Download - Ener Con Best Practices Web Handling Pp t
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Presented by
Rory Wolf
VP / Technology DirectorEnercon Industries Corporation
Best Practices for
Web Handling In & Out
of Corona Treaters
Enercon Technical Forum Series
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Presentation Agenda
Types of Problematic Thin Films
Understanding the Tensile Stress-Strain
Relationship
Web Handling Issues Through Corona Treaters
Wrinkling/Puckering Effects Backside Treatment
Web Drag
Troubleshooting Recommendations
Low friction Rolls Nip Roll
Roll Drive
Spreader Rolls
Process Speeds
Enercon Industries 2013
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Types of
ProblematicThin Films
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Types of Problematic Thin Films
All polymer films driven by mechanical instability
when stress exceeds a critical value.
Highly elastic, thin films
Typical Modulus of Elasticity for Films:
Flexible PVC 350-560 kg/cm2 5-8 kpsi
LDPE 1000-1800 kg/cm2 15-25 kpsi
LLDPE 1400-2100 kg/cm2 20-30 kpsi
BOPP 7700-24000 kg/cm2 110-350 kpsi
OPET 35000-42000 kg/cm2 500-600 kpsi
Source: Nitto Denko
TreaterLaminationRewindUnwindCoater
Dryer
Film
Treater
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Source: Nitto Denko
Types of Problematic Thin Films
TreaterLaminationRewindUnwindCoater
Dryer
Film
Treater
Maximum Web Tension 60 in. wide, 2 mil. LDPE Film
Must calculate tension-to-stress to 1.5% of elastic modulus
Ave. modulus of 20 kpsi for LDPE: 1.5%x 20,000psi = 300psi
Cross-sectional area = 60 in. x 0.002 in. = 0.12 sq. in.
Max. web tension = 300 psi x 0.12 sq. in. = 36 lbs.
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Understanding
the
Tensile Stress-StrainRelationship
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Understanding the Tensile Stress-Strain
Relationship
Films are subjected to dynamic tension
Mechanical behavior of most films depends strongly on the strain
rate (rate of film deformation relative to time).
Tension that exceeds the strength of the film damages it at load cell
and non-load cell locations.
Every roller on a line will alter web tension -
Increasing web tension accelerates roller rotation.
Drive will relieve a webs tension
Drag inertia
Drive
Web tension changes as
webs traverse over rolls
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Understanding the Tensile Stress-Strain
Relationship
Roller Drag Idler rolls, Ground rolls, Nip rolls
Opposes motion, increasing web tension Rolls move air, affected by air resistance
Rolls in nip - rolling resistance hysteresis
Driven rolls drive transmission losses at belts, bearings, etc.
Inertial Tension Torque that accelerates/decelerates rolls
Mass Moment of Inertia of rolls determined primarily by
machine width
Web tension build-up to accelerate idler rolls (acceleration
variations from 1 ft/min/s to 300 ft/min/s)
Tension Tension + Tension
Tension +2 Tension
Tension +3 Tension
Tension +4 Tension
Tension +5 Tension
Tension +6 Tension
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Web Handling Issues Through Corona TreatersWrinkling/Puckering Effects
Most common and costly web defect with primarily
lightweight materials, wider webs.
Improper web management can cause treatment
variation.
Gauge control and managing static are also key
approaches to wrinkling
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Web Handling Issues Through Corona TreatersWrinkling/Puckering Effects
Compressive Buckling
Amount of compression a web can withstand determined
primarily by caliper3
Reason why wrinkles are common for webs < 10 mil.
Adding CD compression to web tension = wrinkles in the
MD
Adding shear stress to web tension = angled wrinkles
Misalignment of rolls
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Web Handling Issues Through Corona TreatersWrinkling/Puckering Effects
Constrained Expansion
Thermal expansion effect with polymer film or foil
Hygroscopic expansion with paper webs
Drop in line tension
Excessive roll/roller deflection Keep < 0.015% of roll width
Slenderness ratio (length/diameter)
10-15 if nipped 15-20 if un-nipped
MD
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Web Handling Issues Through Corona TreatersWrinkling/Puckering Effects
Other Causes of Diagonal Web Wrinkles
Caliper (gauge band) variation
Non-uniform nip pressure on deformed roll
Baggy web
Material skew Non-uniform tension
Web slippage over rollface
CD Wrinkles
Air entrapment (type of nip, web permeability,
caliper, web width, speed)
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Web Handling Issues Through Corona TreatersWeb Drag
Thermal Effects
Hot web will conductively heat up the roller shell.
