Open cell, closed cell, elongated, bcm, lpi, hexagonal, trihelical, channeled engravings—It all comes down to how you specify an anilox roll or sleeve.
Speed may be an issue—spitting or misting, too. Wear is an ever-present concern, as is application of specialized enhancements. Calibration is critical. Opacity targets must be met and results measured to assure quality. Cell volume impacts laydown and requires continual inspection. Audits offer vital assists.
Experts sometimes stand in unison when voicing recommendations on anilox specification and care; at other times they segue to different approaches that may target exact outcomes. Solutions are specific to the firms they represent.
FORUM 2022 highlighted similarities and differences between most all available technologies by showcasing “The Great Anilox Roll Debate 2022.” On the following pages, FLEXO Magazine encapsulates everything that happened on stage and just a little bit more. Questions are the same—thanks to Sean Teufler, Miraclon Corp and Peter Mulheran, Eaglewood Technologies for overseeing their development and moderating the session. Panelists are the same as well. Namely:
- John Batistatos, printing market manager, Aalberts Surface Technologies
- Nick Harvey, technical director, Apex International
- Steve Woodard, VP of corporate services, ARC International
- Bill Poulson, global technical solutions manager, Harper Corporation of America
- Brent Middleton, technical sales account manager, Interflex Laser Engraving
- John Rastetter, VP of sales and marketing, Pamarco
- Stuart Beeson, global distribution manager, Sandon Global
What advantages does an open-cell engraving have over a closed-cell engraving?
BATISTATOS: It depends on the type of open-cell engraving: On our Ultra Z channeled, you can achieve higher lpi/bcm combinations for better color, cleaner print and better combination abilities. The Ultra X, often called the “pins up” technology, is a complete open engraving where we engrave posts on the surface of the rolls instead of cells. This allows for optimal release and laydown of highly viscous materials, such as adhesives and specialty inks—whites and varnishes—that are free of pinholing and orange peel effects.
HARVEY: First, ask yourself, “What is an open cell?” An engraving that has a very light polish is open? An engraving like Channelox, created by over-engraving the walls to create a channel? An engraving that has been created with too much energy/power to break and lower a section of cell walls? GTT, an engraving that has a fixed/optimum opening-to-depth ratio that guarantees against spitting?
Open cells can be used for two functions:
- To allow a thick and viscous UV ink or coating to flow more freely from cell to cell. This can reduce the risk of ink spitting, though is no guarantee, as ink spitting is not only related to the anilox
- Open cells by nature have fewer cell walls on the top surface of the anilox, meaning that additional volume is possible with less depth, compared to a closed cell. This does not guarantee better ink transfer and can be inconsistent
It is important to note that there are many open-cell structures in the market. All have “broken walls” and not clear channels, meaning the walls are distorted. This will result in a random height of the broken cell walls within the engraving.
It’s critical to understand that the many versions of open cells will all perform differently and it is important that you do not confuse open cells with open-channel engravings.
WOODARD: Obviously, open-cell engravings offer better release. This is especially advantageous when transferring highly viscous inks or coatings. In addition, open-cell engravings are easier to clean and less prone to plug. One example is a customer of ours that uses a 100 trihelical engraving to coat lithium battery membranes effectively. Some other customers prefer a 30-degree hourglass channel cell.
POULSON: Open cell has a slightly better transfer percentage rate. This allows for ink to release easier and there are no cell walls restricting transfer. It will also introduce less air into the application. Open cell will recycle inks and coatings more efficiently. This minimizes any cell plugging and makes cleanup much easier; plus, it can support UV inks better.
MIDDLETON: Open-cell design works well for coating applications to fill and release more efficiently than a standard closed-cell engraving. It can also result in fewer plugged cells with less frequent cleanings. Typically, we see the open-cell design being used as an alternative for applications, such as whites, various OPV and printing—depending on the substrates.
RASTETTER: When confronted with the choice between two types of engravings, there is a need for thorough understanding of each category in order to make the best selection.
By providing a higher degree of ink/coating transfer, an open-cell engraving is capable of working with much more viscous fluids than a closed cell. The open-cell category includes channeled or true open-cell engravings. Channeled indicates a partial cell that controls the ink flow by using open sections of the cell wall. A true open cell, on the other hand, has no restriction of ink flow.
Pamarco’s channeled cell is EZFlo, a 30-degree engraving, and our true open cell is trihelical or pins up. Open-cell engravings, however, whether they be channeled or a true open cell, do not have the ink control capability needed to print high-resolution quality graphics.
BEESON: Open-cell engravings have distinct advantages over the standard 60-degree engraving: superior ink transfer, due to oxygen not being allowed to be trapped within the cell, causing turbulence and micro foaming. Another advantage, for water-based or solvent high-speed presses, is keeping the printing plate lubricated. A 60-degree closed-cell engraving cannot do this, due to micro foaming within the cell. The semi-channeled technology of the Xpro by Sandon Global allows for a constant and controlled stream of ink to the plate. Still another benefit (for UV flexography shops) is the way an open cell can stop ink spitting. Due to the channeled technology of Fluid HEX and Fluid UV by Sandon Global, hydraulic pressure isn’t allowed to build within the cell and ink is dispersed to the next cell. So, without the pressure, a doctor blade isn’t placed under extreme conditions and ink spitting is reduced.
Open and semi-channeled cells are less prone to scoring, due to the cell geometry, channels and additional micro finishing that help support the blade. Cleaning is much easier. Since ink can move freely, a cleaning solution, or laser, can get line of sight in the cells.