Paper Technology International 2024 - Journal - Page 46
PAPERTECHNOLOGYINTERNATIONAL
Figure 8: High-resolution image (left) and FEM model (right) of a mountain groove (top right) and a valley groove (bottom right) of
corrugated board.
Against the background of the current state of technology,
research and development, there was a lack of a holistic and
systematic consideration of the interactions and phenomena
that occur during the creasing processing step. The aim was to
investigate the in昀氀uence of the properties of the corrugated base
paper, corrugated board grade, processing conditions, creasing
tools and creasing parameters on the creasing result. The available
knowledge on the creasing of corrugated board was essentially
empirical. Experience from other creasing processes, such as
those available for creasing folding boxboard, could not be used,
as completely different mechanisms are involved in the design of a
crease.
The result of the research project was the development of
improved knowledge of the mechanisms of action in discontinuous
hollow creasing and the correlations between the material properties
of the corrugated board (e.g. grade, grammage, type of base paper)
and process parameters with regard to creasing quality. From these
results, measures could be derived that can increase the quality of
the packaging produced and thus customer satisfaction, as well as
avoid complaints and loss of image in the long term. Furthermore,
this knowledge can signi昀椀cantly reduce the use of resources in
production, tool design and process optimization.
In order to be able to make predictions about correlations
between material parameters, process conditions and creasing
quality, a mathematical-statistical model was developed. A
statistical design of experiments (DoE) was also used in the
project in order to reduce the overall scope of the necessary tests
and material characterizations for the exact determination of the
interdependencies to a minimum. The data collected on the material
properties and test results from the creasing tests formed the basis
for setting up a model, which can be regarded as the main result
of the project. This provides general predictions of creasability and
supports the root cause analysis of creasing errors. As part of a
sensitivity analysis, the main in昀氀uencing factors that signi昀椀cantly
determine creasing behavior were also identi昀椀ed. The model was
implemented using tools based on automated machine learning. The
results were also relevant for the parameterization of the materialside modelling.
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The simulation model based on the 昀椀nite element method is
capable of mapping the creasing behavior of corrugated board and
making a valid prediction of creasability based on individual material
properties. The starting point for the model was the data generated
from the basic material characterization of corrugated base paper
and corrugated board.
With the help of the model shown in Figure 8, it is now
possible to investigate the in昀氀uence of the material and the
creasing parameters and to carry out parameter studies, such as
investigating the location of the creasing, alternating between peak
and valley creasing or gradually in between. It is also possible to
compare different material combinations in the top and 昀氀ute layers.
Until now, creasing tools have only been designed on the basis
of geometric dimensions (thickness of the corrugated board and
thickness of the compressed corrugated board), without taking into
account the properties of the materials used in the corrugated board.
Furthermore, results on the creasing process could be incorporated
into the model through real tests on creasability. In addition to
the metrological recording, an image analysis was implemented
using Digital Image Correlation (DIC) in order to validate the model
accordingly.
The 昀椀ndings on predictions for the creasability of corrugated
board, the main factors in昀氀uencing the creasing result and the
evaluation criteria for creasing quality can be used and implemented
immediately by corrugated board base paper manufacturers,
corrugated board manufacturers and processors. Without additional
investment costs, companies are able to avoid creasing problems
that lead to complaints and machine downtime. Optimized material
selection in the design and dimensioning of their packaging can
lead to immediate cost savings. For corrugated base paper and
corrugated board manufacturers, knowledge of the main in昀氀uencing
factors on the material side in particular allows them to adapt their
products with regard to improved creasability properties.
However, the results of the project have also shown that not
all questions relating to the creasing of corrugated board can yet be
answered. Further investigations into speci昀椀c issues are planned.
PTS welcomes any feedback and inquiries from industry in this
regard.
