Satinage trough

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Calendering trough is a term from paper production and describes a trough that is created in the nip of a calender .

Calenders consist of smaller chilled cast iron rollers (diameter 460 mm) and slightly larger paper rollers (diameter 600 mm). The chilled cast iron rolls press into the elastic paper rolls under the load applied by a hydraulic system , creating a calendering trough.

In the first part of the stress zone (in front of the center line of the press nip), the radius of the elastic paper roll is reduced by indentation. This also reduces the circumferential speed of the same from the beginning of the depression continuously to the center line. As a result, the load is constantly increasing. This leads to a micro-shrinkage of the elastic roll cover, as a result of which there is shear stress on the paper web in the roll nip.

According to an outdated view of the mechanism of action of calendering , the shear forces should in turn be responsible for the microslip and cause the ironing effect, which is important for the production of gloss .

If the point of the highest load (center line press gap) is exceeded, the process described is repeated with the opposite sign, which continues the calendering effect.