Calendering is a process involving a pair of corotating heated rolls which is fed with a thermoplastic melt for the production of sheet or film. Nearly all models proposed in the literature for this process are based on the simplification of the general equations for the conservation of mass, momentum and energy by making use of the lubrication approximation. Actually, most recent theoretical analyses are extensions of Gaskell’s model [1]. Various aspects of the theory can be found in the textbooks of McKelvey [2], Torner [3], Middleman [4], and Tadmor and Gogos [5]. Recent developments in calendering theory include the works of Vlachopoulos et al [6,7,8], Dobbels and Mewis [9], Agassant et al [10,11], Dimitrijew and Sporjagin [12] and Woskressenski et al [13].