Why control of creasing is important Customer expectations Customer expect you to produce high quality packages with no cracks and no splitting on folding.

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.

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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

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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

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Creasing and Folding arecritical steps in the box forming process

Dipl. Ing. Lukas Pescoller

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

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[Source: Hui Huang, KTH Stockholm]

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

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Card board

Male Crease Rule

Crease Channel

The creasing process

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[Source: Hui Huang, KTH Stockholm]

The folding process:

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

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A crease is a double fold

Bead

Spine

Twin fold points

Delamination

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[Source: Hui Huang, KTH Stockholm]

Deformation and delamination of creased card board:

Analyze the Bead with CREASY

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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

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Bead Binding

Extensive Tension

Insufficient delamination

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?

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One-sided crease

Max tensilestress

Reasons for assymetric bead

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

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practice

theory

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:

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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

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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

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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

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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°

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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

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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.

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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

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Thank you…Thank you…

See what happens

Understand why it happens

Take corrective actions

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