Digital printing apparatus and method

A printing system comprising:

• an inkjet head comprising a plurality n of parallel nozzle rows, wherein n is at least 2;
• wherein each nozzle row comprises a plurality of nozzles, wherein adjacent nozzle rows of the plurality of nozzle rows are shifted with respect to each other, such that projected on a line perpendicular on a printing direction, the plurality of nozzles form a regular pattern;
• wherein a distance between two nozzle rows, seen in the printing direction, is d;
• moving means configured for moving the substrate with respect to the ink-jet head in the printing direction at a printing speed v′;
• a controller configured for controlling the firing of each nozzle of said plurality of nozzles with a firing frequency f′;
• so that said plurality of nozzle rows are fired at different instants in time, such that the distance d′ between printed rows of dots printed by said nozzle rows, seen in the printing direction, is larger or smaller than d;
• the controller configured for firing each nozzle of said nozzle rows with a firing frequency f′, and configured to control the firing frequency f′ and/or the printing speed v′ such that f′=k*v′/d′;
• wherein k is an integer.

A method for printing with an inkjet head comprising:

• printing with an inkjet head comprising a plurality n of parallel nozzle rows, wherein n is at least 2;
• wherein each nozzle row comprises a plurality of nozzles, wherein adjacent nozzle rows of the plurality of nozzle rows are shifted with respect to each other, such that projected on a line perpendicular on a printing direction (P), the plurality of nozzles form a regular pattern;
• wherein a distance between two nozzle rows, seen in the printing direction, is d;
• wherein said printing comprises:
• moving the substrate with respect to the inkjet head in the printing direction at a printing speed v′;
• firing each nozzle of said plurality of nozzles with a firing frequency f′;
• wherein said plurality of nozzle rows are fired at different instants in time, such that the distance d′ between printed rows of dots printed by said two nozzle rows, seen in the printing direction, is larger or smaller than d;
• further comprising printing a first image on the substrate at a first printing station upstream of the inkjet head, wherein the substrate has undergone a shrinkage or extension in the printing direction when leaving said first printing station;
• and wherein a second image is printed on said first image using the ink-jet head, wherein the plurality of nozzle rows are fired at different instants in time, such that d′ is smaller than d in case of shrinkage and larger than d in case of extension.