Solutions for the Winding of Nonwovens ©2014 David Roisum, Ph.D. Finishing Technologies, Inc. INDA 2014 80.1 What is a Web? Long Thin Flexible • All webs follow the same laws of physics • If we know the physics, we know the behavior 80.2 What Is Web Handling? • Web Handling – Rollers (3) • Wrinkling – Wrinkle Cause/Cure – Spreading – Tension Control (2) • Web Converting – Nip Control (2) – Slitting – Temperature/Moisture – Winding Effects and Control – Guiding (Path Control) • Other – Material Properties – Physical Properties – Problem Solving 80.3 Why Study Web-Handling? • • • • • • • • Baggy Webs Curl Length & Width (dimension) Registration (location) Web Breaks Winding Defects Wrinkling etc 80.4 Why a Nonwovens Focus? • Material Properties are quite different – – – – Low modulus (favors different defects) Rough surface (no air entrainment) Looser web/machine tolerances Your cousins are tissue • Winding – Different defect set – Different winder settings – Different quality measure 80.5 Winders are Found in • Web-to-roll – Paper machine Film extrusion Foil mill Textile loom etc Cut large master rolls into smaller diameter and/or smaller width shipping rolls Roll-to-roll – Converting at high speeds such as • • • • • • – – – • (Slitter) Rewinder – Manufacturing such as • • • • • • • Calendering Coating Laminating Metallizing Printing etc Offline roll-to-roll process used where inline is to restrictive or too unreliable Roll changes may be automated and made at speed to keep process running Flying splice unwind, winder turret, accumulator Winding enables Web Handling • Salvage (Rewinder) – – – Some roll defects can be fixed by rewinding • Offsets, telescope, soft rolls Also, edit/splice out web defects Invaluable for trials and product inspection 80.6 Winder Classes - # Knobs Center Wind M1 Tension Ni p Center Wind w Layon Roller M1 Tension Ni p Surface Wind M2 Tension Ni p Center- Surface Wind Tension M1 ( M1+ M2) M2 • Knobs to adjust Wound Roll Tightness – Web Tension – Nip – Centerwind Torque differential – ‘s - some products are speed dependent (due to air entrainment) • Known at the TNT’s of winding Centerwind Torq. Diff. ( M1-M2) 80.7 Winder Classes - Range Loose Tight Center Wind M 1 Tension Nip Center Wind w Layon Roller M 1 Tension Nip Surface Wind M 2 Tension Nip Center-Surface WindTension ? M 1 (M1+ M2) M 2 • Centerwind range is from min to max web tension • Layon roll nip adds additional tightness • Surface wind can’t get as loose because of required nip • Center-Surface has widest range Tightness Centerwind Torq. Diff. 80.8 Winder Type - Turret • Continuous production winder • Wind one spindle, index over to new spindle • Wide range of products and processes • Core(shaft) support • Large rolls a challenge • Center, Center w Layon or Center-Surface class or Gap Spindle B Index Layon Roller f er s n t r a ho w n d n a tS Cut No Turret Spindle A Turret Mech 80.9 Winder Type - Reel • Continuous production winder • Start on primary, move to secondary arm • Follows almost every paper machine Primary Arm Secondary Arm Index • Core(shaft) support • Upsets at bottom of roll • Surface wind class Reel Mech 80.10 Winder Type – Duplex • Offline slitter-rewinder • Duplex: wind every other roll wound Inboard Roll on opposite side of drum or machine • Extreme Application Range – Converting: small narrow rolls w/o spreading – Paper Mills: $20M magazine grades Out board Roll Drum View From Top Duplex Mech 80.11 Winder Type – Two* Drum • Offline slitter-rewinder • *Optional 3rd roller known as Rider Roller • Mostly paper, rubber and textiles Rider Roller Wound Roll Drums • • • • Shaftess or Shafted Surface wind class Very Durable Very Productive Two Drum Mech Programmed Nip 80.12 TNT’s and Tightness • Tension: makes roll tighter • Nip: makes roll tighter, especially soft materials or smooth materials at high speeds • Torque diff: makes roll tighter (or looser) • ‘s: makes the roll tighter (when you slow down) Tension