I've searched but haven't found the answers I'm looking for. I guess one reason is there is no one right answer and different folks will give different answers. But I want to verify my limited knowledge of spray gun operation. Please correct me if I'm wrong
On a typical gun there are three basic controls-
1. inlet air pressure
2. fluid control, controls how far the trigger can be pulled back
3. fan control

If you turn down the fan control to reduce the pattern then the pressure should be adjusted down as well because of the venturi principle?

If I adjust the fluid control to allow less paint then I should adjust the inlet air pressure either up or down to get the right atomization?

Does any of this make sense?

 

I've never used a spray gun, Bernoulli says when you increase the pressure you decrease the velocity, and then the inverse of decreasing the pressure, increases the velocity. To create suction to draw the paint up, the pressure has to below atmospheric of 14.7psia. The lower the pressure, the more pressure differential and the more suction is created.

I believe there are two venturi's you need to account for, the chamber where the paint is added to the air flow and the venturi when the paint/air mix is ejected into the atmosphere.

 

Now my head hurts!
I'll keep practicing with the paint gun and reminding myself there not runs but flow indicators.

 

I read a very good book awhile back',custom painting ' by Mr.Kozemoski(?), from H.O.K(House of Color)..., He's could not pick-up a paintgun and start spraying without 1st spraying a 'test' pattern..for smaller stuff..4" wide spray/4 inches from the object, Larger items, like full body panels , a 6" spray/at 6".I can't help but think the test was also to 'familarize" himself to the different paintgun.I have 3 or 4 different guns, they each act different.Primergun,spray-fillergun, finish(basecoat)and one dedicated to clear only.
Alot of technology and modern equiptment goes into a paint booth today, even before you plug in a gun...Larger Diameter air-hose quick-disconnects, clean dry air, the right volume and pressure of the air, a way to evacuate the booth, temp etc,etc..

I am by no means a painter, self taught at best..the whole chemistry thing is enough to give one a head-ache..
Read all you can, " wear a Mask!!", and experiment. Learn as much as you can from the paint manufacture tech-sheets..What type paint are you trying to spray? My limited experience is with the basecoat/clearcoat systems, different type paints spray differently...and can be applied differently.Different paint viscosities may need a different size fluid tip..and pressure.(primer,base,clear,enamel,spray-filler etc..)
Experiment,experiment,experiment...Be sure and keep the gun clean,so a solvent for the type paint used is a must..as may be a thinner to reduce it.Filter the paint before it goes into the gun.Practice on something your not worried about scewing-up..LoL!
Hope this help's some.

 

Thanks Cmoritz, I may check into the book. Actually my painting skills aren't that bad I'm just always looking to improve. I don't paint for a living well, at least not on a daily basis. I just sprayed four gallons of high solids poly today without any runs, drips or errors. I used a test panel to get the gun adjustment right and all the techniques I've pick up over the years. I guess the bottom line is the more you paint the the better you get (if your willing to learn from your mistakes).