Summary

Experts have begun increasingly to question the commonly-held view of satellite printing means good register, blanket-to-blanket printing means poor register. In particular, doubts have been expressed as to whether the benefit of better register justifies the complicated mechanics required by satellite printing units. The arrival on the scene of the eight-couple tower based on blanket-to-blanket printing, and the commercial success of this configura- tion, prove that many parties prefer simplicity. With this project, IFRA undertook to commission a neutral research institute to examine the colour register behaviour of both systems. FOGRA, the German research organisation for printing and reproduction technology in Munich, was duly commissioned with this task. Under the guidance of Harald Pertler, the team of FOGRA scientists came to the conclusion that, under "normal" printing conditions, no serious differences in register could be established between the two configurations. However, differences do occur in the dynamic behaviour, though these remain at a tolerably low level in the lateral register (standard deviation ø of 20 un for blanket-to-blanket printing, and 10 urn for satellite printing). In contrast to this, greater deviations are experienced in circumferential register that, at a higher web tension, can reach a standard deviation o of 130 un on blanket-to-blanket presses. In such cases, the installation of a good web tension and/or register control system can be recommended. We hope that this Special Report shall contribute to an unbiased discussion of the benefits and drawbacks of eight-couple towers, and wish it the attention it deserves.