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Thread: My painting setup - understanding CFM

  1. #1
    Join Date
    Jun 2020
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    3

    Default My painting setup - understanding CFM

    Hi guys, have been reading on here for a while learning what I can. I have a small compressor setup which I only want for painting one panel at a time.

    I have...

    Compressor - 24 ltr | 2.5 hp | 9.5 cfm
    Hose - 10 Meter | 10 mm | 21 Bar
    Filter - 10 Microns | 12 Bar
    Hose - 20 Meter | 10 mm | 21 Bar

    Inline Water Trap
    BenBow Inline Regulator
    Gun - ANI F1/N | 7.77 cfm

    All connections are BSP 1/4 inch XF High Flow | 35 Bar


    From what I understand the CFM is most important. My compressor is small but its rated at 9.5 cfm so by the time the air has passed through all the lines and fittings do I have enough CFM at the gun for my 7.77 cfm gun?

    My other question is when spraying, my compressor will start at around 100% full and turn on when it reaches around 70%. At this point should I stop spraying until it turns off or is it ok to continue and its providing enough CFM?

    I am debating weather its worth me buying a new compressor as its money I don't really have and and I am only doing a panel at a time here and there, however I do want the best finish possible.
    Previous attempts have been fine but left with moderate orange peel which I sanded and buffed out no problem however it would be nice to achieve a better finish.

    Also is the moisture trap at the gun still needed if I have the wall mounted filter 10 meters from the compressor?

    Thanks

  2. #2
    Join Date
    Nov 2005
    Posts
    42,281

    Default

    I have...

    Compressor - 24 ltr | 2.5 hp | 9.5 cfm
    Hose - 10 Meter | 10 mm | 21 Bar
    Filter - 10 Microns | 12 Bar
    Hose - 20 Meter | 10 mm | 21 Bar

    Inline Water Trap
    BenBow Inline Regulator
    Gun - ANI F1/N | 7.77 cfm

    All connections are BSP 1/4 inch XF High Flow | 35 Bar


    From what I understand the CFM is most important. My compressor is small but its rated at 9.5 cfm so by the time the air has passed through all the lines and fittings do I have enough CFM at the gun for my 7.77 cfm gun?

    My other question is when spraying, my compressor will start at around 100% full and turn on when it reaches around 70%. At this point should I stop spraying until it turns off or is it ok to continue and its providing enough CFM?

    I believe that the tank size is as (if not more) important than the CFM because a larger tank allows you to run your gun longer before you see a pressure drop. Your tank size is quite small but you could give it a try on your first panel to see how it works out. Personally I'd probably either add another tank to increase the air volume or purchase a different compressor.

    I am debating weather its worth me buying a new compressor as its money I don't really have and and I am only doing a panel at a time here and there, however I do want the best finish possible.
    Previous attempts have been fine but left with moderate orange peel which I sanded and buffed out no problem however it would be nice to achieve a better finish.

    If you start with this small compressor and you're happy with the result that's all that matters but you may be able to produce a better job with more air capacity.

    Also is the moisture trap at the gun still needed if I have the wall mounted filter 10 meters from the compressor?

    Another problem you can run into using a small compressor is it could generate enough moisture that it can outrun your filter. Again test it on your first panel to see if it rains on your work.

    Let us know how it works out for you.

  3. #3
    Join Date
    Nov 2013
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    olympia,wa
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    1,086

    Default

    just adding a couple of things to what len said,
    the cfm rating can be confusing, and some compressors are hard pressed to actually deliver what they claim. compressors are rated for cfm at a specific pressure. matching that to the gun's consumption at it's given pressure is where the confusion usually happens.
    it's doubtful that small compressor would keep up with continuous spraying, but you're only doing panels so it might work out.
    when you empty the tank enough to cycle the compressor on, you should look at your gauge on the gun and see where it's at. you can continue to spray until the gun pressure starts to fall off. (or maybe stop just before that happens.) you can see the pressure on the gun gauge as it relates to the tank pressure to see where that point is.
    the point is, as long as you are able to maintain pressure at the gun inlet, the required cfm is available.
    i never spray without the extra trap at the gun. it's extra insurance for little cost, especially if you're using an undersized compressor. len was spot on that small compressors like that work harder and produce more moisture. that is why the water traps are so important.
    the extra tank is a great idea, as it extends the time before the compressor kicks on, but also remember it will take longer to fill. longer run times make more heat/water to deal with.
    as far as the orange peel goes, it's more a function of the gun, paint viscosity, and technique more than the compressor. more practice will improve that aspect. or maybe a better gun. i'm not familiar with that particular gun so i don't know how it sprays. sometimes though, changing the inlet pressure can help atomize the paint better, which helps it lay out smoother.
    b marler

  4. #4
    Join Date
    Jun 2020
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    3

    Default

    Thank you for the replies. I really appreciate all the help and I have learned so much on these forums.

