Post on 25-May-2015
description
Gravure Coating:
Webinar – April 26, 2012
John LooserNew Era Converting MachineryP.O. Box 377Hawthorne, NJ 07506Phone: 973-413-4605E-mail: john.looser@neweraconverting.comwww.neweraconverting.com
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One of the Most Versatile Methods in the Industry
Webinar Outline• Classic Gravure Coater
– Section Details
• Improvements – Enclosed Applicator– Sleeve System– Cartridge Systems
• Variations– Reverse Gravure– Offset Gravure– Differential Offset Gravure– Process Handles:
• 2-Roll and 3-Roll Gravure
– Pressurized Gravure– Two-side Coating
• Versatility– Application Range– Coating Types– Products
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Classic Gravure Coater
• Sections:
– Coating Reservoir (Pan)
– Gravure Roll (Etched Metal)
– Doctor Blade
– Impression Roll (Rubber)
• Process:
– Coating Pick-up
• Fill Cells
– Wipe (Doctor) Excess
– Transfer Coating
• “Empty” Cells (Transfer Efficiency)
• Film Split
Impression /Back-up Roll
GravureRoll
DoctorBlade
Coating Pan
CoatedWeb
IncomingWeb
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Classic Gravure Coater
Impression /Back-up Roll
GravureRoll
DoctorBlade
Coating Pan
CoatedWeb
IncomingWeb
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• Terminology:– Direct Gravure
– Forward Application
• Synchronous Rotation
– Pan Fed
Classic Gravure Coater
• Coating Reservoir– Enclosed Applicator Shown
• Gravure Roll– Motor Driven
– Pneumatically Positioned
• Doctor Blade– Integral to Enclosed Applicator
• Impression Roll– Nip/Web Driven
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Coating Pan
• Function: Delivers Coating to Gravure Roll
• Maintain Constant Level– Stand Pipe or Overflow Weir
• Consistent Coating Movement– Continuous Recirculation
– Foam Management
– Avoid Solids Settling
• Enclosure / Covers– Minimize Solvent Evaporation
– Contain Slinging
• Pneumatic Pan Lift
GravureRoll
DoctorBlade
Supply
ReturnReturn
GravureRoll
DoctorBlade
Supply Return
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Gravure Roll• Function: Deliver Consistent Coating
– Homogeneous Transfer (Across and Down Web)
• Etched / Patterned Cylinder
– Determines Coat Weight and Appearance
– Cell Creation: Mechanical / Laser / Electronic
• Driven Roll
– Tension Control
– Idle Mode
– Vector or Servo Controlled
• Cored for Temperature Control
– Heat Management
– Viscosity Control
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Cell Creation – Gravure Patterns• Cell - Coating Reservoir
– BCM: Volume = Billion Cubic Micron per Square Inch• 2 – 200 BCM
– LPI: Cell Density = Lines Per Inch• 10 – 1500 LPI
– Release / Transfer Rate• % Coating Volume Released Onto Substrate
– Patterns / Shapes• Appearance and Flow
• Promote Release
• Methods for Cell Creation
– Mechanical Engraving
– Laser Engraving
– Electronic Engraving
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Cell Creation – Mechanical Engraving• Roll Design
– Steel Core with Soft Copper Layer
– Chrome Plating Over Pattern
• Cell Creation
– Patterned Tooling Stamps/Forms
Shapes
– Material is NOT Removed• Surface is Re-Formed
– Roll Precision Can Be Affected
• Release Characteristics
– Most Angles are 45o
– High Surface Tension
– Average Release 40-50%
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Mechanical Engraving – Common Shapes
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Quad Roto Flo
Quadragravure
Imp
roving Rele
ase Properties
Pyramid
Roto-Flo Pyramid
Tri-Helical Quad Channel
Cell Creation – Laser Engraving
• Roll Design
– Steel Core with Ceramic Covering
• Cell Creation
