Everybody wants to achieve a perfect paint job. However, painting different surfaces can be one of the most challenging things to do, especially for DIYers.
Whether it's a wall, car, fence, gate, or whatever surface you want to paint, painting requires a lot of effort, hard work, and knowledge. So, if you're researching the right CFM for paint gun, we’re here to help.
This article will discuss what CFM is, how it affects the spray paint, what CFM is required for a spray gun, and how to set up the correct recommended operating pressure rating for your spray gun for a flawless paint job.
CFM is an abbreviation for Cubic Feet per Minute. This measurement refers to the quantity of compressed air line released by a smaller compressor under pressure in a minute.
It basically indicates how quickly it can compress air to catch up to the sprayer. The air movement in the cylinder is caused by atmospheric (atm) pressure. As a result, Cubic Feet per Minute - CFM varies with atm pressure.
For us to understand how CFM works in spray guns, let's look at how spray guns work and where Cubic Feet per Minute - CFM comes into play. We'll use an LVLP (low volume, low pressure) spray gun as an example.
This type of gun is one of the most used spray guns because it has less overspray. It's also gravity-fed since the paint cut sits above the nozzle.
One of its benefits is being environmentally friendly since it spits less pain into the air and blows more paint on the surface you're working on. On this type of spray gun, there are many knobs that you should be familiar with, and one of them is the horn.
This allows you to control the direction of the stream of the paint, whether it comes out vertically or horizontally.
So, how does it work? First, this spray gun works on atomization. The fluid will come out of the nozzle and meet with the air that comes up through the tool, creating a perfect mist of paint on your surface. How do you ensure that the paint will come out with air smoothly?
This is where the amount of paint used and CFM distributed through the air supply comes into play.
The compressor size plays a vital role in achieving an even paint. That's why you need to buy a big compressor that can handle better air circulation, allowing your spray gun to function properly.
At the same time, before purchasing a spray gun, ensure that the gun's CFM requirements works with your current compressor.
How Does CFM Affect The Spray Paint?
Spray painting relies on air pressure, and if you don't have enough of it, you won't be able to spray the paint on the surface evenly. This is where CFM comes in.
A continuous air flow is needed for the spray gun to work correctly, and the CFM indicates how much air a gun can produce at a given pressure.
Putting the pressure lower than the spray gun’s requirement will result in poor atomization and separate the paint particles.
This will result in a higher film build than what’s required, as the paint particles will come out larger than expected. Too much film build will lead to a slower drying time, loss of gloss, and popping. It will also leave the wall textured, like an orange peel.
It’s also not a great idea to have a higher pressure than what is recommended by the manufacturer. With low pressure, you get a high film build. In contrast, a higher pressure will result in a low film build. This will also lead to over-spraying and poor metallic control.
If you use a spray gun with a high-pressure setting, the fan pattern will split where the middle part will produce light paint and the edges will have heavier paint. This inconsistent paint pattern will cause streaking, and in turn, will waste your material and compromise the durability of your paint system.
How Many CFM Is Required For Paint Gun?
There are various spray guns available in the market today, and each has its own CFM requirement. At the same time, they also differ in features and capabilities.
For example, spray guns that require high CFM can produce a greater volume of liquid than guns that need low CFM. These guns also have higher atomization, resulting in a better finish.
In addition to CFM, another important factor that should be checked in a spray gun is the PSI (pounds per square inch). This measures how much pressure the air has and is used to help you distinguish the kind of best air compressor you need.
However, one thing to note is that most spray guns, especially those for painting cars, are gravity fed and don’t need much air.
Another important factor is the PSI, or pounds per square inch.  PSI is a measure of air pressure used to determine what air compressor you need. In addition to knowing the CFM, you should also know how much PSI for spray gun is needed for a better painting job.
However, most spray guns used to paint a car are gravity fed and do not require a lot of air. The most common spray gun settings for car paint are 15 or 25 PSI, which will provide a smoother finish.
So, without further ado, here are the required CFM for different types of spray guns, so you won’t have to wonder how many CFM for spray painting:
HVLP Spray Gun
HVLP spray gun stands for High Volume Low Pressure and is a spray technology that has been defined and applied by the SCAQMD (South California Air Quality Management District) in the 80s. It's now used by most states in the US.
