Why control of creasing is important

1. Why control of creasing is important Customer expectations • Customer expect you to produce high quality packages with no cracks and no splitting on folding end points • Customer expect you to provide uniform packaging boxes • Customer expect the shape of the box to represent the quality of the product inside the box. 1

2. Why control of creasing is important Quality department expectations • Documented quality across multiple production sites • Possibility to define and visualize quality standards and tolerances • Increasing quality 2

3. Why control of creasing is important Manufacturing manager expectations • Long live time of creasing and cutting tools • No runability problems on the packaging line • Minimum waste because of un-usable boxes • Full controlled processes • Anticipate potential problems before going into production • Detailed information about potential sources of a problem 3

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5. Creasing and Folding arecritical steps in the box forming process Dipl. Ing. Lukas Pescoller

6. Paperboard is … • A thick, single or multiply paper based material. • composed of several layers of pulp fibres with preferred orientation • bonded by starch or adhesive material • Bending stiffness is one of the most important mechanical properties for paperboard packaging • bending stiffness is mainly attributed to the outer ply's with higher Density [Source: Hui Huang, KTH Stockholm] 6

7. The Creasing process • fibre-fibre bonds between ply's are broken • Some fibres are damaged • Plastic deformation occurs • Sheare, tension and compressing stresses arise • Locally reduced bending stiffness • Creased area = hinge Male Crease Rule Card board Crease Channel 7

8. The creasing process [Source: Hui Huang, KTH Stockholm] 8

9. The folding process: Spine Delamination • Folding uncreased paperboard results in cracks on the outside • The ability to delaminate (fracture surface in parallel to the ply's) is an important property for folding • Tensile stress arises on the outside ply (Spine) • The inner ply's (Bead) are compressed and bulge • Deformation and delamination takes place Bead Twin fold points A crease is a double fold 9

10. Deformation and delamination of creased card board: [Source: Hui Huang, KTH Stockholm] 10

11. Analyze the Bead with CREASY 11

12. The Bead width – a delamination parameterthe distance between the twin folding points Problems with wide bead: • Un-sharp folding points • Insufficient internal delamination and inflexible bead • Low flexibility – bead gets crushed during folding • Hard contact at the intersection between side and bead • Extensive tension stress on spine • Spine fracturing or crease end splitting Extensive Tension Insufficient delamination Bead Binding 12

13. The folding point sharpness defines the symmetry of the bead Non symmetric folding points • Off-center folding • non uniform boxes • Extensive stress in an arrow area of the spine • Fracturing and folding failure • Is the creasing tool well centered and parallel to the crease channel? One-sided crease Max tensile stress 13

14. Reasons for assymetric bead theory • Parallel crease close to each other • limitation in material stretch • Competition in drawing the material • Each crease is poorly formed • With asymmetric bead • Asymmetric internal delamination • The resistance to crease formation grows fast after a critical distance practice 14

15. Reasons for assymetric bead • Rule – channel misalignment • Tool to tool misalignment (tolerance mismatch) • Crease rule dish • Incorrect laser die-board cutting vertically Have a look at the adjustment proposal in 0.01mm resolution: 15

16. The bead height as an indicator for the penetration depth • The knife (position/setting) changes the penetration depth of the rule • changing the tension forces which can result into die-cut edge chipping or flaking, • or breaking the cardboard material • or faster erosion the upper corners of the crease channel •  Cutting knife abrasion leads to resetting of the knife position 16

17. Crease cross section analysis with CREASY • Measure bead • Rotate sample by 180° • Measure crease The software will overlay the two images showing the result in terms of a card board cross section 17

18. Compare crease before and after first break • The first break defines the final location of the twin folding points • The first break defines the final symmetry of the folding • The first break shows problems with cracks, fracturing and folding failures 22.03.13 18

19. Control the final product box quality with CREASY • The box angle should be as sharp as possible • The box angle should be as symmetric as possible • The angle between the folding panels should be close to 90° 19

20. Control the setup process with CREASY • The bead shape and size will differ depending on the orientation of fibres and crease channel • The bead can be optimized by setting the creasing tools properly • The optimisation can be measured with CREASY and a statistic can be created • A PDF Report can be created with CREASY 20

21. Folding box manufactuing control with CREASY • Measure the beads of same orientation with CREASY and use the statistics to collect measurement data • CREASY does support 4 orientations of beads • CREASY creates a PDF Report per folding box • CREASY offers a statistic for the entire job. 21

22. Why control of creasing is important • No customer will accept cracks and splitting on folded packaging products • No customer will accept non-uniform packaging boxes • The paper structures and folding behaviour vary with • fibre lengths, fibre content, fibre orientation • Coatings, bond between coating and paper • Printed ink, varnish • Heat to dry the ink of the print sheet reduces flexibility • Environment – humidity in the pressroom • The cutting & creasing process itself has variations • Help to avoid runability problems on the packaging line • Help to avoid waste because of un-usable boxes 22

23. Thank you… See what happens Understand why it happens Take corrective actions 23