Improved print performance and a more sustainable production process were the fundamental reasons for switching to the alternative plate mounting technology from tesa.
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. For example, the mounting process no longer involves adhesive tapes for plate mounting - this saves time and eliminates waste. Furthermore, immediately after testing and implementing tesa® Twinlock sleeves it became clear there were process advantages that resulted 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 just three months the Ilsenburg production facility made a complete switch to tesa® Twinlock sleeves. These sleeves have a working width of 2485mm and 30 different repeat lengths ranging from 790mm to 2060mm.
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 Gruppe. They have three production sites in France and Germany and at their Ilsenburg facility in Harz they operates two of the world’s largest common impression cylinder flexo presses. Since 2017 they also operate the HP PageWide T1100S digital web press. The Northeim and Garancières-en-Beauce printing facilities have three of the latest belt flexo presses. This combination offers Christiansen Print the benefit of three complementary printing technologies. With strong print compentecies and a workforce of over 170 people the company is able to produce around 450 million m2 of preprint annually.
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 that tesa provides. This analysis looks at the frequency with which the various repeat lengths are used as well as the areas of the forms. 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 tesa® Twinlock sleeves are based on industry standard sleeves, allowing every customer the freedom to choose the basic core. A 1.5mm 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 consist 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 are then sealed in order to protect them from soiling and solvents.
At Christiansen Print, project manager Björn Vorlop und 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 2000mm (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 200m/min to a maximum speed of 500m/min. It was also possible to reduce the bouncing in the press due to the compressibility of the 1.5mm thick layer of PU Foam.
Despite the promising initial test results there was of course a good deal of underlying scepticism 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 in every way. Following the promising test results, the test phase was extended and a second set of sleeves with a circumference of 1250mm were purchased. The second test phase confirmed the positive results delivered by Twinlock technology and the number of those in favor in the mounting, production and management teams steadily increased.
Twinlock really pays for repeat lengths that are used frequently. What tesa® Twinlock sleeves allow Christiansen Print to do in prepress is standardize the mounting process. Adhesive tape is eliminated and the plates are mounted on the acrylic photopolymer surface of the sleeves, which all exhibit a medium degree of hardness. This means the complexity of the mounting process and the supply chain spend is reduced. Many steps in the process are now removed or replaced by the very linear Twinlock process.
When it comes to printing, there have been speed improvements, and for many jobs it was possible to increase the speed by 20-30% We discovered the ability to increase speed was dependent upon the sensitivity of the design to vibration and that a large circumference helps to reduce vibration streaking. The compression behaviour of the sleeves also means that a constant print quality is maintained over a long production time frame. Christiansen Print has 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 are measured with a laser during and after the production process and are tailormade to an accuracy of +2/100 mm.
There were concerns that changing the plate substructure system would increase tone value and therefore the characteristic printing curves. At Christiansen Print, just as with other change-overs, it was found that the characterstic 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 simpler to adjust the printing pressure, since systems can have a greater tolerance due to the foam thickness and properties.
In order to activate the adhesive effect of the 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 Twinlock Activation Machine. The large sleeve formats required that the machine be designed 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 vapour is extracted from the sealed system.
First and foremost, tesa® Twinlock can reduce adhesive tape usage and improve the CO2 footprint thus eliminating waste. The sustainability of the product is graphically demonstrated at Christiansen Print by the fact that there are now three fewer containers of waste every week. Over the space of a year that works out at 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.
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