In Part 3 of the Web Guiding Systems Series we discussed Web Displacement Guide.
Figure 4 – Unwind Guides
Sometimes it is important on roll-to-roll web lines to start the web down an appropriate path despite poor edge quality of the unwinding roll or variations in web width or roll positioning. In these cases, an unwind guide would be used as seen in Figure 4. The unwind guide would be used as seen in Figure 4. The unwind guide consists of an unwind which can be moved sideways on linear bearings, a following roller which (desirably) moves with assembly, and, of course, sensor, controller, and actuator. While the actuator could be any push-pull device which is strong and fast, typically hydraulic cylinders are used.
Figure 5 – Rewind Guides
Sometimes, straight edged rewound rolls are desired despite edge problems with the unwind rolls or the web path between. In this case, often a salvage operation, the rewind may be guided. As shown in Figure 5, winder guiding system closely resembles unwind guiding. In fact, the major difference is that the edge sensor is fixed to ground on the unwind guide and fixed to the winder frame on the winder guide. If the sensor cannot be mounted off the winder, then it must be slaved to follow the movements of the winder. Rewind guides are somewhat less common than unwind guides. In part, this is due to the greater complexity of the winder which does not lend itself to sidelay as easily as an unwind.
In Part 5 of the Web Guiding Series we discuss Guide Accuracy and Response.
Written for Faustel by David R. Roisum, Ph.D.