Deformation Defect
The localized concavity occurring within the individual panels of a corrugated box defines a deformation that degrades packaging appearance and strength. This panel dish warp typically develops after the box has been assembled. It results from a moisture imbalance between the inner and outer surfaces of the board.
Moisture Differential
Differential absorption or desorption of moisture on one side of the panel causes it to shrink or expand while the surrounding scored edges remain fixed. This restriction forces the center of the panel to pop inward or outward, creating a dish shape. In dry conditions, the outer liner might shrink more than the inner liner, pulling the panel center outward.
This issue is most common when the board has been manufactured with linerboards of unequal weight or composition.
Stacking Performance
Structural performance of the shipping container is reduced when the panels are dished, because the load-bearing capacity of the box walls relies on their flatness. When a vertical load is applied during warehousing, the pre-curved panels will buckle under much lower forces than flat panels would. This defect also prevents successful automatic labeling, as the curved surface does not allow the adhesive label to apply smoothly.
Proper climate control in storage areas and using symmetrical paperboards can prevent the development of this structural weakness.
