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FLEXO Magazine : March 2010
FLEXO MARCH 2010 www.flexography.org taking up space and lead to further waste. A proper construc- tion of ink process control includes the use of corrected and consistent ink formulas based on press, anilox volume and substrate. If you are spending time at press matching color then you may very well have an issue getting proper prepara- tion done before press. You can begin to organize the functionality of the ink room by recording exact formulations and using weighing equip- ment that allows for precise measurement. Compare ink production batches to verified wet samples drawn from prior runs. If there is a discrepancy with fresh ink and saved wet samples, you either have an error in the weighing process, a problem of strength with a base ink and/or the wet sample has settled and needs stirring. Any additions made at press to adjust color should be recorded so the formula can be adjusted for the next run. Make sure not to assume from the beginning that the scale system you use or your formulas are calibrated. You will be starting from "square one" in this endeavor. Communication to the ink room of the "customers" prior and current needs for color is essential to a successful print run. Color is the most obvious difference when comparing your product, so make sure to have a good understanding of customer expectations by getting a valid print sample. Customers may have color tolerances, so be sure you have the equipment to measure spectral data, density, dot gain, trap and so on. Evaluate your print capabilities before taking any job to press. The biggest ally in the ink room is a drawdown tool or automated proofing device. Develop your proofing system to create a direct correlation to the press. Make your samples relevant to the customer by printing it. Remember a well- managed ink room thrives or fails on the quality of information regardless of the talent your ink personnel have in overcom- ing obstacles. Make their jobs easier and more effective by giving them the workflow and equipment to do their job. PLATE PROCESSING Once a fingerprint has been conducted, the prepress department will use the results to define compensation curves and colorimetric information. The concern now is making sure the plates are made consistently. Workflow checks and equipment should be implemented for measuring plate hard- ness (Shore A), plate relief and floor thickness. Technical in- formation will come from the plate suppliers and specific data from thickness should come from measuring the fingerprint plates. Conduct exposure tests on a regular basis and use a micrometer to monitor floor and relief thickness. A further step of using a plate measuring device will allow you to check the images and dots themselves for consistency. Proper plate preparation must include a regular maintenance and upkeep program for any equipment used in processing. Lay the plates out on a light table to look for any abnormali- ties in image formation, such as voids and underdeveloped im- ages. In addition, check used plates for cracks. Ideally, plates are mounted before going to press. As such, the workflow will also have to include examination of plate cylinders for cleanli- ness, cuts on the surface, and gear wear. Additional details re- garding plate measurement and control can be found in FIRST 4.0, within Prepress section 17.9 as well as 21.5. Follow up at press on plate performance and always thoroughly examine returned plates if you plan to reuse them. Ideally, you want to keep a finger on the pulse of your platemaking workflow to capture any changes in quality, so be sure to have the verifica- tion equipment available and functional. THE HEART OF THE MATTER As stated many times before, change the volume and you ultimately change the outcome of the job, regardless of what has been said. Yes, we have all heard the one roll scenario will do the trick, but nobody has yet to see that or prove that in a live circumstance or scenario. If an individual can show me that one roll will do all, I will go ahead and retire at 39 and be happy that I witnessed it. The short and sweet of it is similar to color being king. If you vary the thickness (volume) of the ink, regardless of how transparent it is, the color and or image is ultimately affected. With that said, we need to be consistent with the amount of ink being applied to a "raised image" of the plate regardless of what material it is made on. Understanding the factors involved in the control of ink film and verification for consistency is essential to controlling color. All things being equal, when the ink room has color ap- proval and can communicate the volume needed to achieve a given color to the pressroom, we have obtained that next step in ensuring color accuracy. At this point we are relying on our press personnel to make the proper anilox decision. Anilox selection can be tedious; a 10-color press may have 20 anilox rolls to choose from. Get to know the details of your anilox inventory. Suppose the ink lab indicates on the shop order to use a 3.2bcm2 anilox. If you have six aniloxes at that volume, which should you choose? Typically, printers do not have the equipment necessary to confirm or deny that any anilox rolls will meet this requirement. We all have the ability to read journal ends or deadband areas for engraving details, but at that moment, what is the true volume of the roll? Thor- ough cleaning, basic observation and auditing by supplier or internally will give you a good handle on the true volumes of Ideally, plates are mounted before going to press. As such, the workflow will also have to include examination of plate cylinders for cleanliness, cuts on the surface, and gear wear. Press mechanics can be optimized.
Sustainable Winter 2010