Different spray guns meet its distinctive CFM. Hence, you need to know what CFM is required for spray painting before getting your hands on the project so you will have a better insight on the matter at hand..
In this writing, you will see how CFM fundamentally matters the factor in selecting a compressor that would be the air consumption of the sprayer.
CFM – Definition and its Role
Before going into the details, you should get to know some air compressor basics for good measure.
CFM stands for Cubic Feet per Minute, or air delivered referred to as airflow. Different spraying tools you use require different CFM.
Basically, it indicates how fast it can compress air to catch up with the sprayer. Atmospheric pressure is responsible for the air movement in the cylinder. Thus, CFM varies with the atm pressure.
This is the reason why you have to ensure your gun’s specs of CFM meet the air compressor CFM output in line.
The HPLV spray gun manufacturer recommends a 3-5 HP compressor. If you are looking for a new compressor, the measurement you should pay attention to is the CFM.
You can purchase a small compressor from $100 all the way to a rotary screw which starts at $4000. For a small garage workshop, you need the best compressor with CFM per dollar for the least amount of money.
You can purchase a small compressor from $100 all the way to a rotary screw which starts at $4000. For small garage workshop, you need the best compressor with CFM per dollar for the less amount of money.
- HVLP: High Volume Low Pressure
- LVLP: Low Volume Low Pressure
- PSI: Pound-force per Square Inch
- ATM: atmosphere
- HP: hose power
How Does a Spray Gun Work?
To understand further into the technique and why CFM matters, you need to look through the way a spray gun works.
Let’s go with the LVLP spray gun which stands for Low Volume Low Pressure gun to walk you through.
The gun is gravity-fed because the paint cut sits above the nozzle. This type of gun is a favorite nowadays because there is less overspray.
It benefits in being environmentally friendly, spitting less pain to the air, and blowing more paint on your projects.
On the spray gun, you have several knobs to care about. One of them is the horn. It controls whether not the stream of paint that comes out in vertical or horizontal.
The way it works:
Spray gun operates on atomization.
The fluid that comes out of the nozzle and the air that comes up through the tool will meet to create a perfect mist of paint onto the surface.
To create the storm of paint coming out with the air smoothly, you need to care about the amount of paint and CFM distributed through the air supply.
The compressor size is a vital matter and you should purchase a fairly big compressor so there will be a way for the air to circulate and let your spray gun function properly. Before you buy a spray gun, make sure that the gun’s CFM requirement is in line with your compressor.
The Affection of CFM in Spray Paint
Painting using air pressure paint sprayers relies on the right pressure. CFM is vital to your gun’s requirement.
Inappropriate pressure will affect your performance on the coat.
Setting the pressure lower than the tool’s requirement results in the poor atomization and separation of paint particles. The flaw also comes from the excessive amount of film build spraying out in large quantities.
Too much liquid on the project takes longer to dry and causes loss of gloss. If you painted on a wall, it might leave textures.
Adjusting your gun to the extremely high pressure isn’t a good idea either. High levels of pressure results in the uneven concentration of particles on the surface. The pattern then can be split where it is heavier on the edges and lighter in the center.
If you fix the problem by streaking the spraying time, you are wasting the material and failing the durability of the paint itself.
What CFM is Required for Spray Painting?
Since the gun is in cooperation with the CFM and the size of the compressor, you need to identify your project at the beginning.
What I mean is you should make sure that the compressor can supply the amount of air and the pressure indicated on your tools.
Now, let’s say you’re planning on repainting your car and giving it a brand new astounding look. So, how many CFM do you need to paint a car?
The gun you need should have a low CFM but is still able to do the professional work. As mentioned above, the higher the CFM, the more dollars you will spend. So, low CFM, less money.
Consider the spray guns in range of 3 CFM at 22 PSI; you can find one with under $100 which suffices your air compressor for spray painting cars.
Big projects, like painting a whole house, on the other hands, demand larger CFM and other specs. In this case, look for a rotator rated for 6.5 CFM at 90 PSI. You’ll need a gun with a specified nozzle that sprays in a wider range.
What Air Compressor do I Need for Spray Painting?
A Campbell Hausfeld air compressor would ease your job with abundant ranges of the machine with different CFM. A budget horizontal air compress at the suggested numbers costs under $500 which fits the bill nicely.
Powermate minimum size air compressor offers the tank of 24 gallons in vertical shape is also an excellent choice for painting huge objects. It has two models; one has 6 CFM at 40 PSI, the other has 4 CFM at 90 PSI. Both fit the workshop, but you need to ensure you’ll get the right spray gun.
For garage projects, as suggested, both Campbell Hausfeld and Powermate offer suitable air compressor machines with handsome price tags.
Nonetheless, there is one more thing:
Let’s say you’ve got a gun that works with the specs of the air compressor whose tank is a pancake; it isn’t enough to reserve air the gun needs.
The air you need is compressed in the tank, so, imagine after a couple of sprays, you have no air left so the next thing you should do is to stop the work and pump more air into the compressor leaving the unfinished project a flaw when you come back.
Make sure you have an efficient air tank for your project. Painting a car means you keep pulling the gun’s trigger wide open for long periods of time with little rest.
