A method of continuously imparting different visually detectable features to a plurality of articles is provided. The method includes providing a printing unit having two or more printing rolls each having a visually detectable pattern, wherein the printing process may fit rolls that are less than or equal to a maximum circumference. The method further includes providing a web having a print pitch that is greater than one half the maximum circumference, providing a first roll wherein the roll circumference is equal to the product pitch, and providing a second roll characterized in that the roll circumference is equal to either 0<X<1 where X is chosen such that 1/Xan Integer or 1<X<C.sub.max/P, wherein X is a multiple of the first roll circumference, C.sub.max is the largest circumference allowable, and P is the product pitch.

There is described a multicolor letterpress printing press, in particular a numbering press, comprising a printing group (50) with at least a first letterpress (e.g. numbering) cylinder (51) and a second letterpress cylinder (52) which are inked by an associated inking system (60, 71, 72, 81, 81 a, 81 b, 82, 82a, 82b). The inking system (60, 71, 72, 81, 81 a, 81 b, 82, 82a, 82b) comprises (i) a first inking device (81) supplying ink to a first chablon cylinder (71), (ii) at least a second inking device (82) supplying ink to a second chablon cylinder (72), and (iii) an ink-collecting cylinder (60) contacting the first and second chablon cylinders (71, 72) and the first and second letterpress cylinders (51, 52). The ink-collecting cylinder (60) collects a first ink pattern (A, D) from the first chablon cylinder (71) and a second ink pattern (B, C) from the second chablon cylinder (72). As a result, a first multicolor pattern of inks (A-D) is formed on the ink-collecting cylinder (60), which first multicolor pattern of inks (A-D) is transferred onto the first letterpress cylinder (51). The ink-collecting cylinder (60) further collects a third ink pattern (A, D) from the first chablon cylinder (71) and a fourth ink pattern (B, C) from the second chablon cylinder (72), thereby forming a second multicolor pattern of inks (A D) on the ink-collecting cylinder (60), which second multicolor pattern of inks (A D) is transferred onto the second letterpress cylinder (52).

There is described a multicolor letterpress printing press, in particular a numbering press, comprising a printing group (50) with at least a first letterpress (e.g. numbering) cylinder (51) and a second letterpress cylinder (52) which are inked by an associated inking system (60, 71, 72, 81, 81 a, 81 b, 82, 82a, 82b). The inking system (60, 71, 72, 81, 81 a, 81 b, 82, 82a, 82b) comprises (i) a first inking device (81) supplying ink to a first chablon cylinder (71), (ii) at least a second inking device (82) supplying ink to a second chablon cylinder (72), and (iii) an ink-collecting cylinder (60) contacting the first and second chablon cylinders (71, 72) and the first and second letterpress cylinders (51, 52). The ink-collecting cylinder (60) collects a first ink pattern (A, D) from the first chablon cylinder (71) and a second ink pattern (B, C) from the second chablon cylinder (72). As a result, a first multicolor pattern of inks (A-D) is formed on the ink-collecting cylinder (60), which first multicolor pattern of inks (A-D) is transferred onto the first letterpress cylinder (51). The ink-collecting cylinder (60) further collects a third ink pattern (A, D) from the first chablon cylinder (71) and a fourth ink pattern (B, C) from the second chablon cylinder (72), thereby forming a second multicolor pattern of inks (A D) on the ink-collecting cylinder (60), which second multicolor pattern of inks (A D) is transferred onto the second letterpress cylinder (52).

There is described a multicolour letterpress printing press, in particular a numbering press, comprising a printing group (50) with at least a first letterpress (e.g. numbering) cylinder (51) and a second letterpress cylinder (52) which are inked by an associated inking system (60, 71, 72, 81, 81a, 81b, 82, 82a, 82b). The inking system (60, 71, 72, 81, 81a, 81b, 82, 82a, 82b) comprises (i) a first inking device (81) supplying ink to a first chablon cylinder (71), (ii) at least a second inking device (82) supplying ink to a second chablon cylinder (72), and (iii) an ink-collecting cylinder (60) contacting the first and second chablon cylinders (71, 72) and the first and second letterpress cylinders (51, 52). The ink-collecting cylinder (60) collects a first ink pattern (A, D) from the first chablon cylinder (71) and a second ink pattern (B, C) from the second chablon cylinder (72). As a result, a first multicolour pattern of inks (A-D) is formed on the ink-collecting cylinder (60), which first multicolour pattern of inks (A-D) is transferred onto the first letterpress cylinder (51). The ink-collecting cylinder (60) further collects a third ink pattern (A, D) from the first chablon cylinder (71) and a fourth ink pattern (B, C) from the second chablon cylinder (72), thereby forming a second multicolour pattern of inks (A D) on the ink-collecting cylinder (60), which second multicolour pattern of inks (A D) is transferred onto the second letterpress cylinder (52).

A printing system comprising a flexographic printing machine comprising at least one impression cylinder, on which the material in sheet form to be printed is wound and around which at least one printing station is arranged. Each printing station comprises a plate cylinder, which is provided with a graphic element, and an anilox roller. Downstream of each printing station there is at least one drying unit for the inks which emits at least one first air flow and aspirates at least one second air flow; there are also elements for acquiring a coverage value of the graphic element present on the plate cylinder of each printing station and elements for automatically adjusting a flow rate of the first air flow and of the second air flow as a function of the coverage value of the graphic element acquired by the acquisition elements.