The present study treats a paper wrinkle appearing in a fixing roller unit of printers or copiers with electro-photographic process. An experiment shows that a wrinkle always occurs, when an A4-sized paper is tilted by 3 degrees against a horizontal fixing roller unit without a heating devise and is fed to a roller nip. The wrinkle appears in the middle of the paper width. Computer simulations were carried out to illustrate this wrinkle occurring process. The simulation model consists of a rigid cylindrical driving roller, a driven rubber roller, a paper, and a guide plate. The paper is assumed to be an isotropic elastic-plastic body. The results reveal the following wrinkle occurring process. When the tilted paper is fed to the rollers, the center part of the paper leading edge firstly enters the roller nip and is pulled by friction forces in the nip. Then paper wavy bending deformations appear in front of the nip. A steep slope of the deformation is crushed and yielded in the nip. After this, a neighbor area of the yielded point gathers together and a folded wrinkle is formed. Further, this type of wrinkle is liable to occur when the paper tilt angle, Young's modulus, or coefficient of friction is large, or when the paper yield stress is small.

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