To Örebro University

Delamination strength is an essential property for the creasing and folding operations of paperboard into boxes. Due to fixation during creasing, the paperboard suffers in-plane straining. In the present study, we aim to increase our understanding of how in-plane straining affects the delamination properties of paperboard. Samples of paperboard were first strained in in-plane tensile loading, both in the machine-direction and in the cross-direction. Afterward, the paperboard is loaded in the out-of-plane (ZD) direction. Three different grades of commercial paperboard from two major manufacturers were tested in a climate-controlled lab. The results showed similar results for all grades of paperboard, with the delamination strength and the out-of-plane stiffness decreasing virtually linearly with pre-straining. With about 5% plastic in-plane straining, the strength was reduced by about 20% and the stiffness decreased by more than 50% for all grades of paperboard. Normalizing the strength and the stiffness with their values without pre-straining reveals virtually the same relation for all grades of paperboard. If proven to be a general result, this will prove valuable in reducing the demand for experiments. Application: The results from this study are important for the understanding and modeling of creasing and folding of paperboard.

Paperboard packaging is made by processing board materials into sheets or rolls and shaping them through creasing, cutting, folding, and erecting. The conversion process generates residual moments at the folds that cause panel bulging. This study experimentally investigates how the bulging introduced during the converting processes influence the mechanical response of paperboard packages during point load testing within the elastic deformation range. The study shows that panel bulging may significantly affect packaging performance as-perceived strength and stiffness. Bulging, influenced by the board's basis weight, can affect the package performance even more than packaging stiffness. Point load tests in the elastic region were performed on empty packages (78 mm & times; 50 mm & times; 110 mm) with force applied at specific points along their long sides. The packages evaluated in this study were made of two identically processed materials of different grammages. The heavier material showed more pronounced bulging than the lighter one, leading to overlapping force-displacement curves for the packages, and to that, a lower force and stiffness may be measured at a certain indentation depth for the package of heavier material. This complicates material choice according to functional requirements. The results show that a highly bulged package might resemble one with less bulging of another material. According to the results, it is not certain that a higher grammage package shows a higher indentation force and stiffness than a lower grammage package when measured at a certain indentation. This indicates that optimizing the creasing and folding processes can be a way to enhance performance rather than simply increasing board weight. The study underscores the importance of controlling converting parameters, especially creasing and folding behavior. Well-performed creasing and folding gives a low residual momentum, little bulging, and a high stiffness and compression strength at point loading in the elastic region. Proper optimization can improve packaging performance and manual handling user-friendliness. Application: The results from this study are of significant importance for the package industry, especially in package design, as the results show that a lower grammage may give a higher stiffness, depending on loading position.

Micro-CT analysis of experimentally creased and folded multilayer cardboards reveals insights into how the material deformation due to the creasing and folding process of cardboard impact the material concerning delaminations and position of broke particles. Delaminations were found in various locations and varied in size from just under a tenth of a millimeter to up to four times the thickness of the cardboard. The particles varied in size, ranging from a few micrometers to slightly larger than the cardboard thickness. Characteristic dimensions for the creased and folded cardboard were measured for selected cross sections. The differences in characteristic dimensions for the cross sections among the samples were typically a few hundredths of a millimeter. There are differences between cross-sections that are a few hundredths of a millimeter apart.

Förmågan att kommunicera och samarbeta över olika gränser är en nyckelkompetens för blivande ingenjörer, samtidigt som känslan av tillhörighet till det egna utbildningsprogrammet är central för studenternas motivation och engagemang. I denna studie har vi utvecklat och prövat en modell i form av studentledda tillämpningsseminarier, där äldre studenter fungerar som seminarieledare för yngre studenter. Syftet har varit att skapa aktiviteter som både tränar kommunikations- och samarbetsförmåga och stärker programtillhörigheten genom länkning mellan kurser och årskurser. Aktiviteten genomfördes med tredjeårsstudenter som seminarieledare och med förstaårsstudenter som deltagare i en kurs i mekanik. Aktiviteten utvärderades genom intervjuer, enkäter och kursansvarigas observationer. Resultaten visar att seminarieledarna upplevde aktiviteten som meningsfull träning i att anpassa kommunikation till en annan målgrupp och att seminariedeltagarna uppskattade kontakten med mer erfarna studenter, vilket bidrog till inspiration och ökad förståelse för programmet som helhet. Samtidigt framkom utmaningar, bland annat variationer i svårighetsgrad och förberedelser mellan grupperna. Slutsatsen är att modellen är resurseffektiv, uppskattad av både studenter och lärare och kan återanvändas med vissa justeringar. Den erbjuder ett konkret sätt att både främja kommunikativa färdigheter och stärka studenters programtillhörighet. 

