Troubleshooting
6-2
Part 1108061-02
E 2015 Nordson Corporation
Common Problems (contd)
Problem Possible Cause Corrective Action
1. Spray guns are
surging or spitting;
powder flow is
inadequate or
intermittent
Insufficient air volume in feed
hose; powder is settling out
Increase the atomizing air pressure
and decrease the flow rate air
pressure. Refer to the spray gun and
control unit manuals for
recommended air pressures and
ratios.
Powder in feed source
inadequately fluidized; cavities
forming in powder below pickup
tube ends
Adjust the fluidizing air pressure.
The powder should be gently boiling.
Refer to problem 5.
Low powder level in feed source Add powder to the feed source.
Powder pump venturi throats worn;
pickup tube sucking air at
connection to pump mounting arm;
pump or pickup tube clogged
Clean the pump and pickup tube.
Replace any worn parts. Replace
any damaged O-rings.
Obstruction in powder feed hose Disconnect the feed hose from the
pump. Blow the powder out of the
hose with compressed air. Make
sure the hose is clear. Eliminate
kinks or severe bends in hose. Hose
should be no longer than 7.6 m (25 ft)
with a maximum 2.7-m (9-ft) vertical
rise.
Severe tribo-charging in powder
feed hose
Contact your Nordson representative
for a suitable hose material. Contact
your powder supplier.
Obstruction in spray gun Clean the spray gun.
2. Problems with
coating uniformity,
edge coverage, film
build, wrap, or
penetration into
recesses
Poor workpiece grounding Resistance from the workpiece to the
ground must be less than 1 megohm.
For best results, resistance should
not be more than 500 ohms. Clean
the workpiece hangers, fixtures, and
hooks if necessary. Check the
conveyor ground.
Spray gun placement incorrect Position the spray guns 254−355 mm
(10−14 in.) from the workpieces.
Stagger the spray guns 304 mm
(12 in.) apart vertically and 381 mm
(15 in.) apart horizontally to avoid fan
pattern and electrostatic field overlap.
Contact your Nordson Corporation
representative for advice.
Powder pump flow rate and
atomizing air pressure incorrect
Refer to the spray gun, pump, and
control unit manuals for the
recommended air pressures and
ratios.
Continued...
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