Modeling Hygral Stress Profiles and Edge Waving in High-Bulk Recycled Cartonboard Skids
Modeling transient moisture gradients and hygral stress in high-bulk recycled cartonboard skids establishes barrier wrap limits to prevent press edge waving
Sheet Distortion
Structural Deviation
Dimensional instability defines the irregular geometric transformation of a flat substrate during storage or high speed print operations. Sheet distortion emerges when moisture absorption or thermal expansion creates localized tension across the web. Cellulose fibers within paper products behave anisotropically, meaning these expand along the grain direction at different rates than across the grain.
Dimensional accuracy suffers when environmental conditions vary significantly from those established during the original paper production.
Thermal Response
Friction generates heat at the contact point of rollers or printing blankets during continuous processing. This heating cycle dries out specific zones of the stock while other areas retain ambient moisture levels. Uneven moisture loss causes localized shrinkage patterns that pull the corners or edges of the substrate out of flat alignment.
Such mechanical changes force equipment operators to adjust tension settings on the press to compensate for the resulting wavy or puckered stock. Adjustments prevent registration errors where successive color passes fail to align perfectly on the page.
Production Boundary
Converting facilities manage the risks associated with this instability by implementing climate controlled storage zones before the conversion begins. Paper stock left exposed to fluctuating factory humidity levels for extended periods loses the ability to maintain the necessary flatness for precise die cutting or automated insertion. Packaging lines depend on perfect geometry to move sheets through folding apparatus without jamming.
Rigid adherence to defined moisture equilibrium cycles ensures that the substrate remains within the operational tolerances required for high volume throughput. Proper handling of the climate prevents the mechanical issues that arise when the physical form of the material fails to remain stable.