Creates axial load against locked bearing collars.
Oxidation Effects
Oxidation degrades bearing performance.
Moving web will entrain ozone gases not removed from
corona treaters.
High Wrap, Cantilevered Rollers
Torsional load from cantilevered shafts deflections mayincrease bearing load, wear rate.
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Troubleshooting RecommendationsLow Friction Rolls
Designed for reduced weight and high critical speed
Key Advantages for Corona Treating
Reduced mass moment of inertia by up to 80%
Less web drag, wrinkling
Reduce vibration Less roll deflection, web bagginess
Easier roll acceleration
Less bearing wear, web drag
More accurate transducer measurements.
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Troubleshooting RecommendationsNip Rolls
High speed webs - boundary layers of air can cause webfloat over treater ground roll
Air ionizes in gap, producing a corona and backside treat.
Adding a nip roll breaks-up any boundary layer air,
squeezed out entrapped air without high nip pressure.
Types include Hypalon, Nitrile rubber, Ethylene Propylene
Diene Monomer (EPDM), Silicone, Polychloroprene and
Polyurethane.
60 durometer Hypalon preferred Ozone-resistance
Heat resistance to 140 C
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Troubleshooting RecommendationsNip Rolls
Position of nip roll to ground roll critical to web
tension and uniform treatment.
Ground roll
Nip
Roll
Ground roll web wrap below the nip
Ground roll
Nip
Roll
Ground roll web wrap above the nip
Ground roll
Nip
Roll
Opening nip affects line load cells
Load cell
Wrong Right
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Troubleshooting RecommendationsSpreader Rolls
Key to avoiding wrinkles coming into treater
Bowed RollersVery aggressive, high friction
Can cause web stretching/distortion in many webs.
Expanding Surface RollersHigh friction; polymer band design
Can require separate drive
Rubber Spreader RollersOutward-spiraling grooves with angled soft polymer
As web exits roll, compression force goes to zero and the rubber
lands go back to where they started.
Reverse Taper RollersLarger diameter at the outer edges and smaller diameter at roll
centerline.
Creates surface speed differential at each roll diameter, resulting
in the material climbing outward toward the larger diameter
edges of the roll.
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Troubleshooting RecommendationsProcess Speeds
High speed webs coming into corona treaters can
introduce entrained air, CD wrinkles, backside treatment.
Integrate incoming nip roll to treater
Install spreader roll prior to treater
Calculate material tension-to-stress, max web tension Maximize web wrap angle to ground roll
Slow Speed High Speed
Treater
Ground Roll
Treater
Ground Roll
Contact
Area
Contact
Area
.. ..
Boundary Air Boundary Air
Contamination Contamination
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Problems Attributed to Station
Cleanliness
Dirty ground roll surface
Back side treatment
Variations in web treat levels
Reduced flow of cooling air
Over heating of electrodes
Residue Accumulation
Arcing
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Ceramic Electrodes & Ground Rolls
Tough Stains
3M Scotch-Brite Pad with Household ceramic
cleaner
Wash, rinse, wipe surface with alcohol
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Presented by
Rory Wolf
VP / Technology DirectorEnercon Industries Corporation
Best Practices for
Web Handling In & Out
of Corona Treaters
Enercon Technical Forum Series
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"Certain information contained in this presentation reflects the Company's assessment of
possible results and is dependent upon many factors over which the Company has no
control. Nothing in this presentation shall constitute a warranty regarding any product. Theonly warranties granted by the Company are contained in the Company's terms and
conditions of sale, which shall constitute the entire agreement between the Company and
any buyer of Company products. Nothing contained in this presentation that is not
contained in the Company's terms and conditions of sale shall be valid or binding with
respect to any sale of products."
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