Tips & Tricks - Crease Formation
During printing, creases often are generated on paper that is
poorly air-conditioned, or does not lie in a flat plane, as well as
from paper that is wavy edged, baggy-centred, or statically
charged. Incorrect settings on the sheet-feeder or during paper
transfer may also lead to the formation of creases.
In order to ensure that the printing stock during the printing process lies flat, it should be kept properly air-conditioned during storage and transport. Paper is very sensitive to fluctuations in humidity. This is why one must be careful to maintain atmospheric humidity and temperature at constant levels during storage. Paper should demonstrate a relative humidity from 50% to 55%; the temperature should be constant between 20°C and 22°C (68°F and 71.6°F).
Should creases develop, this may also be the fault of incorrect machine settings - most likely on the sheet-feeder. Among the reasons creases may form are incorrectly set or jamming front lays, side lays that draw with too much force, a hold-down device that has been set too tightly, or an air-blast that is too strong. An incorrect air-pressure setting at the point of sheet transfer may also contribute to the formation of creases. Further sources include poorly functioning or dirty grippers, which warp the sheet, as well as a printing pressure between the rubber and the impression cylinder that is set too high, or is uneven. This tumbles the sheet, and will result in creasing.
Remedy:
In order to ensure that the printing stock during the printing process lies flat, it should be kept properly air-conditioned during storage and transport. Paper is very sensitive to fluctuations in humidity. This is why one must be careful to maintain atmospheric humidity and temperature at constant levels during storage. Paper should demonstrate a relative humidity from 50% to 55%; the temperature should be constant between 20°C and 22°C (68°F and 71.6°F).
Should creases develop, this may also be the fault of incorrect machine settings - most likely on the sheet-feeder. Among the reasons creases may form are incorrectly set or jamming front lays, side lays that draw with too much force, a hold-down device that has been set too tightly, or an air-blast that is too strong. An incorrect air-pressure setting at the point of sheet transfer may also contribute to the formation of creases. Further sources include poorly functioning or dirty grippers, which warp the sheet, as well as a printing pressure between the rubber and the impression cylinder that is set too high, or is uneven. This tumbles the sheet, and will result in creasing.
Remedy:
- Employ printing stock that is good and flat
- Inspect the front lays
- Inspect the side lays
- Do not set the hold-down device too tightly
- Reduce the air-blast on the sheet-feeder
- Optimize the air-pressure adjustments at the point of sheet transfer
- Optimize the print lateral feed
- Inspect, clean, and adjust the grippers as needed