Of course, you can keep your compressor running concurrently with spraying if the tank empties so often. However, the compressor will get hot and lose its efficiency so in order for it to perform in top shape you should give it some time to to cool down, a good resting time the compressor will be ready to work right away. Therefore, what you have left in the tank is hot air and moisture into your material.
You don’t want that. So, the advice is:
Do some calculations with the average corresponding to your favorite air tools’ CFM.
An occasional painter can go for a lower CFM paint gun if the large high-output compressor is unaffordable. Otherwise, get the best oversized compressor you can pay to extract the most effective performance.
What is the Correct Pressure For Spray Painting?
The best pressure for spray painting (PSI) depends on the projects you’re working on the gun you have. For a clear coat, it is recommended to spray at 26-29 PSI.
The way you test it here:
Attach the dial to the gun and start pulling the trigger. It is the dropping number the needle points your needed PSI.
Typically, the configuration differs in each spray gun. Some pros can tell how much pressure is coming out by hearing the sound or checking the spray pattern.
Air Pressure Setting on LVLP Spray Guns (Low Volume Low Pressure)
Most people suggest you should set your gun at 10-15 PSI when spraying base coat. These guns use 5-7 SCFM (standard CFM) with the volume of air at 40 PSI. With the LVLP guns, you can set about 17 PSI for base coats, 20-25 for clear coats.
Air Pressure Setting on HVLP Spray Guns (High Volume High Pressure)
You’ll want to use 26-29 PSI for the base coat. For a clear coat, how you set it up is to put up the number to 2-3 PSI for more atomization and a better stream of mist. In particular, setting the air pressure at 28-29 PSI will ensure a flawless flow out.
For newbies, air pressure setting on spray guns can be done by adjusting and valve accordingly to how many pounds the manufacturer suggests.
But here is how it confuses people:
The manufacturer says you should set 10 pounds of pressure while the recommendation tells you to set it to 27 to 29 PSI and this is because they use a particular way to test it inside the cup called cat pressure which is a completely different measurement so there will be slight change when you using but it will be fine since it won’t affect the overall performance much.
So, all in all, depending on how thin and thick you want the layer to be, you can set it up the way I showed you. It should be around 25 to 29 PSI for the perfect condition to work its best. In that range, you can use 26 to 27 for a base coat, 28 to 29 for a clear coat.
If you’re doing single stage enamel, you can lower the PSI down to get more paint on it.
What Size Tips to Use on a Spray Gun?
We will talk about spraying base coats and clear coats. Obviously, larger tips have greater air demand.
But I recommend using a 1.3 to a 1.4 tip. The 1.2 tip is a little small for laying down the heavy paint which is more suitable for woodwork people.
Again, for cars or regular base coat, clear coat painting, think about using 1.3 to 1.4 tips. This tips size can be used across all spray guns for beyond base coat clear coat paint from waterborne paint, single stage acrylic enamel to synthetic enamel.
Tips for Choosing a Spray Gun And Compressor that Match Each Other
Spraying is all about air volume, not the pressure itself. You need a gun that works in harmony with the air compressor. If CFM requires far more than a compressor can aid, the machine thus has to work to keep up constantly.
HVLP guns demand high volume as its name emphasizes; no pancake compressor suffices that amount. You need a brawny one with large storage. I know a 16-20 CFM air compressor is not cheap, but this 2-stage compressor will bring lots of benefits in the long run.
Typically, small cheap guns require lower air consumption, but they tend to run at a slightly higher pressure and create more waste of material so be wise when choosing these types of gun because they can be useful if you know how to use them properly.
Modern HVLP guns of the HVLP type demand much higher CFM’s that even a 3-HP single phase compressor finds difficult to supply. But the advantage of HVLP is less paint wastage. The less solvent into the air, the less overspray.
2 Compressor Power
Its motor hose power designates compressor power though it is not the best indicator. Again, CFM plays a role here in determining the volume of air delivered.
CFM also varies with the air temperature and humidity. The CFM and PSI ratings are important because they specify the compressor that can drive with the tool.
When you choose a compressor, make sure it supplies the amount of air and the pressure that your sprayer demands.
3 Project Scale Air Compressors
For home garage set up, you will find a 20 to 30-gallon air tank fit the workshop. This volume is ideal for painting a small car or motorcycle using a LVLP gun. Though condensation could occur but it should go to minor care because it also happens with large air tanks.
Hard-cord projects had better seek for a 60 to 100-gallon compressor with hose power rating of 4-6 HP or higher. This volume is in favor of shops. For home garages, make sure you own the 240 VAC wiring system to feed the machine.
4 Water Filter
There is a minor factor that has something to do with water in the air. Paint sprayers need dry air, but no compressor cares if the air it’s pumping contains moisture.
Water in the air leads to the amount of paint in the storm exceeding causing a thicker layer than you expect. Then you purchase an air filter to catch water and banish it as much as possible.
There are airless sprayers available that you may want to have a look at. Notice that they are not on the cheap side.
These small tools are designed for meticulous work like in the auto painting industry, but you can make use of them.
Airbrushes are low volume tools that can pair with most compressors. They can require from 20 up to 100 PSI depending on the brush.
Still, you need a water filter for dried air separately.
To Gather it all
I understand mastering all these above knowledge is not an overnight business. But you can achieve it by reading through the manual and some internet instructions to get the best outcome.
I hope you have figured what CFM is required for spray painting for your next project and you can do it better than any time before. Good luck.