Changing over to gravity feed gun? - created 04-22-2009
Fleck, Mike - 04/22/2009.23:55:33
I have been using a Warwick HVLP gravity feed gun with with a Ingersall Rand SS-3 compressor and 30' of black iron pipe then filter to gun. Before making the switch to this setup I was using a Campbell Hausfield HVLP with turbine.
I have had the Gravity feed for about a year and I still cannot get my finish to lay flat compared to my old HVLP suction feed setup.
Anyone out there getting good results with gravity feed setup shooting nitro.. If so do you mind sharing your needle size#,brand,PSI,fluid control setting ETC...
Are you spraying at a different viscosity than you did with suction?
One thing I do like about new setup is the amount I can lay down in a session, I just cant get it tuned in to lay very flat.
Thanks for your time.
I just bought a Sharpe Finex gravity feed gun yesterday and sprayed a neck with it today. It's the mini-HVLP, sprays nice better than my other gun (which was a primer gun). The cup is a little small but enough for 1 coat. I tend to spray heavy and I'm trying to break that habit. The tip is 0.40 or 1mm which when spraying seemed a little small. I do think I'm going to get the 1.2mm tip instead. I've sprayed nitro only 3 times and its not like paint that will flow out and lay flat. Instead sand and buff. Nitro is a dream to buff compared to automotive finishes. As far as PSI I'm shooting about 25psi, I set that to the material I'm shooting, more of a feel thing. I set the material first about 1/4 in then adjust the pressure till I like the quality of fan, testing on a flat sheet looking for a good pattern. Overall I'm happy It's small, easy to operate. The cost was $120 and sprays like it costs more.
I've used a Fuji turbine HVLP system with gravity feed for my last five guitars, and it works fine. I'm using the standard aircap (1.4 mm), and shooting nitro thinned according to the manufacturer's recommendations (21-24 seconds to drain through a viscosity cup). I bought the rig with both a gravity and suction feed. But, given the simplicity of clean up with gravity, I haven't bothered to even try the suction setup. It takes some experimenting with adjustments to the volume, pressure, and aircap settings. But, once I get it right, it flows out nicely. No need for any retarder to this point either - but I also only spray in my garage in May or October, when it is still warm enough to spray outside (here in Ottawa) and yet the humidity is manageable - i.e., close to 50%.
I am using a 1.4 mm also and a 1 mm on my smaller gun. I am shooting at 40-25psi at filter regulator and I adjust with cheater at gun.I also have fluid control almost all the way open 1/4 turn in.
It seems like the atomization on both guns are not correct and when I get them close to correct the guns start to spit. I cannot figure out what I am doing incorrectly. It being both guns, I am thinking it may be a psi,cfm or viscosity issue. I shoot McFadden at 3 parts Laq. to 2 parts thinner. and 1 part to 1 part. on final coats.
The guns work OK for new builds when clear coating but on color matches,bursts and touch ups they are to sloppy.
Thanks for reply
Mike, every situation is different. Every gun, every finish, and every environment will require different settings. You must learn (or experiment) how to dial in the settings that will work for you.
If you can give us more information on your specific problems, we might be able to come up with some suggestions. In other words, what do you mean by too sloppy. Is the gun spitting droplets of lacquer?
Barry thanks for the reply.
Yes both guns are spitting droplets of lacquer.
When adjusting gun, I am missing the spot where the atomization would be fine enough to not have orange peel issues without having the gun start spitting droplets.
How much reducer are you using? Meaning, maybe the lacquer needs to be thinned a bit more. I shoot polyester, urethane, and nitro and had some orange peel problems until I just thinned it a bit more. Goes on like glass now. It took a little bit of experimenting to get the right viscosity. Be sure to write down your mix ratios as you go along & adjust.
I'm using a Devilbiss touch-up gun (the Demon) w/ a 1.0 tip & 8 oz cup for my topcoats. Of all things, I use a Kobalt (yeah, the Lowe's brand) hvlp gravity gun for my bursts (1.2 tip I believe)... gotta laugh, but it bursts VERY well. Using a Devilbiss air filter/dryer & shooting @ 35psi.
Forgot to mention.. do you have a gun cleaning kit? Manditory stuff to make sure that the fluid tip & cap are cleaned right after spraying. I like to disassemble the gun after a few cycles to make sure the needle isn't gooping up, too.
I apologize if you already know this stuff. If you're getting the same results from two different guns from two different mfgs, then I'd tweak the mix. Personally, I like it a bit thinner and shoot a few more coats rather than thicker with peel.
I was going to say the same thing as Joe. Check to make sure your tip and cap are cleaned properly. Any little bit of dried finish can really effect the air flow.
The other thing is to make sure and not put to much pressure into the gun. Check the rating either on the gun or in the manual to make sure you're not putting in more than the gun requires.
I just got the Devillbus finishline WB gun and it only needs 23 psi to get 10 psi at the tip. That all it needs to attomize the material properly.
If you can, go to your library or buy this book, http://www.rockler.com/product.cfm?page=16758&cookietest=1 it has great details on setting up your spray gun correctly.
These bodyshop guys are always knowledgeable about this sort of thing:
http://autobodystore.com/forum/index.php
Like Joe said, the bodyshop guys, specifically painters will be your best source for help. My daytime job is in the service department at a car dealership. I got the painter from our body shop to help me learn how to set everything up. I'd recommend finding a local car painter to come to your shop for a couple hours. A little bit of hands on instruction is worth a BUNCH of reading.