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FLEXO Magazine : March 2011
Technologies & Techniques deposit efficiency. In printing screens you may lack proper plate dot support. Streamline the inventory by removing worn anilox rolls and then by setting aside any considered obsolete. What remains will be your viable inventory. Keep in mind that every anilox roll has a single volume, not multiple volumes. What you put in is what you get out. Don’t be confused by claims that anilox rolls may be manipulated and transfer different film thicknesses with one volume. The only way to get different percentages in solids in the dry ink film thickness is to change viscosity or volume drastically, which takes the ink completely out of optimization. Once you have optimized ink release, you will have to maintain consistency in ink delivery. You can keep the volume cur- rent and forge an ability to guarantee it by inspection: The ability to examine anilox rolls and verify cell conditions of cleanliness and wear at the microscopic level is crucial. There are a couple of methods for doing so, including the aforementioned periodic audits over time and visual/scope inspection. Audits give you a long-term view of the inventory, but for frequent checks, it is best to use a microscope, preferably one that is illuminated through the viewing area because side shadows can make discernment difficult. You can purchase microscopes that measure volume and provide results in the same fashion as the anilox roll supplier. But my advice is to start simple, then determine if you need more information to make the proper decisions on anilox roll condition, before going to press. Table 2. Anilox Inventory A Target: 800 2.2, need four aniloxes (3) 800 2.2 BCM Good for process (1) 500 2.2 BCM Different deposit efficiency, less dot support Anilox Inventory B Target: 800 2.2, need four aniloxes (2) 900 2.2 BCM Workable in most situations (2) 800 2.2 BCM Good for process Anilox Inventory C Target: 800 2.2, need four aniloxes (2) 800 1.8 BCM Too weak, struggle to get color (2) 700 2.5 BCM Too strong, wasted ink thickness after extension PeRIODIC MaINTeNaNCe Once the inspection is complete, you will be ready to examine the anilox roll cleaning process. Anilox cleaning can be the greatest asset to optimized ink films. First-hand experi- ence as an ink technician has shown me how much better I am at color matching using clean, quality anilox rolls instead of dirty, plugged anilox rolls of unknown volume. Strongly consider whether your anilox roll cleaning methods are current, fast and effective. Inks change and some- times the cleaners you previously used will no longer work as well to emulsify and remove dried ink. Telltale signs of poor cleaner performance are print shops with five or more cleaners. If you don’t have different ink systems, then you shouldn’t need more than two types of cleaner to get the job done. All that is required in a liquid cleaner is something that emulsifies the dried ink without attacking the metal base of the anilox roll. Do some field testing that includes before-and-after examination of the cells. If there are still cells full of dried ink after the cleaner has had an opportunity to emulsify it, then the cleaner does not work well enough for your application. Options for the secondary cleaning process include mechanical blasting, chemical bath with pressure rinse or chemical bath with ultrasonic. Any one of these systems needs periodic mainte- nance. Broken cells or pitting or missing cell walls indicate that the cleaning unit is no longer functioning properly. Minimizing the amount of wasted ink and substrate produced during color matching is a sure way to improve the bottom line. If you struggle to match col- ors and achieve print quality, consider optimizing ink release from the anilox rolls. A scientific approach will greatly stabilize the moving target of color. Re- member, it is the difficulty of achieving color that creates the most waste during setup. Follow the procedures suggested in this article to rein in variables and control results. Specifically: • Use a banded roll. Borrow a banded roll from your anilox roll supplier, if necessary; or, if you have particular targets, have one made to specification. • There is no greater predictor of repeatability than getting the right volume and cell count. Conduct an audit to determine if the existing inventory meets your new specifi- cations. • Once the inventory meets your needs, maintain it properly. Pinpointing issues and resolving them quickly may be daunting at first, but the development process of banded roll/ inventory adjustment/anilox roll main- tenance does not take very long, so do not hesitate to get on the path. Once achieved, optimization of ink release will continue to provide benefits via re- duced waste. It is well worth the effort. n About the Author: Sean Teufler proudly serves the central United States as a technical graphics advisor for Harper Graphic Solutions, a division of Harper Corporation of America. He is currently leading the Flexo Quality Consortium project on Narrow Web UV Ink Spitting. www.flexography.org march 2011 FLeXO 43 www.flexography.org march 2011 FLeXO 43 TAKE CONTROL Control your roll quality, speed, workflow and bottom line. Rotoflex Genesis - the newest, most advanced control system in the industry - gives you more control. Exclusive to Rotoflex inspection/rewind machines, Genesis guarantees fast, accurate fault recognition and placement, includes 100% matrix and missing label detection, and simplifies set-up and calibration. Best of all it lets you take control of your profits. www.rotoflex.com FLX_March11.indd 43 3/18/11 1:33 PM