Calendering is generally carried out at high temperatures.Heating rolls that were polished at room temperature (cold polish) to such high temperature can lead to generation of thermal distortions such as abnormal deformation of roll cylindricity (thermal crowning), errors in out of roundness and concentricity of rolls (rotational runout of rolls) and can cause thickness errors in the profile direction and machine direction of calender films.To remove these errors, in the hot grind process, the roll is heated to the same temperature as during the forming process, and the thermal deformations generated in the roll are removed by machining, making it possible to produce high accuracy, high quality calender films.