My first Spray Job, HVLP

Phetishboy

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First off, what a pain in the ass. Assemble the gun, tighten 17 fittings, set the air pressure on the compressor, then on the regulator, mix the paint and try to thin as you go, etc, etc, etc. My question is, why isn't my paint swath wider? It seems I'm hitting no more surface area in one pass than a rattlecan does. I've tried 6, 9, 12 and 14 inches away from the cab, not much change. 2nd, how long do I have to wait to sand? It's been 2 hours, 60 degrees and breezy outside and the thing is still tacky. It also looks thin and spotty, like you can see the pass lines, and I overlapped them all at least twice. Me not a huge fan of this yet.
 
what kind of paint did you use? auto body stuff is dry in 15 mins. ( even in cooler weather is you use the correct reducer)

there should be a knob on the side of the gun. rotate that to change the width of the fanspray. Youll want to set it almost as wide as itll go( about 8-10 inches width)


If your air pressure isnt right or the paint is too think it simply wont spray well..
You should be approx 8 inches away while painting.

a true hvlp gun should have 18-23 psi in, some cheaper guns they call hvlp but are not( theyre just gravity feed spray guns) and you need 70-80 psi to get a good spray pattern out of them


the trigger is also progressive, press halfway to start air, then slowly squeeze it more to get the paint flowing. Always keep the air going/trigger held halfway while your painting-add paint( pull trigge rmore) when you start every "sweep" to adjust the max ammount of paint that comes out, rotate the larger knob on the rear of the gun. the further counterclockwise you go, the more paint will come out at full trigger pull..
I run mine maxed out full but ive gotten pretty good aitht he trigger control. Just starting out id set it to the max you want so you dont accidentally pll too much and cause a big nasty run from too muvh paint.

If you let the trigger go completely, and fully squeeze repeatedly it will never output nice smooth atomized paint, itll be all globby


Have a little more patience before calling it krap. You might just find a new favorite way to paint.

First off, what a pain in the ass. Assemble the gun, tighten 17 fittings, set the air pressure on the compressor, then on the regulator, mix the paint and try to thin as you go, etc, etc, etc. My question is, why isn't my paint swath wider? It seems I'm hitting no more surface area in one pass than a rattlecan does. I've tried 6, 9, 12 and 14 inches away from the cab, not much change. 2nd, how long do I have to wait to sand? It's been 2 hours, 60 degrees and breezy outside and the thing is still tacky. It also looks thin and spotty, like you can see the pass lines, and I overlapped them all at least twice. Me not a huge fan of this yet.
 
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Phet it takes a lot of practice and the gun must be set up properly to get good results.
Google"How to set up HVLP gun"and there is a lot of good info on how to properly set up your gun.
The gun must be tuned up every time you use it just like a guitar should before you play it.
You also need the proper size tip and needle for the material you are shooting
Hvlp needs to be no more than 6" from the surface to be painted.
I agree that your fan setting is probably too small and needs to be wider.
 
I set it as I sprayed a scrap piece, and if I dial the knobs the other direction from where they are now, nothing comes out. I am at 35-40 PSI on the gun, 45 psi on the compressor. I thinned with 10% PENETROL, 7% Mineral spirits, using Sherwin Williams oil based all-surface enamel.
 
I set the fluid knob at 2 1/2 turns out and the fan knob about 1/2 way out.
I then set the regulator on compressor at 90psi @ the regulator on the gun @ to manufacturers specs.
Mine is 29-54 psi.
I copied this from a good place for HVLP setup info.
SETTING UP HVLP GUN
Set the fan width as needed (you don't want to change it after you have "tuned" the gun). Turn out the material knob about 2 1�2 turns. This is the "mixture" adjustment, kind of like the idle screw on a carburetor. The farther in it is screwed the lower the fluid to air ratio is and the smaller the droplets will be. The farther out it is, the higher the fluid to air ratio is and the larger the droplets.

Set the air pressure at the inlet to the gun to the manufacturer's specs. On an HVLP gun, this spec is usually found on the gun, and is the maximum PSI it can have while still maintaining the maximum 10 lb at the cap for legal HVLP transfer efficiency (68 %). You are now ready to do a test sprayout.

Tape a piece of masking paper on the wall for the test. Hold the gun at a right angle to the wall, just as if you were going to paint the wall. Hold the gun at a spread out hands distance (about 8 inches, or 22 centimeters). Pull the trigger to completely open for a split second and then close it. You want an ON-OFF wide open-completely closed in ONE movement. You should have a cigar shaped pattern with complete coverage in the center with fading coverage going away from the full coverage cigar shape in the center. The center should be fully covered without any runs. If you have runs, either you are holding the trigger too long, you are too close, or the gun is simply applying too much material; in which case you need to screw in the material knob or turn the air pressure down. But most likely if you have turned the material knob out the 2 1�2 turns and the air is set at the factory specs, you are just too close or holding the trigger open too long.

