troubleshooting   color index    



 



Phenomenon Possible cause Suggested solution
Powder spills out of the powder hopper

Fluidization air pressure is too high

Proportion of fine-grained particles is excessive

Reduce fluidization air pressure

Reduce the proportion of recycled powder in relation to virgin powder in the powder hopper Discuss with the powder supplier the possibility of supplying powder with a lower proportion of fine-grained particles.
The powder is not fluidized

Insufficient air pressure

Clogged membrane in the bottom of the powder hopper

Powder packed down in the bottom of the hopper

Check the compressed air supply. Examine and if necessary, increase the pressure in the compressed air network Examine the condition of the supply lines.

Empty the hopper and check if the membrane is clogged.

Manually stir the powder in the hopper and increase the air pressure in order to start fluidization.
Poor fluidization

Too little powder in the hopper

Compacted or damp powder

Clogged or damaged membrane

Add virgin powder so the hopper is approximately 2/3 full under fluidization

Increase the air pressure and manually stir the powder in the hopper.

Check the moisture in the compressed air (dew point <3ºC)

Empty the hopper and examine the membrane

 
Lumps of powder in the hopper Air velocity is too low in relation to the amount of powder

If possible, increase supplemental air flow pressure on the ejector

Change to hoses with a smaller diameter

Install new ejector plug
Consider using ejector plugs made of another material

 
Dust from the spray booth – insufficient ventilation

Unnecessarily large openings in the booth

 

Clogging of filters in the booth or of the final filter

 

 

Amount of powder sprayed is too large

Close unused openings

Adjust the entrance and exit to the size of the objects

Clean and if needed, replace filters or filter cartridges

If possible, increase the ventilation in the spray booth

Reduce the number of spray guns or reduce the amount of powder per gun

 

Powder is not sufficiently charged

Insufficient wrap-around – poor deposition efficiency

The high-voltage generator is not providing enough voltage to the spray gun’s electrodes

 

 

Poor earthing connection

 

 

 

 

Too much powder per spray gun

 

 

Proportion of fine-grained particles are too high

 

 

 

 

Inappropriate type of powder

Ensure that cables and fuses are intact Ensure that the electrodes are in good condition
Increase the generator voltage Ensure that the actual spray gun voltage is the same as that shown on the control panel

Check the connection between the object and the conveyor and between the conveyor and the earth

All contact points must be free of powder coating and other insulating materials

Reduce the amount so that as much of the powder as possible that passes the spray gun is charged.

 

Reduce the proportion of recycled powder in relation to virgin powder

Check with the powder supplier on the possibility of supplying powder with a lower proportion of fine-grained particles

 

Check with the powder supplier if the powder is appropriate for the specific use/powder application equipment
Insufficient penetration in corners and recesses Air velocity in the spray gun is too high – the powder is blown off Reduce the supplemental air flow
  Incorrect distance between the spray gun and the object Increase or reduce the distance between the spray gun and the object
  Amount of powder per spray gun spray gun and the object Increase the air pressure on the ejectors
  Poor earthing connection Check the connection between the object and the conveyor and between the conveyor and the earth. All contact points must be free of powder coating and other insulating materials
  Spray could is too wide Change to a smaller deflector or to a flat jet beam nozzle
  Voltage is too high on the high voltage generator Reduce the voltage in order to even out the differences in coating thickness on interior and exterior corners
  Air velocity is too high Reduce the supplemental air flow pressure, and if necessary increase the distance between the spray gun and the object to prevent the powder from being blown off
  Incorrect spray gun adjustment Adjust the spray guns so that the cloud of powder is directed as much as possible towards the most difficult areas of the object
  Proportion of fine-grained particles are too high

Reduce the amount of recycled powder by optimising the spraying process

Check with the powder supplier on the possibility of supplying powder with a lower proportion of fine-grained particles
Difficult to build up sufficient film thickness Not enough charging / charging effectiveness Ensure that cables, fuses and electrodes are working
The powder slides off   Increase the voltage from the generator Check the spray gun voltage
Poor earthing connection

Check the connection between the object and the conveyor and between the conveyor and the earth

All contact points must be free of powder coating and other insulating materials
Air velocity is too high Reduce the air pressure, and if necessary increase the distance between the spray gun and the object
Adverse moisture in the work area Avoid relative humidity below 30% and above 70% - the ideal range is 45-55%  
Back-ionisation/uneven powder layer Unnecessarily high voltage Reduce the voltage
  Insufficient distance between the spray gun and the object Increase the distance
  Poor earthing connection Check the connection between the object and the earth
Large variation in film thickness Incorrect spray gun adjustment Check the adjustment and ensure proper over-lapping
  Incorrect distance between spray gun and object Increase or reduce the distance
  Improperly adjusted conveyor and reciprocator speed Adjust the conveyor speed and/or the stroke and speed of the reciprocator
  Air flows in the spray booth that disturb the spray pattern Contact the equipment supplier
  Improper hanging technique Ensure that objects are as uniform as possible, correctly hung, and at the proper distance
  Uneven powder delivery

