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Location:
Perth, Western Australia
Registered:
October 2004
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Spray Gun Advice - HVLP?
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Thu, 08 December 2005 06:42
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Ive recently bought myself a compressor, with the intention of giving my car a respray. Its a 3hp direct drive 15 cfm and 80 litre tank.
It will be sprayed in acryllic and through my research most people have recommended a gun nozzle size of 1.8-2.0mm. Some people have recommended a HVLP (High volume low pressure) gun, but others say these need large compressors (20 cfm) is needed, and some others say I don't need a HVLP gun at all, just a normal gravity fed gun.
Can anyone tell me what the difference between a decent gravity fed gun, and a HVLP gun, in terms of usability and final finsh... apart from price  .
Thanks all
- Matt
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Location:
Lismore, NSW
Registered:
February 2003
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Re: Spray Gun Advice - HVLP?
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Thu, 08 December 2005 06:54
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I think the HVLP gun is mainly used for primer where a high build is required. When spraying 2pac you use about a 1.2-1.4mm nozzle so maybe 1.8-2mm might be still to big to spray acrylic. Also you will need to get a regulator to control air pressure. I could be wrong on all the above but then again I could be right.
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Location:
Forster NSW
Registered:
September 2004
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Re: Spray Gun Advice - HVLP?
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Thu, 08 December 2005 06:59
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I'd recommend using a gravity feed gun. There won't be a great difference in the finish which each gun will produce, the main difference comes down to personal preference.
HVLP guns can be more difficult to spray roofs and stuff with because of the can being on the bottom of the gun - causes problems with obscure angles when the can is nearly empty it won't spray any paint, and secondly it can simply get in the way.
With a gravity feed it's on top and out of the way - some people say this makes them top heavy, but having sprayed two cars with gravity feed guns I can't say it's a real issue for me. You can clearly see when it runs dry and it needs topping up, which tends to be fairly often, but I don't believe HVLP guns to have a huge advantage over this anyway.
You won't need to spend a fortune on a good gun, I think I spent <$150 on mine and it's easily got me through two cars, and will last me a long while yet!
Your compressor sounds very ample for what you will be doing, make sure you set up a water trap on it!
Dale
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Location:
Perth, Western Australia
Registered:
October 2004
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Re: Spray Gun Advice - HVLP?
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Thu, 08 December 2005 07:25
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It has a good water trap and regulator.
Im sorry i should have specified, im looking at the difference between gravity fed hvlp and just a normal gravity gun.
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Location:
Adelaide
Registered:
July 2004
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Re: Spray Gun Advice - HVLP?
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Thu, 08 December 2005 09:51
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HVLP stands for high velocity low pressure. Basically it reduces the overspray significantly. It also needs a very high volume of air. If you are doing it in acrylic laquer then a 1.8mm fluid tip on a suction feed gun will work fine. Gravity fed and suction fed all depend on personal preference, the gravity feed gun can get into harder spots though, but not to difficult for suction feed, just dont fill right up when spaying roof or bonnet as it called leak out the breather hole.
have fun, matt.
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Location:
Binningup WA
Registered:
April 2004
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Re: Spray Gun Advice - HVLP?
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Thu, 08 December 2005 10:51
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I've have a cheap 100 buck standard gravity feed gun and I find it does quite a good job considering I'm a newbie at painting.
I've sprayed 2pac and Enamel with it no worries(last year) and recently(last two weeks) I've used it with Acryllic for the first time. Seems to produce a good finish on the Acrylic though I'm still learning. I got a little bit of orange peel on a section of my left rear panel(MX83 project) but I'm still experimenting. Re-sand and touch up tommorow.
The finish with 2pac was awesome. My 4WD's suspension and diff housings(plus other minor bits) came up a treat. I found the 2pac to be easiest to spray with(hard to run) and by far the best finish. Just a lot of prep involved.
I'm using a cheap 99 buck GMC compressor (2hp + 24L) with a quality SMC regulator and water trap. My mini pressure gauge is mounted on the gun. The compressor keeps up fine, though since this morning I've coupled this setup to another small and very old compressor and tank(1.5hp + 60L) for piece of mind.
Good luck.
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Location:
brisbane
Registered:
September 2005
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Re: Spray Gun Advice - HVLP?
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Thu, 08 December 2005 11:18
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just something to note, locate the water trap a good distance of hose from the tank, i was told this by a sprayer when doing my car, because when u compress the air it gets hot, like a turbo  , and is more than 100 degrees apparently and the water is gas and goes straight thru the trap, the further away the more the air has cooled so more water will be in the liquid form
g/l with the job mate 
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Location:
Perth, Western Australia
Registered:
October 2004
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Location:
brisbane
Registered:
September 2005
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Re: Spray Gun Advice - HVLP?
