Impressionist
With impression roller is in the printing technology of the impression cylinder in roll gravure presses referred. In most printing processes , such as offset , flexographic or gravure printing, the printing cylinder exerts such a force on the printing material that it could be damaged or at least unintentionally deformed. To solve this problem, the impression roller is used as an impression cylinder. It also enables the paper to suck the printing ink out of the cells of the printing form cylinder by pressing the printing material against the printing cylinder. The impression roller also takes care of the transport of the paper web through the printing unit .
The impression roller is usually made of a hard material such as wood or metal covered with a rubber layer. The respective hardness of the cover determines the contact area, the so-called print stripes , between the printing form cylinder and the printing material.
Since a corresponding force has to be applied to the legs of the impression roller facing the axis, the impression roller and the impression cylinder can sag, especially with wider machines, and this leads to irregularities in the printed image. Such errors can be avoided with special impression systems. Impression systems with deflection correction are mainly used on machines with a web width of more than 2,000 mm. This correction prevents the impression roller and printing forme cylinder from bending.
Impression types
There are different types of pressurizers:
The flexible impression roller has a flexible jacket and adapts to the contours of the printing plate cylinder. With the K impression roller , the force is transferred to the rotating jacket of the impression roller via the bearings in the middle third of the bearings. The K stands for compensation. With the K2 impression roller, hydraulic pressure is exerted on the drive and operating side of the impression roller at two points, the axis and the jacket, in order to prevent bending. With the S-impression roller , oil is pumped under the rotating impression roller in the direction of the printing forme cylinder through several channels in the stationary core. The Nipco Print impression roller consists of a highly elastic, rotating impression roller casing . This is pressed against the pressure cylinder by a hydraulic piston.
An electrostatic printing support is achieved by a top or side of the impression roller mounted electrode. The opposite static charge improves the transfer of ink from the cells in gravure printing and prevents so-called missing dots .
See also
literature
- Helmut Kipphan: Handbook of the print media . Springer, Heidelberg 2000, ISBN 3-540-66941-8 .
- Dieter Liebau, Hugo Weschke: Polygraph specialist lexicon of the printing industry and communication technology . Polygraph Verlag, Frankfurt am Main 1997.
- Bernd Ollech: Gravure, basics and process steps of modern gravure technology . Polygraph, Bielefeld 1999.
- Hans-Jürgen Scheper: Examination knowledge printing technology . Verlag Beruf und Schule, Itzehoe 2005, ISBN 3-88013-623-8 .