how to test hvlp cap pressure

[jamesmacc]

hey guys, got myself a new bergen hvlp mini spray gun as suggested on here, tested it tonight, my sealey regulator/water trap wont seem to go above 70 psi anymore and its 15 metres from that to the spray gun, how do i test the cap pressure as the manufacturer recomend 50-70 psi at the cap.
paint came out nice, a little orange peel but it was very cold in my workshop
if anyone can tell me how to test the pressure at cap then that would be great

 

[Daz1968]

Seems high for hvlp but you can get a small inline gauge to put on air entry to gun but cap pressure I think can only be measured on expensive guns with digital gauge. My devilbiss sri pro only needs 29psi, when I get orange peel a bit more thinners in the paint usually sorts it.
Also your hose will make a difference I have a 10mm bore hose and large bore fittings and see no noticeable pressure drop from the regulator

 

[jamesmacc]

i didnt have any thinners, just 2-1 with hardener. dont usualy use thinners and seem to get good results but maybe some thinners would help

 

[the snooper]

you have to use thinners to get the correct finish, paint continues to flow once on the panel and thinner helps this happen, you must get very textured finish without thinner

 

[jamesmacc]

that does make sense, no its not textured, infact i have some photos of a set of wheels i did in the summer that came out like a mirror, no orange peel at all just 2-1. but its doesnt always go so well, i will try add 10% thinners and keep the coats light incase of runs

 

[the snooper]

small areas like wheels are easier to achieve good results, but try the same on a full panel where you need a good fan for even coverage and you will see why thinner is a must

 

[jamesmacc]

ok cheers for that, will 10% be ok or should i use less? does it just help melt the paint so it floats into the next pass with the gun/paint

 

[the snooper]

try 10% first you can add more to get the desired finish

thinner is needed so the paint atomises correctly and also helps the paint flow, you dont want the gun spitting it out, it needs to be a mist

also the thicker the paint the more pressure you will need to get the gun to spray

 

[jamesmacc]

thanks for that, should i just take it lighter with the coats when using thinners or try screw in the fluid adjustment a bit, i have it most of the way out just now (wet as possible to stop peel) probably because i havent been using thinner

 

[the snooper]

yeah lighter coats and yeah you got it fluid adjustment in and test on some scrap, not something that will absorb paint because you wont see a finish, you will find it much easier with thinners, if you didnt have thinners how did you clean the gun

 

[jamesmacc]

i do have thinners, i just was not putting any in the 2k paint mix, i also have 2k thiners for using with basecoat but i havent used it yet, i clean my guns out with thinners straight after use

 

[Hog-Rider]

My compressors are at least 50 or 60 feet away from where I occasionally spray things,I could not work out why when I sprayed the rear of my Transit the finish was rough..I had been spraying with nozzle pressure about 70 pounds.That night I got out the instructions for the spray gun,I had bought it from M/Mart.I had bought a HVLP gun.It said max pressure 40 pounds.So I bought a in line pressure gauge from M/Mart. I put it in the end of air hose at the spraying area,Then I walk back to workshop and adjust it so I have 40 pounds pressure at the spray gun end ....Then I remove the pressure gauge.Big difference.

 

[langy]

ok cheers for that, will 10% be ok or should i use less? does it just help melt the paint so it floats into the next pass with the gun/paint

The product spec sheet will tell you the ratio, usually 10-15%
HVLP is usually 40psi or less, adding thinner will get you a much better and easier to apply finish.

 

[MG David]

Am I correct in thinking that the pressure at the gun needs to be measured with the air flowing?

 

[langy]

Am I correct in thinking that the pressure at the gun needs to be measured with the air flowing?

I've never measured it at the gun, just set it up by practise, reg at 40psi and adjusted gun up or down.

 

[anjum]

Don't use gunwash/cheap thinners for paint or lacquer. It affects the colour. Use the best thinners you can get hold of as you only use a bit for each pot.