Curl, bias or diagonal

1. Correct for wire side or top side curl with dryer temperatures or pressures.

2. Alter the fiber orientation on the forming fabric by setting sheet on forming fabric as fast as possible (pressure formation) and reducing stroke of the shake where used.

3. Increase short fiber content in sheet.
— increase refining or increase hardwood content in furnish.

4. Check that dryers are properly evacuated.

5. Alter the moisture pick-up on each side of sheet at size press or calender stack.

6. Check for edge or deckle waves and/or excessive cheeking bleed..

7. Adjust headbox variables to prevent uncontrolled side currents.
— check for unbalanced slice pressure front-to-back.

8. Check for high wall friction in headbox (build-up).

9. At slow speeds, use short, rapid shake.

10. Check for plugged edge tubes or bent apron.

11. Slice opening and head not correct for wire speed.

12. Check for misalignment of top slice to apron.

13. Eliminate stock skating or streaky formation.

14. Check alignment between forming board and dewatering devices.

15. Level the forming board.
— the leading edge should be slightly higher than trailing.

16. Ensure uniform stock spouting velocity from headbox to forming fabric.

Note: Diagonal curl is usually a result of fiber misalignment that occurs before the tube bank and carries through to slice or misalignments caused by tube bank itself; also results from stock velocities differing from one area of headbox to another. Sometimes can reduce the effect by slightly dragging
the sheet.

See Formation notes.