- Industrial solutions
For more than 30 years, INOMETA has been creating innovative impulses for the development and production of rotating components for any kind of printing process. As a specialist for rollers made of aluminum and fiber composites such as CFRP and GFRP, INOMETA is able to draw on a broad range of user knowledge, and thus provide answers to growing requirements regarding ever higher machine speeds and greater print widths. INOMETA is specialized on high-end and innovative lightweight design solutions, as well as the development and production of functional surfaces.
The surface quality of the ceramic coating is essential for the use of an anilox roller in high-quality flexographic printing. It is a decisive factor for the print characteristics and the long-term performance.
The INOMETA ceramic coatings made of chromium oxide ceramics exhibit a very high hardness of 1300 Hv 0.3, and are highly resistant to wear. The anti-adhesive properties can be used to control the ink absorption or respectively the ink release of an anilox roller.
This was the starting point at INOMETA for the development of a new anilox roller generation with an improved ceramic layer for a constant and uniform ink release. This property greatly depends on the discharge behavior of the cells and the lasting resistance of the ceramic surface to aggressive chemicals regarding printing inks and cleaning media.
The new INOflex® Superior-AS ceramic surface has a surface structure with a low residual porosity and a highly favorable porosity distribution. Through the excellent melting behavior of the ceramic surface during the laser engraving, it is possible to create smoother cell structures, which in turn enable an improved discharge behavior of the cells. In addition to the cell shape, smooth cell walls with a good ink release are the decisive criteria for the ink release properties of this anilox roller generation.
The excellent measurement results were confirmed during the print tests conducted at the DFTA Technology Center. The extensive test program comprised the testing of 60 different engravings, which differed in terms of volume and resolution fineness. Further test parameters included rollers with different ceramic surfaces, which were used to print with a speed of up to 400 m/min at varying printing speeds. A standard hexagonal roller with comparable engravings and a high-quality corrosion protection with covering layer was used for comparison.
The new ceramic surface INOflex® Superior-AS demonstrated a lower dot gain across all engraving bands, with a volume of 3-10 cm³/m² and a line-pattern of 180-400 lines/cm, compared to standard anilox rollers. At the same time, the new ceramic surface showed a higher ink release regarding the color delivery properties, which was illustrated by the measuring technique with a higher color density of D 0.3 -0.4.
The good ink release of the ceramic surface was also clearly visible through a comparison of the video microscope imagery of the grid fields. Especially in the area of the 2% halftone dots (Fig. 1), the dot area of the individual halftone dots printed with INOflex® Superior-AS anilox rollers is closed to a greater degree and exhibits sharper edges.
Since the anilox rollers come into contact with a broad range of ink systems and cleaning media during day-to-day operations, the corrosion resistance of the anilox roller surfaces against aggressive chemicals is another important quality criteria. In order to demonstrate the high corrosion resistance of the INOflex® Superior-AS anilox rollers, the anilox roller surfaces were exposed to the direct influence of aggressive liquids. The pH range was from acidic solutions with a pH 5, to strongly base solutions in the range of pH 14. This pH spectrum is particularly critical when using anilox roller sleeves with an aluminum outer sheathing, since the protective oxide layer of the metal becomes largely ineffective when subjected to a strongly acidic or a strongly base environment.
While the standard anilox roller surface exhibited strong under-surface corrosion after 192 hours of test time in highly concentrated hypochlorite, no change of the surface could be detected or measured for the INOflex® Superior-AS ceramic surface even after 420 hours of exposure.
In addition to the good resistance to corrosive materials, the new Superior AS ceramic surface also demonstrated significant advantages for a further material property. With its melting properties, it possesses excellent engraving characteristics that allow a decrease of the depth-to-volume ratio for the engraving by about 30%, and to precisely transfer cell shapes almost at the geometric end of the hexagonal cell design. The significantly improved cell shape achieved by this, yields an increased ink release volume in practice, and at the same time improves the cleaning behavior of the anilox rollers. The benefit to the user lies in reduced cleaning intervals during the use of the new anilox roller generation, and thus significantly contributes to the reduction of set-up times in the printing room.
The test program at the DFTA technology center has confirmed the good printing behavior of the engraving shape with an elongated cell design. The print patterns show that the color density with the elongated cell shape can be increased with the same cell volume compared to the hexagonal engraving. They demonstrate a more uniform and vibrant print image across the entire range, from the highlights all the way up to the solid tones.
The new anilox roller generation with a INOflex® Superior-AS ceramic surface and the elongated cell design boasts convincing properties and clear printing technology advantages. The high quality of the ceramic surface provides an improved process reliability for the printing, and ensures a long-term reproducibility of the anilox roller ink release. Through the superior corrosion resistance, the ink release behavior remains constant for a long time, so that color deviations are minimized by this influencing factor of the ink release chain.
Overall, the attained process reliability leads to shorter downtimes, and thus to an improvement in productivity, as well as a reduction of the printing costs.
The new anilox roller generation, with its improved ink release behavior with a low cell volume, offers a slightly broader range of use for the anilox rollers. Solid surfaces print homogeneously, just like fine halftone dots.
The better volume-to-depth ratio of the cells also has a very positive influence on the cleaning behavior. Fewer downtimes are required due to cleaning, the consumption of cleaning agents is reduced, and through this also the costs for cleaning agents and the disposal.
With the new anilox roller generation INOflex® Superior-AS, 20-25% smaller cell volumes are possible with the same resulting color density compared to the standard. Overall, there are many arguments that speak for the new anilox roller generation.