HVLP Questions

G

Greg T.

Hello everybody, I am new to this forum and I appreciate all of the info. that I have been reading on this site. I have a few questions if you don't mind. I have posted on other forums but want to get as much advice as possible.
My dad and I are attempting to spray his 57' vette. We have sprayed before in the past and took a few courses but has been a while since we have sprayed. We have a Sharpe Finex 3000 HVLP (obviously not top of the line) and are trying to get use to it. We are used to spraying w/ conventional gravity fed guns. I keep reading where folks spray anywhere from 29-35 psi w/ their HVLP. My question is doesn't this pressure defeat the purpose of an HVLP? I thought you spray at a lower pressure than that. I'm not being argumentative at all, I am just confused and trying to get an understanding on HVLP's. We have practiced on the trunk and I sprayed @ 32 psi, fluid turned out 3-3/4 turns and air knob all the way out. The clear looks like it has layed out good but their is what appears to be trash but I can't tell if it is trash or some type of small bubbles. They are in random spots. Thank you for any and all advice you can give me and I hope I can be a help to some in the future. Have a great evening. Sorry my first post is so long, LOL!!

Thanks Again,
Greg T.
 
I guess the question is whether you want to strictly comply with the letter of the law, or whether you want the highest quality finish possible. For regular production work, the spray gun manufacturer's recommendations are close enough, but if your main concern as a hobbyist restoring a high-end vehicle is quality, different techniques may be called for. Sometimes pressure in excess of recommendations does partially defeat the purpose of the HVLP setup, trading greater material use and more overspray for better appearance, but I think the HVLP guns still are much more efficient than their conventional counterparts even when run beyond spec. I don't even know what the spec is for the Finex you have, but to go about 20% beyond it as a starting point is pretty common.
 
Crash,
Thanks for your response and you are right. I would rather have a better looking finish than follow the "letter of the law". I guess I was just wanting conformation that we were ok spraying at that pressure. If I have 32-35 psi at the gun regulator, how many psi is actually coming from the gun? Once again, thanks for your help.
 
Greg,

Welcome to the SPI Forum. I'm working on my '72 Vette and will one day spray the body. I've migrated from the old siphon and pressure feed guns so I'm pretty much in the same boat.

Last week I sprayed two layers of paint on the lower control arms. First layer was a second coat of SPI epoxy (previous coat sanded) using an Iwata LPH400 silver cap with fluid 1/2 turn from wide open and pressure at 18. Second layer was Eastwood Chassis Black (gloss) using a DeVilbiss Finish Line HVLP mini with fluid and pressure the same as the Iwata. There was so little overspray with the Iwata that I had to re-check my settings. The DeVilbiss created its usual cloud all around the work piece. Both coats of paint came out fine but the more expensive gun put a lot more paint on the target.

My tool collection is mostly Craftsman and Harbor Freight and I avoid paying big bucks for tools. Based on the recommendations on this site, I've modified my cheapskate approach on spay guns and D/A sanders. The Iwata (and probably the Sata) guns are really that much better. Same goes for the Dynabrade (and probably Hutchins) Dual Action sanders.
 
Every HVLP gun requires a different input PSI, anywhere
from 14 to 45 PSI.
BUT, they all have one thing in common, at the tip it will be
10 PSI, hence the low pressure.
the gun actually regulates the pressure down to that, provided you
supply it with the right inlet PSI.
It's important to know the requirements for your gun, not anyone elses.
 
I have the Finex 300, it is a very capable gun for $100.
I have not used the Finex 3000 to be able to say anything about it.

I also have an Iwata LPH400.
It is probably me, but it blows a huge amount of overspray when shooting clear, every bit as bad as the Finex 300.
Last time I used the Iwata I shot it at 22 at the gun and the cloud wasnt as bad, but definately not what I hoped for.
 
Bob, thanks for the welcome. I wish you great success on your vette. JC, thanks for clearing that up for me. I just didn't realize that there was that much pressure drop from the regulator at the gun to the tip. Old Fart (LOL), thanks for your input as well. I hear everyone talking about the Iwata and Sata and was surprised to hear that you weren't as satisfied as everyone else. My old instructor said that he has a $750.00 gun and all he sprays is base as he can not get it to lay the clear down. I would not be a happy camper, LOL!!! You folks have a great day!!
 
