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Old 06-01-2006, 04:19 AM
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Help with compressor/spray gun setup

After reading around I'm pretty confident on how I should setup my compressor for paint spraying but have a few questions anyway.

I take it I should set my compressor pressure to something like 80-90psi, but then regulate this to around 40psi at the gun (non HVLP), so to do this I'm guessing I need a gauge on the end of the gun right? If the gun has an air adjustment on the inlet do I still need a gauge with regulator?
What sort of fittings do I need? I'd prefer quick release style at the gun.
Also what bore size is recommended for the air hose? We have plenty of air hose at work rated to at least 7 bar, would this be OK?
Also, length of hose, does it make much difference, or should I keep my run as short as I can be comfortable with?

I've read about the spray gun adjustments using a cigar shaped patternand looking at the paint build up in the centre. How would I know if I've got the pressure just right though, what should I be looking for?

Also I've read about holding the gun fully open and watching how long it takes to drop 5 psi at the gun, whilst spraying if pressure drops by 5psi is this a time to let the compressor catch up, or should the pressure not even get that low?

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Old 06-01-2006, 05:30 AM
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I will say that I am not a professional painter. I am also not one to advise on gun adjustment. I will say that I always use a regulator and gage at the gun. It doesn't matter what the pressure is at the wall, it's the pressure at the gun that determines what it will do. As far as the fittings, I use the ones designed for HVLP, since most of my guns are HVLP. They permit more air volume thru. I usually get mine at Lowes. They have a larger than normal ID, causing less restriction. I use 3/8" ID hose long enough to go around the vehicle comfortably. You will have some pressure drop with increased hose length. The regulator and gage at the end of the hose should figure for that. I also do not regulate the air from the compressor. My compressor is set to maintain 115-130 PSI, and I want to make sure it is available.


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Old 06-01-2006, 08:33 AM
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I am no expert either, but I have found that by the time you hang a regulator/gage, filter and quick connect fitting on the end of an HVLP gravity feed gun with a 1000cc cup that it gets rather ungainly. What I do is set the air pressure at the end of the air hose by the main regulator. You can do this by attaching what I described above and pulling the trigger on the gun. Once you have used the main regulator to set the gun supply pressure you can then remove all that stuff from the gun and just use the quick connect.

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Old 06-01-2006, 12:17 PM
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well I must admit I always thought you set air pressure at the compressor until I read about it on here. My paint spraying mate doesn't have any gauge or regulator on his gun.

The compressor I will be using has a filter/regulator at the tank, as well as a automatic cut out. So basically I should set this as high as it will go, or max pressure the line can take, then regulate down at the gun to around 40psi?
My hose length will by quite short, probably only 5m tops, I'm only spraying the odd panel at the mo, but if I get into doing the whole car I'll prob need to buy a bigger compressor.
Will I need a water trap?

If I find it a bit much having a gauge/regulator on the gun I'll do as you suggested vince, but I guess I was worried about excess pressure drop whilst spraying and not noticing.

What do I do with the air adjuster at the gun? Leave it open adjust on regulator, then close it off with trigger open until sound changes then turn back a touch?

Last edited by Hallsy; 06-01-2006 at 12:22 PM.
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Old 06-01-2006, 12:35 PM
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We discussed this a lot before and this is what I did.
I removed my regulator at the gun, it restricted the air.
I made a quick disconnect with a gage I install and adjust the pressure
at the compressor untill I get what I need at the gun w/ trigger pulled,
then I remove it.

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Old 06-01-2006, 04:08 PM
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OK thanks.

Is there any advantage to having the tank at a higher pressure than you're psraying with though? i.e. tank presure at 100psi, gun pressure at 40psi, so as volume drops pressure does but compressor keeps it topped up, buf if tank at 40psi as soon as you start using the air the compressor needs to keep up straight away, or is the difference only seconds worth?
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