Calendering is a method used to produce plastic film and sheet. It would appear, therefore, to be in direct competition with extrusion. But this is not true. In fact it finds its main applications in the production of PVC sheet since with calendering there is much less risk of material degradation. Some film is also produced in this way from ABS, cellulosics, and toughened polystyrene.

Basically the process consists a plastic formulation being passed between the nip of heated rolls. Usually four rolls with three nips are employed although a varierty of combnation is possible. The first nip controls the feed rate, the second nip acts as a metering unit and the third nip controls the sheet thickness. The last roll may be matt, glossy, or embossed to provide the disired surface finish on the product. The other calender rolls must be highly polished and concentric to a very high degee of accuracy and hence, the equipment is expensive. Indeed since there is very little mixing during calendering the total plant requires very much more than the calender. A lot of preparatory work on the feedstock needs to be done before it reaches the calender rolls. This includes mixing, blending, gelling, and straining the formulation of resin, lubricants, plasticizers, stabilizers, and pigments. Also, since repairs to rolls can be very costly, it is essential to remove any foreign particles before the strip feed passes into the calendar.