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FLEXO Magazine : May 2012
important to be mindful of the fact that there are two different tolerances: one out of the inkroom and another when it comes to print. For practical purposes, ∆e 1.5 is a good starting point for print. But I will address that later in this article. So far, so good: a consistent color coming out of your inkroom and nothing is coming out of the inkroom outside of the chosen ∆e 1.5 tolerance. The next step is time to check the vol- ume requirement. ANILOX VOLUME One might think it is simple to know what a volume requirement is. Many printers have been doing this for a long time and have a “good feel” for what is required. But, have the anilox roll volumes ever been measured? Can a 440-cell count volume of 5.0 be relied upon? Has a roll ever been dirty or plugged? Chances are it was never dirty or plugged. More likely, it was not the volume originally expected. The largest contributor to ink toning (thus variation) is not weak ink or a dirty or worn or plugged roll, but rather the fact that your anilox roll is too thin for the ink set. That volume five anilox roll may actually be a three or a four vol- ume. What if volume could be checked as easily as colors? The answer is: it is possible. There are measuring devices available that are relatively inexpen- sive. What kind of dollar number is reflected in a 20 to 40 percent decrease in ink toning? Most likely it is more then enough to justify the purchasing of a measurement device within a six-month period. It is imperative to check volume requirements against particular ink sets. To achieve this you need to con- duct a banded roll test. BANDED ROLL TEST [Author’s Note: It should be men- tioned that hue problems out of the inkroom are a big difficultly. This article is addressing tonal strength.] It is expected that an ink resource is blending color accurately enough to be within hue—again no more then ∆e 1.5 in any of the LabCH values. This is why you need to have a consistent draw- down to your standard. Results of a banded roll test, conduct- ed using inks that came out of the ink- room at ∆e 1.5 , can be found on page 60. They were put in press “as is”—they were not altered in anyway. Of course, the decks were dry before the inks were placed and the operators were careful not to contaminate the inks during setup. This test determines the required volume for a particular ink set that will have a proprietary pigment load from a supplier. Before getting started with a banded roll test, take a look at the volumes ordered versus the actual volumes delivered. The results can be surpris- ing. It is recommended to have a sales representative demonstrate an anilox roll measuring device at this time. The actual volume is not what is important. What is important is what volume is needed to achieve the desired toler- ance with ink set at ∆e 1.5 to the agreed standard. Chart 1 aims for a printing tolerance of ∆e 3.0 to standard but a tighter toler- www.flexography.org may 2012 FLEXO 59 Your finishing operators know this too. The new VLI delivers greater precision and speed of inspecting, slitting and rewinding. And that means quicker turnaround and perfectly finished rolls, every time. Speed and precision. www.rotoflex.com IT’S NOT ONLY THE SPEED OF THE STEEL,BUT THE PRECISION OF THE CUT AT THE CUTTING EDGE Do you make the cut? Find out at rotoflex.com/thecut RF_FlexoMag_4.5625x7.375.indd 1 4/16/12 4:29:48 PM