Powder Coatings Troubleshooter - Application Problems

Powder Coatings Troubleshooter - Application Problems

 

Poor Penetration into Recessed Areas (Faraday Cage Effect)

  • The Faraday Cage Effect occurs when surfaces closer to the gun attract the powder before it can penetrate into corners and recessed areas.
  • Turn voltage settings down.
  • Increase or decrease the powder delivery air setting.
  • Check your ground. Hooks with heavy coating build up will become insulated from the part.
  • Adjust powder spray pattern with different nozzles.
  • Increase the powder feed velocity to penetrate the recessed area.
  • Adjust gun placement, so powder cloud has more direct access to area.
  • "High Fluidity" powders provide better penetration.

Inadequate Film Thickness

  • Increase voltage setting.
  • Adjust gun placement closer to the part and try different nozzles.
  • Adjust part density (racking) so that powder can be attracted equally to each part.
  • Excessive air velocity may be blowing powder past the part.
  • Poor ground. Check your hooks.
  • Excessive humidity may limit the charge on the powder particles.
  • Powder may be too fine. Always maintain a consistent blend of virgin and recycled powder. Contact your Diamond Vogel® Technical Service Representative for a particle size analysis.
  • Some powder technologies charge better or are meant to be applied as thin films. Contact your Diamond Vogel® Technical Service Representative.

Back Ionization

  • Back ionization occurs when powder layers start being repelled from the part during application.
  • Turn voltage settings down.
  • Excessive powder build up can cause back ionization. Lower powder feed rates and adjust gun distances.
  • Check your ground.
  • Having gun too close to the part.

Poor Fluidization in Hopper

  • Air should be slowly percolating through the surface of the powder.
  • Check your fluidizing membrane for plugged pores. Can be caused by moisture or oil in the air supply.
  • Increase air pressure to fluidizer.
  • Check for packed powder by stirring manually with a paddle or air.

Powder Blowing Out of Hopper

  • Lower air pressure in fluidizing hopper.
  • Powder may be too fine. Consult Diamond Vogel® Technical Service Representative for a particle size analysis.
  • Check hopper for proper venting.

Geysering

  • Geysering is caused by air blowing holes through the surface of the fluidized powder.
  • Lower air pressure to the fluidizer.
  • Add more powder. Hopper should be about 3⁄4 full when fluidizing.
  • Check for plugged pores or other obstructions in membrane.
  • Powder may be packed or moist. Check air supply for contaminants.

Impact Fusion

  • Impact Fusion is the hard build up of powder particles that occurs in hoses, tubes and nozzles. Clean and replace tubes, hoses, venturi pumps and nozzles on a regular basis.
  • Powder may be too fine. Reduce your reclaim.
  • Excessive air pressures and powder feed rates will increase the amount of impact fusion.
  • Check air supply for contaminants.

Surging or Inconsistent Powder Flow

  • Increase air pressure and/or volume of air.
  • Check powder hoses for kinks or obstructions. Keep hose length to a minimum. May need to replace powder hose with a smaller inside diameter hose.
  • Clean all tubes, hoses and guns of impact fusion build up.
  • Check powder delivery and air pressure settings.
  • Check hopper for powder level and fluidization.
  • Check air supply for contaminants.
  • Excessive temperature and humidity in application area can cause application problems.
  • Check for sintering or clumping in powder.

Poor Spray Patterns or Powder Feed

  • Replace worn feed tubes, orifices, and deflectors in spray guns.
  • Clean impact fusion from areas of accumulation.
  • Increase powder feed (see notes in "Inconsistent Flow" section)
  • Choose correct nozzle for part configuration.

Powder Drift From Spray Booth

  • Clean or replace filter cartridges and final filters.
  • Check pulse air pressure and for contaminants in air supply.
  • Excessive drafts or pressure from outside the spray area causing turbulence.
  • Using excessive amounts of compressed air during clean up.
  • Insufficient air volume or velocity in recovery/reclaim.
  • Excessive amount of fines.
  • Part temperatures in excess of 110˚F may produce a “chimney effect”.
  • If guns are added to a booth or flows are run at their maximum it may exceed the filter surface capacity and lead to powder migration out of the booth. Decrease flow rates.

Spitting and Dry Spray of Metallics

  • Spitting is caused by particles collecting on the diffuser and electrode.
  • Periodically clean the electrode with air and adjust KV’s and powder delivery.
  • To reduce dry spray, adjust KV’s and lower delivery volume and powder velocity.
  • Control film thicknesses for more consistent color.
  • Check KV Output at the gun.