Coating Plate Troubleshooting

Backtrapping or ink on the coating plate

Remedy

  • Adjust timing for coater start
  • Adjust contact to “kiss” pressure. Reduce pressure until coating does not transfer, then tighten to 0.001
Build-up of coating on blanket outside of sheet

Remedy

  • Adjust packing to proper height
  • Adjust roller to “kiss” setting – 1 to 1 mm
Build-up of coating at trailing edge of sheet

Remedy

  • Check roller speed and adjust packing to minimize speed difference
  • Increase setting speed of ink, use stronger body inks
Cracking of the coating during drying

Remedy

  • Reduce wax, only use PE wax or don’t use wax inks.
Crawling, Fish Eyes or Pinholing

Remedy

  • The coating does not contain enough wetting agent.
Problems with drying – despite no changes from last job

Remedy

  • Check the output of lamps, warm air knives and make sure exhaust is not restricted in any way.
Blocking in the delivery

Remedy

  • Check and adjust IR output for correct load temperature.
  • Try stronger or tighter body ink for extra stability under the coating.
Scuffing in the delivery

Remedy

  • Use faster drying coating or run slower to allow a longer setting time.
Colour shifts with Reflex Blue, Rhodamine or Violet ink

Remedy

  • Ask your supplier for drawdowns to test the coating on or before printing the job.
Loss of gloss

Remedy

  • Use sheet with better hold-out. Apply a heavier layer of coating if possible. Use coating that is resistant to ‘dry-back’.
Foaming

Remedy

Increase level of coating in the pan.
Offsetting of ink

Remedy

Apply more coating.
    Orange peel appearance

    Remedy

    • Reduce warm air supply.
    • Specify a medium drying speed coating.
    Rings or ridges on rollers, blanket or sheet

    Remedy

    • Increase the pressure check for any low areas in the roller or blanket.
    Sandpaper “feel”

    Remedy

    • Increase warm air or run the job slower.
    Sheet curling

    Remedy

    • Specify a ‘high solids’ coating to apply less water.
    • Use paper stock of 80 lbs or higher.
    • Run the coating as close to the edge as practical to provide a uniform size change in the sheet.
    Spitting of coating:

    Remedy

    Check that the coating is at proper application temperature.
      Thickening of coating:

      Remedy

      • Reduce viscosity to original value. Mix partial drum into fresh coating and adjust viscosity as needed