HVLP painting - help needed

[Fred Munro]

Hi Mike;

I have used Imron (over Corlar & 1044R) with a conventional siphon-fed HPLV
gun and found it to be a very easy to use and forgiving paint - great
coverage, ultra-smooth finish, tough as nails. It is one my favourite paints
to use - and I only paint once every few years, so I'm not an experienced
pro by any means.

I have just purchased a set of HVLP guns for my next job (the UrS4 needs a
lower belt paint job to deal with 11 years of salt bath) but haven't used
them yet.

DuPont does publish a list of settings and tips to use with their paints for
HVLP guns - I'll send you a copy separately to avoid spamming the list. The
Fuji is not listed.

I suspect your problem is your Fuji paint system. The pros don't use turbine
systems; they use compressed air fed HVLP guns. Maybe the turbine systems
are great and the pros use compressed air because that's what their shops
have; I don't know. You can bet, though, that DuPont has formulated their
paint and reducer systems to match what the shops use for equipment. The
DeVilbiss FinishLine guns I bought take 38 psig/13 cfm (38 psig/8 cfm for
the touch up gun) inlet air to produce 10 psig at the air cap. I suspect
your turbine system uses lower pressure and higher volume and it sounds like
you are not getting the atomization you need for the Imron. With all the
issues you list, it seems like the operational envelope for the Fuji system
is quite narrow with the Imron and it's a hit and miss affair (mostly miss
by the sounds of it).

Orange peel is usually caused by the paint flashing before it levels -
reducer too fast, gun too far away.
Runs, drips - reducer too slow, gun too close, gun speed too slow
thin spots - gun speed too fast, variable paint flow
no shine - paint flashing too fast (as per orange peel)
bugs & leaves - hmm, no downdraft paint booth, eh? That's OK - I paint under
a carport :)

I sounds to me like your Fuji system may not be giving you consistent paint
feed and atomization. You should be able to adjust for a lot of those issues
with gun distance and speed - the fact that you can't indicates to me
varying paint flow and atomization.

For instance, I sometimes paint with a very fast reducer and lay the paint
on with slow gun speed to get the shine - the fast flash solves the bug
problem, but film thickness is high :)

Do you have a conventional HPLV gun you can try? Granted they overspray like
crazy and use more paint, but not more than you've used already.

If you have to stick with the Fuji I'd suggest trying a lower viscosity
paint mix; try adding more of a faster reducer to your blend. This will
decrease coverage and is a bit of a bodge but it may help.

Let me know how you make out.

HTH

Fred Munro
'94 S4 (I HATE, HATE, HATE bodywork)
Did I mention that I dislike bodywork?



-----Original Message-----
From: quattro-bounces+munrof=sympatico.ca at audifans.com
[mailto:quattro-bounces+munrof=sympatico.ca at audifans.com]On Behalf Of
Mike Arman
Sent: August 21, 2005 6:51 PM
To: quattro at audifans.com
Subject: HVLP painting - help needed




I'm having a bad time using a Fuji Q3 HVLP spray system, and I need some
guidance.

Using a #3 tip, I find I am able to do a reasonably good job with Corlar
(epoxy) primer. I don't get many runs, but sometimes I do get some orange
peel, which I understand is from putting too much paint on and/or being too
close. I can sand the Corlar down smooth, and come back to it - I'm by no
means good at it, but with enough cussing and sufficient tries, it works OK.

The problem is when I try to spray the Imron top coat - this stuff is too
expensive to screw up, and I am screwing it up royally. I have gotten the
correct finish, deep, smooth, shiny "wet look", ONE time - and everything
else has been an unmitigated disaster - orange peel, rough surfaces, no
shine, thin spots, runs, occasional drips, and of course every bug and leaf
in the entire state insists on admiring the wet paint close up and
personally, and commits hari-kari, flopping and struggling in the drying
paint . . .

I'm following the instructions on mixing the Corlar (mix per ratio on can,
thin to 20 seconds in drip cup, wait three hours, then spray) and on the
Imron (mix per ratio on can, spray any time), and I think I have the
correct nozzle size (#3). The end of the needle is flush with the nozzle
with the trigger in the off position. The air supply from the turbine isn't
adjustable.

Can someone in this group send me some words of wisdom on this? I'm making
a godawful, expensive, frustrating mess, and I am going to have to strip
and redo more than a few items because they have turned out just plain
awful. I'd like to learn how to do this right, because I am becoming right
weary of doing it wrong over and over, not to mention the serious amounts
of time and money (Imron is EXPENSIVE, and a lot of paint goes a short way)
I'm wasting.

If the word is "do the prep and let someone else do the finish coat", I can
handle that, but I cannot believe it is THAT complicated. Do I need to wait
for five minutes, ten minutes, a week between coats? Should I paint
vertically, horizontally, or standing on my head? Am I better off trying
this early in the AM or late afternoon, should I wait until it is cooler
outside and the humidity is lower, do I make a human sacrifice to DuPont?

Help Help Help -I confess to rapidly discovering that I am clueless here,
and I need some advice.

Mike Arman
90 V8, not just a car, an ADVENTURE!



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