Effect of creasing tool dimensions on the quality of press-formed paperboard trays

Effect of creasing tool dimensions on the quality of press-formed paperboard trays

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Procedia Manufacturing 00 (2018) 000–000 Available online atatwww.sciencedirect.com Available online www.sciencedirect.com Procedia Manufacturing 00 (2018) 000–000

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Procedia Manufacturing 25 (2018) 397–403 Procedia Manufacturing 00 (2017) 000–000 www.elsevier.com/locate/procedia

8th Swedish Production Symposium, SPS 2018, 16-18 May 2018, Stockholm, Sweden 8th Swedish Production Symposium, SPS 2018, 16-18 May 2018, Stockholm, Sweden

Effect of creasing tool dimensions on the quality of press-formed Effect of creasing tool dimensions on the quality of press-formed trays 2017, MESIC 2017, 28-30 June Manufacturing Engineering Societypaperboard International Conference paperboard trays 2017, Vigo (Pontevedra), Spain Ville Leminen a,a,*, Sami Matthews aa, Panu Tanninen aa, Juha Varis aa Ville Leminen *, Sami Matthews , Panu Tanninen , Juha Varis

Costing models forUniversity capacity optimization in Industry 4.0: Trade-off Lappeenranta of Technology, Skinnarilankatu 34, Lappeenranta FI-53850, FINLAND Lappeenranta University of Technology, Skinnarilankatu 34, Lappeenranta FI-53850, FINLAND between used capacity and operational efficiency a a

A. Santana , P. Afonso , A. Zanin , R. Wernke Abstract Abstract a University of Minho, 4800-058 Guimarães, Portugal Press forming is a method to produce packaging products,89809-000 such as trays or plates from sustainable materials made from renewable b Unochapecó, Chapecó, SC, Brazil Press forming is a method to produce packaging products, suchtypically as trays utilizes or platespre-cut from sustainable materials madeblanks, from renewable resources, for example paperboard. The press forming process and -creased paperboard which are resources, for to example paperboard.shapes. The press forming process typically utilizes pre-cut and -creased paperboard blanks, which are press-formed three-dimensional press-formed to three-dimensional This paper focuses on the effect ofshapes. creasing tool (creasing wheel) dimensions on the quality of the sealing surface of the pressThis paper focuses on the effectresults of creasing (creasing dimensions on has the an quality of the pressformed trays. The experimental show tool that the width wheel) of the creasing wheel effectofonthe thesealing qualitysurface of the formed trays Abstract formed trays. The on experimental results show that the width The of theresults creasing an effect when on theplanning quality of formed trays and is dependent the thickness of the formed material. can wheel act ashas a guideline thetheproduction for and is dependent the of the material.processes The resultswill can be act as a guideline planning the production for creasing and concept presson forming. Under the of thickness "Industry 4.0",formed production pushed to bewhen increasingly interconnected, creasing and press information basedforming. on a real time basis and, necessarily, much more efficient. In this context, capacity optimization © 2018 The Authors. Published by Elsevier B.V.maximization, contributing also for organization’s profitability and value. goes beyond the traditional aim capacity © 2018 The Authors. Published by of Elsevier B.V. © 2018 The under Authors. Published by B.V. committee of the 8th Swedish Production Symposium. Peer-review responsibility of Elsevier the scientific Peer-review under responsibility of the scientific committee of the 8th Swedish Production Indeed, lean management and continuous improvement approaches suggest Symposium. capacity optimization instead of Peer-review under responsibility of the scientific committee of the 8th Swedish Production Symposium. a

