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 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
•
– Manufacturing such as • • • • •
•
(Slitter) Rewinder – Cut large master rolls into smaller diameter and/or smaller width shipping rolls
Paper machine Film extrusion Foil mill Textile loom etc
Roll-to-roll – Converting at high speeds 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 • Knobs to adjust Wound Roll Tightness
Center Wind Tension
– Web Tension – Nip – Centerwind Torque differential – ‘s - some products are speed dependent (due to air entrainment) • Known at the TNT’s
of winding
M 1
N i p
Center Wind w Layon Roll er Tension M 1
Surface Wind
N i p
Tension 2 M
N i p
Center-Surface Wind Tension (M1+M2) 2 M
M 1
Centerwi nd Torq. Diff. (M1-M2)
80.7
Winder Classes - Range Tightness
• Centerwind range is from min to max web tension
Loose
Center Wind Tension
1 M
• Layon roll nip adds additional tightness
Center Wind w Layon Roller
• Surface wind can’t get as loose because of required nip
Surface Wind
• Center-Surface has widest range
Tight
N i p
Tension
1 M
N i p
Tension
2 M
N i p
Center-Surfac e WindTension
?
(M1+ M2)
2 M
1 M
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 Index Layon Rol ler
r s f e n r a o w n d t S h n t a N o t u C
Turret
Spindle A
• Core(shaft) support • Large rolls a challenge
• Center, Center w Layon or Center-Surface class or Gap Spindle B
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
Out board Roll
– Converting: small narrow rolls w/o spreading – Paper Mills: $20M magazine grades
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
• Shaftess or Shafted • Surface wind class
Wound Roll
• Very Durable • Very Productive
Drums
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
Tension
N i p
• Torque diff: makes roll tighter (or looser) • ‘s: makes the roll tighter (when you slow down)
2 M
M 1
Centerwi nd Torq. Dif f ( 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 + Material properties
Wound Roll: WIT, tightness, 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 • What > Automatically vary nip pressure as a function of current diameter • Why – – – –
Structure a roll Compensate for geometry Compensate for gravity All of the above
• How – Cam – PLC • Calculation • Lookup table
e r u s s e r P r e d n i l y C p i N
e r u s s e r P r e d n i l y C p i N
e r u s s e r P r e d n i l y C p i N
Roll Structure Tight Start Looser Finish
e r ( Curr ent) o C
Roll Diameter
Geometry Compensation
e r ( Curr ent) o C
Roll Diameter
Roll Weight Compensation
e d i s t u O
e d i s t u O
Swinging Arm Wgt
Variable Mech. Advantage Rider Roller
Roll Wgt
Drum Nip
e r ( Curr ent) o C
Roll Diameter
e d i s t u O
80.17
Nip Calibration Example • Here is a modern twodrum with two gross calibration oversights – 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
) I L P ( p i N20 r e l l o R r e d i R10
Actual
‘
P r o g r a m m e d
22.9 7.8
’
10
20
30
40
Curr ent Roll Diameter ( 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 >
• Tight Defects >
• Damage Roll
• Damage Web
– Flat spots
– Blocking
– Out-of-Round
– Core Crush*
– Telescoping
– Corrugations
– Etc.
– Gage Bands > Bag – Tin Canning, etc.
• Defects Not affected by Tightness – Offset core – Wrong roll width
Tight and Loose Defects
80.20
Wound Roll Structure • What – Tight Start – Smooth Transition – Looser Finish
• How
T I W r o T , N , T 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 -I nterl ayer Pressure
10
Interlayer Pressure
0
) i s p ( s s -10 e r t S l a -20 i d a R
30” Roll
10” Roll 20” Roll
-30
40” Roll
e d i s t u O
e r o C
-40 0
5
10
15
Ra dia l Position (in)
20
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 dur able mat erial Lower windi ng ti ghtness
e r u s s e r P
r e p i l a C e r o C
Position
D O
e r o C
Position
D O 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
Windi ng 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 gi ven condit ions Max Safe OD For given Core etc
80.28
Telescope Case IA - Remedies • Winding -Maximum taper (especially tension) • Product Re-Design – Change Web • Increase web-web friction for torque induced • Increase density for nip induced – Core diameter increase – Roll diameter decrease
• Operational
Max
– Sideguards
T I W
– Living with waste
Min
e n o s Z u i p i l d S a x R a M e r o C
Diameter
D O
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 Offset Wrap Rough Ro l l Edge
Web Moved Rol l Moved
Wrap Width Var
Tension,
Slitter 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 Diameter Profile
Outer layers i n wound rol l shear and collapse into hollow Large diameter slowed down by nip against rol ler
Small diameter sped up by nip against r oll er
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
Buckle and Stars - Types •
Poor Roll Structure
s s e n t h g i T
– 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
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 Def ect Termi nology by Duane
Smith 1995, 2007 •
Wi ndi ng M achi nes, M echani cs and M easur ements 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
