be from 0.021”-0.027”, like most flame-retardant paints, take the nozzles in the middle of this spread, 0.023”-0.025”, and then, if anything, adjust to the place. Well, again, rely on the previously selected spray angles you need If the passport for the paint indicates that it can be applied by airless spray, but does not specify which nozzle, then the following nozzles are used approximately:

0,007″ — 0,011″

- for painting wooden products with lacquers and stains, for applying liquid primers, for applying paints with a viscosity similar to water.

0,011″ — 0,013″

- for applying paints to windows and doors, for painting furniture facades, for painting with low-viscosity paint materials.

0,015″ — 0,017″

— for applying primers, oil paints, and paints when painting wagons, cranes, in the aircraft industry, when painting helicopters, when applying paints, for example, PF 115 or GF 021

0,019″ — 0,023″

— for applying facade paints, anti-corrosive coatings, zinc-filled compositions of the type (Cynol, Cynotan), liquid thermal insulation (such as Corundum, Atsratek), fire protection on wood or metal.

0,023″ — 0,031″

- for applying flame retardants for metal, for example, Cup 2, Phoenix, Preterm Steel, Nulifayer, Ograx, Unique, Joker, Krause, and the like. Also, waterproofing materials are applied with these nozzles, for example, Hyperdesmo

0,033″ — 0,067″

- for the application of viscous, pasty compositions, super-viscous or viscous flame retardants, waterproofing, sprayed by an airless method of putty. If you already have an airless spray nozzle, then before you buy another one, look at the three-digit number on the plastic nozzle flag.

It can be engraved or hung on a separate metal tag. Insert this nozzle into the spray gun and try to "dust" the paint. If the torch turns out to be clear, the width suits, there are no paint stains, then take the same nozzle. If you are not satisfied with the width, then take the nozzle either narrower or wider.

If there are smudges, then take a thinner nozzle. If your nozzle is constantly clogged, then take a nozzle with a larger hole. If the torch is streaking, then play with the pressure, look at the filter in the handle of the spray gun (it is most likely clogged there). After trying everything, play with the solvent. If it does not help, buy neighboring nozzles, with them, most likely, you will succeed.

And one last thing: If you still completely trust the seller of paint equipment and rely on his experience, be sure to tell him the name of the paint, what exactly you will paint, and your wishes when buying a spray gun. Then he will write out the nozzles you need, and not sell them with an abstract set

How to choose a compressor for a spray gun

If the characteristics of the spray gun determine the quality of painting a lot, then everything else depends on the compressor: whether the gun will receive the necessary amount of air with the right pressure and how long it will be able to work without stopping.

Receiver volume

The main task of this device is to equalize the outgoing airflow (the pump supplies it with shocks) and accumulate the necessary pressure. There is a directly proportional relationship here – the larger the volume of the receiver, the more stable the airflow and the longer the compressor engine will rest until the pressure drops. On the other hand, a large receiver will take longer to gain the right pressure.

For the use of spray guns at home, a receiver with a volume of 25-50 liters is quite suitable – this is the golden mean between compactness, performance, and frequency of inclusions during continuous operation – this volume is enough even for professional painters.

A larger volume of the receiver – 100-500 liters-may be needed only to ensure the operation of production lines.

If there are doubts about the correctness of the choice or you 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 it is necessary 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 an operating pressure of up to 6 bar.

At the same time, in the store, you can see two seemingly identical engines, but one shows the power of 1.3 kW, and the other shows all 1.8 or 2 kW. Of course, there is a temptation to think that a more powerful engine is better – it will pump air faster, just more reliable, and the seller is likely to say the same.

But here we must understand that theoretically, it is possible to increase the power of the engine due to the quality of the winding, but basically, the more powerful it is, the larger its size.

To check the veracity of the seller's words, it is enough to look at the pumps of these compressors – if they are the same size, it is almost 100% likely that this indicates the marketing delights of the manufacturer.

The fact is that the power has nothing to do with the speed of air injection – everything 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 corresponding increase in speed is required for a significant increase in the speed of air injection.

Even if the seller insists on the version about the supermodel of the engine, it must be remembered that a large number of revolutions is proportional to the rapid wear of the bearings and the piston group.