HVLP Pressure

[turbotim2]

What are you guys running for pressure to an HVLP gun? I have sprayed some primer and on the directions it said use +/- 12 psi to the gun but was reading some other gun specs and they are calling for more like 30 psi. The stuff I have sprayed already came out ok but it seemed like rather large droplets and the finish isn't really smooth like it should be. Thanks.

 

[357Bronco]

30psi at the gun, is 10-12psi at the tip. Spray some test panels to get it where you want it. Adjust the pressure with the trigger pulled.

 

[turbotim2]

Thanks! I was trying to figure out how to get the 10-12 at the tip with no way to measure it.

 

[VT_Don]

Get a Sharpe digital gauge at the gun and a descant filter. Analog gauges don't have the resolution for exact pressure setting. Set down and read the damn directions before you paint. Insure paint is properly reduced and you have the correct tip for the viscosity. I've got some amazing good results with an inexpensive, Devilbis Finish Line kit. The key is, FOLLOW THE DAMN DIRECTIONS.

 

[turbotim2]

Get a Sharpe digital gauge at the gun and a descant filter. Analog gauges don't have the resolution for exact pressure setting. Set down and read the damn directions before you paint. Insure paint is properly reduced and you have the correct tip for the viscosity. I've got some amazing good results with an inexpensive, Devilbis Finish Line kit. The key is, FOLLOW THE DAMN DIRECTIONS.

I have a gauge, I read the directions, I have the correct tip and I know how to mix paint. None of those were my questions but thanks for the asshole response.

 

[kaw550]

He should have READ YOUR DAMN POST
"I have sprayed some primer and on the directions it said use +/- 12 psi "

 

[Amac70]

You can not measure the psi at the tip with out expensive equipment. That being said what kind of gun are you using, everyone is different. Saying it only needs 12 + or - at the tip doesnt' really mean anything unless you are really trying to be compliant with laws. Unless you are in a shop i don't think you are trying to be compliant, crank it up till it sprays nice. How big of a compressor do you have. 60 gallon 5hp compressors are a bit small to paint with but it can be done. You need volume of air with hvlp guns so if you have to crank the pressure up at the inlet to maintain the volume you might be well passed the 30 or 40 psi spec'd for most guns at the inlet. The best thing to do is practice. start with a base like 100 psi at compressor and 35 at gun hold the gun wide open and see how much pressure drop you get at the gun regulator. crank the gun regulator up till it maintains at least 30 to 35 psi. through some water in the gun and see how it sprays and if you can get a pattern. Adjust up and down from there to get something you like. Now try some paint with same procedure.

 

[turbotim2]

I know there is some fine tuning once everything is set up, just needed a baseline to start with. The 12 psi at the tip I got from the paint manufacturer, I have no laws to comply with. I wasn't sure what inlet pressure would produce 12 at the tip. Thanks, I'll start there.

 

[pcf_mark]

If your gage is at the compressor and you have a long hose (ha ha ha) the pressure drop can be 5-10 psi for a 50 ft hose. Crank it up until it sprays nice without creating a paint cloud. If your gage is at the gun then set it to 30-35 psi at the gun with the trigger pulled.

As someone noted get an inline desicant can. Water in primer do not mix. If you spray clear it will be destroyed by any water contamination.

If you are setting up your gun use some laquer thinner, avoid water as someone suggested. Not legal/compliant on mist areas but makes for good gun set up, it cleans out any last minute particles and mixes with everything you may put in the gun.

 

[beaux312]

I run a Sata NR2000 at work, the pressure depends on what you are spraying. You can spray on some old sheet metal or a spot that you cant see. A lot of primer are very thick and will have orange peal, but I wouldnt worry about it alot you still have to sand it slick before you paint. Now, you can over reduce the primer to get it to lay down better. Hope this helps.