Wire drawing is one of the oldest and most common cold metal forming processes. Wire is drawn through a single die or a set of conical dies to make it longer and stronger. In the drawing die there are three geometrical parameters that affect the drawing force: die diameter, die angle and bearing length. The force required to pull the wire through the drawing die has been investigated numerous times over the years and new drawing force equations have been developed. However, some of today's most widely used equations do not include the influence of the bearing length. In this paper the most common methods to calculate the drawing force are evaluated by means of wire drawing experiments and finite element studies. From the results, a novel equation for calculating the drawing force is proposed. The proposed equation is dependent on the bearing length and was compared with experiments and validated using finite element simulations with promising results.

Carton board packages with different creases have been manufactured and loaded with point loads to see if there is a difference in point load behavior depending on crease. A carton board was creased in four different ways. The differences of the creases were judged according to appearance and residual moment. Three of the four creases showed divergent appearances. The re-sidual moment was as expected lowest for the hardest creased sample and vice versa. The packages with the different creases were loaded with a point load. The registered force - displacement curves were analyzed according to stiffness and collapse load. No statistically significant difference could be seen in the collapse load of the package or in the stiffness measured, indicating that with a standard point load measurement it was hard to distinguish a difference in packaging behavior due to creasing. In future work it might be interesting to further study the average stiffness, since a trend of higher average stiffness for lower matrix channel depth exists in the measurements, however not statistically ensured. One possibility to discern possibly existing differences in the resistance of packaging to point load due to crease differences could be to study the interaction in more detail.

Recent process developments in Fused Filament Fabrication (FFF), such as the possibilities to use high end polymers (for example PEEK) or to manufacture metal parts and parts reinforced with continuous fibers, have increased industrial interest. Previously, this additive manufacturing (AM) technology was mostly popular among hobbyists thanks to its low investment cost. With the increased industrial interest comes higher demands on product strength and production efficiency.

The FFF process has many parameters that should be optimized to meet these tougher requirements. One of these parameters is the size of the nozzle through which the filament is extruded. Today a fairly wide range of sizes are available on the market, but most standard-sized printers come equipped with a 0.4 mm nozzle.

In this study, a wide range of nozzles of different sizes have been manufactured to investigate how the nozzle size affects both the printing process and the mechanical properties of the printed parts. Tensile bars have been manufactured in polylactic acid (PLA) using 7 different nozzle sizes. The samples were investigatedby means of computer tomography (CT) and optical microscopy and subjected totensile testing.

The perception of mechanical rigidity when touching a package is important for purchasing decisions. This perception will depend both on the material and geometry of the product packaging, but also on the position where the package is grasped. Both kinaestethic (globally) and cutaneous cues (locally around the fingertip) play a role in the perception of compliance, but cutaneous cues are more important. We therefore use a tactile sensor to investigate the mechanical interaction between the tactile sensor and a cartonboard package; we study the changes depending on the measuring position and the material. Using linear discriminant analysis (LDA) on the measurement result we show that we can separate these two changes for separate analysis.

The importance of sensory information in product purchasing decisions has gained increasing attention in recent years. Tactile properties of packaging are usually measured with the help of trained evaluators. An objective, fast and repeatable method that describes the mechanical interaction and does not rely on a panel would have many benefits. We propose and evaluate such a method for measuring the mechanical interaction between a deformable finger-like shaped sensor and a package. Evaluation of the method shows good repeatability, the variability in the measurement result is within a few percent in most cases. The method captures indentation differences at contact between sensor and package due to measurement position and package design.

This work reports the evaluation of a tactile sensor for the potential of using it to measure the compliance of folding cartons. A tactile sensor would make it possible to measure the mechanical behavior locally around the contact point, in contrast to existing methods that measure the global mechanical behavior of the carton. Research on the haptic sense has shown that the local mechanical behavior is more important than the global behavior when humans assess compliance of objects. It is shown that the response of the tactile sensor correlates strongly with the bending stiffness of the board, but also with geometric features. A method for reducing the 22-dimensional output of the sensor to single meaningful feature using linear discriminant analysis is proposed and tested. The results show that the sensor is a good candidate for a method that incorporates both cutaneous and kinaesthetic information in the measure of carton compliance.