    Im now considering if I should just buy a new compressor. In my price range I could get one with double the tank size and a slightly higher CFM, would this be a worth while upgrade? Or would it only make a difference If i upgraded to something much larger?

    I was also considering buying exactly the same compressor again and coupling them together, as this would be a cheaper option. In theory this would give me double the tank size and CFM?

    Which of these would be the better option?


    Also, maybe i'm being completely stupid here but when I attach the moisture trap to the line just before the regulator I can only get minimal pressure though the gun, hardly any air whatsoever. Without the trap the airflow is fine and the gun works fine.

    Am I missing something on the water trap? There doesn't appear to be anything I can adjust or move?

  5. #5
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    Nov 2005
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    If you intend on spraying more projects I'd recommend a compressor that puts out at least 13 CFM or more and a tank size of 60 or 80 gallons. You'll have less to worry about when a decent compressor is the heart of your projects.

  6. #6
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    olympia,wa
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    Quote Originally Posted by DarrenLS View Post
    Thank you for the replies. I really appreciate all the help and I have learned so much on these forums.

    Im now considering if I should just buy a new compressor. In my price range I could get one with double the tank size and a slightly higher CFM, would this be a worth while upgrade? Or would it only make a difference If i upgraded to something much larger?

    I was also considering buying exactly the same compressor again and coupling them together, as this would be a cheaper option. In theory this would give me double the tank size and CFM?

    Which of these would be the better option?


    Also, maybe i'm being completely stupid here but when I attach the moisture trap to the line just before the regulator I can only get minimal pressure though the gun, hardly any air whatsoever. Without the trap the airflow is fine and the gun works fine.

    Am I missing something on the water trap? There doesn't appear to be anything I can adjust or move?
    nobody ever said they wish they'd bought a smaller compressor. always get the best one you can fit either size wise or budget wise. adding another small one will just double your trouble.
    i wonder what the flow rating might be on the water trap you're using. might be too small if you can't get pressure at the gun.
    b marler

  7. #7
    Join Date
    Nov 2005
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    15,159

    Default YES - What you said!

    Quote Originally Posted by bmarler View Post
    nobody ever said they wish they'd bought a smaller compressor. always get the best one you can fit either size wise or budget wise. adding another small one will just double your trouble.
    i wonder what the flow rating might be on the water trap you're using. might be too small if you can't get pressure at the gun.
    AGAIN, with you! About the time I read he was thinking of "doubling his pleasure" with another like small compressor, I (seriously) thought 'about' exactly what you wrote herein.

    He should be able to land a 5 horse 60 gallon for around $500 or an 80 gallon for near $800. (BE SURE and check electrical requirements on either in your electrical service panel!)

    I think his first filter/trap is set too close to the main outlet of the compressor thus making it less effective!

    Henry

  8. #8
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    Jun 2020
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    Ok thanks guys, Il look into getting a bigger compressor then instead of coupling them together.

    I have a 10 meter hose out of the compressor to my water filter and then another 10 meter hose to the water trap, gun regulator, then gun.

  9. #9
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    Nov 2005
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    Quote Originally Posted by DarrenLS View Post
    Ok thanks guys, Il look into getting a bigger compressor then instead of coupling them together.

    I have a 10 meter hose out of the compressor to my water filter and then another 10 meter hose to the water trap, gun regulator, then gun.
    You could PIPE your air for better performance. I usually recommend coming from the compressor to the wall, up the wall, around the room then drop down past the regulator with a T to the regulator and a drain at the bottom of the T so help drain the water before it gets to the regulator. I've been using "good" PVC pipe for years with no issues. If you purchase a compressor try to get one that has a valve at the bottom of the tank for easy draining, I have a hose rolled up at the bottom of my compressor and installed a lever type valve for easy draining.
    Last edited by Len; 07-28-2020 at 06:15 PM.

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