Causes: -Fluctuations in flow rate -Mechanical vibrations -Coating bead Oscillations Solution: Minimize or eliminate vibration and/or oscillation
Ribbing
Cause: Instability in the coating bead Solution: Reduce the coating gap
Air Entrainment
Cause: Air is drawn in at the dynamic wetting line Solutions: -Utilize vacuum systems -Apply an electrostatic field -Ensure surface energy compatibility with surface tension (using corona, plasma, flame, or primer treatments)
Air Entrapment
Cause: Air in the fluid before it reaches the pump Solutions: -Allow time for air to dissipate -Implement cone flow -Use a dampening chamber -Apply sonic techniques
Dewetting
Cause: Surface tension gradient Solutions: -Use a vacuum system -Apply an electrostatic field -Ensure surface energy compatibility with surface tension
Streaks
Causes: -Presence of particles -Bubbles -Non-uniform wetting at the slot exit Solutions: -Clean the surface -Simulate and adjust the process
Particles
Causes: -Contamination -Gel formation Solutions: -Clean the affected area -Minimize recirculation zones
Chevrons
Causes: -Acoustic waves in the vacuum chamber -Close proximity to the substrate Solutions: -Measure frequency and clean/replace as necessary -Adjust vacuum level -Move closer to the substrate
Hashmarks
Cause: A gravity-driven defect in curtain coating Solution: Adjust flow rate and line speed to control fluid impact
