Another "Newbie needs help" Thread
Let me start by saying great forum. I've been searching for an autobody forum for a while and just came across this one. I haven't had much of a chance to search through all the topics but the posts I've read have all been filled with very valuable information!
Where to begin....
I'm a complete newbie that was toying with the idea of repainting the fenders and hood of my 2002 Dodge Dakota before I sold it. My original clearcoat was "burning" off and I needed to make it look as good as possible before I could put it on the market. I didn' want to spend the $1200 that my local shop quoted me for repair so I took the newbie approach and said I'll do it myself. I normally try to research tasks I undertake as much as possible but I failed miserably with this one.
I purchased the generic blue anodized HVLP gun on Ebay and ordered colormatched SW paint from autobodytouchup.com.
I started by stripping the panels with stripper and sanding the remaining residue with my DA sander and some 80 grit paper.
I constructed a makeshift paint booth in my garage and attempted to spray primer on all the panels. By the way, I'm using a craftsman 25 gallon compressor. Primer went on well but I could never seem to get the gun adjusted right. I sanded the primer with 600 grit and all was well. I attempted to shoot my black base coat and again, couldn't seem to get the gun to spray right. The paint went on very rough and being a newbie, I figured it would "flatten out" as it dried. I was wrong! I shot clear over it thinking I would be able to make it at least shine. Wrong again! After doing some reading, I believe that I didn't have my gun setup properly. The gun didn't come with any instructions so I set the compressor at 40psi (says 9.0scfm @ 40psi) and the regulator that came with the gun was set at around 10 psi. When I shot the paint, it came out very spotty....So basically I knew something wasn't right but I continued anyway. I thought about sanding the clear with some 1000 grit and polishing it with some 3M but I'm not sure if that would fix anything since the base coat was so rough....I realize I should be bashed, flamed and banned from this forum for this but I'm a firm believer that you learn from your mistakes and I'm looking for a little advice here. Can anyone point me to some websites where I can learn a little more before I take on the task again? When I do, I'm looking into stripping all the panels again and shooting primer with my cheap gun and shooting base/clear with a devilbiss finishline gun...I'd also like to know how to setup the gun properly...
Again, great site and I apologize for my ignorance.
Len has a pretty smooth method of setting up his guns.
Basically its sounds like your gun pressure was way to low. You need to crank your compressor up and set your at gun 40-50.
I set my gun up a little different then most but lets try and explain.
First I close everything on the gun. Set my air to 40-50, take my fluid
and turn it back 2-3 threads and pull the trigger. Open up your fan and as you unscrew it your want to see a relatively even pattern from top to bottom about 8 inchs long. As you open up your fan you will need to add more air pressure.
Take a peice of old metal or paper and spray on it to check it once more.
You want to see a wet film with 2 pass's.
From there you go to your fender and take a couple quick pass's in the lower portion. Stop and look at it. You want a wet film, not dry and rough or heavy and lumpy. You can make more adjustments as you go but your best bet is to use 40-50 psi at the gun and apply thin wet coats. It may take 2-3 coats.
On your clear you want a very thin coat to begin with and then put it on
wet for your last coat.
Its a hard thing to explain in one post because each painter has a feel of there own.
Sounds like your spray gun was the normal Sata NR-92 Asian knockoff. The 10 psi that everyone hears about is the 10 psi MAX at the tip in order to fall within HVLP guidelines. Set the inlet pressure on your spray gun to 30 - 35 psi with the trigger pulled all the way back and air flowing through the gun. To finish setting up your gun - open the fluid control knob wide open and leave it there permanently. (wide open is pull the trigger back as far as it will go and keep turning the fluid control knob counter clock wise until the trigger is no longer affected by the fluid control knob). Open the spray fan wide open then with air and fluid coming out of the gun start adjusting the fan inwards a little then stop and leave it there. Thats it - your gun should spray fine at that point. Clearcoat HAS to be sprayed in equal medium coats. You can't spray a thin coat of urethane clear without ending up with a bunch of orange peel when you're done. Each coat of clear including the first coat should be thick enough to flow out properly. What you will learn is that there is a fine line between the paint going on too dry and going on too wet and getting runs. You're shooting for something in between.
So 40-50 psi at the compressor and 30-35 psi at the gun regulator?
Any recommendations on a better gun? Is the devilbiss finishline with a 1.3 tip o.k.?
I have one and it works fine on everything. Conventional feel but HVLP efficientcy. But DAMN I paid 145.00 for mine..
Pardon my ignorance but the gun I want (devilbiss finishline) shows 16cfm@30psi in the specs. What does this mean? Does it need to be set at 30psi at the compressor?
