Powder Application Problems

Trouble

Possible Causes

Solution

Poor charging – inadequate powder film thickness or poor coverage

High voltage source not providing enough KV at charging electrode

a)  Check if high voltage source is on.  Systematically check continuity from voltage source to electrode, including cable, resistors and fuses.

b) Replace missing or broken electrode.

c)  Clean electrode insulated by powder build-up or impact fusion.

 

Poor Ground

Check ground from conveyor rail (or rub bar when used) through hanger to part.  All contact areas must be free of powder build up, heavy grease and other insulating materials.

 

Powder delivery rate is too high

Reduce powder delivery rate until material is adequately charged.

 

Excessive moisture in powder booth air

Moisture in humid air will tend to dissipate the charge on the powder particles.  Control the humidity in the powder spray area.

 

Powder too fine

a)  Maintain consistent blend of virgin and recycled powder.

b) Check particle size of powder.  Contact your powder supplier.

 

Powder type or formula

Some powder formulations charge better than others and some formulas are designed for thin film application.  Contact your powder supplier

 

Powder delivery air too high.  Powder blowing by part.

 

Turn down air setting or move gun position farther away from part.

 

Poor penetration – powder will not coat Faraday cage area (holes, grooves, channels, inside corners & recesses)

Powder delivery too low

Turn up powder delivery air settings.

 

Poor ground

Check ground.  Refer to ‘Poor ground’ above.

 

Incorrect powder spray pattern

a)  Adjust powder spray pattern

b) Try alternative nozzle selections.

 

Voltage too high

Turn voltage setting down so that surfaces closer to gun do not repel powder from corners.

 

Powder delivery velocity too high

Turn air setting down so powder air stream does not blow powder into corners.

 

Poor gun placement

Adjust gun position so powder cloud has a direct path to recessed areas.

 

Back ionisation – powder layers are repelled from part

Voltage too high

Turn down voltage settings.

 

Gun positioned too close to part.

Change gun placement farther away from part.

 

Poor ground

Check ground.  Refer to ‘Poor ground’ above.

 

Excessively heavy powder build up

Refer to ‘Powder delivery rate is too high’ above.

 

Powder feed surging or spitting -

interrupted powder feed

Insufficient air pressure or volume

Check air supply.  Determine if air supply piping to equipment is large enough.  Enough air volume must be provided so that air pressure to powder feed does not drop.

 

Hoses, kinked, flattened or too long

Check powder feed hose routing & condition.  Refer to ‘Obstruction of powder delivery system’ in ‘Powder Supply Problems’ section on page 30.

 

Hoses, powder pumps or suction tubes

a)  Clean hoses, powder pumps & guns.

b) Check air supply for moisture.

c)  Check powder delivery settings.

d) Check coating area relative humidity & temperature.

e)  Check powder delivery system for vacuum leaks.

 

Incorrect powder delivery

a)  Check powder delivery settings.

b) For low powder delivery rates, increase powder transport air function settings.

c)  Replace powder hose with smaller diameter hose.

 

Incorrect feeder hopper fluidising

a)  Adjust fluidisation air pressure.

b) Check porous fluidising membrane for clogging or defects.

c)  Refer to ‘Powder fluidisation/air blowing large holes through powder surface’ in ‘Powder Supply Problems’ section on page 30.

 

Low powder level

Add powder