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3. COATING METHODS - PREMETERED
• Pre-metered vs Self-metered
• Pre-metered = amount of liquid applied to the web per unit area is
predetermined by a fluid metering device upstream
• Self-metered = final wet thickness of the coated film is controlled
by the interactions of the fluid flow with the coating applicator
• The average cross-web weight (thickness) is predetermined before
the fluid is applied to the substrate (Pre-metered)
4. FLUID DELIVERY SYSTEM
• Fluid Delivery and Line Speed
o Coating weight (thickness)
o Ratio
• Fluid Delivery System
o Positive displacement
o Rheology of fluid
o Density
o Particle size
o Shear sensitivity
7. TECHNIQUE
• Direct coating
o Advantages
Cross-web uniformity predictable
Precision surfaces
o Disadvantages
Narrow gaps
12 micron coatings or thicker
8. TECHNIQUE
• Curtain coating
o Balance of liquid momentum and surface tension
o Uniform pressure across fluid flow between edge guides
o If the coating thickness is smaller, then the web velocity
has to be higher
o Sharp lip edge geometry
9. TECHNIQUE
• Curtain coating
o Advantages
Large gap (irregular surfaces)
Increased fluid velocity
Higher line speed
Thinner coatings
o Disadvantages
Air/Vibration
Minimum line speed & flow rate
Neck-in
10. TECHNIQUE
• Tensioned web
o Elasto-hydrodynamic interaction
Web tension
Line speed/flow rate
Wet coating thickness
Wrap angles
Lip geometry
Web penetration
11. TECHNIQUE
• Tensioned web
o Advantages
Overcome gap issues
Follow profile of web
Thinner coatings
o Disadvantages
Web dependent (tensions)
Process dependent (idlers)
12. SYSTEM
• Slot Die
• Positioner
• Backing roll
• Fluid delivery system
• Substrate
13. SYSTEM
• Slot Die
o Manifold design
o Manufacturing tolerances
o Lip offset
o Lip geometry
Distribution
chamber
Feed port
Slot gap
Lip land
14. SYSTEM
• Slot die design
• Rheology
• Manifold
• Body sections
• Fluid flow control