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Old 06-15-2005, 06:38 AM
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HVLP Pressure

I'm hearing from others that the mfg. recommended air
pressure for the HVLP guns is to low and most people
are spraying with 10 to 15 lbs more. I've tried this and
it does seem to do better. Is this what the rest of you
have found? Are you spraying at higher pressures than recommended
to get a better finish? I'd really like to hear what works best for you.
Thanks: Jim

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Old 06-15-2005, 08:08 AM
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Some times you need to bump it up a little to make up for a poor CFM, however 10 or 15 lbs is quite a bit.

What gun are you using and what is the recommended PSI AT THE GUN that is recommended?

Describe your air supply, compressor, length and size of pipes and hoses, filters, etc.

Brian
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Old 06-15-2005, 08:22 AM
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Well right now I'm using a Astro HVLP that is suppose to
be a Sata copy, I love this gun, it sprays really nice.
I also use a DeViilbiss Finish Line series HVLP that I like
for the "bag system" Tips are 1.3 to 1.7 and I haven't noticed
much difference between them. I use the 1.3 most.
They call for something low, like 20 to 25 psi. (if I remember right).
But I've been told by a salesman that most are spraying with 35 psi
and even up to 40 psi.
My compressor isn't big, only 6.3 cfm at 90 psi. but it keeps up with
these guns just fine. I use a 5/8" hose usually only 25 ft long.
I have been spraying at 25 psi but yesterday I bumped it up to 35
and it does seem to do better. A lot more overspray though.
Is there any downside to bumping it up?
I wondered if the mfg low pressure recomendations were more for
good pollution stats. Thanks.
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Old 06-15-2005, 08:39 AM
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Your compressor is not producing nearly enough CFM, those SATA HVLP guns require over twice that at about 14 at 29 CFM I believe. The Finish line has an 11.4 CFM requirment but that is at 23 PSI and at 23 you are probably producing something like 3 or 4! So, bumping it up is not only "better" it is absolute nessisary to make that gun atomize.


This is how it goes, these guns need ten pounds PSI MAX at the cap to atomize properly and STILL stay at the 68% transfer efficiency to qualify as an HVLP gun. So, the 23 lbs at the gun WITH the 11.4 CFM will do that. If you don't have the 11.4 CFM it is impossible to get the 10lbs at the cap. It is likely with the gun set at 23 lbs you are getting more like 5 lbs at the cap. That is just not enough to atomize properly. If you bump up the PSI it will increase you cap pressure but you will loose transfer efficiency, it is a trade off.

Brian

Last edited by MARTINSR; 06-15-2005 at 11:21 AM.
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Old 06-15-2005, 09:33 AM
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Jim

If it is the same gun that I just bought (and I believe it was you that recomended it) it requires 10 CFM @ 41-44 PSI

They do also make a LVLP Gun but it looks like it even wants 40 PSI.


BTW so far I am really happy with the gun.
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Old 06-15-2005, 10:43 AM
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Shakey: You're right, I looked up my gun on the internet and confirmed what
you said. I believe I have the regular HVLP model but as soon as I get home
I'll check. I can't understand how my compressor can keep up with it so
easily, of course at the lower pressure it has a lot more air.
I don't know why I thought it needed to be so low.
Just goes to show you, just because you have been doing it a certain way
for years doesn't mean it's the best.
Well thanks a lot, I'm going to crank er up!
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Old 06-15-2005, 09:21 PM
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Jim did you get that Sata copy at our local hang out??? Just wondering what they are chargin versus spraygun world or something like that?? I am going to buy one of those guns....

Hey Brian, I have heard soooo many people say that they like the DX3 much better than the Finishline lll... Would not one think that the finish line would be a better gun because of who makes it??? I can buy them both at the same price pretty much, and I am having a hard time determing which to get..
Many years ago I bought a Sharpe SGF98 that was a let down from the begining. That gun at the time cost me $200 ( it was 1998 or so ) and I have had much better luck with those cheap Astro air hogs... What gives??