Ni p M2 M1 Centerwind Torq. Diff ( M1-M2) 80.13 TNT’s add up to WIT • Wound-In-Tension is the tension in the WIT current outer layer of the roll Tension + Nip + Torque WIT + Mat erial propert ies Wound Roll: WIT, tight ness, hardness, Stresses, etc 80.14 TNT’s > Same Tightness • If TENSION is giving you trouble, lower it and RAISE NIP in its place • If NIP is giving you trouble, lower it and RAISE TENSION in its place • If you need to tighten, raise both • If you need to loosen, loosen both • Nip most effective with compressible materials80.15 Nip and Compressible Materials • WIT is a result of interlayer slippage under the nip • Non-uniform slippage can cause defects • Nip is extremely effective for bulky materials such as nonwovens, textiles and tissue • Nip tightening requires a pad of soft material to work • Thus, the layers just above the core are a bit looser than elsewhere • Thus, the possible justification for centersurface winding 80.16 Programmed Nip – Cam – PLC • Calculation • Lookup table Outside Core Nip Cylinder Pressure ( Current ) Roll Diameter Outside Core ( Current ) Roll Diameter Swinging Arm Wgt Variable Mech. Advantage Rider Roller Roll Weight Compensat ion Roll Wgt Drum Nip ( Current ) Roll Diameter Outside • How Looser Finish Core Structure a roll Compensate for geometry Compensate for gravity All of the above Nip Cylinder Pressure – – – – Tight Start Geometry Compensation Nip Cylinder Pressure • What > Automatically vary nip pressure as a function of current diameter • Why Roll Structure 80.17 Nip Calibration Example • Here is a modern twodrum with two gross calibration oversights Rider Roller Nip ( PLI) – Zero was offset by 7.8 PLI on tissue! – Hysteresis (uncertainty) was greater than the range of the fancy roll structure computer program being run 30 Actual Actual 20 ‘P ro 10 10 gr am 20 me 22.9 d’ 7.8 30 40 Current Roll Diamet er ( in) 80.18 How Tight to Wind the Roll? • Baby Bear Theory: • Not too tight to damage web • Not too loose to allow roll damage 80.19 Defects and Tightness • Loose Defects > • Damage Roll – – – – Flat spots Out-of-Round Telescoping Etc. • Tight Defects > • Damage Web – – – – – Blocking Core Crush* Corrugations Gage Bands > Bag Tin Canning, etc. • Defects Not affected by Tightness – Offset core – Wrong roll width Tight and Loose Defects 80.20 • What – Tight Start – Smooth Transition – Looser Finish • How T,N, T or WIT Wound Roll Structure Core Outside Current Roll Diameter – Taper any of the TNT’s • Why: reduce defects due to – Roll Handling – Starring – Telescoping 80.21 Radial Stress or Pressure ZD Radial St resses -Interlayer Pressure 10 Int erlayer Pressure 30” Roll 10” Roll -10 20” Roll 40” Roll Outside -20 -30 Core Radial Stress (psi) 0 -40 0 5 10 15 20 Radial Position (in) 25 Pressure is highest at core Without taper, pressure is roughly level through most of the roll S-shaped pattern is the trend common to most winding situations 80.22 Width Will Be Nonuniform • Physics allows only three solutions • Wind under zero tension • Variable width slitting (variable width when unwound) • Saw cut roll (variable web width when unwound) 80.23 Bulk (Thickness) Loss • Interlayer pressure can cause a loss of bulk (thickness, caliper etc) if the product creeps (with time) under those loads • Permanent losses can vary from less than 5% on a newsprint reel to more than 50% on finished rolls of tender nonwovens More durable material Position OD Core Position OD Core Caliper Pressure Lower winding tightness 80.24 Bulk Loss and Core Support • Pressure over the core/mandrel can cause bulk loss • Which source of pressure is bigger? – Calculation (very difficult) – Compare losses of ½ size and full size rolls wound under same tension Core Support Pressure Winding Pressure 80.25 Telescoping Case IA - Initial • Winding core supported roll • Roll begins wind OK 80.26 Telescoping Case IA - Latter • Winding core supported roll • Roll begins to shift • Latter part of