Why control of creasing is important
Download
Report
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.
1
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
2
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
3
4
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]
6
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
The creasing process
[Source: Hui Huang, KTH Stockholm]
8
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
9
Twin fold points
Deformation and delamination of creased card board:
[Source: Hui Huang, KTH Stockholm]
10
Analyze the Bead with CREASY
11
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
12
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
13
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
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
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
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
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
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
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
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
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
Thank you…
See what happens
Understand why it happens
Take corrective
actions
23