Abstract: A film production process having a film tentering step and a recovering step, characterized by detecting the side edge positions of the film running toward the recovering step, transferring the film running direction based on the detected information, and controlling the clamp start position of the film arriving at a tenter in the tentering step by clamp means, in the transverse direction of the film. A film production process having a film tentering step, characterized by controlling the clamp start position of a film arriving at a tenter by clamp means, in the range from 5 mm to 1,000 mm from the tip of the film in the longitudinal direction of the film.

Abstract: An object of the present invention to provide a sheet manufacturing method and a sheet manufacturing die, in which a process of extruding a molten material from the die and winding it around a cooling roller can be performed at a high speed such as 60 m/min or more, and with which a sheet having a uniform thickness and a smooth surface can be obtained. In order to effectively charge the sheet with static electricity, the distance between paths of product portion and end portions of the sheet from a die to a cooling roller is reduced by adjusting the temperature of the sheet at the end portions thereof. The die is constructed such that the sheet is not influenced by deformation of a slit formed in the die, which is caused by heat expansion of the die and adjustment operations.

Abstract: The thickness distribution across a sheet material, formed by biaxially stretching a molten material web delivered from a die, is automatically controlled by a control processing wait. A correspondence relationship between adjustment of adjusting means arranged on the die and the variation of thickness distribution of the sheet material after formation thereof is sequentially estimated using a Kalman filter built into the control processing unit. Responsive to the estimated relationship, the adjusting means are controlled by optimum amounts in order to enable the thickness distribution to approach a target distribution. The accuracy of thickness control of the sheet material can be greatly increased and accurate control can automatically follow any variation in the conditiond of a sheet forming process. The correspondence relationship between the thickness distribution of the sheet material and the adjusting means on the die can be monitored and displayed.