Coating & Laminating Industrial UV inkjet takes the hurdles
out of printing tube laminates By Dieter Finna of
pack.consult.
P
rinting on tube laminates using UV inkjet poses several application-specific challenges. The tubes, which are bent and crushed during squeezing, require a flexible ink film. It must adhere well to the substrate, must not crack during handling and must meet all compliance requirements. In addition, the cost-intensive substrate requires a machine concept that includes the shortest possible web.
Seen in this light, it was not an easy task that the well-known laminate printers entrusted product development at Gallus Ferd. Rüesch AG with. The challenge for ink development was to prevent the UV inkjet ink film from cracking under mechanical stress, as is known from solid areas in folding carton printing when they extend beyond the fold edges.
A FLEXIBLE UV INKJET INK
For this reason, Gallus launched the ‘Flexible UV Inkjet Ink’ project for folding carton printing along with a well-known brand manufacturer at the start of 2019. For this purpose, the UV inkjet ink system developed in the project with the product name ‘UVF01’ not only had to exhibit the mechanical properties, but also had to pass the sensory test programme in the tobacco sector and fulfill all the requirements in the Regulatory Compliance & Toxical Assessment. The UVF01 ink passed the tests and has been released for commercial production in the brand manufacturer’s folding box production since the beginning of this year. This provided the prerequisites for transferring the results of flexible UV inkjet inks from folding carton printing to the solution approach for tube laminates.
THE PRINTING PRESS SYSTEM Modifications to the Gallus Labelfire 340 were necessary to use the UVF01 ink system. These related to the drying technology and web guide. The latter had to be designed for the shortest possible web paths for the cost-intensive substrate.
Gallus has broken new ground in radiation curing. In the Gallus Labelfire version for the new flexible UV ink system, UV-LED curing systems replace the mercury vapour lamps previously used. The advantage of UV-LED technology is that the energy penetrates the ink layers more effectively thanks to the high intensity of the UV-A beams, resulting in more uniform curing. An added benefit is that a very good adhesion of the flexible ink film to the substrate is achieved without the use of primers. The machine layout of the modular Gallus Labelfire ‘Tube Edition’
was designed to keep the web path in the machine as short as possible. The ultra-short web path of only 1.1m between the flexo printing units of the ECS series flexo, which significantly reduces waste during makeready and production. For example, the web path between unwinding and rewinding on the ‘Tube-Edition’ is only around 25m, compared to around 80m on a comparable press for tube laminate printing. Given the high material costs of tube laminates, this is a major factor contributing to high profitability in the printing process.
QUALIFYING COMPARISON OF DIGITALLY AND CONVENTIONALLY PRINTED TUBES For the upcoming practical comparison, Permapack AG contributed its printing expertise in laminate printing to the project producing the conventionally printed tube samples. These were printed on a Gallus RCS 330 as a benchmark for digital printing and joint assessment with Gallus. The digital benchmark samples were printed on a Gallus Labelfire 340 running in industrial use and equipped with the “UVF01” inkjet series and modified dryer technology. The designs for the benchmark and the different tube laminates were selected according to typical market requirements.
The test results with the UVF01 inkjet ink showed excellent results across all fastness requirements for the tube laminates PBL and ABL, which are predominantly used in the market, as well as on paper laminate. The evaluations exclusively show results in the “1-very good” range. “During the tests, we found that the adhesion and flexibility of the
new flexible UV inkjet ink showed good values. The digitally printed tube material could be processed in the same way as conventionally printed material,” said Günther Forster, prepress manager, business unit printing product manager cosmetics at Permapack, in describing the analysis of the test results. Only the digitally printed PP laminate, which is only used to a very limited extent on the market, showed a deviation in the aging test. With PP laminates, printing conditions and inkjet inks still need to be modified somewhat.
The Gallus Labelfire “Tube-Edition” together with the flexible UVF01 inkjet ink presents itself as a pioneering alternative to purely conventional tube printing. Thanks to the high native resolution of 1200x1200 dpi, digital printing can score points in terms of print quality by outperforming the motifs usually printed in 54 screens in flexographic printing. A break-even analysis of the costs of the print samples from the print comparison shows that the digitally conventionally printed runs up to a run length of approx. 5,000 running metres are cheaper to produce than purely conventionally printed tubes. With a standard tube of 200 ml, this corresponds roughly to a quantity of 53,000 tubes and is considered an average run length in tube printing. This project provided all of the evidence that qualifies the flexible UV inkjet ink for use in tube printing. This means that the Gallus Labelfire ‘Tube Edition’ and the UVF01 inkjet series are now ready for use in industrial laminate printing.
Xwww.gallus-group.com/en/home
16
November 2022
www.convertermag.com
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