– Focused Pulses Create Shape
– Laser Vaporizes Surface Material
• Release Characteristics
– Relatively High Surface Roughness
– Medium Surface Tension
– Average Release 50-60%
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Multi-Hit Single-Hit
Laser Engraving – Common Shapes
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Imp
roving Rele
ase Properties
30o Channel
60o Hex
Tri-Helical
30o Hex
Cell Creation – Electronic Engraving• Roll Design
– Steel Core with Hard Copper
Layer
– Chrome Plating Over Pattern
• Cell Creation
– Electronically Positioned
Diamond Tip Stylus
– Material is Precisely Removed
– Roll Precision is Maintained
• Release Characteristics
– Low Surface Tension
– Average Release 65-75%
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Electronic Engraving – Common Shapes
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Doctor Blade• Function: Remove Excess Coating
– Coating in Cells Only
– Cell Determines Coat Weight
• Angle of Attack– Trailing Blade
• Low Speed / Low Viscosity
• Hydraulic Forces Can Lift Blade
• Traps Contaminates
– Reverse Angle / Chisel / Plowing• Increased Speed and Viscosity
• Hydraulic Force Helps Hold Blade
• Rejects Contaminates
• Loading Pressure– 0.5 – 4.0 pli
GravureRoll
Coating Pan
Trailing Blade
25-30o
GravureRoll
Coating Pan
Reverse Angle
30o
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Doctor Blade• Materials
– High Carbon Spring Steel– Stainless Steel– Mylar– UHMW– …………
• Different Shapes– Most Common = Simple Bevel
• Pneumatically Loaded
– On/Off Control
• Angle Adjustment
– Coarse: Trailing and Reverse
– Fine: Attack Angle
• Oscillation
– Motor Driven
Typical Blade Holder
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Impression Roll
• Supports Substrate
– Rubber Covered Roll
– 65-90 Shore A Durometer
• Nip Footprint
– Impression: 0.25” – 0.375”
• Controls Coating Width
– Undercut Roll
– Lift Edges Off Gravure Roll
– Unique Roll for Each Web Width
Web
Gravure Roll
Impression Roll
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Impression Roll
• Impact on Coating Quantity and Quality
– Roll Durometer Impacts Amount of Coating Transferred
• Thick Soft Covering (60-70 duro) = Large Footprint = More Coating
• Thin Hard Covering (80-90 duro) = Small Footprint = Less Coating
– Higher Precision Leads to Better Coating Uniformity
• Soft Roll = .002 - .004” TIR
• Hard Roll = .0005” - .001 TIR
– Thin Precision Coating• Hard Cover – Small Footprint – Precision Roll
Impression Control• Pressure Only
– Pressure in Loading Cylinders Set Impression
– No Position Stops Between Rolls
– Difficult to Control
• Cylinders Lift Roll / Pan / Motor AND Sets Impression
• Pressure Changes Impact Impression
• Adjustable Stops– Cylinders are Utilized for Positioning
– Stop Setting Dictates Impression
– High Loading Pressure = Stability
– Fine / Repeatable Adjustment
• Stop Configurations– Coarse Thread
– Differential Screw
– Taper Wedge Block 20
Improvements
• Enclosed Applicator
• Sleeve System
• Cartridge Systems
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Enclosed Applicator
Supply
Impression /Back-up Roll
CoatedWeb
IncomingWeb
Return
• Enclosed System– No Slinging of Coating
– Minimizes Solvent Evaporation
– Reduced System Volume
• High Rate of Recirculation– Minimizes Air Entrapment
– Foam Control – Flows Out of Chamber
• Easy to Clean– Simple Flushing Systems
– Minimize Waste
GravureRoll
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Enclosed Applicator
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Impression Roll: Sleeve System
• Impression Roll:
– Rubber Covered Sleeve
