Coating chambers tend to leak under certain circumstances. This article will discuss some common causes and remedies to prevent leakage.
Suspect 1 – Doctor Blades are worn out
Replace doctor blades and auxiliary blades
Suspect 2 – Sealings are worn out
Sealings, depending on the deployed material, may harden and lose tight contact over time.
- Replace sealings
- Treat sealings with silicone grease (applicable to felt sealings only)
Suspect 3 – Doctor blades mounted the wrong direction
Some doctor blades have an intended mounting direction in order to provide maximum stamina.
- Consult the documentation provided with the blades
Suspect 4 – Sealings mounted the wrong direction
Some felts have an intended installation position. If sealings are not mounted correctly, the chamber will not seal.
- Consult documentation and fix mounting position
Suspect 5 – Flow pressure too high
If the flow speed or pressure is too high for the medium pumped through, the chamber will be pushed away from the anilox roller. This causes lifting of the sealings and results in leaking.
Reduce flow speed (pump speed) or media pressure.
Suspect 6 – Coating viscosity too high or too low
Adjust viscosity accordingly to the chamber system requirements. Aqueous coatings may be thinned using a mix of water+alcohol. UV-Coatings may be adjusted by adjusting the temperature.
Suspect 7 – Doctor blades or auxiliary blades cut to the wrong length
Depending on the coating chamber construction, a certain length of the blades must be maintained.
- Replace blades with new ones cut to the exact specification