Ink spitting

Problem case

Causes for ink spitting
Usually happens during printing of UV ink. UV ink does have an up to five times higher viscosity compared to water and solvent based ink. This leads to a higher dynamic pressure, which is lifting the working blade slightly and let the ink spit from the blade onto the substrate. The viscosity can be reduced through shear effect after a while and ease the problem during doctoring. Damages to to doctor blades or anilox rolls can be root cause too. This problem occurs in chamber and open systems.

Solution

Solutions for ink spitting
1. If the doctor blade lamella is too thin, it can not withstand the dynamic pressure of the high viscosity ink, use here a thicker lamella or stable design.
2. Use doctor blades with higher tensile strength, like TKM PowerPrint.
3. Check the doctor blade for damages and nicks, especially in the edge areas of the anilox roll. Change the doctor blade if necessary.
4. Check ink temperature and adjust if necessary.
5. Anilox roller can be worn out, check anilox roll for wear and tear and replace if necessary.
6. Deep cleaning the anilox roll to avoid plugged cells.

TKM recommends a periodical deep clean with TKM enpurex and TKM Optiprint or TKM PowerPrint UV Stable doctor blades.