Patent ID: 7813829

Claim:
A sheet manufacturing method comprising the steps (1) to (5): (1) extruding a sheet material to a sheet form using a die including plural thickness adjusting means; (2) forming a desired sheet by performing a predetermined processing involving dimensional change in a transverse direction of a sheet; (3) measuring thickness distributions in the transverse direction of the sheet before completion and after completion of the predetermined processing; (4) calculating a manipulated variable to be applied to the thickness adjusting means corresponding to each measuring position based on a thickness distribution measurement value in the transverse direction of the sheet after completion of the processing; and (5) controlling the thickness of the sheet by operating the thickness adjusting means by the manipulated variable; wherein in the calculation of the manipulated variable of step (4), a correspondence position in the transverse direction of the sheet after completion of the processing with respect to the thickness adjusting means is determined through the following steps A and B, and a thickness control is performed based on the determined correspondence position in the transverse direction of the sheet, A. obtaining unknown parameters such that an evaluation function including a mapping function representing a correspondence relationship between a position in the transverse direction of the sheet before completion of the processing and a position in the transverse direction of after completion of the processing and including one or more unknown parameters, a thickness distribution measurement value in the transverse direction of the sheet before completion of the processing, and a thickness distribution measurement value of after completion of the processing becomes an extreme value, and B. determining the mapping function based on the obtained unknown parameters and determining the corresponding position in the transverse direction of the sheet after completion of the processing with respect to the thickness adjusting means based on the determined mapping function.