History of Calendering

In 1798, Nicolas Louis Robert invented the paper machine. It took more than fifty years, however, until calenders were installed in the paper machine. These calenders - also called machine calenders - consisted of at least two hard rolls. A decade later the supercalender appeared with a large number of alternating hard 

Conventional rolls deflect under the influence of the load and their dead weight, which would result in a nonuniform distribution of Knear load in the press nips. To avoid this, the rolls had to be crowned, i.e. ground with a camber. The selected crown does, of course, only apply to a certain load. If it were desired to alter the load, the rolls had to be re-crowned. 

the introduction of the Swimming RoU in the 1950s by Kusters was of decisive importance for the further development of both the machine calender and the supercalender. This roll consists of a fixed shaft with a shell rotating around it. Between the shaft and the shell is an oil-filled chamber. By adjusting the oil pressure in this chamber the shape of the roll shell can be changed (Fig. 6.66). Thus the operating window of calenders was suddenly expanded. 

Since 1994 multi-zone control rolls have been in operation with up to sixty supporting elements arranged horizontally close together. These can be individually controlled so that even more precise profile corrections can be made (Fig. 6.68). 

Machine calenders and supercalenders with width about 5000 mm and above are today equipped with zone-controlled rolls as standard. Narrower machines still use the simpler overall control type rolls. 

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