Corrugations, winders

1. Corrugations result from regions of low-caliper web between two strips of high-caliper web where differences in web tension are relieved by formation of diagonal ridges across the section with low tension.
— poor caliper profile should be corrected back at the headbox.
2. Corrugations usually mark the web; if mark is light, roll may be salvaged by using spreader bar with higher tensions.
— check set-up of spreading devices.
3. Heavy marking of the web requires cutting out the corrugations.
— try to salvage narrower rolls on each side.
4. Soft starts and excessive tension on roll contribute to ropes and corrugations.
5. Poorly structured rolls will give more problems with corrugations.