winding 26.27 Telescoping Case IA - Appearance • Winding core supported roll When It Slipped Where It Slipped Min Safe Core Dia For given condit ions Max Safe OD For given Core et c 80.28 Telescope Case IA - Remedies • Winding -Maximum taper (especially tension) • Product Re-Design Diameter OD Min Core – Sideguards – Living with waste WIT • Operational Max Slip Zone Radius – Change Web • Increase web-web friction for torque induced • Increase density for nip induced – Core diameter increase Max – Roll diameter decrease 80.29 Telescoping Case IV • More formally known as Progressive Outward Dishing • During Winding (most commonly a 2 Drum) • Multiple rolls wound on same axis grow in width due to • Interlayer pressure and • Poisson effect • Diagnostics – No J-line motion needed – Rolls wider above core than at outside – Progressive outward roll edge pattern • Remedies – Winding Minimum winding tightness (T, N and T) – Increase spreading of multiple rolls wound same axis – Web or roll product design 80.30 Rough Roll Edge - Other • Nip friction > sawtooth edge • Web Vibration > feathery edge • Machine Vibration > feathery or corduroy • Unslit edges • Trim jump • Slitter Rings 80.31 Rough Roll Edge Tree • Simple tests can determine which branch of the troubleshooting tree you are on Of f set Wr ap Ro ug h Ro l l Edge Web Moved Rol l Moved Tensi on, Wr ap Wi dt h Var Sl i t t er Moved Wri nkl e at Sl t r 80.32 Winding With Gage Variation • Winding • Unwinding The size of the diameter variation that might do this could be as little as 1/1,000 The web gage variation that caused this diameter variation could easily be below the threshold of ordinary web measurements and controls Roisum, David R. The Secrets of a Level Process and Product. Various venues, 2001. 80.33 Corrugation Description • A.K.A. Ropes, Chain Marks, ‘Tin Can’ • Narrow annular band, wrinkles at an angle • Caused by Winding – A caliper-varying product – Tight, especially with nip 80.34 Corrugation Mechanics Web Gage Profile Wound Roll Diamet er Profile Out er layers in wound roll shear and collapse int o hollow Large diameter slowed down by nip against roller Small diameter sped up by nip against roller 80.35 Ridges (and Valleys) • You don’t need a lab test or scanner to know this web has gage variation issues 80.36 Buckles and Stars - Mechanics • What – Known as buckles, stars, wagon wheel and spokes – Seen as wavy layers and/or spokes on the end(s) of a roll – Caused by layers buckling due to MD compression like earthquake faults • Observe – Symmetry of (angle between) points • Symmetric – ‘natural’ • Asymmetric – unnatural often a blow or squeeze due to handling – Symmetry of one end versus other • Symmetric – symmetric gage • Asymmetric – starred end is the low gage side 80.37 • Poor Roll Structure – OD tighter than ID – Tight over loose … but • Collapse over unsupported layers – Roll offset/dish/telescope – Core inset – Core collapse • Gage Variation – Intentional • Coating short of edges – Unintentional • Rough handling Tightness Buckle and Stars - Types Core Outside Current Roll Diameter • Air Buckles – – – – Wound-in entrained air escapes Smooth low gage materials High speed 1 hr to 1 day – Asymmetric pattern – Blow – Squeeze 80.38 Paro Roll (Hardness) Tester • Instrumented version of a billy club 80.39 (Overall) Roll Density • Measure Wound Roll Density 80.40 Winding Books • Roll and Web Defect Terminology by Duane Smith 1995, 2007 • Winding Machines, Mechanics and Measurements Dr Keith Good and Dr David Roisum 2007 • Winding by Ken Frye 1990 • The Mechanics of Winding by David Roisum 1994 • Winders the Complete Guide by Jan Gronewold 1998. • Anthology of Winding by Jan Gronewold 2000 • TAPPI PRESS, tappi.org, (770) 446-1400 80.41 Questions? Answers: David Roisum, Ph.D. http://www.webhandlingblog.com/ http://www.roisum.com [email protected] 920-725-7671 office 920-312-8466 cell 80.42
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