a,*

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maximization. The study of capacity optimization and costing models is an important research topic that deserves Keywords: press forming; creasing; tool; paperboard; tray contributions both the practical and theoretical perspectives. This paper presents and discusses a mathematical Keywords: press from forming; creasing; tool; paperboard; tray model for capacity management based on different costing models (ABC and TDABC). A generic model has been developed and it was used to analyze idle capacity and to design strategies towards the maximization of organization’s 1. Introduction value. The trade-off capacity maximization vs operational efficiency is highlighted and it is shown that capacity 1. Introduction optimization might(i.e., hidetray operational Press forming pressing,inefficiency. press moulding or stamping) is a process that is used to form three-dimensional © 2017 The Authors. Published Elsevier B.V.moulding Press forming (i.e., tray pressing, press or stamping) a process that ismain usedcomponents; to form three-dimensional (3D) shapes from paperboard.byThe process uses moulding tools thatis consist of three a male mould Peer-review under responsibility ofThe the process scientificuses committee of thetools Manufacturing Engineering Society Internationala Conference (3D) shapes from paperboard. moulding that consist of three main components; male mould (punch), female mould (die), and a blank holder (rim tool), similarly to deep-drawing.[1-4, 7] Various food products, 2017. (punch), female mould (die), and a blank holder (rim tool), similarly to deep-drawing.[1-4, 7] Various food products, such as fast food, ready eat meals and frozen food are packed in press-formed paperboard trays, and also press-formed such as fast food, ready eat meals and frozen food are packed in press-formed paperboard trays, and also press-formed Keywords: Cost Models; ABC; TDABC; Capacity Management; Idle Capacity; Operational Efficiency

1. Introduction

* Corresponding author. Tel.: +358-40-169-3485 * E-mail Corresponding Tel.: +358-40-169-3485 address:author. [email protected] The cost of idle capacity is a fundamental information for companies and their management of extreme importance E-mail address: [email protected]

in modern©production systems. In general, it isB.V. defined as unused capacity or production potential and can be measured 2351-9789 2018 The Authors. Published by Elsevier 2351-9789 2018responsibility The Authors. Published by Elsevier B.V.hours Peer-review of the scientific committee of the 8th Production Symposium. in several©under ways: tons of production, available of Swedish manufacturing, etc. The management of the idle capacity Peer-review underTel.: responsibility the761; scientific committee the 8th Swedish Production Symposium. * Paulo Afonso. +351 253 of 510 fax: +351 253 604of741 E-mail address: [email protected]

2351-9789 © 2017 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the Manufacturing Engineering Society International Conference 2017. 2351-9789 © 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the 8th Swedish Production Symposium. 10.1016/j.promfg.2018.06.109

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plates are widely used. Paperboard trays provide an alternative for oil-based plastic packages in various packaging applications. In many applications the quality, especially surface quality in the tray flange area is critical for the functionality of the tray in the packaging chain, for example heat sealing of the lidding film onto the tray [4]. Typically, the press forming utilizes pre-cut and –creased paperboard blanks, which are subsequently press-formed to three-dimensional shapes [1]. The fiber-material tends to wrinkle [8], and the pre-creasing is done to control the folding of the material and prevent uncontrolled wrinkling. The creasing process and its effect on the press-formability has been previously researched in previous work, which investigated different creasing factors such as tool dimensions using flatbed die cutting, which uses tools consisting of rounded creasing tools and corresponding grooves on the other side of the creased substrate [6]. Another common method used to produce blanks in packaging industry is a digital cutting and creasing table, e.g. sample maker. The creasing method differs from flatbed die cutting by using a crease wheel, which presses the crease into the material by following the designed creasing pattern. The blanks are cut by using a sharp blade, and the material is held in place by a suction table, which utilizes a vacuum pump. The creasing tool and the suction felt can be seen in Fig. 1.

Fig. 1. The creasing wheel, cutting tool casing and suction felt

This paper focuses on the effect of creasing tool dimensions (creasing wheel width) on the quality of the pressformed trays and the sealing surface of the trays. A series of creasing and press forming experiments was performed and the formed trays were analyzed with macroscopic and microscopic analysis. 2. Materials and methods 2.1. Materials The substrates used in the die cutting tests and tray pressing were Stora Enso (Finland) Trayforma Performance 350 + 40 WPET and Trayforma Performance 190 + 40 WPET, a polyethylene terephthalate (PET) extrusion-coated paperboard with a base material grammage of 350 g/m2 and 190 g/m2, respectively. The coating grammage in both materials was 40 g/m2. The baseboard consists of three solid bleached sulfate (SBS) layers. The main component of the substrate is hardwood fiber with alkyl ketene dimer (AKD) hydrophobic sizing additive. The fiber dimensions of the paperboard were measured using an L&W Fiber Tester (ABB, Stockholm, Sweden). The fiber length, fiber width, and kink index were measured at 1.1 mm, 22.5 µm, and 1.13, respectively.



