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FLEXO Magazine : June 2014
most up to date printing machine with modern plate, ink and anilox technologies, press a button and achieve brilliant results in a second. But the latest technological developments within flexo printing can be combined to support the printer on its way to achieving excellent printing results not just once, but in a repeatable manor, every day. THE ANILOX PERSPECTIVE Looking at the HQ discussion from the perspective of an anilox manufacturer, it is clear which rolls deliver the greatest control of ink transfer. “With patented genetic transfer technology (GTT) anilox rolls, it is possible to overcome some inconsistency of standard anilox designs. Achieving higher and higher quality results is impossible without a predictable ink transfer,” said Georg Selders, sales director, Europe at Apex Group of Companies. “The unique open slalom ink channel geometry of GTT delivers a controlled ink transfer and is the key to a constant and predictable print result.” Many converters who had to deal with washboarding have been able to minimize or even completely reduce the problem with a com- bination of GTT and new plate technologies. Due to their special surface structure, GTT engravings can be produced in a much more controlled fashion than standard anilox engravings, which means with much less variation in densities, even with the same specs. Image 1 illustrates a density comparison between three different GTT rolls with the same specs and three different conventional anilox rolls with the same specs, ordered at different times. The GTT rolls show a far more constant density compared with the conventional anilox rolls. This is due to the fact that GTT’s screen structure and the widths and heights of the walls are completely under control, because the ceramic is engraved with a constant laser beam. The profile (90 percent ink channel/10 percent wall) of these rolls enables a much more controlled ink transfer than is possible with conventional anilox rolls. Conventional anilox rolls are laser engraved with a pulse laser beam, which burns the cell structure into the sur- face hole by hole. Combined with operator variation, the pulse laser engraving makes it very difficult to give a 100 percent guarantee on the density when the same roll is reproduced, even if measurements result in having matched the same technical specs. The required finishing process is also one of the most critical parts when it comes to a controlled ink transfer. And control is exactly what printers need to achieve the quality the market demands. THE OEM’S PERSPECTIVE Andre Göpfert, CEO at Göpfert Maschinenbau GmbH, said that his company’s customers “are demanding HQ machines more and more frequently. In the last 10 years we saw a tremendous increase toward HQ.” Looking at the quality of a printing job, he notes: “The operator needs to be well trained on the printing machine and the whole print- ing process, especially when he wants to achieve the highest possible quality by teasing out the full functions of the machine and achieve the same results at the same, high quality level.” THE PRINTER’S CHALLENGE Frank Patzt, head of prepress at Hans Kolb Wellpappe, one of Germa- ny’s leading printers in the corrugated carton box sector, gets to the heart of the matter: “The main goal is to print in a way that’s perma- nently reproducible. Our initial aim was to achieve predictable, high quality results for screen/solid combinations. Therefore, we chose to test the possibilities of Apex GTT on our preprint machine extensive- ly. After finetuning of dot size and GTT’s line thickness, we are now successfully printing consistent high quality with a set of GTT Corr S, M and L. And our high quality standards are the same in preprint and in postprint jobs, with graphics up to 175 lpi which can rival offset quality.” Besides the proper anilox roll that enables a controlled ink trans- fer and brings consistency to the printing process, Patzt mentions another point that is very important for achieving HQ standards. “We need maximum control of the entire printing process, which is only possible by reducing subjectivity to a minimum. Today’s printing machines are automated to such an extent that they can nearly work Image 2: An operator at Hans Kolb Wellpappe controls the printing process at one of the company’s Göpfert “Ovation” HQ printing machines. 76 FLEXO | JUNE 2014