The ink does not form complete coverage on the surface of print. Random small holes occur in the print. Generally this is a problem caused by poor ink transfer on to the print and has several possible causes and solutions
1 The ink dries on the anilox roller and fails to transfer onto printing forme.
2 The printing form is not transferring ink correctly
3 The ink cannot build a uniform ink film on the substrate.
4 The anilox roller has lost volume due to dirty cells or is worn out.
5 Dirt on the impression cylinder.
6 Substrate has strong surface variations and rejects the ink.
1 Use a solvent with a slower evaporation and adjust the power of the dryers. Increase the printing speed.
2 Adjust the ink viscosity. Increase the ink film thickness. Increase printing forme to substrate impression. The surface of the substrate may be irregular, pitted or polluted. Check the metering system.
3 Check the condition of the anilox roller and replace if necessary.
4 Clean the impression cylinder.
5 Use softer printing forme or a softer mounting tape. Check the validity of the surface treatment of the substrate.
Helmut Mathes, troubleshooting defects supplied curtesey of Flexo & Gravure Int''l 2011
INK TRANSFER - FLEXO PRINT FORM
The flexo print form is a fundamental part of the printing process and has a significant impact on ink transfer and cleanliness of the inking process.Read more
INK TRANSFER - ANILOX
The shape and consistency of anilox cells makes a huge impact on ink transfer and cleanliness of the inking process to the printing plate.Read more
Flexo is a contact and pressure sensitive process. Increasing printing pressure, influences ink transfer and has a significant impact on print quality and performanceRead more