I have a large enough compressor now for sure

Jim I knew you would not mind the question bro

Matthew
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Old 06-15-2005, 10:47 PM
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Matthew, I don't have anything to offer you on the D3X or Finishline, haven't used either. But I did use the Sharpe SGF98 for a while. I was not too impressed. But this is the funny thing. The first time I used it was when I was working for S-W. I was at the Reno training center at a regional meeting. In the morning I was handed this gun to spray some panels. The gun was BRAND NEW and not even available at the time. The center gets the latest and greatest in guns and usually has about fifty on hand from every manufacturer imaginable. One of the trainers gave me and a couple of other reps a glowing report on it and handed it to use to see for our selves. I couldn't believe, that darn thing was great. Great for ANY price and being it was half as much as the top of the line guns, wow, we were all very impressed. I liked it so much I was scheduled to do a demo for some S-W big wigs (my boss' boss' boss'.......) and choose the SGF98 to do it.

I called the Sharpe marketing dept and asked for one (cool thing about the job, just ask and you had stuff like that for free) for my paint demos. All the reps that were there did the same, we all got our new SGF98s a few months later when they went into production. Well, we soon found that this production gun did NOT shoot the same as the demo we had used! I am sorry, that demo gun and the one I found on my door step in a UPS box were NOT the same gun, that is for sure and all the other guys felt the same way.

Where they lost track and changed it, I don't know.

Brian
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Old 06-15-2005, 11:55 PM
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Quote:
Originally Posted by MARTINSR
I called the Sharpe marketing dept and asked for one (cool thing about the job, just ask and you had stuff like that for free) for my paint demos. All the reps that were there did the same, we all got our new SGF98s a few months later when they went into production. Well, we soon found that this production gun did NOT shoot the same as the demo we had used! I am sorry, that demo gun and the one I found on my door step in a UPS box were NOT the same gun, that is for sure and all the other guys felt the same way.

Where they lost track and changed it, I don't know.

Brian
Brian,

Thanks for this post I have one of the early SGF98 and it works great , a friend of mine bought one and complained to me about it ,so I had him let me adjust it for him , (like I know what I am doing) it doesn't shoot like mine.

Keith
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Old 06-16-2005, 04:58 AM
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I bought my Astro from Spraygun world so I don't know what the price
is on the open market.
I also have a Finishline series gun made by DeVilbiss and sold at Sears.
I don't think they still sell them at Sears though.
It came with two tips, a 1.7 and a 2.2.
My astro sprays better than the Finishline but I love the Finishline because
it has a bag system that you can seal the paint in like a babby bottle.
You can shake the heck out of it while painting and shoot upside down
and never spill a drop. It also uses less air. I use it for my bascoats
because I can keep the paint shook and mixed good.
It's a great gun with hardly any overspray, but for my clear the
Astro does better.
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Old 06-16-2005, 06:53 AM
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Cool, seems like an aweful big tip to shoot base with though? Hey what do I know anyways lol

Matthew
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Old 06-16-2005, 07:43 AM
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Jim, Try getting a 1.4 tip for the Finishline. That's what I use and it lays base out nice. The only issue I have with clear,is it dosen't produce as wide a fan as my "purple" gun.It does OK but not as wide of coverage.
The bag is very convient and makes color changes a snap besides not using a lot of thinner for clean up.
I generally run my hose reg. at around 75 (true 3/8 hose & conn.) and the gun reg is between 23-25 depending on product.
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Old 06-16-2005, 09:08 AM
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You're spraying around 25 lbs of pressure?
That's what I was doing but thought it was wrong for hvlp guns.
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Old 06-16-2005, 02:21 PM
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hvlp

Heres my take on the subject,my former paint rep had a special tip with a pressure guage attached,with my compressor,it took 40 + - at the gun to maintain 10 psi at the tip. Cfm is the key. I have an Asto for primer and general paint ,can`t even think of name of other one,"$300 range" Both work good if kept clean and the guy at the controls knows what he is doing. Jerry
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Old 06-16-2005, 03:50 PM
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That's the great thing about HVLP, It seems all guns are different as to what they want/need.

My Finishline is a low CFM gun and is "supposed" to work with a small compressor like most homeowners would have. Say a 33 gal job,which I had at the time and it did panel work OK but I never shot a whole car with it.

It's a guessing game for the most part and I just gave up trying to be "correct" with all the "recommended" settings. I use a true 3/8 hose & conn.,sufficient compressor and just adjust the gun to where it lay's out good. Being a "little" up on the PSI isn't going to hurt you IMO and may help you.

It really comes down to what product your shooting and some test shot's,then adjust from there. Praying and a sacrifice or 2 dosen't hurt either.
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