– Steel Mandrel
• Drive Side
– Cantilever Support
• Operator Side
– Removable Bearing Support
• Quick Width Change
– 5 Minute Task
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Impression Roll: Sleeve System
• Air Pressure Expands Sleeve
– Floats Off Mandrel
• Straight or Tapered Mandrel
• Sleeves
– Nickel
– Composite
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Cartridge System• Base Frame and Drive Stand
Fixed in Web Line
• Gravure Roll, Impression Roll and Coating Applicator on Cartridge
• Quick Change System– Off-Line Clean-up
– Coating Change
– 10 Minute Change-out Time
• Typical Features– Precision Rails Maintain
Alignment
– Quick Connects for Air and Electrical
– Tool-less Quick Disconnect Drive Coupling 26
Cartridge System
• Base Frame with Applicator Roll, Impression Roll and Drive Stand Fixed in Web Line
• Gravure Cartridge Installed
• Five Motors on Drive Stand
• 5-Roll Transfer Coating – Two Rolls on Base
– Three Rolls on Cartridge
• Quick Change System– Switch Between Methods
– Clean-up Off-Line
– 10 Minute Change-out Time
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Variations
• Reverse Gravure• Offset Gravure• Differential Offset Gravure• Pressurized Applicator• Two-Side Coating
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Reverse Gravure
• Reverse Application– Speed Range: 90-120%
• Benefits– Removes Cell Pattern
– Film Split Avoided • Minimizes Ribbing
– Adjust Coat Weight with Roll Speed
• Impression Control is Critical– Light / Controlled Impression
– Precision Required – Better Rolls
• Driven Impression Roll– Suggested for Tension Control
– Overcome Reverse Action
Impression /Back-up Roll
GravureRoll
DoctorBlade
Coating Pan
CoatedWeb
IncomingWeb
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Offset Gravure
• 3-Roll System– Gravure is Offset from Substrate
– Removes Substrate from Coating Nip• Protects Sensitive Substrates
• Roll Rotation– All Roll Same Direction
• Synchronous Rotation
– Two Film Splits
– Thinner Coatings
• Roll Speeds– All Rolls at 100% Line Speed
– Single Drive is Possible• Gravure Roll is Typically Driven – Idle Mode
• Applicator Roll is Nip Driven
• Back-up Roll is Web Driven
SteelBack-up Roll
Gravure“Forward”
DoctorBlade
Coating Pan
CoatedWeb
IncomingWeb
RubberApplicator Roll
“Forward”
FilmSplit
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FilmSplit
Differential Offset Gravure
• 3-Roll System
• Roll Rotation– Gravure: Forward / Reverse
– Applicator: Forward / Reverse
• Roll Speeds– Gravure: Variable
– Applicator: Variable
– Back-Up: Controls Tension
– All Rolls are Driven
• Roll Function– Gravure: Coat Weight Control
– Applicator: Appearance Control
DoctorBlade
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SteelBack-up Roll
GravureFwd / Rev
Coating Pan
CoatedWeb
IncomingWeb
RubberApplicator Roll
Fwd / Rev
FilmSplit
FilmSplit
Differential Offset Gravure
• Cartridge Coater
• All Driven Rolls
– Additional Drives for 5- Roll Coating
• Wide Range of Set-ups
– Gloss Top Coat
• Gravure = 100%, Applicator = 100%
– Silicone Coating
• Gravure = 5%, Applicator = 95%
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Process Handles: 2-Roll GravureCoat Weight and Appearance
• Direct Gravure - Forward Application1. Gravure Roll Selection
2. Gravure / Back-up Roll Nip Footprint
• Direct Gravure – Reverse Application1. Gravure Roll Selection
2. Gravure / Back-up Roll Nip Footprint
3. Gravure Roll Direction
4. Gravure Roll Speed
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Process Handles: 3-Roll GravureCoat Weight and Appearance
• Offset Gravure1. Gravure Roll Selection
