HVLP paint gun setting

[redgum78]

Any experts on HVLP paint guns?

I am not an expert spray painter but I have dabbled enough in the past and managed reasonable results.

I wanted to put a coat of yellow on my Challenger so I brought a new HVLP gun (always used conventional venturi guns in the past).

Well I got the yellow on but struggled with the gun settings. The only way I could get good flow out of the gun was by making the pattern very narrow.

I was painting a 2 pack polyurethane, 1.4mm nozzle in the gun.
The paint instructions recommended 10psi which was terrible. A quick google suggested 20-25psi which did work better.

I was telling my mate and he said he runs his HVLP gun at 65psi!

Any tips?

Thanks

Dan

[Rich G.]

They always say 10 psi at the cap which it NOT 10 psi going in the gun. You need a special cap gauge to measure that so don't go by that. I run around 40-50 psi.but that depends on a few things also. Always test the spray pattern on something first and adjust accordingly. They also recommend the HVLP fittings which are a little bigger. I'm sure others here a advice also but this works for me.

[Cuda Cody]

The fan pattern will also change the PSI of the gun and each gun model is different.  I run about 18 to 36 depending on the paint, temp and pattern I'm using.  Do practice spray outs. 

[1 Wild R/T]

This is a cut & paste from the Auto Color Library painters forum.....  & is pretty much what I do.....  But I don't have the talent to actually paint....I paint stuff but leave the important stuff to people with more natural talent..... (I'm a klutz)  I'm great at fixing stuff, great at electrical/electronics but artistic stuff I long ago accepted isn't my forte.... 


" your spray fan should be shaped like a cigar. What I do with just about every gun is adjust the fan wide open then turn the adjusting knob until the fan starts to narrow a little. I normally leave it right there. If the fan is too wide then you'll get a lot of dry edges from the overspray. If the fan is too narrow then you'll get tiger stripes in the metallic of the basecoat and very possibly runs in the clearcoat. Adjust the fluid control knob just about wide open and leave it there. Thats how most of the pro painters adjust their spray guns. Keep in mind that an HVLP gun is held closer to the surface that you're painting and so the fan works a little better when its a little wider than how a conventional high pressure gun would be adjusted to. You normally have to move a little slower with an HVLP gun compared to the conventional high pressure guns. Most HVLP guns are "slower" than conventional high pressure guns."

[redgum78]

Thanks for the advice guys and for explaining the 10 psi at the tip part. I was loathed to go too much higher than the 25psi I was using as I was thinking the paint manufacture was suggesting 10psi to the gun. Now I understand that is not the gun supply pressure I'll experiment with higher pressures. Pretty sure that's going to be the answer.

Thanks for the help.

PS- I'll post some pictures of a yellow U code shortly!

[wldgtx]

This subject is very special to me as I just got a new gun and dialed it in this past weekend.

First of all, you have to remember that there is a difference between inlet psi and tip psi.  I am not sure about all guns, but the ones I have all came with their own pressure adjustment at the inlet.  I do not have a tip pressure reading but I have learned how to "dial" in a gun properly, and IMO this is not a quick simple adjustment of the inlet and flow. 

That said, I did not see what brand of gun you have, but typically the gun manufacturer will tell you what inlet pressure to set the gun at to create a baseline.  Also the paint manufacturer will list out options based on the gun being used.  Another thing that many forget about is the tip size.  I have found that my style prefers the smaller tip sized (1.2/1.3) to lay the easiest.  However this changes depending on what I am spraying.

All of that said, I can tell you that with my Devilbiss GTi, FL4, and Iwata LP400 all layed down clearcoat like glass with a 1.3 tip and the flow setting to 2 turns out, with the pressure set at -1 turn from baseline, with the fan pattern opened up and then dialed back in 1.5 turns.  Basecoat lays down a little easier and I have numerous settings that have achieved favorable results.

[redgum78]

This subject is very special to me as I just got a new gun and dialed it in this past weekend.

First of all, you have to remember that there is a difference between inlet psi and tip psi.  I am not sure about all guns, but the ones I have all came with their own pressure adjustment at the inlet.  I do not have a tip pressure reading but I have learned how to "dial" in a gun properly, and IMO this is not a quick simple adjustment of the inlet and flow. 

That said, I did not see what brand of gun you have, but typically the gun manufacturer will tell you what inlet pressure to set the gun at to create a baseline.  Also the paint manufacturer will list out options based on the gun being used.  Another thing that many forget about is the tip size.  I have found that my style prefers the smaller tip sized (1.2/1.3) to lay the easiest.  However this changes depending on what I am spraying.

All of that said, I can tell you that with my Devilbiss GTi, FL4, and Iwata LP400 all layed down clearcoat like glass with a 1.3 tip and the flow setting to 2 turns out, with the pressure set at -1 turn from baseline, with the fan pattern opened up and then dialed back in 1.5 turns.  Basecoat lays down a little easier and I have numerous settings that have achieved favorable results.

Thanks for that info wldgtx. My gun is a middle of the road unit (I forget the brand now). It was right in the middle of the shelf between the $399 Devilbiss  and the $59 no name unit. It think I paid $169 for it. A couple of local painters use the same gun so I know the problem is me not the gun!! In saying that I am getting better, now that I have educated myself a little on supply v tip pressure I am not as concerned about experimenting at different pressures.

[wldgtx]

If you can get yourself a test panel to shoot on.  I would recommend creating zones with taped off areas to set the gun up different to see the results of the various settings and pressures.  I do this with a hood that I have and found that I can dial in a gun really fast based on the settings I mentioned above. 

Also, watch your flash times.

[redgum78]

If you can get yourself a test panel to shoot on.  I would recommend creating zones with taped off areas to set the gun up different to see the results of the various settings and pressures.  I do this with a hood that I have and found that I can dial in a gun really fast based on the settings I mentioned above. 

Also, watch your flash times.

That is a good idea, I have a few old hoods laying around i could test on. 

[wldgtx]

Good luck, let me know if you run into a road block.

[redgum78]

Good luck, let me know if you run into a road block.

Thank you my friend 

[Bills Auto Works]

 Lots of great advise given!

  All I can add is the gun manufacturers should add a little note after the (recommended pressure) that states "tip pressure" & "gun pressure" are different! I am sure the reason they don't is because most folks that are buying a gun (especially a high end one) are already aware of this. I doubt the manufacturers concern themselves with the hobbyists as much as the pros'

  However we ALL had to start somewhere! Back in the  early 80's when I started shooting, I was fortunate enough to have a business partner
who was already an expert painter & he taught me well. We didn't have the ability to go to GREAT forums like this to get advise from those more knowledgeable, because the "interweb' didn't exist yet LOL

God Bless
Bill

[YellowThumper]

These forums are what have promoted the vast majority of do it yourselfers.

I will be painting mine someday just because of these discussions.