 

[Rustytruck]

On my home compressor I have long hose runs so I use 2 regulators. one set at the compresser set 10 lbs below the low point of the compresser switch so I feed constant high pressure flow. Then at the hose end I use another filter regulator to bring the line pressure down for the gun. Then I use a jumper hose and a disposable filter at the gun. The hlvp guns I have have 1.4 tips and 1.5 tips so I start at the pressure to the gun at 35lbs and go up from there. I do not worry about the number I just worry about getting the right spray control. I am a slow painter so I adjust down the trigger throw so I dont feed as much paint as the gun could flow. Then I adjust the air pressure up until I get the spray I desire with the fan width adjustment I want. I never spray with the gun wide open on any of the control settings. Wether its with fan width, material flow or air flow. Take the time to adjust the gun to the way you want to spray and not adjust yourself to how the gun is shooting. I use mostly cheap guns and with those the setting are very course so a little adjustment can go along ways. I agree with pratice spraying with water. Get a bunch of cardboard sheets and spend a couple of hours learning just what happens when you adjust those knobs and how much change you get when you do adjust it. wet cardboard will show the spray patterns very well. The time to learn how the gun is working is not when your spraying $500.00 worth of paint. Pratice setting the gun and then really screw up the settings and see what it takes to get back to where your happy with the way it is spraying. Once you can predict what adjustments you need then clean the gun and have at it. Just remember you adjust one setting it effects the spray and you may have to re-adjust the other settings too. The better the gun you use the easier they are to set and the results of adjustment are more predictible.
Have fun and learn to take all the time you need to get the results you are after. I always have to push myself to slow down and get it right. I get a spray gun in my hand and all I want to do is get it done and over with so I can stop worrying if I am going to screw it up.

 

[G's Baja Bronco]

i have a gauge, i read the directions, i have the correct tip and i know how to mix paint. None of those were my questions but thanks for the asshole response.

jajajaja;d

 

[allenfahey]

Your only spraying primer so some orange peel isn't a big deal. Orange peel is caused my improper air pressure, too large of a tip (for primer a 1.5-1.7 is good), or wrong viscosity ( material too thick).

I use SATA's and I set the fan wide open and the trigger wide open. I tend to shoot close and fast so those settings work for me. If you mess around with your gun you will see where the sweet spot is with the spray pattern, distance from the panel, and your overal spray technique. The sweet spot is where the gun is atomizing the material the best. If you have too little pressure you don't atomize it. If too much all you are doing is throwing out material and it bounces off the panel. The distance from the panel also determins the sweet spot. You just need to practice and primer is good practice

Another huge tip..... For the best results use the proper air fitting. You wouldn't believe how many professional painters are not using the proper air fitting on the end of their gun. The HVLP gun manufacture designed the gun to use an HVLP fitting. If you use a regular "A" or "M" style air fitting you are choking your gun. HVLP guns require a very high volume of air to work correctly hench the HV (high volume) the LP is low pressure at the cap. As stated before, to measure the air pressure at the cap requires a special cap that has a guage that sticks out of the cap. If you have a cheap gun there might not even be one available. You also need at least a 3/8" air hose and a big air compressor to be able to keep up with the gun when you spray your base/clear.
Here's an HVLP fitting http://www.finditparts.com/products/milton-industries-s761

As someone else said DON'T use water, use laquer thinner. Cheaper guns like you are probaly using don't have a stainless steel gun body, nozzle, and needle and will/can rust. The SATA's I use have the stainless steel parts for water bourne paint.

 

[turbotim2]

Thanks for the tips, I am going to spray primer/sealer today on the bottom of the tub. I'll let you know how it turns out.

 

[allenfahey]

Thanks for the tips, I am going to spray primer/sealer today on the bottom of the tub. I'll let you know how it turns out.

Are you painting the underside of the tub? Are you planning on sanding the primer on the underside of the tub? That's a lot of work. If I were you I would mix the primer as a sealer and go wet on wet with the paint. Spray the sealer, let it flash, then paint it. No sanding which will save you a ton of work. Do you have the tub off the frame upside down or are you going to spray upside down. If you need to spray upside down I would use 3M's PPS system which uses a bag in a liner. Hold the gunn upsidedown and pull the trigger till all the air is out.

 

[turbotim2]

The tub is off and upside down, and done! (At least the bottom).

 

[turbotim2]

I got the gun dialed in pretty good. I am happy with the results. I set the air pressure to 30 wide open and it worked much better. Thanks for all of your suggestions.