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The materials were stored in a constant humidity chamber at 80% relative humidity (RH) to ensure sufficient humidity. The high humidity was used to obtain the desired moisture content, which was verified with a moisture analyzer (Adams Equipment PMB 53, New York, USA). The measured moisture contents of the materials were approximately 6 % for 190 + 40 g/m2 and 7.5 % for 350 + 40 g/m2. Typically, the moisture content in press forming should be above 6 % and under 11 %, since a low moisture content can result in cracks in forming, while moisture content too high can result in unwanted evaporation of the water and damaging (bubbling) of the extrusion coating. 2.2. Methods The converting experiments consisted of creasing the blanks for the tray forming and after that of press forming the creased blanks into 3D-shape. After that, the samples from the tray flange were prepared and analyzed with a microscope. The creasing roller widths in industry are usually presented in point (pt.) widths. Four different widths were used to perform the experiments; 2, 3, 4, and 6 pt. The widths correspond to widths of 0.706, 1.058, 1.411 and 2.117 mm, respectively. The blanks were prepared using a digital cutting and creasing table (Kongsberg XE-10). A creasing force of 100 N in the vertical direction was used. The used blank and creasing pattern can be seen in Fig. 2 a. and the creased blank in Fig. 2 b.

Fig. 2. (a) The tray blank geometry, creases are shown in red. (b) Corners of a creased blank and a press formed tray.

The press forming experiments were performed with the following parameters. Female mould temperature 170 °C, male mould temperature 21 °C and dwell time 1 s were kept constant throughout the experiments. Two different blank holding forces (BHF) and forming forces were used, 2 kN and 1.5 kN for the BHF 150 kN and 40 kN for the forming force. A detailed explanation of the press forming process is presented in previous work [1]. The corner of a formed tray is shown in Fig. 2 b. The formed trays were first visually observed to detect cracks or other clearly visible defects. After that, the samples for the microscopic analysis were prepared by cutting a cross-sectional sample of about 30 mm, which was installed into a silicon mold. The mold was filled by a clear acrylic resin (Clarokit, Struers). After hardening, the cast sample was removed from the mold and polished. The finished samples were studied with an optical light microscope (Olympus Tokyo). The folding of creases in the tray flange area has been discussed previously [4-6], which state that the creases should be evenly folded and there should be no big capillary tubes or other gaps in the surface of the flange, as the surface should be as flat as possible.

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3. Results and discussion Figs 3-6 show the microscopic images of all creasing tool widths, with both material thicknesses, with two different press forming parameter combinations.

Fig. 3. Microscopic images of the tray flange with material thickness of 190 + 40 g/m 2 with different creasing wheel widths (a) 2 pt., (b) 3 pt., (c) 4 pt., (d) 6 pt. Pressing force 40 kN and BHF of 1.5 kN was used.

Fig. 3. shows that the increase in the creasing wheel width results in a clear reduction in the compression of the creases, resulting in insufficient formation. 2 pt. width resulted in a flat sealing surface, while the increase of the width up to 6 pt. results in an uneven surface.

Fig. 4. Microscopic images of the tray flange with material thickness of 190 + 40 g/m 2 with different creasing wheel widths (a) 2 pt., (b) 3 pt., (c) 4 pt., (d) 6 pt. Pressing force 150 kN and BHF of 1.5 kN was used.



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Fig. 4. shows the samples formed with a higher forming force (150 kN). Still, a similar phenomenon as in Fig 3. is repeated; the increase in creasing wheel width results in insufficient folding of the creases. The smallest width of the creasing wheel resulted in best result with both forming forces.

Fig. 5. Microscopic images of the tray flange with material thickness of 350 + 40 g/m2 with different creasing wheel widths (a) 2 pt., (b) 3 pt., (c) 4 pt., (d) 6 pt. Pressing force 40 kN and BHF of 1.5 kN was used.

Fig. 6. Microscopic images of the tray flange with material thickness of 350 + 40 g/m2 with different creasing wheel widths (a) 2 pt., (b) 3 pt., (c) 4 pt., (d) 6 pt. Pressing force 150 kN and BHF of 2 kN was used.

