Modeling nip induced tension in wound rolls

Abstract

Web materials are wound into coils by a variety of winders. Some winders center wind only. In this type of winding torque is provided to a core and web winds up on the core. Other types of winders have a roller, often called a nip roller, impinged into the outer surface of the winding roller. In this type of winding equipment the torque required to wind the rolls of web may either be provided to the core or to the nip roller and in some cases torque is provided to both. When the winding torque is provided only or mainly to the nip roller the winder is called a surface winder. When the winding torque is provided only or mainly to the core the winder is called a center winder with an undriven nip roller. When substantial components of the winding torque are provided to both the core and the nip roller the winder is called a combination winder.

It has been documented that the nip roller induces an increment in tension in the outer layer of a winding roll called the nip-induced-tension (NIT). The NIT combines with a component of the web tension to form the wound-in-tension (WIT) in the outer layer of a winding roll. The magnitude of the component of the web tension that becomes part of the WIT is dependent on whether the winder is center, surface, or combination driven. An objective of this paper is to show what wound roll and winder parameters affect the WIT based upon winding experiments. A second objective is to show the derivation of an introductory model whose output yields results that are consistent with winding tests.