Causes for scoring lines
The surface damage in the anilox roll usually comes from grind-in of foreign particles. These particles cause a scoring into the roll ceramic surface. Because flexo printing does not have an oscilating doctor blade, as in gravure printing, foreign particles have the opportunity to become stuck underneath the doctor blade tip and grind in a scoring line over time. The is a difference between cosmetic and severe scoring. Cosmetic scoring is visible scoring, which does not have a deep groove and does not pose any printing problem apart from the visual effect. This usually happens with a new anilox roll after the last “finish” with the first doctor blade application. Severe scoring however has a noticable deep groove on the anilox surface which is causing printing problems.
Solutions to avoid scoring
Check ink for particles and dirt, check ink filtration system. Replace ink if necessary.
1) Check for particles stuck under the doctor blade, then remove particle.
2) Check for excessive doctor blade/chamber pressure and reduce if necessary. Excessive pressure can lead to splinter formations which quickly lead to point 2.
3) Replace doctor blade when changing anilox roll as doctor blades wear in for a specific anilox. Changing the anilox and using a worn blade can lead to splinter formation.
4) Always clean the ink filter and change the ink after the first doctor blade change when using a brand new anilox roll. The new roll will be ground-in and detached particles must be removed to avoid scoring.