11
DEFECTS
CAUSE
CORRECTION
Coarse spray
Low pressure
Increase the pressure.
Excessive fogging
High pressure
Reduce the pressure to satisfactory pattern distribution.
(overspray)
Material too thin
Use less thinner.
Pattern too wide
Spray angle too large
Use smaller spray angle tip.
Pattern too narrow
Spray angle too small
Use larger spray angle tip (if coverage is OK, try tip
in same nozzle group)
Too much material
Nozzle too small
Use next smaller nozzle.
Material too thin
Pressure too high
Reduce pressure
Too little material
Nozzle too small
Use next larger nozzle
Material too thick
Thin distribution in
Worn tip
Change for new tip.
center of pattern
Wrong tip
Use nozzle with a narrow spray angle.
"horns".
Thick skin on work
Material too viscous
Thin cautiously.
Application too heavy
Reduce pressure and/or use tip in next larger nozzle
group.
Coating fails to
Material too viscous
Thin cautiously.
close & smooth over
Spray pattern irreg-
Orifice clogged.
Clean carefully.
ular, deflected
Tip damaged
Replace with new tip.
Craters or pock
Solvent balance
Use 1 to 3% "short" solvents remainder "long" sol
marks, bubbles
(this is most likely to happen with material of low
on work
viscosity, lacquers etc.)
Clogged screens
Extraneous material
Clean screen
in paint.
Coarse pigments
Use coarse screen if orifice size allows.
Poorly milled pigments
Use coarser screen, larger orifice tips. Obain ball milled
(paint pigments glocculate
paint. If thinner has been added, test to see if a drop
cover screen. Incompatible
placed on top of paint mixes or flattens out on the
paint mixture & thinners.
on the surface. If not, try different thinner in fresh
batch of paint.
TEST THE PATTERN
Good, full
Spotty
pattern.
pattern
Increase Pressure.
AIRLESS SPRAY GUN OPERATION
