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FLEXO Magazine : February 2012
FTA TODAY UV Ink Spitting FQC Team Isolates Variables, IDs Factors Increasing Likelihood of Phenomenon By Sean Teufler UV ink spitting, nemesis for many a narrow web printer, has been an elusive quarry for quite some time. It is a rare but certainly troublesome aspect of printing flexo. The process of inking an anilox roll, shearing off excess ink via the use of a doctor blade and transferring a consistent ink film is the basis of today ’s flexographic printing. Unfortunate- ly, there are times when this process does not behave as one would expect. A recurring challenge for flexographic printers is the UV ink spitting phenomenon. Spitting can be commonly described as the escape of the ink from the confines of the blade/anilox contact point. Once past the blade, the ink builds up on the opposite side of the blade. Accumulation of ink releases and creates print flaws, typically in the form of a randomly-placed teardrop shape. The frequency of UV ink spitting is often so small for a converter that the incidents tend to be treated as isolated oc- currences. This method tends to find individual cures but no overall understanding of the cause. Combating the spitting phenomenon by a converter typi- cally consists of trying any number of solutions, including changing inks, blades, anilox rolls and even manipulating any or all of the three, moving to different print stations, etc. Unfor- tunately this does not allow for the isolation of the causes, and every day brings yet another solution to make the problem go away. The enigma of spitting persists in the endless need for so many solutions. The Flexo Quality Consortium (FQC) assembled a team of experts to explore the problem in hopes of coming up with a better approach. Consisting of representatives from the fields of converting, doctor blade, ink, anilox, measuring equipment, press manufacturers, statistics and educational institutions, the team was very well-balanced and contributed mightily to the conclusions. By charter, the goal was to determine possible preventative setup measures and isolate variables to the process. FQC analysts do not think there is anything inherently wrong with anilox rolls, inks, blades or press equipment, so the question FQC—FOCUS & FINDINGS • FQC team chartered to explore ink-spitting phe- nomenon, isolate variables and determine possible preventative setup measures • There is no universal cure for UV spitting • Discovery of causes linked to measurements and controls • Use of a matrix evaluation isolates spitting to more identifiable root causes • A fingerprint is the prescribed method to understand the nuances of any particular situation Photo courtesy of Mark Andy. 62 FLEXO FeBruArY 2012 www.flexography.org