Definition, Direction, Shapes

Transcription

1 Web a Plant Practical Series Curl Definition, Direction, Shapes ZD CD MD 2016 David Roisum, Ph.D. Finishing Technologies, Inc a.1

2 Wrinkling Cases Wrinkle Troubleshooter AbbottApp Taxonomy ordering by appearance/character Based on Source of Buckling Compression Machine Direction (CD compression) Diagonal Shear (Mohr s circle compression) Transverse Wrinkle (laminate, winding) Baggy Web (MD tension profile variation) Corrugation (winding nip) Curl (laminating strain mismatch) Roll and Web Defect Terminology, 2 nd edition. TAPPI PRESS, 2007 Alternative taxonomy: Walker, Timothy J. The Taxonomy of Wrinkles 10th Int'l Conf. on Web Handling Proc., Oklahoma State Univ, June 7-10, a.2

3 Curl - Directions CD Axis of tube is in CD Also called MD curl Mismatch in MD strains most common type MD Axis of tube is in MD Also called CD curl Mismatch in CD strains Chiral (corner or diagonal) ZD CD ZD MD CD MD a.3

4 Curl - Shapes Conventional Red shorter than blue Mismatch in Strain Tunnel Wrinkle Red shorter than blue Mismatch in Strain Conventional + adhesive delam Most common with no green tack Cracked Red shorter than blue Mismatch in Strain Conventional + brittle failure Most common with coatings a.4

5 Web b Plant Practical Series Curl Quantification 2016 David Roisum, Ph.D. Finishing Technologies, Inc b.5

6 Why Quantify? Determine if and how much curl has changed for trials and troubleshooting Determine suitability for your customers With the wishful thinking that all customer s have an equal threshold of pain With the wishful thinking that you have struck a good balance between supplier and buyer risk Adequate Sample Size and Test Resolution? b.6

7 Curl Measurement X Cut Swanson, Ron. Measurement of Web Curl. AIMCAL Web Handling Conf., Charlotte, May 7-10, 2006 Radius Template Hanging Angle b.7

8 Handling and Cutting Specimen handling needs to be very careful Loosely wind on top of large diameter core Pay out loosely onto table No wrinkles of any kind introduced Cutting induces/changes curl b.8

9 Web c Plant Practical Series Curl Laminator T A T B 2016 David Roisum, Ph.D. Finishing Technologies, Inc. T C c.9

10 Why So Common? Plies often have widely dissimilar moduli Tension is overconstrained (tension of high modulus ply is not a factor) \/ tension of low modulus ply to reduce curl /\ tension of low modulus ply to improve laminator runnability /\ tension of low modulus ply to help with bagginess Curl can be created by materials with certain hygrothermal or green shrink properties c.10

11 Curl Model Curl is a Result of a Mismatch in Strains Curl Determined before leaving nip Curl Determined by Knobs Material Properties of two plies Tension Ply A can be adjusted (I) Tension Ply B can be adjusted (II) Web Handling Goals Tension A: not too high, not too low (1) Tension B: not too high, not too low (2) Two Knobs (I & II), Two Goals (1 &2 ) T A T B T C c.11

12 Curl Constraints (3) CD Curl (MD Strain Matching) T A /T b = (t A /t B ) (E 1A /E 1B ) Makes differing modulii challenging (4) MD Curl (CD Strain Matching) T A /T b = (ν 21A /ν 21Β ) (t A /t B ) (E 1A /E 1B ) (5) Bagginess (6) Mismatch thermal properties (7) Mismatch hygroscopic properties (8) Mismatch in green shrink/cure properties c.12

13 Executive Overview Existing Products Reduce tension of low modulus ply until painful and then some Choose your balance of laminator runnability problems and curl complaints from the customer New Products Go to school 2 plies Laminate Curl Calculator by AbbottApp 3 or more plies Top Web New Machine Design Dual Drive on nipped rollers with ultra large motors Ultra Low Tension leg in front of laminator Heat/Cool or Dry/Moisten in front of laminator c.13

14 Web d Plant Practical Series Curl Coating Roller Pump Die Lips Die Web 2016 David Roisum, Ph.D. Finishing Technologies, Inc d.14

15 Is Coating a Ply? Coating typically applied on one side Coating can shrink differently than base web during Cooling Curing Drying Analogous to one ply shrinking differently when tensions are removed (due to differing moduli) Coating can have stiffness Pulls base web into curl due to tensions All of above are just like lamination d.15

16 One Important Difference Coating properties are nonlinear and not well measured Therefore: coating induced curl is difficult if not impossible to model d.16

17 Still, We Know Direction Coating tends to shrink more than base web so will tend to pull toward that side Paper curls to the last side that saw water Curl is higher with higher relative coat weights Balance Coat is one possible treatment Balance Coat Web Main Coating d.17

18 Web e Plant Practical Series Curl RollSet 2016 David Roisum, Ph.D. Finishing Technologies, Inc e.18

19 Roll Set Curl Web Takes on (some of the) Curvature of of the wound roll Superposed onto any manufacturing/laminating curl that might already be present Worse Near core vs outside Small core Thick material Low yield strain material Winding Tight Time, temp etc Decurling e.19

20 Web f Plant Practical Series Curl De - Curling Counter Up Curl Or Counter Down Curl 2016 David Roisum, Ph.D. Finishing Technologies, Inc f.20

21 De-Curling Applications Paper sheeters Paperboard sheeters Reduces residual stress differences across the thickness of the web Baggy Web IF they could be fixed after the fact Would reduce residual stress differences across the width of the web f.21

22 De-Curling Mechanics Mechanical Break over Radiused bar Small radius roller Intensity Radius Wrap, tension Other Anneal with High Temperature Moisture Counter Up Curl Or Can be programmed Counter Down Curl f.22

23 Questions? Answers: David Roisum, Ph.D cell f.23