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Fig. 5. shows that with the thicker material the wider creasing roller functions better and results in a flatter surface. However due to the smaller forming force and BHF there are some irregularities in the folding, caused by uneven force distribution and lower flattening force. In Fig. 6. it can be seen that with higher forces in the press forming operation the wider creasing wheel has the best functionality, and the folding of the creases with the 6 pt. wheel is in a sufficient level. The results indicate that when a creasing wheel is used to produce the creases, the suitable tool width differs a bit from the instructions made for flatbed die cutting, but is correspondent to the material thickness. With the tested materials, a wider creasing wheel (4 pt. to 6 pt.) functioned well for the 350 + 40 g/m2 material, while a width of 2 pt. functioned best for the thickness of 190 + 40 g/m2. Based on the experimental results, the width of the creasing wheel seems to correlate with the material thickness, i.e. with a thicker material; the creasing wheel should be wider. This is suspected to be caused by the folding phenomenon – a too wide of a crease for the thinner material will cause insufficient sealing of the polymer layer in the crease area, and vice versa. Even though a wider creasing wheel results in a lower creasing pressure, the pressure on the material seems not to be the dominating factor with the tested materials and parameters. If the pressure would decrease too much, this could also be an factor, which can happen with thicker materials and would be an interesting topic to research. However, the differences in surface quality are not always very clear and there is some variance in the geometry of the folded creases, which should be taken into account. Also, the forming force and blank holding force play a significant role in the folding of the creases, which can be clearly seen from the results. The results of Tanninen et al. [6] showed that the suitable width of the creasing tool in flat bed die cutting was 2 pt. for the thicker material, which contradicts with the results of this study to some extent. This is suspected to be caused by a much higher creasing force and the use of counter tool in the flat bed die cutting process, which cause differences in the crease geometry, and the subsequent folding of the creases. The results also suggest that only the width of the creasing tool cannot be considered when a commercial creasing operation is planned, but the final testing with the creased substrate should be done with the actual production machine. 4. Conclusions The results show that when the blanks for press forming process are creased with a creasing wheel, the width of the creasing wheel has a correlation with the material thickness, and a wider creasing tool should be used with a thicker material. The results also suggests that only the width of the creasing tool cannot be considered when a commercial creasing operation is planned, but the final testing with the creased substrate should be done with the actual production machine. In the future, a more thorough investigation of different die cutting methods and forming parameters could give more insight into the folding of the creases during the forming process, and the subsequent effect onto the quality of the formed products. Acknowledgements Mr. Aleksi Lento is thanked for participating in the practical work. References [1] V. Leminen, P. Tanninen, P. Mäkelä, & J. Varis, Combined Effect of Paperboard Thickness and Mould Clearance in the Press Forming Process, Bioresources 8 (4) (2013) , pp. 5701-5714. [2] P. Tanninen, M. Kasurinen, H.Eskelinen, J. Varis, H. Lindell, V. Leminen, S. Matthews and M. Kainusalmi, The effect of tool heating arrangement on fibre material forming, Journal of Materials Processign Technology, vol. 214 (8), (2014), pp. 1576-1582 [3] M. Hauptmann, J. Weyhe, J-P. Majschak, Optimisation of deep drawn paperboard structures by adaptation of the blank holder force trajectory. Journal of Materials Processing Technology Volume 232, (2016), pp. 142-152 [4] V. Leminen, P. Tanninen, H. Lindell, & J. Varis, Effect of Blank Holding Force on the Gas Tightness of Paperboard Trays Manufactured by the Press Forming (2015)



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[5] P. Tanninen, Press forming of paperboard- advancement of converting tools and process control. (2015). ISBN 978-952-265-897-5 [6] P. Tanninen, V. Leminen, H. Eskelinen, H. Lindell, & J. Varis, Controlling the folding of the blank in paperboard tray forming, Bioresources 10(3) (2015), pp. 5191-5202. [7] M. Hauptmann, J. Weyhe, J-P. Majschak, Optimisation of deep drawn paperboard structures by adaptation of the blank holder force trajectory. Journal of Materials Processing Technology Volume 232, (2016), s. 142-152 [8] A. Vishtal, M. Hauptmann, R. Zelm, J.-P. Majschak, E. Retulainen 3D Forming of paperboard: the influence of paperboard properties of formability, Packag. Technol. Sci., 27 (9) (2013), pp. 677–691