Text 2 Web-fed Printing Presses

Web-fed printing presses differ less from sheet-fed presses in the configuration of their printing and inking units than in all the machine elements actually transporting the substrate. In principle it is much easier to transport a web through the various press units than a sheet. The continuous web to a great extent guides itself, because the start of the web is pulled and the web is held under tension in a stabilizing, defined way. Therefore web presses are more suitable for higher printing speeds than sheet-fed presses (sheet-fed printing up to approximately 4m/s,web printing up to approximately 15m/s).

Web presses are production systems that are able to produce finished printed products, that is, finishing is an integral part of web offset printing. Web presses are relatively inflexible with regard to format variation compared to sheet-fed presses, only

the web width is variable. The format is defined in the circumferential direction of the printing plate and in the direction of web travel by the cut-off length. The advantage is here that, depending on the printing process, there is no printing gap (or at least almost none). In flexographic and gravure printing the cylinder circumference can, within certain limits, be adapted to the cut-off length, whereas on web offset presses the cylinder diameters are invariable.