confused about HVLP gun pressure

[carl0s]

Hi.

I have a mini-regulator on my gun (a proper diaphragm one now).

It's set for 30 psi like the gun (Iwata AZ3 HTE2) says. It's one of these HVLP-like but slightly lower volume than normal, type guns - High Transfer Efficiency they call it.

Anyway I feel that the paint was massively over-applied, and I got some heavy runs in the clear (OMI Cron 2K, with 10% thinners added) It was literally dripping off some edges. It's only a test panel anyway, sort of.. it's a small part of the bumper that I'm intending to paint properly.
This video says to set the pressure *while the gun is open*, which has got me a little confused I think. Is it right? I just set to 30psi on the regulator but then when the gun is open it drops down. Or is this just a sign that my regulator isn't a good regulator?
Here's the video:

 

[ajlelectronics]

Pull the trigger so that the gun is passing air, then set the pressure.

 

[carl0s]

Ah.

So i have been painting with about ~20 psi then!

Might this explain why I had some difficulty getting the filler-primer on close to flat? I know it's to be sanded flat anyway, but I felt the amount of flatting required was quite unexpected.

 

[carl0s]

I've just been to check the gun/gauge, and it seems like I was using about a quarter of the required pressure.
The difference when I set it to 30psi with the gun open, is quite dramatic. It was so light and gentle before, now it's quite a blast. In fact I can only get 30psi at the on-gun gauge, with gun open, if I set to about 75 psi on the wall regulator. The wall regulator is then feeding through a long reel of hose though, and then into the gun. Does this sound right?

 

[Daz1968]

Yes that would explains it as at 20psi it wouldn't atomise the paint properly.
I also set mine with anything else on the line like my airfed mask drawing air so that I am sure I maintain 30psi at the gun.

 

[carl0s]

OK thanks. I have some serious runs to get out of this paint! I'd rather have another go from the start though, just not sure I fancy all that sanding again!!

I am using a turbine breather thing for my mask so that's all separate (breathe-cool thingy). The turbine is great, mask could be more comfortable..

 

[Daz1968]

I like the idea of those turbine masks, as I am limited to a devilbiss sri pro spraygun when painting 2k as my compressor can't provide enough air for anything else.

 

[carl0s]

I am well pleased with the breather. I thought I was going to have to build some kind of second out-door shed/housing next to the garage (for another compressor), and then get the very pricey 3-stage filters to remove oils etc from breathy air.. it was looking unfeasable. I got the one with the air-fed visor/mask.

 

[vw1]

Tell me more about the air turbine mask set up ? How much was it please?

 

[carl0s]

It's one of these:
http://www.ebay.com/itm/Supplied-fr...133?pt=LH_DefaultDomain_0&hash=item589e90744d
I went for 75-foot of hose (kit starts off with 25'), and I went for the full-face mask (options are Tyvek hood, and something else too i think).

I rang the guy up and did it over the phone. His website is terrible, barely works - broken links. Actually I just had a look now and the website says it's closed 'til August 18th so maybe a long overdue rebuild of the site is happening?

To be honest I was pretty surprised when I came across them - pretty surprised I'd never heard of it before. I'd spent ages looking at masks, compressors, CFMs, coalescing filters, etc..
There are a couple of other brands of the same thing in the USA. A little more expensive (HobbyAir rings a bell but I could be mistaken).
Didn't find any UK suppliers.

It's basically like a vacuum cleaner in reverse I suppose :-)

 

[vw1]

Oh looks ok and not to much not using 2k so mite wait for uk sellers . Thank you .

 

[carl0s]

I'm still not getting this.
It makes no sense.

My primer gun (1.8) fast mover, when the gun's air valve is opened up all the way, it flows so much air that it's next to impossible to have 30psi backed up in the line with the gun open & the valve all the way open.

This "30 psi with the trigger open" makes no sense. I can alter the air valve on the gun any time I want to get 30 psi to register on the gauge... and it has no bearing on the air supply.

 

[ajlelectronics]

Leave the throttle adjustment in the flat out position, somewhere near the middle. Then ignore it. Pull the trigger and set the regulator on the compressor to give you the pressure you want.

 

[carl0s]

Leave the throttle adjustment in the flat out position, somewhere near the middle. Then ignore it. Pull the trigger and set the regulator on the compressor to give you the pressure you want.

I was doing that, and to do this, my wall regulator has to be wide open, and, well, there's some serious air coming out of the gun.. some serious air. I can imaging a huge amount of bounce back off a panel.

 

[the snooper]

I'm still not getting this.
It makes no sense.

My primer gun (1.8) fast mover, when the gun's air valve is opened up all the way, it flows so much air that it's next to impossible to have 30psi backed up in the line with the gun open & the valve all the way open.

This "30 psi with the trigger open" makes no sense. I can alter the air valve on the gun any time I want to get 30 psi to register on the gauge... and it has no bearing on the air supply.

are you referring to the valve next to the air inlet ? if so leave it wide open and use your regulator

 

[carl0s]

Although to be fair, with this primer gun (FMT 3006), they do say 22 psi.. so let me see if that's much difference.

It's a static pressure of 110 psi to get 30 psi with this gun open & throttle open.

On my Air Gunsa 1.3 gun, it's only 75 psi or so static pressure.

So the primer gun flows a lot more air.

 

[carl0s]

are you referring to the valve next to the air inlet ? if so leave it wide open and use your regulator

Yeah except it's on the back on this FMT 3006 primer gun, and that is what I was doing, but it's like this gun flows so much air....

 

[carl0s]

Altering the fan adjustment also makes a huge difference to the what the pressure gauge/regulator shows when the trigger is pulled.

 

[carl0s]

sod it, I've just done some test patterns with some left-over slightly thickened basecoat, and it looks ok. Going to put the outfit on and hit it with some primer again.

 

[carl0s]

I should've just bought two of the air gunsa guns.