The process of web wrinkle formation on a roller and its prevention with a curved axis roller (A web transfer simulation for roller tilt)

Abstract

The process of a trough stepping into a wrinkle during web transfer is simulated by FEM commercial software. Two models are employed. The first one consists of a web and four cylindrical rollers, while the second one has a curved axis roller instead of a cylindrical roller to prevent wrinkles. After applying tension to the web, a roller is inclined and then the web is transferred by a roller rotation, if necessary, the curved axis roller is bent before tilting. The main outcomes are as follows. (1) As the trough of the web reaches the inclined roller and flattens at the inlet of the roller, a CD compression stress of the web increases due to slippage of the flattening and accumulates there. A wrinkle occurs when the maximum CD compression stress exceeds a critical value. The value increases with MD strain calculated by tension and Young’s modulus. (2) The wrinkle tends to occur when the MD strain is smaller or when the roller tilt angle and coefficient of friction are larger. (3) A boundary of the wrinkle occurring area is shown by a figure with the axes of the MD strain and the roller tilt angle. (4) The wrinkle is prevented from forming when parameters of the curved axis roller are suitably selected. There was a case where the wrinkle doesn’t occur for a large area of a bent direction angle ranging from -90° to +45°. (5) Spreading or shrinking of the web on the curved axis roller can be qualitatively illustrated by considering both the vector distribution of the roller surface velocities and the expansion or contraction of the bent arc of the roller.

Keywords

• simulation
• fem
• web handling
• membrane
• wrinkle
• trough
• roller tilt
• curved axis roller
• tension
• friction force