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Whenever you see compressor ratings, CFM decreases as pressure increases. One can use a regulator to decrease pressure at gun, but does that increase CFM?

Or would it be better to use setting at tank to only go to pressure that delivers most CFM? Obviously, the compressor would run more often, right?

Curious

Mike

What I have found is that restrictions in the filter and hose can starve the gun so what I do is turn up the pressure at the tank and control the pressure at the gun. This keeps plenty of air available to keep from starving the gun.

You can diagnose that your gun is starved if you see plenty of pressure on the gauge at the gun during idle, but see the pressure drop precipitously low when you pull the trigger.

The best is to have the regulator on the gun. All my guns have their own regulator.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I totally agree with regulator at gun. I guess what I was getting at is optimizing an air system for maximum flow rate.

There are ways to do that. I replaced my air hose with one that has a 3/8" interior diameter instead of the more common 1/4". I shortened the hose to about 10 feet long. I also got some high flow quick connect fittings. Seemed to make a difference. Also make sure your filter and regulators are sized appropriately.

What problems are you experiencing?

The CFM is a measure of how much air the compressor will produce at a given psi. The tank kind of acts as a "buffer" and allows the pressure to rebuild when air is not being used. A larger tank gives a greater reservoir of air to draw from. It can allow the compressor to run less often but for a longer duration when it does kick on.
The spray gun and the material being sprayed will determine how much air is required for it to work properly. Generally smaller spray guns use less air than full size guns, and high pressure guns often use less air than HVLP conversion guns ( kind that use a compressor.)
Regulating the pressure at the gun can be done by a small cheap regulator - you don't really care what the pressure is, you just want the gun to spray properly.
Air tools are often regulated at the compressor. You need enough pressure to make them operate, but not so much you blow the seals.
As Barry mentioned longer hoses will cause a pressure drop, so the pressure at the tool will be less than the pressure at the tank, and a larger diameter hose will have less of a pressure drop than a smaller diameter one. Larger diameter hoses tend to be harder to handle so often a small diameter flexible hose will be used for the last 10 feet.

I've always found CFM specs to be a bit misleading...sure, they give a comparative idea, but my test has always been to put an air blower on a hose and open it up fully and then observing at what pressure does it end up at after the tank has been depleted and only the compressor is supplying air flow...for instance the compressor I use for spraying will hold at about 55 lbs...one of my smaller compressors might hold at 35, my current jobsite compressor would be lucky to hold at 20

smaller diameter hoses while lighter really restrict air flow because of friction...3/8" is the minimum ID I use for spraying...the shorter the hose the better (friction of air in the hose is of course determined by ID and length of hose)

if you're using a proper set up of a fair amount of hose then your oil and water traps going to something like PVC pipes can give a boost in air flow

Many cheap regulators are not regulators, but simply a flow control valve.
Mine was restricting the air volume. I removed it and set the pressure at the tank.
Made a huge difference with my HVLP gun. I was able to get a wide wet coat of lacquer.

I believe our friend Barry identified a “real” regulator on a previous thread.

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My blue lines for distribution are 1/2”. I’m gonna change my rubber access lines to 1/2”. Since my blue lines distribute to all locations in shop, I’m gonna shorten my rubber access lines significantly. This should help. Ty!

Edit: gonna change all metal parts to 1/2” too