To comply with HVLP spray gun, the air pressure measured at the air cap must be between 0.1 and 10 PSI maximum, or the application must be at least 65% transfer efficiency. Compared to a conventional air spray gun, these requirements reduce overspray pollution and material waste.
HVLP spray guns should have a high volume of air of 10-25 CFM at a low air pressure of 10 PSI/0.7 Bar or less. For this type HVLP spray guns, atomization is accomplished through the volume of air, not through high air pressure, which reduces forward velocity, resulting in a softer spray.
The softer spray of hvlp spray guns allows more material to adhere to the part rather than bouncing off into the atmosphere, lowering air pollution and material waste. HVLP guns are designed with larger air passages and air caps with multiple or larger atomizing orifices around the fluid nozzle to achieve this.
LVLP stands for Low Volume Low Pressure and is a combination of an HVLP spray gun and a conventional air sprayer. It uses less air volume than HVLP guns, which only require low CFM pressure of around 5 to 18 and lower air pressure than conventional air spray of 10-30 PSI.
LVLP guns also have a large air passage like the HVLP gun, but the air caps have smaller holes.
The smaller holes allow more air pressure at the air cap, which results in better atomization. Depending on your application, LVLP spray guns can still be compliant by delivering transfer efficiency of 65% or better while not being restricted to 10 PSI at the air cap.
While automotive painting isn’t technically a type of spray gun, it’s still a common question to ask how much CFM rating you need to paint a car. The volume of air you need to paint a car depends on the output of your air compressor and the CFM rating of the spray paint gun you’ll use.
Different types of guns require different CFMs to produce the perfect coat, so it’s best to ensure that your compressor’s output and your gun’s requirements work together.
We recommend you use an air compressor that can produce more air volume than the spray gun needs to ensure that the CFM is steady, creating consistent atomization of the paint as you work. It is currently recommended to use a CFM in the array of 14 – 18 at 90 PSI to paint a whole car.
Setting The Correct Pressure For Spraying
So now that you’re familiar with how to know CFM of spray gun, it’s time to discuss the ideal pressure needed for spray painting. The best way to determine the right pressure is by looking at various factors.
For example, some paint sprayers come with a pressure usage chart, which can give you the information you need to set your gun on the right dial. If you use too little or too light pressure, you’re going to have an uneven paint flow which will result in an unbalanced spray pattern.
You should also be careful with other factors when preparing your spray paint. These include the actual stain or how much thinner the paint is, the length of the hose you'll use, whether you're using a spray booth, and outside temperature variation.
Once you've checked all of these factors, you can now start setting up the correct pressure for spraying various surfaces.
If you want to use air spray guns to paint cars, you need to be careful in setting the pressure of the sprayer right. If you don't adjust it correctly, you'll end up with a bad painting job, and no one likes that.
Generally, spray-gun manufacturers provide the information you need to set up their products, and this should help you to get the optimum pressure you need. However, note that some instructions do not include the stain or finish you'll be using, which can also affect the painting job.
In many situations, especially in the auto painting industry, you'll be required to attach a gauge to the air cap to measure the maximum needed pressure for the gun.
The gauge will cost you money, though, and for personal use, this isn't really necessary. Instead, you can use a regulator and a simple test to find the best setting for your air tools.
The best way to adjust your gun to the ideal pressure is to set every control of the gun to the maximum level and turn the regulator down a level below the recommended level. Then, spray it on a piece of cardboard or brown paper.
This test will give you a linear pattern with relatively large dots around the sides.
Continue increasing the pressure by 5 or 10 PSI and continue spraying it on the cardboard until you can find the right pressure and pattern to serve your need.
Another way to determine if you've reached the optimum setting is to ensure that the pattern does not widen and you don't get smaller dots on the side. You should also ensure that when you're testing the pressure, the gun is placed at the same distance from the cardboard.
The best way to do this is by placing the tip of your finger against the target while the tip of your thumb is against the cap of the sprayer. We recommend a distance of 8 inches to achieve a perfect finish.
Painting Bed Liners
Are you planning to paint a bed liner? If so, the first thing you have to check is the CFM needed for spraying bed liner. The CFM required depends on the air tools you’ll be using. Almost all air tools are bigger air hogs than you think.
