We don’t like to speak in certainties when it comes to flexo printing defects. Any number of variables can cause any number of defects within your printed image.
Our list of the 12 most common flexo printing defects is compiled with that in mind. These variables yield uncertain results in some instances, while time-tested experience has proven certain realities to be true in most pressroom situations.
Such is the case for the defect known as feathering. In our comprehensive diagnostic guide (available for download below), we’ve listed feathering with one major cause: Pressure. That’s predominantly true, but other secondary causes can lay claim to this printing defect.
So let’s put on our thinking hats and start troubleshooting.
Flexo Printing Defect Analysis: The Root Cause of Feathering is Pressure
Feathering can be characterized as uneven edges around printing areas. Appropriately named, they look like the tiny, hair-like projections around the edges of a bird’s feather.
Most often, too much pressure between the print cylinder and substrate is causing ink to extend beyond the intended printing area. Or earlier in the process, too much pressure between the anilox and the print cylinder or too low a line count on the anilox can cause excess ink to transfer.
Then, once the ink contacts the substrate, increasing ink builds up around dots and increases the printing surface area. But once excess ink buildup becomes a problem, a host of secondary issues could begin amplifying your defects.
Dried Ink on the Image Carrier
Excess ink dries when it doesn’t transfer completely to the substrate. Problem is, it dries on your sleeve/cylinder/plate. Consider this like painting a room in your home. If too much ink accumulates and then dries in your roller, it’s going to limit your:
Back to flexographic printing, too much ink can cause feathering and other similar defects including:
You can remedy this with some routine cleaning and maintenance, simply enough.
Debris on the Substrate
Unless you’re printing in a vacuum (which you’re not) and it’s possible to perfectly clean your pressroom environment (which it’s not), dirt and debris will be a fact of life. It’s how you minimize this contamination that ultimately leads to quality printed images.
Industrialized pressrooms and all their working electrical components naturally generate static electricity, attracting microscopic dust particles to positively or negatively charged objects in the room. This means, just as naturally, they’ll collect on your press and thus your substrate.
An antistatic device would address this issue. And once again, routine cleaning and maintenance is another common-sense solution.
Ink Drying Too Quickly
As we’ve mentioned, ink drying on the image carrier will cause ink transfer issues that inhibit printing quality and efficiency. In that light, ink drying too quickly on the substrate can certainly lead to the uneven edges seen in feathering.
Flexo printers must balance printing speed with ink drying speed. You can slow down the drying process by adding a retarding agent and covering the ink trays.
What’s more, the proper use of solvents (in solvent-based ink) will impact everything from ink evaporation, pH level, and viscosity to this next potential feathering cause: Ink surface tension.
Ink Surface Tension Too High
Surface tension is the tendency of liquids in contact with air to form droplets, as if they’re surrounded by an elastic membrane under tension. (Think of this like water beads forming on a freshly waxed car.) It arises from liquids - like ink - being drawn together more strongly than they’re drawn to air.
Surface tension is measured in dynes/cm. In general, it can be too high, resulting in poor ink release from the image carrier. As solid objects, substrates have surface energy that liquids are attracted to. This is measured in joules/sq. meter. The surface energy of the substrate also may be too low, which can be treated to a higher level to accept more ink.
Troubleshooting Feathering: Analyze Pressure First and then Check Secondary Issues
Feathering: A defect so evil, so sinister, it makes you wish for gear marks. OK, so all joking aside, feathering can be a pain for many flexographic printers. As an initial troubleshooting solution, if possible, reduce your impression settings between your anilox and image carrier and then between your image carrier and substrate. If that doesn’t work, check the aforementioned secondary issues.
Good news! We’re always here to help with troubleshooting solutions. Call (888) 545-2270 to speak with a Luminite customer service representative. The free guide below offers a more comprehensive view on printing problems.