The droplets you see trailing off the center are what you will use to "tune" your gun.

Turn in the material knob to make the droplets smaller (and or raise the air pressure). The balance you need to attain is the smallest droplet size possible before you lose the coverage desired. In other words, if you turn in the material knob too far, not enough material will be coming out to cover the panel!

Now, you'll notice that I said, "raise the pressure to the gun", while earlier I said to set it to manufacturers specs. We are talking a very small adjustment. It is a fine balance in material-to-air ratio and a little more air than specified is okay. Even if it is an HVLP gun the inlet pressure recommended is to maintain the 10 lb limit at the cap. Well, about three quarters of the country has no regulations for HVLP use, so if you go over the 10 lbs all it will do is atomize the material a little better. You may lose a little of the benefits of HVLP though. But remember you have a lot of control with the material adjustment knob.

After you are happy with the droplet size, DON'T TOUCH THE FAN CONTROL. It will change the PSI at the cap and will change the atomization you worked hard to get.

AIR REQUIREMENTS FOR HVLP

An HVLP gun requires more VOLUME of air to operate (the V in HVLP, High Volume Low Pressure). Now you may notice that your HVLP gun is adjusted at maybe the same PSI as an old conventional gun, around 50 lbs at the gun (many HVLP guns are set at much lower though) so where is the "Low" in PSI they are talking about? It is at the actual air cap where the air and paint come out. An HVLP gun has only 10 lbs at the cap while a conventional has upwards of 50! So the VOLUME of air (CFM -- Cubic Feet per Minute) is the key to proper atomization with an HVLP.

If you have a gun that requires 15 CFM you will need a compressor and plumbing that will produce that at a very minimum. There are HVLP guns that need as little as 7.5 CFM so you can get good results even from a smaller compressor. Air supply is a complete subject by itself, so let's assume that you have the air supply needed and move on to gun setup.

So atomization is the key, but why? Why can't you just lay it out wet and let it "flow", as an old painter will say. Picture a jar full of bb's; they will represent small, atomized droplets of PSPC. The gaps in between the bb's is solvent. Now picture a jar filled with marbles, they will represent large, poorly atomized droplets of PSPC. The gaps in between are, you guessed it, solvent.

If you apply your PSPC in large poorly atomized droplets, what you will have is a film full of solvent. This can and will cause slow curing, shrinkage and dieback (the loss of gloss in the hours and days after application).

So, now that we have learned the need for gun setup, how do we do it? Let's start with the fluid tip choice. The newer high-solids low-VOC PSPC products need to be broken up more, so a smaller fluid tip is needed.

Basically you want the smallest fluid tip that will still allow you to PSPC the particular part you are PSPC'ing, keeping the entire thing wet and in a fair amount of time. In other words, a 1.0 tip would be beautiful for clearing one fender, but would be lousy to paint a complete. The application would be way too slow, and the first panel would be way too flashed by the time you got back around to it. So you need to compromise -- a 1.3 is a great all-around tip, while a 1.5, though getting a little big, can get you by. If you read the tech sheet on the particular product you are shooting, it will have a recommendation for fluid tip size.

There are needs for other tips. For instance, when shooting polyester primer you may need as big as a 2.3, but for urethanes and epoxies, the 1.3 or 1.4 will work great. If you plan on using a pressure pot or painting a bus, all bets are off and we would need to study a little bit more.

As an example of the use of a 1.3 tip, I did a test once that proved the point well. I shot two panels of metal with a medium solids urethane primer. One was shot with a 1.3 super high atomizing top of the line topcoat gun. The other was shot with a 1.5 (or a 1.7 I can't remember) "hoser" primer gun. Three coats were applied and after a full cure (the one shot with the larger gun took MUCH longer to flash and cure by the way) the film thickness was measured. The one shot with the 1.3 tip was 2 tenths of a mil thicker! The larger gun laid out the marble sized droplets full of solvent, and when the solvent flashed the film shrank.

You need to "tune" your gun EVERY TIME you use it, just as you would tune a guitar before you perform. This is done with a very basic sprayout pattern test. This very basic test tells you how your gun is atomizing and you adjust it to achieve the best atomization you can.
 
Which button is which? Which is the fan control? I have one near the nozzle, one on the bottom of the gun and then a 2 part dial/valve on the back of the gun. With the 2 part dial, which do I turn? Lower or upper? Fuck I wanna finish painting the cab this year.
 
This should help.


