Anilox Cell Structures
When selecting an anilox roller, you typically think of a 30, 45, or 60-degree engraved pattern. There are several variations of engraves in the industry, some of which are extremely unique and dependent on the engrave entirely. What is the point in having a unique pattern?
“Over 2000 years ago Greeks mathematicians first debated the honeycomb as the most equal way of dividing any given area, what was known as the Honeycomb Conjecture. In 1999 mathematician Thomas C Hales proved that a regular hexagonal grid or honeycomb is the best way to divide a surface into regions of equal area with the least total perimeter.
The 60 degrees hexagonal pattern allows for more cells to be compacted in an area and provides the most efficient distribution of volume. There is less wasted space (less land area) if compared to diamond shape patterns (traditional 45 deg. engraving). This is the reason, the most uniform distribution of ink of the 60 deg hexagonal engraving became the norm in flexo printing.” (Lee, 2020)
There are some disadvantages to using a 60-degree anilox pattern, however. The layout of the closed cells can trap air in the cells. This creates defects such as foaming and uneven ink displacement across the face of the substrate. At high speeds, this can also result into some additional problems as well. Leading to clogged cells, uneven ink placement, and even dried ink residue that can hinder the true depth of the anilox cells. All these issues can be prevented by introducing a different cell structure, such as an elongated cell at a 70-72-degree angle.
As the geometry of the acting laser beam pulse is round and has a Gaussian energy distribution, the question of how the hexagonal cell structure is generated remains. As described earlier, the re-melting of the ceramic surface is a phenomenon of engraving ceramics. The cells will be generated from circumference line to circumference line. The corona of a newly engraved cell will contact three cells from the previous circumference line. (Bower, 2020)
The cells structures are typically one of five types: Trihelical, Pyramid, Quadrangular, Hexagonal or Hexagonal Channel Screen. A Trihelical screen is a line engraved at a 45-degree angle. These are primarily used in coating applications of viscous fluids. A Pyramid cell essentially an inverted pyramid. This engraving is very commonly used in the industry. They are typically used in metered roll systems that do not require a doctor blade. The ink transferred is a vital function in the printing process. A quad engraving is very similar to a pyramid engraving, it’s just cut short. This engraving type most commonly appears with a doctor blade system. Finally, we have the hexagonal cell. Hexagonal cells have superb release qualities and can be used in both chrome and ceramic engravings. Each cell is linked together be a shallow channel. Due to the fine structure, it can be utilized with a variety of inks, adhesives, etc. Hexagonal cells typically hold more ink than a quad engraved pattern and generate a more even and predictable flow throughout the printing process.
Bower, M. (2020, Feb 17). https://www.flexography.org/. Retrieved from FTA Flexography Corporate Website : https://www.flexography.org/industry-news/anilox-selection-ink-strength-drying-curing/
Foy, D. (2008, July 22). https://www.labelandnarrowweb.com/. Retrieved from Label and Narrow Web : https://www.labelandnarrowweb.com/issues/2008-07/view_features/anilox-roll-specifications/
Lee, D. (2020, Feb 7). Flexo Global. Retrieved from https://www.flexoglobal.com/blog-articles/2018/focuslabelmachinery-01-choosing-the-right-anilox-for-each-label-printing.application.html