Corrugating rolls are the core components of flute forming, and their condition has a significant impact on corrugated board quality. Worn or rounded flute tips, uneven roll temperature, or incorrect roll parallelism may not be immediately noticeable, but they can gradually make show-through more severe.
Flute Tip Wear
As the flute tips wear, they become more rounded and wider. This increases the contact area between the flute tips and the liner during gluing, making show-through more likely to become visible on the liner surface.
Uneven Corrugating Roll Temperature
When the corrugating roll temperature is uneven, flute formation can vary across the working width.
Areas with lower temperatures may produce lower flute heights and weaker flute formation, making the flutes more susceptible to deformation during pressing. Areas with higher temperatures may form the flutes more effectively but can also be exposed to excessive heat.
When the temperature varies across the roll width, the severity of show-through may also vary from one side of the board to the other.
Corrugating Roll Crown Wear
This issue can occur after long-term production with narrow-width sheets. The crown is the intentional compensation built into the center of a corrugating roll to offset the reduced pressure in the center caused by roll deflection during operation.
As the crown wears, flute height in the center area may gradually decrease. When producing wider sheets, operators may increase glue application to maintain bonding performance. Excessive glue application in this situation can contribute to the development of show-through.
The problems associated with corrugating rolls are often gradual rather than sudden. Roll performance does not usually deteriorate in a single day; changes can accumulate slowly over several months.
That is why regular inspection and maintenance records are important. Without consistent inspection data, it can be difficult to determine when roll performance first started to decline or how quickly the condition has changed.
