Transcript Why control of creasing is important

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
Possibility
quality across multiple production sites
to define and visualize quality standards and
tolerances
Increasing
quality
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Why control of creasing is important
Manufacturing manager expectations
Long
No
live time of creasing and cutting tools
runability problems on the packaging line
Minimum
Full
waste because of un-usable boxes
controlled processes
Anticipate
Detailed
potential problems before going into production
information about potential sources of a problem
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Creasing and Folding are
critical 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
[Source: Hui Huang, KTH Stockholm]
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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
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The creasing process
[Source: Hui Huang, KTH Stockholm]
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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
Spine
Delamination
Bead

Tensile stress arises on the outside ply
(Spine)

The inner ply's (Bead) are compressed and
bulge

Deformation and delamination takes place
A crease is a double fold
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Twin fold points
Deformation and delamination of creased card board:
[Source: Hui Huang, KTH Stockholm]
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Analyze the Bead with CREASY
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The Bead width – a delamination parameter
the distance between the twin folding points
Problems with wide bead:
Un-sharp
folding points
Insufficient
internal delamination and
inflexible bead
Extensive Tension
Low
flexibility – bead gets crushed during
folding
Insufficient delamination
Hard
contact at the intersection between
side and bead
Extensive
Spine
tension stress on spine
fracturing or crease end splitting
Bead Binding
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The folding point sharpness defines the
symmetry of the bead
Non symmetric folding points
Off-center
non
folding
uniform boxes
Extensive
stress in an arrow area of
One-sided crease
the spine
Fracturing
and folding failure
Is
the creasing tool well centered
and parallel to the crease channel?
Max tensile
stress
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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
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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
22.03.13
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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
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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…
See what happens
Understand why it happens
Take corrective
actions
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