flexo banding
Hi all,
There is no section for flexography, and even if the issue i'm dealing with is not directly related to color management, I'd post it here seeking either some ideas on how to deal with the problem, or a suggestion for another forum to ask a question.
The application is wide format flexo, printing on corrugated boards (B, C, E flute). We got two 1628 martins and one 924 martin, with anilox rolls of 300-360 lpis. All units are mobile, with the exception of the feed unit.
Starting at 8 inches of the lead edge of every box, we have alternate areas of heavy and light coverage. The circumference from the chamber blade to the nip between the anilox roll and the plate cylinder is also 8 inches, so I know that the print comes out smooth over that area because nothing is causing the chamber or chamber blade to bounce till then. After that, we are getting these banding stripes at a frequency related to the speed of the press. The higher the speed, the less the severity of the stripes, and the greater the distance between them. The stripes end anywhere from 14 to 25 inches on the box, so it is not related with the revelations or total circumference of the anilox roll. By the way, this happens in all presses and all units.
We've tried pretty much everything we were able to think of, and even more. We have been able to alleviate the problem by using surfactants on the ink, or turning the underpack of the plate around, or adjusting the pressure, but the problem is still there... masked. We've measured the rotation frequency of the rolls for vibrations and we couldn't find a pattern that matches the banding frequency on the printed box. This would say that there is no mechanical problem. We printed sheets isolated from the delivery, so the gear of the delivery isn't causing this either. We've actually tried more stuff than I could recount...
I am about to give up and attribute this to the age of the equipment or demons. We've been having the same issues two years ago... even the frequency of the banding was identical, only not as severe.
Any ideas would be more than welcome!
-D
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