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Thu, 08 December 2005 13:03
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Just letting the air transfer heat to the surrounding area as well will cool the air down. according to my thermodynamics the only other thing past the tank that will heat up the air is friction, but the length of hose isn't really that long.... so the temperature from the tank would only be decreasing
thats sorta wat i was gettin at, the cooler it is the more likely the water will be a liquid, i mean if water was a gas at 120 psi and wateva temperature we have in our compressor line the water trap would be pointless but ill tell u now that my water trap catches alota water on a humid day, so the further away the better rite,coz the air will have cooled off inside the line, escapin to the atmosphere so itll be cooler and thus more water as a liquid to trap. i duno, im probably wrong 
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Location:
Perth, Western Australia
Registered:
October 2004
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Re: Spray Gun Advice - HVLP?
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Thu, 08 December 2005 13:33
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Say the spray gun works at... 8 cfm... or 4 Litres per second, with air passing through a tube of roughly 8-9mm i think you find the air will be travelling at a rather high velocity, and that the temperature drop along the length or line would be negligable, which makes me think that there wont be any more water vapor condensing if the water trap was place a few metres away.
Your water trap catches more water on a humid day simply because there is just alot more moisture in the air.
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Location:
brisbane
Registered:
September 2005
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Re: Spray Gun Advice - HVLP?
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Thu, 08 December 2005 13:38
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corect, but i also found that it caught slightly more water when moved about 12 metres of hose away from the tank. its probably negligible tho. i just used the humid day example to show that the water is a liquid in the compressor hose. meh, g/l with the paint job, just thought id share what id heard, it cant hurt now can it
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Location:
Perth, Western Australia
Registered:
October 2004
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Re: Spray Gun Advice - HVLP?
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Thu, 08 December 2005 13:42
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your right, it can't hurt.. thanks mate.
Just really wanted to know about the choice of gun tho
gravity fed hvlp or just a gravity fed gun...
Such a silly choice as nobody really seems to know which is better
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Location:
brisbane
Registered:
September 2005
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Re: Spray Gun Advice - HVLP?
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Thu, 08 December 2005 13:49
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hmm sux when ppl dont have the answers you want, there was a car sprayer person who wrote something about orange peel, cant remember his name and hes not very active, ill try find his name and u can try and pm him, if not just ask a paint store, or panel beaters spray guy, maybe someone trying not to sell you somethin
i sprayed mine with just a gravity fed i think, and it came up alright for a first job 
ill get back to u with that name
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Location:
brisbane
Registered:
September 2005
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Location:
Forster NSW
Registered:
September 2004
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Re: Spray Gun Advice - HVLP?
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Fri, 09 December 2005 00:02
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| Matt-itude wrote on Fri, 09 December 2005 00:42 |
your right, it can't hurt.. thanks mate.
Just really wanted to know about the choice of gun tho
gravity fed hvlp or just a gravity fed gun...
Such a silly choice as nobody really seems to know which is better
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Well bassy pretty much summed it up for you, neither is better, it's just personal preference. HVLP can guarentee a certain amount of paint actually hits the panel, rather than ends up in the atmosphere. But you also have to be a pretty competent sprayer to match the figures they'll claim.
What do you want? If it's your first spray job, why spend $500+ on a gun?
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Location:
Perth, Western Australia
Registered:
October 2004
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Re: Spray Gun Advice - HVLP?
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Fri, 09 December 2005 00:53
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Yer i see what ur saying now. At the air tool shop, there was a pretty decent panel beaters hvlp gun in 1.4mm nozzle for $190 but that would probably be unsuitable to my application. The other gravity fed guns look around the $100 mark for a decent one. That looks like the go
Ive read pedro the painters posts previously. GOLD. I think i am satisfied with where i am going to go with this. Stay tuned for probably more silly questions regarding paint
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Location:
Brisbane
Registered:
August 2003
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Registered:
November 2002
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Re: Spray Gun Advice - HVLP?
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Sun, 11 December 2005 13:04
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I've sprayed a few cars now. The best job I did was no my TA22 GT that you can see on my site.
I wrote a section on painting that might help.
http://users.chariot.net.au/~stmezz/paint.htm
I always use acrylic and as you can see you can get excellent results. You need a minimum 8cfm compressor with moisture trap, I use a suction feed gun with 2mm tip and 275kpa pressure. Works great. Also you need to thin out the paint enough to get a good finish. I use around 30% paint and 70% thinners.
The gun I use for final coats is an Iwata W77 with 1 litre pot, had it for years and its a great gun.
Yes, 2Pac is easier to use and more durable etc. BUT unless you have a booth and all the gear forget about using it. Without the right safety gear its nasty stuff.
Hoep this helps,
Simon
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