Trouble getting good results with Devilbiss GFG 670

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PostPosted: Sun Nov 29, 2015 2:19 pm
Background...I've been painting for about a year now and have since done a few complete paint jobs. Originally, I started out with a cheap HVLP gun (http://www.amazon.com/Vaper-19220-Triple-Set-Up-Spray/dp/B0009IQ2FA) and have been able to get great results...smooth, even base coats and clear coats with very little orange peel.

Recently, I decided I wanted to see what all the hype was about with these 'better guns', so I picked up a Devilbiss GFG 670 Plus. After spraying a few test panels, I can say I don't exactly love it...I'm finding it very difficult to get a perfectly smooth and even finish in my base coat. I've tried all sorts of adjustments (fluid, fan, psi, travel speed, overlap), but I'm either left with a finish that is in some areas a little blotchy / dry or a finish that is starting to strip / molt. I'm practicing with various metallic PPG JB base coats I have left over, using medium reducer with a 1.3 tip.

I do like how well this gun atomizes the paint, but I don't particularly care for the fact that it absolutely BLASTS the paint onto the panel...I've never seen so much over spray. My HVLP gun is so much softer, has drastically less overspray, and seems much more forgiving...every time I can lay down a perfect coat.

Is there a different technique to spraying with HVLP vs. a compliant gun? If anyone has a 670, what are your settings? Any other advice or thoughts to help get me off the struggle bus would be greatly appreciated!



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PostPosted: Sun Nov 29, 2015 6:19 pm
You may want to return it for another one if you bought it new. Maybe it is defective. If you bought it used you may need to clean it real good.

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PostPosted: Sun Nov 29, 2015 10:43 pm
What size is your compressor? CFM output rating?
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PostPosted: Mon Nov 30, 2015 7:52 pm
Mmonney...bought the gun new and cleaned it real good before I ran any paint through it. For kicks, I shot some clear with it last night and found the results to be marginally better than my HVLP...maybe my problem is operator error, but I'll definitely consider making a call to Devilbiss tomorrow to make myself (hopefully) feel better.

R/T...compressor is big...20CFM from the one pump and if I need more air (sand blasting), I can turn on the other pump for another 20. It's got a 200+ gal. tank. Even use 1/2" ID hose for spraying because I've always been too lazy to swap out the small fittings on the 3/8" hose...definitely helps to keep the arms strong.

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PostPosted: Mon Nov 30, 2015 9:11 pm
That rules the compressor out.
I believe that gun should be up around the 35 psi mark when spraying. Does that sound about where you had it?
Could just be getting it set up right.
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PostPosted: Wed Dec 02, 2015 9:58 am
R/T...experimented shooting the base from 25 - 30 psi and shot the clear at 35 psi. In the manual that came with the gun, Devilbiss recommends spraying base from 25 - 30 psi and clear from 30 - 35 psi. I've always set my HVLP around 25 or so for base and around 30 for clear.

Later this week / weekend I have to paint a few bumpers to finish off a car. I'll try bumping the pressure to see if I can get some better results...somewhere else in the forums I think I remember reading someone setting the gun up around 40 psi. So maybe it is just getting the right setup.

If I still run into some troubles, I'll post a pic...hopefully that'll give us some more information.



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PostPosted: Thu Dec 03, 2015 5:09 am
too much psi will result in more peel right??
i have my gtiprolite on around 1.9 bar for my 2k solids and clears, havent done any base yet tho, but i would have thought too much pressure would result in a mottle/blotchy effect in base,
check out youtube and search for the gunman, he does heaps of gun demos and reviews, tells you wat pressures are good, how close, settings and you can watch him actually use the gun, it may not be the specific gun you have, but something close anywyas
krem

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PostPosted: Thu Dec 03, 2015 12:09 pm
Setting a gun by checking the spray pattern on masking paper will let you know that you have a correct full pattern with consistent sized droplets throughout. The trick is to hold the trigger full open for one second while holding the gun at the correct distance from the paper.
This will approximate a spraying speed of about 1' per second. Obviously people spray at different speeds so your gun needs to be tweaked to your spraying style. Satas and RP guns seem to be happier at faster spraying speeds, Iwata LPH and LVLP guns seem to be geared to slower spraying speeds.
Once you get your gun spraying correctly and you are happy with the results be sure to make note of where it is set. How many turns out on the fluid knob, fan knob and the PSI when trigger is pulled full open.
I find that epoxy, sealer, and base are equal settings on my Tekna Copper with a 1.4 tip. Clear and single stage require about 7 PSI more to atomize and lay down correctly.
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PostPosted: Sun Jan 31, 2016 3:42 pm
I love my Devil gfg-670 plus,but I only spray clear with it @ 35 -40 psi.

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