2. Gravure / Applicator Roll Nip Footprint
3. Applicator / Back-up Roll Nip Footprint
• Differential Offset Gravure1. Gravure Roll Selection
2. Gravure / Back-up Roll Nip Footprint
3. Applicator / Back-up Roll Nip Footprint
4. Gravure Roll Direction
5. Gravure Roll Speed
6. Applicator Roll Direction
7. Applicator Roll Speed
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Pressurized Coating Applicator
Pressurized Applicator Tri-Helical Gravure Roll
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Pressurized Coating Applicator
Conventional Applicator:No Pressure
Pressurized Applicator:Low Pressure
Pressurized Applicator:Higher Pressure
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Pressurized Coating Applicator
Pressurized Applicator
• Adjustable Coat Weight with a Single Cylinder
– 50-100% Weight Increase
– Reduced Gravure Roll Inventory
• Extended Coat Weight Range
– Thicker Coatings
• Constant Coat Weight with Increasing Speed
– More Efficient in Filling Gravure Cells
– Less Recirculation and Foam Generation
• Higher Viscosity and % Solids
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Simultaneous Two-Side Coating
GravureRoll
GravureRoll
• Very Cost Effective– Coat Both Sides at One Coating Station
– Single Dryer vs. Dual Dryers
– Reduced Overall Line Length
• Direct Application (Kiss Coating)– Forward or Reverse Apply
– Coat Weight is Susceptible to Tension Variations
• Limited Range of Applications– Thinner Coatings
– Same / Similar Functional Coatings on Both Sides
Two-Side Coating
• Offset “Kiss” Coat– Unsupported
ApplicatorRoll
GravureRoll
GravureRoll
ApplicatorRoll
• Offset Coat– Supported
ApplicatorRoll
ApplicatorRoll
GravureRoll
GravureRoll
Versatility• Application Range
– Speeds: 0 - 2000+ fpm– Widths: 0 - 200+ inches
• Substrates:– Papers – Boards – Films– Foils– Wovens / Non-wovens– ………
• Coating Types:– Water Based
– Solvent Based
– 100% Solids (UV and E-Beam Cure)
– Hot Melt: Adhesives and Waxes
– ………
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Versatility• Viscosity and Wet Coating Thickness:
– 2-Roll Gravure:• 10-1000 cps
• 0.0005” – 0.0015”
– 3-Roll Gravure• 50 – 2000 cps
• 0.0001” – 0.001”
– Pressurized Gravure• 100 – 5000 cps
• 0.0005” – 0.005”
• Coatings:– PSA’s: Solvent, Aqueous and Hot Melt
– PVDC and other Barrier Coatings
– Primer Coats
– Topcoats: High Gloss and Protective
– Laminating Adhesives
– Silicones: Solvent, Aqueous, 100% Solids
– ……….. 41
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• Top Coats for Wear Resistance on Magazines
• Gloss / Color Snap Coatings for Automotive Brochures
• Adhesives for Wood Grain Patterned Coverings on Furniture
• Gas Emissive Coatings for Medical Packaging
• Protective Coatings on Appliance Overlay
• Optically Clear Adhesives for Protective Window Films
• Silicone Based Release Liners for Medical Bandages
• Pressure Sensitive Adhesives for Medical Bandages
Versatility• Lamination Adhesives for Medical
Drapery
• Primer Coatings for Aluminum Layer in Cigarette Packaging
• Optically Clear Adhesives for Bottle Labels
• Adhesives on Masking Films
• Reactive Coatings on Thermal Papers
• Pre-Paste on Wall Coverings
• Tinting of Decorative Fabrics
• Laminating Adhesives for Lottery Tickets
• Bonding Layer for Foam / Fabric Headliners
Questions?
Thank You!Graphic References• Doctor Blades
– Benton Graphics• Gravure Roll Slides:
– Zecher– Pamarco
• Enclosed Applicator– Harris and Bruno
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John LooserNew Era Converting MachineryP.O. Box 377Hawthorne, NJ 07506Phone: 973-413-4605E-mail: john.looser@neweraconverting.comwww.neweraconverting.com