Like painting a car, the pressure needed to paint bed liners also depends on what paint gun you’ll be using. In general, a lower CFM paint gun requires higher pressure.
To find out how to find the right pressure for painting bed liners, be sure to check the manufacturer’s information on your tool. If you don’t have it, you can try the test mentioned above.
Spraying lacquer requires different pressure than spraying paint. It’s essentially a clear coat that is applied on top of a painted surface to protect the underlying base coat.
Ideally, the pressure required to spray lacquer is about 20 to 25 PSI. Still, you need to ensure that your air regulator gauge is a bit higher than that to maintain a 20 to 25 PSI while spraying since the atmospheric pressure drop once the gun is activated.
So, if your air regulator is set to 20 or 25 PSI and you start spraying, your gun will only have 12 to 14 PSI air pressure during the process. This will cause the lacquer to spit or dribble from the gun, which will not have a good result.
So, it’s best to experiment with different settings and see which works well for your setup.
In many cases, setting your regulator to around 30 to 35 PSI will give you a good spray of lacquer without the mess. Lastly, make sure you watch the air regulator gauge as you spray and see what the initial setting archives the 20 to 25 PSI requirement when you’re pulling the trigger.
Choosing An Air Compressor For Spray Painting
For powerful and quick painting jobs, a spray gun and air compressor should come hand in hand. If you only have the gun, it's going to be difficult to achieve an even spray.
There are different types of air compressors, and choosing the right one can be challenging, but don't worry. We have rounded up different factors to consider when choosing an air compressor.
Pressure, CFM, and Tank Size
These three factors are the most important things you should look at when purchasing air compressor. When it comes to pressure, there are two types of guns to choose from: HVLP spray gun and LVLP spray gun. Both these guns don’t require much pressure, so their air consumption is also pretty low.
After air consumption, the next is the compressor CFM. This is arguably the most crucial factor to consider when buying a new compressor. Before you buy an air compressor, you need to check the compressor CFM of your power tools.
Once you've determined that, you need to ensure that the air compressor can produce sufficient CFM or more for the spray gun you'll be using. Don't buy one that's less or the same CFM, as it may cause your spray gun to act badly.
The last thing you need to consider is the tank size. The tank size will determine how much air is available to be drawn down at any time. Compared to other pneumatic tools such as nailers pneumatic tools, tank size use air intermittently to fire nails, sprayers need a continuous flow of compressed air from the air compressor.
This means that it requires more air over time. So, a small-size air compressor may not provide consistent power to handle a paint sprayer.
We suggest a large high-output air compressor, preferably 50 gallons and above, to keep up with your spray gun.
Air Compressor Type
When it comes to air compressor types, there are many choices to choose from, including piston, helical, screw, centrifugal, and axial. While most air compressors serve the same purpose, there are specific models built specifically for different kinds of uses.
For example, a more powerful size air compressor that runs on impellers is not needed when searching for spray-painting air compressors.
If you need a small air compressor to power your small tools, there are various options; the pancake compressor (air compressor), hot dog air compressor, and pontoon air compressor are some of the different types you can use to run low-volume tools like spray painters.
More CFM and Paint Gun Questions
What size tips to use on a spray gun?
Tip size for spray gun depends on the type of paint. Light coatings like stains, lacquers, enamels need small tips while heavier coatings require larger tips.
Should you use the spray gun intermittently or continuously?
Continuous spraying is recommended for achieving an even finish, but intermittent use can be okay as long as the whole surface is covered eventually.
What should be the distance of spray gun from the compressor?
A longer distance between the two is better than a short distance. Around 50 to 100-foot lines are ideal.
Does CFM change with PSI?
Not necessarily. But you will get more CFM with lower pressure (PSI).
If you are an occasional painter and still unsure about the CFM you need for paint guns, hopefully, this article has given you the information you need.
At the same time, keep in mind that paint sprayers need dry air. Compressed air usually has water in it, and an air filter is needed to remove this water. So you will need an air filter to catch the water and remove as much of it as you can. Lastly, be mindful of using air compressors constantly when panting.
The machine will get hot and will start producing hot air, which contains more water trap and ruins your painting job. Be sure to keep this in mind to achieve a better painting.