Calendering bowl deflection

The distortion suffered by calender rolls resulting from the pressure of the rubber running between them. If uncorrected the deflection produces a rubber sheet thicker in the middle than at the edges. See Camber, Crossed Axes and Roll Bending, all techniques to compensate for calender bowl deflection. 

The correction of calender bowl deflection by application of hydraulic pressure to counteract the forces tending to produce deflection. 

The slight curvature given to calender bowls to counteract the deflection produced when the calender is running, thus enabling a rubber sheet of uniform thickness across its width to be obtained. 

This basic operation utilises a two-bowl calender in horizontal or vertical configuration. The feed material, either in strip or pig form, is fed into one side of the nip and is squeezed by the bowls, thereby emerging as a sheet which is pulled from the bowl by some manual or mechanical means or supported by a liner cloth. Because of their versatility, three-bowl calenders are now more widely used for sheeting as well as other basic calendering operations. Thickness control is accomplished by use of the adjustable nips and may be further refined by automatic control systems using thickness sensors. It should be noted here that the force required in the nip to flatten the feed material causes deflection of the bowls, however slight. If some corrective steps are not taken, the product thickness will vary across the sheet, resulting in excessive variations of the product and possibly excessive use of expensive materials. In order to overcome these problems, three basic techniques are used to achieve uniform product thickness ... 

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