Moving Web Tension Determination by Out of Plane Vibrations Measurements Using a Laser

The tension measurement is a key point in the operation of web systems handling thin materials such as textile, paper, polymer or metal. An experimental procedure is proposed to compute the web tension using a contactless sensor, which can be implemented on existing industrial web handling machines. A laser sensor measures the position of the web during the process and identifies out of plane vibrations. Using a sliding FFT, those vibrations can be separated into forced vibrations created by the process and machines, and free vibrations. It is then possible to compute the web tension as the frequencies of free vibrations are directly related to web tension. A test bench has been set up to represent a classical web handling systems and measurements have been made to identify free and forced vibrations. The procedure to compute web tension from measurements is then detailed.