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This article was originally published in German in Flexo+Tief-Druck 3-2019.
There must be compelling arguments for changing a tried and tested production process and this was indeed the case when Christiansen Print switched to tesa® Twinlock Sleeves.
The switch produced a variety of advantages for the preprint corrugator line. The plate mounting process now no longer involves adhesive tapes for plate mounting - thus saving time and eliminating waste. Furthermore, after testing and implementing tesa® Twinlock sleeves it became clear there were process advantages resulting in higher print speeds for many jobs.
The project, which began with a set of test sleeves, now takes the very visible form of over 300 bright green tesa® Twinlock sleeves held in the Christiansen Print mounting department. In the course of only three months the Ilsenburg production facility made a complete switch to tesa® Twinlock sleeves. These sleeves have a working width of 2485 mm and 30 different repeat lengths ranging from 790 mm to 2060 mm.
The European market leader for preprinted reels of corrugated liner for packaging and displays was founded in 2005. Since 2016 they have been a wholly owned division of the THIMM group. They have three production sites in France and Germany and at their Ilsenburg facility in Germany (Harz) they operate two of the world’s largest impression cylinder flexo presses. Since 2017 they also operate the HP PageWide T1100S digital web press. The Northeim (Germany) and Garancières-en-Beauce (France) printing facilities operate three of the latest belt flexo presses. This combination offers Christiansen Print the benefit of three complementary printing technologies. With strong print compentencies and a workforce of over 170 people, the company is able to produce around 450 million m2 of preprint annually.
New in the tesa® Plate Mounting Portfolio
The tesa® Twinlock sleeves were added to the tesa range in 2018 and now users have to ask themselves whether adhesive tapes or tesa® Twinlock sleeves are the most economical plate mounting solution. Answering this question requires both discussions about the specific technical requirements and possibilities, and also an application-focused ROI analysis which tesa provides. In the case of Christiansen Print, this comprehensive analysis revealed that covering the complete range of repeat lengths produced a commercial benefit through savings on adhesive tape. This provided sufficient grounds to test tesa® Twinlock sleeves.
The Buildup of tesa® Twinlock Sleeves
The tesa® Twinlock sleeves are based on industry standard sleeves, allowing every customer the freedom to choose the basic core. A 1.5 mm thick open cell Polyurethane (PU) foam is then applied to this core. Many years of practical experience confirm that the foam layer remains compressible even after years of use. It is this PU foam that forms the basis of the printing properties of the sleeves.
The next layer consists of a PET stabilization film serving as the carrier layer for the cross-linked, permanently sticky acrylic photopolymer layer on which the plates are mounted.
The side edges of the sleeve are then sealed in order to protect them from soiling and solvents.
The Initial Test Delivered Convincing Results
At Christiansen Print, project managers Björn Vorlop and Michael Schmidt from the lean management team oversaw the project and decided to carry out the initial tests on seven sleeves with a repeat length of 2000 mm (one of the longest the company uses).
Past experience suggests that what works with large circumferences usually also works with smaller ones, and this also turned out to be the case here. The results in terms of print quality and press performance were positive from the beginning. It was possible, for example, to increase the speed of a print job from 200 m/min to a maximum speed of 500 m/min. It was also possible to reduce the bouncing in the press due to the compressibility of the 1.5 mm thick layer of PU Foam.
Despite the promising initial test results there was of course a good deal of underlying skepticism amongst the staff when it came to working with the new sleeves on a daily basis. There were concerns about the resulting process changes and also whether the sleeves would be suitable for every job. Following the promising test results, the test phase was extended and a second set of sleeves with a circumference of 1250 mm was purchased. The second test phase confirmed the positive results delivered by the tesa® Twinlock technology and the number of those in favor in the mounting, production and management teams steadily increased.
What Does the tesa® Twinlock Technology Deliver?
tesa® Twinlock especially pays off for repeat lengths that are used frequently. For Christiansen Print, the introduction of tesa® Twinlock sleeves meant a standardization of the prepress mounting process. Plate mounting tape is eliminated and the plates are mounted directly on the acrylic photopolymer surface of the sleeves, which were all chosen with a medium degree of hardness. This reduces the complexity of the mounting process and supply chain costs.
When it comes to printing, there have been speed improvements, for many jobs it was possible to increase the speed by 20-30%. It was discovered that the ability to increase speed was dependent upon the sensitivity of the design to vibration, and a large circumference helped to reduce vibration streaking. The compression behavior of the sleeves also means that a constant print quality is maintained over a long production time frame. Christiansen Print also found that print register is very precise in comparison with adhesive tape assembly due to the lower thickness tolerances of the tesa® Twinlock sleeves. The thickness of tesa® Twinlock sleeves is measured with a laser during and after the production process and is defined with an accuracy of +2/100 mm.
Do the Characteristic Printing Curves Have to Be Adjusted?
There were concerns that changing the plate substructure system would increase tone value and therefore the characteristic printing curves. At Christiansen Print it was found that the characteristic printing curves tended to remain very similar and that additional changes were not necessary. The tone value increase can be slightly lower in the highlights, up to a tone value of 5%, but for the printer it is generally rather simple to increase the printing pressure accordingly.
Fully Automatic tesa® Twinlock Activating Machine
In order to activate the adhesive effect of the tesa® Twinlock sleeves it is essential to remove ink residues, dust and dirt from the acrylic photopolymer. At Christiansen Print this step is carried out entirely automatically in a tesa® Twinlock Activation Machine. The large sleeve formats required the machine to be designed in close cooperation with Christiansen Print.
The activator, which is used as the cleaning agent, is an alcohol with a high flame point, meaning there is no need for precautions against explosion. The vapor is extracted from the sealed system.
Substantial Waste Reduction
First and foremost, tesa® Twinlock can reduce plate mounting tape usage and improve the CO2 footprint by eliminating waste. The sustainability of the product is graphically made obvious at Christiansen Print by the fact that there are now three fewer containers of waste every week. Over the course of a year this sums up to the equivalent of eight football fields of adhesive tape. The environmental and economic aspects were two reasons for Christiansen Print to switch to tesa® Twinlock Sleeves, whilst improved print performance was a third.