Analysis of the causes of register errors in a rotorgravure printing press.

The cause of register errors that develops in a rotogravure printing press under particular conditions of printing speed has been analysed. The print defect in magazines causes waste printed paper and prevents from fully exploiting the productive capacity of the rotary press. It has been observed that the defect is not consistent with the natural vibrations of the rotating bodies in contact with the paper during the printing process. A new approach based on the analysis of the register markers printed on the pages of a magazine, has allowed to show a probable oscillatory phenomenon of the entire rotary press structure, not easy otherwise detectable. This new method consists on the reconstruction and interpretation of the curve corresponding to a series of register markers printed along a line of a paper sheet. It has been so possible to determine that the cause of the print defect is due to the oscillations at low frequency of the rotary press structure. A simplified model of the deformations of the tightened paper web confirms the results.