Most wrinkles are measured by viewing or counting the creases in the web.
For all wrinkling defects (i.e., buckling on rollers), observe and note 1) the angle and position any troughs in the span immediately upstream of where the wrinkles form, 2) the angle and crossweb position of the wrinkles, and 3) whether the wrinkle shifts or walks laterally.
View wrinkling in high speed processes by projecting a visible laser beam crossweb at a small spacing above the roller’s surface. Any wrinkling that buckling into the laser’s path will reflect the laser light for easy observation.
CD buckles in rolls are measured by direct observation. They may appear as CD ridges in the roll, sometimes visible at the outside of the full roll, but commonly only seen in layers near the core. From an end view, the CD ridges will form starring, spoking, or wavy ring patterns as several layers will buckle as a set, nesting upon each other.
Note width and radial positions where CD buckles occur – Full width vs. in specific lanes across the roll’s width, throughout the roll or only in specific radial positions, such as in layers near the core or at the roll’s outer diameter layers.
Direction observation of MD buckled ridges.
Note if the MD buckles have a uniform or variable pitch or CD wavelength.
Note if the MD buckles form across a portion or the entire width of the roll.
Note if the MD buckles appear throughout the roll or only in radial zones (e.g., only in the roll’s outside layers).
Note if the MD buckles are in the roll immediately after winding or either develop later or increase over time.
Note if MD buckles are seasonal or align with humidity variations.
Observe surface imperfections while winding.
Note if surface imperfections change with winding additional layers.
Note the position of surface imperfections, both their CD and radial position within the roll. Unwind the roll to see if the slip knot was initiated by surface debris or other surface imperfection.