I have a craftsman air compressor I believe it is; 1.5 HP, 26 gallon, output 9.1scfm at 40 psi, 7.1cfm at 90 psi. I have a new husky Pro HVLP spray gun (not that great) with a 0.047 fluid tip, scfm 6.5 avg. at 40psi, max inlet pressure 80psi, HVLP inlet air pressure 40 psi.
What PSI should I have my air compressor set at before I start fine tuning the gun?Any tips on fine tuning the gun would also be great. I will be spraying lacquer.
From contributor F:
I have a regulator at my compressor set to 110psi and this feeds the shop. Right at the gun I have a little restrictor/regulator with a gauge that I use to adjust gun pressure.
I spray keeping the pressure high enough to of course move the lacquer nicely and fast enough to move the work on through. But I keep the pressure low enough to minimize the overspray fog that will make for a rough finish when it settles on the product. A good fan moving lots of air and adding retarder keeps the overspray down, but watching my pressure helps a bunch too.
When spraying Sherwin Williams cab acrylic lacquer, medium rubbed effect, I add 2 oz. of thinner, 1 1/2 to 2 oz. of retarder and fill the quart cup up the rest of the way with lacquer. Stir really well before spraying. I spray only clear finishes in lacquer, so some adjustment may be needed for paints.
Take a piece of cardboard or something and start dialing the pressure up as you take really short bursts on to the cardboard. You will reach a point where you have nice even droplets (good atomization). Once you reach this point, you can typically back the pressure off just a tad to reduce overspray. Now spray a test piece. Judge it about a minute after you spray it to give it a chance to level out. The goal is to find the lowest possible pressure where you get a nice finish.
Sometimes you will find with the pressure a little low, you donít get a glass-like finish immediately after spraying, but after a minute or so, it will flow out and be nice and level. There is no one correct pressure setting. Outside temp as well as fluid temp play a role in the correct gun settings. If itís really hot outside, your part may flash really fast so the fluid wonít have enough time to level. If itís cold, the fluid will be thicker. You can add thinner to reduce the viscosity, or turn the air up a little to get the atomization you require.
It seems a lot more difficult than it actually is. Set your gun at say 30lbs and start working up a little till it looks good. After spraying a few times with different weather conditions, you will get the hang of it really fast. You should also have a couple different tip sets for different products. Thin stuff like NGR's will spray nice with a 0.8mm tip, typical lacquers and CV's will be good somewhere in the 1.3 to 1.5mm range, and primers and thicker stuff will like something around 1.9mm. CAT makes some nice sets that come with a couple aircaps and a few tip sets that work well with typical wood finishing products. Somewhere around 35 psi at the gun will be in the ballpark.