From what I can find on the Sharpe website the Finex 3000 calls for:

  • Air Consumption (cfm): 9.5 SCFM
  • Max Inlet HVLP psi: 29 psi (2.0 bar, 200 kPa)
The Iwata LPH400 with a 1.4 tip requires a Max inlet 16 psi (13 psi less) and the same 9.5 CFM of air. So just in the level of PSI requirements to get 10 psi Cap pressure there is a marked difference in the two guns.
Thus running a LPH at 24 PSI is 50% over its maximum while the same pressure on a Finex is still under its max. pressure. Therefore I would say trying to compare them one to another would require setting up each gun to run within its design parameters.
Another factor is spraying style. When you set up an IWATA to run at 16 psi you have to crank the fluid knob in and work to get the paint atomized correctly. What I find is it seems like I am not able to paint fast enough to suit me when set like that. I want to move faster so I have to back the fluid knob out and then increase the air pressure. Thus painting style also comes into play when setting up a spray gun and with that sacrifices must be made in other areas OR you need to find a gun that fits your style better.
I am beginning to think for me a SATA RP might be a better choice however I won't sell my LPH400 until I am certain. In fact, I probably won't sell it at all since it is a very nice gun.
 
small bubbles are usually from spraying too close, or pressure too high, puddling...all related, all of which i have done!
 
Spraying too close may also be one of my problems. I am probably anywhere from 4-6 inches away from the surface. Also getting the air knob on the gun adjusted correctly is another problem. On clear, I sprayed it at 32 psi. at the gun regulator with the air knob on the gun all the way out. I guess this is just something you have to experiment with. If it weren't for shift work, I would head back to the community college painting courses, LOL!!!!
 
you just need practice and experimentation on practice panels, fender or tank until you dial in the right settings...4' to 6" isnt too close if the is pressure right and youre moving along at the right speed...
 
Post up a pic of the bubbles or trash and I'm sure the members here can decipher the problem. Sand it out and spray it again-that's how you learn!
 
Bob,
I will try and get a pic up as soon as I can. Thanks everybody. This is a great place.
 
Greg T.;13589 said:
Spraying too close may also be one of my problems. I am probably anywhere from 4-6 inches away from the surface. Also getting the air knob on the gun adjusted correctly is another problem. On clear, I sprayed it at 32 psi. at the gun regulator with the air knob on the gun all the way out. I guess this is just something you have to experiment with. If it weren't for shift work, I would head back to the community college painting courses, LOL!!!!
Click to expand...

First thing to do is make sure the regulator at the wall or compressor is at least 125 lbs or higher, then adjust the air at gun.
Also first ting in morning drain the main compressor tank for a minute to get the water out, then put an air fitting in the hose and let blow for about 5-10 seconds.
 
I have been using the lph400 with a 1.3, and find I"m up around 30+ psi otherwise it just seems too low. It does seem that an Iwata 1.3 puts out way more material then my sata 3000 hvlp, and the finish isn't any better, find I'm getting runs more easily as it floods on the material compared to the sata 3000 and 2000 hvlps.
 
I highly recommend an automatic drain valve on compressor tanks and air receivers, especially if you are as forgetfull as I am.

I purchased one a few months ago at a local supply house for under $100.

I should have installed one when the compressor was new, but got in a hurry to get it online, then forgot about installing one. After I got tired of getting on the floor to reach the drain valve for the umpteenth time I went and bought one, LOL. ( I knew better too, being pipefitter by trade. what is it they say, the cobblers child goes shoeless? LOL)

Summit sells this one which is similiar to what I purchased locally for $50 less:
dvr-130512_w.jpg
 
danp76;13835 said:
I have been using the lph400 with a 1.3, and find I"m up around 30+ psi otherwise it just seems too low. It does seem that an Iwata 1.3 puts out way more material then my sata 3000 hvlp, and the finish isn't any better, find I'm getting runs more easily as it floods on the material compared to the sata 3000 and 2000 hvlps.
Click to expand...

Cut your psi back to around 22-25 and set your fluid knob at 3-3.5 turns out with fan full open. This seems to be the setting nearly 95% of LPH400 users like when spraying clear and that's using a 1.4 tip.
 
1.3 fluid tip, 22-25 psi, 2 1/2-3 turns out on the fluid knob, fan wide open or choked 1/2 turn-that's my basic starting point for most clears. 4" distance from panel and spray it how you want it to look, I spray slow but strive for a thin, wet, flat coat. Clears of different viscosity will require different settings, same goes for all paint products.
 
^ i do exactly what bob does with my mini iwata. i used to hammer it on, but that made me an expert at producing runs and mini bubbles, and an expert at removing runs. 5 minutes to spray, half an hour to remove runs... so multiple thinner coats it is... of course my thin coat may be someones elses medium...
 
I think the questions I was going to as have been answered. Spraying epoxy primer, high build, and urethane SS with an Eastwood Concours Pro I've got a lot of overspray. 1.3 tip except for the high build, tried different pressures from 15 to 28. Got the best finish so far at 25 psi but couldn't keep a 1 bay divided room clear with 4 22" fans with filters. Used to only use 1 24" in a similar size room with my old Binks 62 spraying Imron. I've got an Iwata coming 1st of the week, from what I'm reading here that might address the excessive overspray I'm getting.
 
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