by clicking the arrows at the side of the page, or by using the toolbar.
by clicking anywhere on the page.
by dragging the page around when zoomed in.
by clicking anywhere on the page when zoomed in.
web sites or send emails by clicking on hyperlinks.
Email this page to a friend
Search this issue
Index - jump to page or section
Archive - view past issues
FLEXO Magazine : January 2012
As a result of these issues, production waste can increase and productivity can drop to the point of losing money on a job. And yet when the root cause is discovered to be dirty ink, it becomes obvious that it is largely and easily avoidable. There are two instances where size does matter: First, the size of debris circulating in the ink, and second, the size of the in-line ink filters being used in the pressroom. CONGLOMERATING INK For years ink companies have been telling printers of the importance of filtering ink on press. The reason being, even though hard pigment and resin particles are ground to ±10 microns (μ) when ink is first made, they often conglomerate when in circulation and suspension. During a run, particles can grow to be 10x to 20x bigger and become super hard particulate at 200μ. And these particles are non-magnetic. At the same time, other debris finds its way into the mix if the ink is exposed to press atmosphere. It’s important to know that any particulate greater than 50μ can cause problems and any particulate greater than 100μ will cause problems. Particles this large cannot pass beneath the blade. Instead, they collect behind the blade causing blade edge damage or imbed in the anilox cell, reducing the cell’s capacity to carry ink causing light streaks to show up. These super-sized particulates can also damage anilox cell walls causing darker streaks. It has been proven that this type of debris easily migrates between the anilox and end-seal, accelerating leaking and premature seal failure. WORK-OFF INK Another major contributing source of dirty ink is the re-use of unfiltered or under-filtered ink. Most printers save ink left at the end of a job for use on future jobs. Unfortunately, the introduction of compromised ink to fresh ink triggers the same problems from the outset rather than gradually. But, how do printers using in-line filters still suffer from defects, press stops and damage? Once again — size matters. To be effective, a filter must remove all hard debris greater than 50μ. Because they are physically small, today ’s most commonly used filter vessels would quickly plug if a 50μ filter were inserted. Let us first consider the two most common filters currently in use: Y-Strain Filter Vessels—It’s the most commonly used and “ e c onomical” filter vessel in the industry. About the size of a soda can, it contains a small stainless basket and usually in- corporates a rare earth magnet. It’s placed in-line with the hose returning ink to the print deck. Several versions are marketed by a number of reputable indus- try suppliers. They effectively remove particulate ranging upward from 400μ. Canister Filter Vessels—Sometimes referred to as torpedo filters, tend to be larger than the Y-strain type filters with volume capacities of ± one quart or one liter. They have either stainless baskets or a wire mesh basket and also incorporate a magnet. Most of these filters are designed to also remove particulate over 400μ. VALUE OF FILTERS It’s important to under- stand that compared to an inexpensive throwaway filter bag, ridged permanent filters such as stainless bas- kets or wire mesh baskets are limited in their ability to filter fine particulate – to a level where they don’t cause problems. The mesh rating of these baskets does not directly correlate to microns. The most effective filter materials are made from non-woven fiber and are rated by the micron size of the particulate they remove. Filter vessels using these dis- posable bags need to be of a large enough capacity to allow for long runs without stopping the flow of ink. THE IDEAL FILTER VESSEL Ink, free of particulate greater than 50μ, is essential to a successful run. So, FLXON set out to make a filter that can do the job without getting in the way of the operator. After all, the filter has to be fine enough to filter down to 50μ while big enough to provide enough surface area to allow it to flow without clogging or restricting. After years of development, the ideal filter and vessel is now available for use in press- rooms everywhere. The G2 QUBETM 3.0 is the only filter we know of that can easily and consistently remove problem causing particles and debris from all inks and coatings. www.flexography.org january 2012 FLEXO 27 y-Strain Filter vessel Torpedo or canister filter Back pressure gauge