Bob Nogueira wrote:
> The Paint
> manufacturer states 10 PSI at the cap ( PPG Concept ) .
10 psi at the cap is the legal maximum for hvlp. It is very common for paint
manufacturers to recommend this. If you're not in an area that mandates hvlp
equipment, it's OK to turn it up a bit higher. Does your manual anywhere
state a maximum inlet pressure? If so, that is almost certainly the pressure
that will provide 10 psi at the cap.
> I asked the guy at the paint store how you measure cap
> pressure and he says it
> requires a special instrument that is very expensive.
This is true. Did you buy the gun from the store? If so, they should be able
to tell you the inlet pressure for 10 psi at the cap.
> Now in cleaning the gun I see where the air take off to
> pressurize the cup is
> taken off from the same chamber as the one that feeds air
> to the cap.
> Can I assume that if I have the cup pressure at 10 PSI the
> cap will also be
> at 10 PSI?
Not unless the take off is right at the cap (which I've never seen on a
gun). The cap pressure on all guns I've seen is significantly lower than the
inlet pressure. Most hvlp guns require inlet pressures between 29 psi (2
bar), and 45 psi (3+ bar) to achieve 10 psi at the cap. Also be aware that
if you do find a recommended inlet pressure to produce 10 psi at the cap,
the inlet pressure must be measured at the gun (not at a regulator in front
of 25' of hose), and with the gun triggered. Also be aware that changing the
fan setting will require changing the static inlet pressure to attain the
proper triggered pressure.
> Any suggestions for setting the pressure?
I'm surprised that the manual does not state the inlet pressure that will
result in 10 psi at the cap. Try posting your question on the discussion
board at autobodystore.com:
http://www.autobodystore.com/cgi-bin/config.pl?index
Be sure to be specific about the make and model of the gun. There are a lot
of people with experience with a lot of different guns who frequent that
forum.
> I've tried spraying a test panels and while it looks okay
> right after I spray
> it by the time I let it flash off I end up with a lot of
> orange peel.
Peel can result from many factors other than incorrect pressure, including:
Too high a travel speed
Too little reducer
Too fast/low temp a reducer
Holding the gun too far from the surface
Angling the gun relative to the surface
Harry Phinney
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