You can crank the compressor air up to max 110-120 is usually fine. The compressor air doesn't affect the pressure at the gun. You may get a little burst of air when you hit the trigger but it had never bother'd me.
CFM is Cubic Feet per Minute. This is flow or volume.
So its 16 cubic feet per minute at 30 psi. Psi is pressure.
Your compressor is running 110 psi. Your regulator reads 30 psi. All you have at the gun is 30 psi. You set your regulator at 40 psi, all you have is 40 psi at the gun. Now with 30 psi at the gun your going to get a considerable drop at the aircap maybe be as low as 7 psi. The compressor is irrelivant unless its set at 40-50psi. You lose pressure with the lenght of your airline. Theres a formula for it but i don't know it off hand. Set your compressor to 90-110-120, or what ever is recommended by the manufacturer.
How that helps.
APO That formula of 16 cfm @ 30 psi means that spray will use 16 cubic feet of air per minute at 30 psi. The reason the spay gun manufacturers provide those numbers is because a lot of homeowner compressors put out 8 cfm or less ( just about ALL 110V compressors with the 20 - 30 gallon tank size ). What they're telling you is that their spray gun will use twice as much air as a compressor that puts out 8 cfm. Obviously you will run out of air in short order if you spray with a gun that uses twice as much air as the compressor is able to pump out. Most pro painters set the wall air regulator to around 70 psi then set the gun inlet regulator to 30 - 35 psi with the type of gun you're using (actually a pro wouldn't use the kind of gun you're using for BC/
CC, no insult intended).
Thanks for the help guys. Phil, I understand that a pro wouldn't be using a Devilbiss finishline but do you think that this gun would give me good results forgetting the fact that I don't know what I'm doing. I may let someone who does spray it.
Thanks again for all the help!
i think that gun should do you just fine for what your doing, but i would try to get the "feel" of the gun before you go to actually paint
Spray guns (like other tools) usually perform as well as their R&D, engineering and manufacturing dictate. There's a lot of competition in the spray gun world and with China coming online with good engineering at low prices there are many good low priced guns on the market and the DeVilbiss Finishline III is one of them. However like everything else in life "you get what you pay for" and more expensive guns tend to last longer and perform better and are constantly being improved in order to keep up with the competition. So I say that the Finishline III is a good gun for the money but if you can afford and justify (based on the value of the project) spending more money you would probably get better results with other guns.
Originally Posted by ap0352
Brings me to my next question about my compressor. It says on the side that it produces 9.0 scfm at 40psi and 7.0 scfm at 90psi and the regulator on the tank goes up to 200psi....4hp/25gal tank
Will this compressor be suffcient?
APO, originally you posted that you had problems spraying paint with you imported HVLP spray gun. That is what I was referring to when I said a pro would not use a gun like that for spraying BC/CC. Actually the Devilbiss Finishline II and III are in a "grey area" as far as getting professional results spray BC/CC. The Finishlines are the least expensive readily available spray guns that DO deliver acceptible results. Notice I keep referring to spraying BC/CC when I make a statement about spray guns. That Taiwani Sata knockoff HVLP is actually a decent gun for all primers, for spraying lacquer paint, synthetic and acrylic enamel paint. They fall short of the doing a decent job with acrylic urehtane single stage and clearcoat because the urethane topcoat paints require finer atomization than any of the other paints mentioned. The Sata knockoffs just can't atomize the urethane topcoat paints correctly. Its not a matter of crappy workmanship etc, the problem comes from the original design of the spray gun. The original Sata NR-92 was a crappy spray gun for urethane topcoat paints so the Asian knockoffs are going to be any better than the expensive original German Sata gun. What all this means is --- if you plan on spraying urethane topcoat paints (single stage and clearcoats) then you have to have a gun that is designed to handle those type of paints.
Now about your compressor - It is most definately too small to use with just about every spray gun made. A bare bones MINIMUM air compressor for spraying a whole car or truck is -- 220 v, 60 gallon tank, puts out a minimum of 12 cfm @ 90 psi.
clarification - in my previous post I made a reference to your Sata Taiwani knockoff. I was referring to the original gun you said you have problems spraying with and NOT the Finishline II or III.
Couple more questions...sorry...
Is my compressor big enough if I'm only spraying one panel at a time..Allowing time for the compressor to catch up in between panels?
I will be using a single stage urethane base coat as well as a single stage acrylic lacquer clear so what gun would you recommend I purchase to give me acceptable results?
Thanks again for all the help! I couldn't do it without you all!!