Missing Dots (gravure print)

Missing dots are isolated, unprinted cells in half and full tones, which are not caused by poor drainage from the impression cylinder onto the substrate. This is either due to cells that are already blocked or because the impression cylinder cannot make sufficient contact with the substrate. In vignettes and halftones, excessive doctoring can also lead to premature emptying of the cells.

Solutions to reduce/eliminate missing dots:

• Uneven surfaces of the substrate (e.g. paper) can make it difficult to achieve uniform contact with the impression cylinder. Activate electrostatic assistance (ESA) to draw the oppositely charged ink from the impression cylinder to the impression roller onto the substrate.
• Check the angle of attack of the doctor blade and reduce it if necessary, or use a more flexible doctor blade attachment (e.g. thinner support doctor blade).
• Check the impression roller for suitability for the substrate in question, change it if necessary and adjust to the correct shore hardness.
• Check the impression cylinder for dried cells and clean them.