Improving web tension regulation during zero-speed splicing operation
In this paper we discuss some of the issues that cause web tension variations during an unwind roll change employing a festoon and an automatic splicer. Due to deceleration of the expiring roll, stoppage for splicing, and acceleration of the new roll, the festoon carriage undergoes a motion profile that includes acceleration, deceleration, and constant velocity travel. In addition, the idle rollers within the festoon undergo varied amounts of speed changes. The combined effects of festoon idle roller and carriage speed changes result in tension variations that significantly affect transport of the web during the roll change event. The goal of this paper is to study these effects and provide insights into the amount of spike or drop in tension levels that can be expected during the zero speed splicing event. Given the festoon capacity and the stoppage time required to splice the web, we first provide an upper bound on the maximum line speed that is possible for a splicing operation, which includes two design parameters: (1) the time to decelerate the expiring roll from line speed to zero speed and (2) the time to accelerate the new roll from zero speed to line speed. Employing governing equations for the carriage motion and festoon roller angular motion, we derive expressions for web tension variations in festoon spans due to acceleration/deceleration of the carriage and the idle rollers caused by the acceleration/deceleration of the unwind spindles. This derivation results in expressing web tensions in festoon spans in terms of reference tension, carriage velocity, and the system parameters such as carriage mass, roller inertia, roller radii, etc. We provide some observations based on these derivations and measured data obtained from an experimental web line containing dual unwind spindles and a festoon.
author list (cited authors)
Pagilla, P. R., & Rauly, P. R.