Ener Con Best Practices Web Handling Pp t

7/27/2019 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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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


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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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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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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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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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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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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Ener Con Best Practices Web Handling Pp t