K Mean Black

• Name: Printing Technology
• Branch: Printing Technology Diploma 6th Sem
• Published: May 25, 2025

Flexography Defects Part - 2

 

8. Ghosting effect:

 

The ghosting effect is a weak printed image that is visible in one part of the motif where it should not be. Usually this effect occurs in the case of a solid print with negative fonts or with windows.

Causes	Remedies
The amount of ink available is too small as the transferred volume of the anilox roller is too low.	Use an anilox roller with a higher transferred volume.
The ink dries in the anilox roller cells	Add retarder to the ink.
The anilox roller cells are inadequately filled.	Increase the pressure in the chamber doctor blade system.
The printing speed is too low.	Increase the printing speed or the viscosity of the ink.

 

9. Halo effect/squeezed edge on the screen dot:

The screen dot is surrounded by a line or a ring.

Causes	Remedies
There is a difference in the speed between the plate and impression cylinder.	Check the thickness of the doublesided adhesive tape and the printing plate.
The transferred volume of the anilox roller is too high.	Select an anilox roller with a lower transferred volume.
The pressure setting between the plate cylinder and substrate is too high.	Reduce the pressure setting.
The pressure of the chamber doctor blade system is too low.	Increase the pressure in the chamber doctor blade system.
The pressure setting between the anilox roller and the plate cylinder is too high.	Reduce the pressure setting.

 

 

10. Inaccurate printing of the screen dots:

Uneven edges around the screen dot.

Causes	Remedies
The ink dries on the printing plate.	Clean the printing plate and adjust the solvent mixture. Add the retarder. Make sure that the hot air fan is not blowing onto the printing plate.
The pressure setting between the anilox roller and the plate cylinder is too high.	Reduce the pressure setting.
The ink viscosity is too high.	Adapt the ink viscosity by adding solvents.
The lint particles from the cleaning cloth are on the printing plate.	Clean the printing plate. Use a lint-free cleaning cloth or a cleaning brush.
The ink recipe is not suitable for the printed motif.	Replace the ink.
The pressure setting between the plate cylinder and the substrate is too high.	Reduce the pressure setting.

 

11. Ink build-up on motif edges:

Ink build-up on the relief edge of the screen dot.

Causes	Remedies
The transferred volume of the anilox roller is too high.	Use an anilox roller with a smaller transferred volume.
The printing speed is too low.	Clean the printing plate and increase the printing speed.
The ink viscosity is too high.	Reduce the viscosity.
The wrong solvents were used.	Replace the ink.
The pressure setting between the plate cylinder and substrate is too high.	Reduce the pressure setting.
The ink recipe is unsuitable.	Replace the ink.
The printing plate is worn, the relief depth is too small.	Replace the printing plate.
The relative humidity is too high. The water condenses into the solventbased ink.	Adjust the solvent mixture – use retarder and anhydrous solvent.

 

12. Ink mottling:

Dotted or marbling printed image of the solid printing area. Weak ink strength, grainy large-format printing.

Causes	Remedies
The surface of the printing plate is cloudy/uneven. Damage to the surface of the printing plate can be seen.	Create a new printing plate.
The viscosity of the ink is too low.	Add fresh ink and/or a blend of inks and ensure that the resulting viscosity is appropriate.
There are foreign bodies or impurities on the plate cylinder or the anilox roller.	Clean the plate cylinder carefully.
The surface of the substrate is uneven.	Use softer printing plates.
The film surface is soiled.	Filter the ink or use fresh ink.
The ink viscosity is too high.	Add solvent to the ink.
The doctor blade pressure is too high or too low.	Adapt to the doctor blade pressure accordingly.

 

13. Large-area printing defects:

Lack of contact between the substrate and the printing plate or between the printing plate and anilox roller results in the poor transfer of ink.

Causes	Remedies
The thickness fluctuations in the printing plate or double-sided adhesive tape are too large.	Change the printing plate or the double-sided adhesive tape.
The printing pressure is too low.	Increase the pressure between the plate cylinder and anilox roller or between the plate cylinder and the substrate.
The thickness of the substrate is out of tolerance.	Increase the delivery pressure of the plate cylinder or replace the reel of substrate.
The plate cylinder or the anilox roller are imbalanced.	Check the running of the printing plate cylinder (concentricity etc.).
The transferred volume of the anilox roller is too low.	Increase the anilox roller volume.
The filling level of the chamber doctor blade is too low.	Increase the ink level in the chamber doctor blade. Check whether the ink pump is working correctly.

 

14. Longitudinal stripes:

Printing error owing to parallel lines in the direction of printing.

Causes	Remedies
The doctor blade is worn.	Replace the doctor blade.
There is dried ink on the doctor blade.	Clean the doctor blade.
The anilox roller is damaged.	Replace the anilox roller.
The anilox roller is blocked or the drive of the anilox roller is faulty.	Please contact the maintenance service department.
The anilox roller is dirty or the ink on the anilox roller has dried.	Clean the anilox roller.
There are particles in the ink.	Clean the pump system, printing plates, doctor blade and anilox roller after you have filtered the particles out of the ink.

 

15. Mechanical damage of the printed image:

Insufficient mechanical resistance of the print. Further information can be found in our brochure 'Rapid tests and test methods for production control in packaging printing'.

 

Causes	Remedies
The ink recipe is not suitable or the ink is damaged.	Empty the ink tank, clean the ink feed system and replace the ink.
The transferred volume of the anilox roller is too low.	Replace the anilox roller.
An unsuitable solvent has been selected.	Use fresh ink with the appropriate solvent mixture.
The corona pretreatment of the film is insufficient.	Use inline corona pretreatment.
The abrasion resistance is poor.	Add a wax additive to the ink.