Understanding Common Flexo Print Defects
The world of flexographic printing continues to evolve with new, innovative processes and systems that improve the quality of products being printed, and expand the possibilities of what converters are able to offer their customers. But even with these improvements in technologies and efficiencies, converters still face challenges that can affect the quality and the consistency of print jobs. Here are some of the most common flexo print defects that printers encounter.
Bleeding occurs when an ink that has already been applied bleeds into a subsequent ink or coating this is applied. Also known as smearing, bleeding is typically caused by the initial ink drying too slowly, and can be resolved by reducing the ink’s viscosity or by using a faster solvent.
Clients demand consistency, so any variations in color within a single press run creates an obvious issue. Color variations can result from differences in batches of ink or ink from multiple vendors. A dirty or plugged anilox roll can also result in color variation due to inconsistent ink transfer to the printing plate.
There can be multiple reasons why too much ink is being used, ranging from the wrong anilox roller to incorrect ink viscosity or ink color. It is always a best practice to test your print job to ensure that the proper amount of ink is being transferred, and to make any needed adjustments before running the full job.
Ghosting occurs when part or all of the image is being duplicated onto the substrate. While this can sometimes be an issue with the ink or anilox being used, the most common cause of ghosting is press speed. Try slowing down your press to resolve this issue.
Mottling is the appearance of uneven spots or speckles within a print run, and can be caused by overly thin ink, a dirty printing plate surface, or inconsistencies in plate pressure.
Striations are thin lines of excess ink, or conversely lines with no ink at all, and are typically caused by incorrect anilox pressure, dirty or defective plates, or improper plate mounting and installation.
Pinholing, generally the result of contaminated ink or film surface, is when the doesn’t lay down complete on the substrate, leaving tiny areas unprinted. Typically a thorough cleaning of all surfaces and ink chambers will resolve this issue.
Dirty printing refers to spots, hickeys, speckles on the substrate and can be caused by different situations. Some of the most common would be foreign debris trapped in the ink chamber, or the printing plate not thoroughly cleaned or wiped.
Flexo print defects can result in press downtime, which means lost productivity, lost time, and lost revenue. Regular inspection, cleaning and maintenance of all equipment helps reduce incidences of print defects so that you can continually operate as efficiently and profitably as possible.