Pressure Adjustment: Open your compressor regulator up so there is plenty of air pressure in the line to the gun (I set mine to about 90 psi). Next set the regulator on the gun handle to 50 psi (what I use for DP40 and K36) with the trigger pulled and leave it set there. Close the valve at the bottom of the handle (on the gun, not the regulator) and then with the trigger pulled, open it to the point where the air volume starts to stay the same (just listen to it) and leave it there (it should be pretty far open at this point). I never mess with this after this unless I think it has been changed.

Note: On my two year old gun they say the maximum pressure is 60 psi. On my new gun it says 40 psi. Instead of the 50 psi above you might try 40 psi if your gun says 40 psi max.

Fan Adjustment: Next open the fluid volume control about 3 turns for starters (at the back of the gun). Close the fan control down (on the left side of the gun behind the nozzle) so when you spray you only get small round circle. With the gun about 6 to 8 inches from a test surface (I use the garage door or better yet some sheet rock, or masking paper) move the gun across the surface (about 6 to 8 inches from the surface) and pull the trigger. As you are moving turn the fan control until you get the desired fan shape/width (about 5-6 inches wide top to bottom oval shape for overall painting) (remember if you are spraying up and down on a surface you can change the nozzle at the front of the gun 90 deg. so the fan is horizontal).

Fluid Control: Next after getting the fan the right size continue spraying and adjust the fluid volume at the back of the gun for the final adjustment to get the fluid right for the gun speed (how fast you sweep it across the work). You want to be laying on the paint at a pretty good volume, but not causing runs at a normal gun sweep speed.

Changing the pressure to match spec sheets: Now you're ready to paint and with 50 psi at the handle the gun is spraying about 10 psi at the cap. If you want 5 psi at the cap put 25 at the handle regulator (8 psi = 40 psi, 7 psi= 35 psi, etc.). You can't actually see the pressure at the cap which is what the spec sheets are referring to. The gun is internally regulating the pressure down based on the inlet pressure. Some expensive guns have a gauge off the back of the handle that tells you the cap pressure and then they also have a regulator and gauge at the bottom of the handle like this gun that regulates the pressure into the gun.

Painting: Look at what your painting and the way the paint is going on the surface right behind the gun and adjust from there. For instance if you want to spray some small areas/parts you can turn the fan down to a small round size. You will also have to greatly shut the fluid volume down at the back of the gun (clockwise) at the same time to avoid runs. I usually turn the air pressure at the regulator on the handle down to around 25 to 35 psi to do spot work like this.

Proper Pressure: Remember you need a high air pressure (Set as the spec sheet calls for) so that you get proper atomization and so you can turn the volume up. The higher pressure will actually mean fewer runs since the atomization is better. This is not so critical with the primers, but you really need it with the sealer, base, and clear coats so you get good coverage without runs and with little orange peel.
 
Also, I've noticed that I've had to thin my paint much more than you did to get a nice spray from the gun.

Same here.
Just keep thinning little by little till it you get a consistent fan with no spitting or pulsing.
 
Hi - do you guys thin right there in the cup (pour in a little water, stir it while holding the gun / spray until you think you reach the new batch?) or do you pour it out / mix in a bucket?
 
You must mix in something else. I use a cheap, clear, 2 cup measuring thing. Reason is, you then pour it through a cone filter, into the paint gun cup.
 
I thin it in a separate container till it has the consistency of milk.
I then try it in the gun and add more thinner,if needed,right to the cup then spray away if all is good.
That gives me a good idea of how much more I need to add to the rest of the paint.
Always strain the paint right into the cup.
Adding a little more thinner won't get the paint in the cup dirty as long as there isn't dirt on top of the thinner can.
 
Sprayed the final coat on Saturday. I think I finally got it right. I hadn't thinned the paint enough, and even though my gun is rated at 45 psi max, I cranked the psi on my compressor to like 100 and then regulated the gun pressure to 60. My fan was finally the 11 inches it should be, and other than some very very slight pebbling (probably due to the higher pressure), the finish is soooo nice. Clean up wasn't really that bad. My next spray job will be Gorf, then a Punch Out. By the time I hit my SI Deluxe and Pacman, I should be pretty good at it. Thanks for the help Jim.
 
Gorf, Punch-Out, Pac-man...stop copying me!


Congrats on getting the gun working. Once you get the hang of it, you won't want to go back to the roller.

I only wish I could copy you. If my spray jobs turn out as nice as yours I think I am going to make love to myself. I really think this method will speed up my restos. I also think my Ninty cabs will thank me.
 
Thinning is the key with a spray guy and latex. I use flotrol from
home depot or lowes to thin the paint.. almost a 3/1 mixture.

It goes on super smooth at roughly 40 psi.. small passes and never
stop the gun on the material you are spraying.

Malice95.
 
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