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FLEXO Magazine : July 2008
TECHNOLOGIES & TECHNIQUES suppose our goal is to have anticipated anilox volume at press, with the benefit to your ink preparation being ink strength opti- mized to a press-ready condition. For example, if an ink is going to run with an 800 line-screen 3.Sbcm roll, the color strength (ink properties withstanding) can be made pre-proofed in a lab or ink room environment. When the finished and quality-controlled ink goes to press and the anilox conditions have been met, a good color match will result . . . every time. Press-ready ink greatly reduces toning time and is part of a re- alistic scenario where proper pre-planning of tooling installation, deck and anilox selection is used. To the contrary, if consideration is not given to outline press needs, (Le. the right equipment is not available because the proper anilox is being used in another sta- tion, the anilox is not clean, etc.) the ink pre-matching process is corrupted and is left more to chance and to the skill of the color matcher instead of method. If this is often the case in your facil- ity, understand that other compensation factors become common practice. These practices include ink strength hedging and mul- tiple formulations, which make it difficult to shorten press setups. For example, in anticipation of an ink strength issue, press-ready inks will be hedged to the stronger side, so press operators can achieve color on a weak or plugged anilox. This may work once in a while to give it some merit, but the percentage of success is low and creates unwanted development of ink inventories to meet multiple formula standards for the same color. Unfortunately, the common occurrence is ink maxed in strength and a compromise of ink properties result from at- tempts to boost the printed color. For example, where a color was matched to the same 800 line-screen/3.Sbcm anilox and due to improper cleaning procedures the roll only delivers 3.0bcm, the ink supplier may have difficulty adjusting the ink dramatically enough to achieve color strength and maintain other important properties, such as adhesion to the substrate. In other words, the strength reduction in a 14-percent loss in volume is nearly impossible to overcome on a full strength color. The net result of any press-side color matching issues should concern any cost and time-con- scious printing company. Wasted mate- rial, longer make-ready time, increased ink inventory dollars and less produc- tion can all result from marginal anilox preparation and misunderstanding of the basics. those equipped with auto wash units in addition to those using a manual flushing method through a pump system are considered on-press. The second classification of anilox roll cleaning is referred to as off-press. This method uses a stand-alone piece of equip- ment designed specifically for cleaning the cells of anilox rolls. Off-press cleaning includes ultrasonic, chemical soak, water jet, baking soda and poly bead media blasting. No matter what type of cleaning is used, the end result must be clean cells with no damage to the roll. Keep in mind the systems and methods used to clean aniloxs must also be maintained and used correctly for the desired effects. On-Press Cleaning. This occurs when a cleaning agent is intro- duced to the cell surface of an anilox roll after the ink has been removed or flushed from the ink pan or the enclosed chamber. Once the ink has been secured, the anilox must have a cleaner on its surface working to remove all residual ink, or plugging will occur. If the cleaning agent is effective in removing the excess ink, it should break down/emulsify the ink residue. This result is accelerated when used in conjunction with a stainless steel brush on ceramic anilox rolls. It is important to note that some cleaning chemicals are ex- ceedingly harsh and extreme pH values (above 11.8 or below 6.5) can cause corrosion of the anilox base. Make sure you test the chemicals and check their MSDS for ease of use, effectiveness, and safety to the anilox as well as others. No particular anilox cleaner works for every application. Claims made regarding cleaning power are only relevant if it meets your situation. Many cleaner types boast of complete effectiveness but actually do little to remove the ink and wind up damaging the anilox. Work with your ink and anilox suppliers to come up with the right combination of cleaners that are safe and effective for anilox rolls and those using them. Primary advantages of on-press cleaning are: the desired roll remains in press, cleaning is done In a managed anilox inventory, proofing becomes a valuable tool. CLEAN I NG AN I LOX ROLLS In order to accomplish anilox prepara- tion, we need to analyze the cleaning methods. Let's concentrate on some common ways printers currently have their aniloxs cleaned, potential hazards, and suitability of use. There are primarily two classes of cleaning methods; on- press and off-press. On-press cleaning of ceramic aniloxs involves the utilization of chemicals and a stainless steel brush. In the instance of wide-web presses, www.flexography.org J U L Y 2008 - FLEXO
Flexo Sustainable Fall 2008