Ensure proper fluidisation and that the powder hopper is more than half full

Examine the diameter and length of the hoses
Spray problems after mixing in recycled powder Change the particle size distribution Reduce the amount of recycled powder as much as possible through the hanging technique, spray gun adjustments, and charging effectiveness
Spitting Accumulation of fine-grained powder in spray guns/delivery system

Reduce the amount of recycled powder as much as possible

 

Reduce the time between each cleaning/ blow through

Check with the powder supplier on the possibility of supplying powder with a lower proportion of fine-grained particles
Poor flow Film thickness is too low Measure the thickness with appropriate and calibrated equipment. Adjust the thickness by changing the air pressure on the ejectors
  Heating up metal too slowly Increase the oven temperature, or adjust the temperature profile. If possible, begin using IR heating in the entrance zone
  Spray gun voltage too high Reduce the voltage or increase the distance between the spray gun and the object
  Inappropriate type of powder (reactivity is too high or powder particles are too coarse) Check with the powder supplier if the powder is appropriate for the specific use/powder application equipment
Low gloss on a high gloss finish

Contamination with another product that is not compatible

Extreme temperature stress during heating

Thorough cleaning of the spray booth, delivery system and recycling system before adding virgin powder

Reduce the effect in the IR-zone

Pinholes in the finish

Film thickness is too high

Moisture

Reduce the film thickness

Check if there is moisture in the compressed air or if drying after the pretreatment is insufficient

Check the degree of porosity in the substrate (cast iron)
High gloss on a low gloss finish Insufficient curing Increase the temperature and/or time in the oven
Discolouration in the finish Contamination from powder used earlier in the equipment Thorough cleaning of the spray both, delivery system and recycling system before adding virgin powder
  Contaminated virgin powder Check with the powder supplier
Craters in the finish/surface Contamination with another product that is not compatible Stop and do a thorough cleaning before adding virgin powder
  Grease on the metal surface after insufficient pre-treatment Check and replenish the pre-treatment baths
  Moisture and/or oil in the compressed air Examine the oil and water separators
Porosity in the coating Moist substrate Check the material after pretreatment/ drying
  The powder quality is unsuitable for the specific substrate Contact the powder supplier
Incorrect or uneven colour Curing conditions exceed the specified range Refer to the product data sheet and make necessary adjustments
  Variation in film thickness Measure the thickness and make necessary adjustments
  Varying substrate thickness Switch to polyester-based powder coatings
  Unsuitable type of powder Check with the powder supplier if the Check with the powder supplier if the
Drop formation/sagging Film thickness is too high Check the thickness and make necessary adjustments
  Type of coating is unsuitable for the specific use (flow too good) Contact the powder supplier
Poor coverage of edges Sharp cutting edges on the metal Contact the metal supplier/processor for changes Alternative hanging technique (sharp edges down)
  Type of coating is unsuitable for the specific use (flow too good) Contact the powder supplier
Poor mechanical properties – impact
strength/flexibility 		Insufficient curing Take measurements of the metal’s temperature profile
Increase the temperature and/or time in the oven
  Film thickness is too high Check the thickness and reduce it by reducing the amount of powder or possibly increasing the conveyor speed
  Poor adhesion due to insufficient pre-treatment Check and replenish the pre-treatment baths
  The nature of the powder coating Check with the powder supplier
Poor adhesion to the substrate Inadequate pre-treatment Check and replenish the pre-treatment baths
  Insufficient curing Increase the temperature and/or time in the oven
Poor chemical resistance Insufficient curing Increase the temperature and/or time in the oven
  Improper choice of powder type Check with the powder supplier
No charging Short circuit in the spray gun Change to a special nozzle for metallic powder coatings
  Improper spraying equipment Contact the powder supplier
Changes in the metallic effect over time Uneven consumption of base and metal pigment (dry mixed powder) spraying process Reduce the amount of recycled powder as much as possible by optimising the spraying process Frequent addition of virgin powder

Textured powder coatings

The substrate is visible under the texture Film thickness is too low Increase the thickness
Uneven texture Uneven film thickness Optimise the spraying process for the most even thickness possible
Variation in texture over time Variation in particle size distribution Reduce the amount of recycled powder as much as possible by optimising the spraying effectiveness

Recoating

Phenomenon Possible cause Suggested solution
Poor flow The first layer insulates thus limiting the earthing connection Reduce the spray gun voltage to 30-40 kV
Poor adhesion between

Impurities on the surface of the first layer

 

The powder coating is unsuitable for respraying

Ensure thorough grease removal and rinsing

 

Contact the powder supplier

Oven problems

Phenomenon Possible cause Suggested solution
Smoke/odour from the curing process comes into contact with the zone. Check damper and fans to ensure Dry powder is blown off and comes into contact with the heating elements Reduce air speed in the oven’s entrance zone. Check damper and fans to ensure that the oven is properly aired out.
  Overheating of the powder coat Take measurements of the metals temperature profile and reduce the temperature if necessary
    Check the effect and distance between lamps and materials in the IR zone, if one exists