Corrugated board warping is a common issue in corrugated production. It can affect board appearance, converting efficiency, and packaging quality. Understanding the main causes and applying proper control methods can help manufacturers maintain stable production and improve board quality.
Common warping types include:
- Upward warp: It is caused by high liner moisture content, slow production speed, low liner grammage, excessive glue application on A-flute in the double face machine, and excessively high hot plate temperature on the automatic line.
- Downward warp: It is caused by excessively fast machine speed, high moisture content in the face paper, excessive glue application on B-flute in the double face machine, and insufficient hot plate temperature.
- S-shaped warp: It is caused by uneven glue application on both sides of the board, uneven transverse moisture distribution in the base paper, and improper tension adjustment of the bridge or face paper.
To prevent warping, we recommend three key measures:
- Base Paper Control: Maintain base paper moisture at 8%±1% with uniform distribution. Avoid pairing base papers with high and low moisture content. Limit grammage differences between face and liner to 50g/m², use papers with similar fiber composition, and ensure stable water absorption/desorption properties.
- Production Process Optimization: Adjust preheater drying area and hot plate temperature based on moisture levels. Optimize production speed and glue application to balance moisture evaporation and board bonding.
- Post-Production Treatment: For finished warped boards, use reverse stacking, pressure flattening with cold air blowing, or controlled rewetting and stacking for 2 days to restore flatness.
By implementing these steps, corrugated packaging manufacturers can effectively reduce warping defects, improve product quality, and enhance production efficiency.
If you would like to learn more about improving corrugated board quality and production efficiency, feel free to contact us. Our team will be glad to support your corrugating operations.
