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FLEXO Magazine : June 2011
Technologies & Techniques If you are having difficulty getting scoring under control, isolate an ink station to see where it is capturing contamina- tion. Examine every part of the press that makes contact with the ink, including ink pumps, hoses, connectors and stirrers. Try using a large handheld rare-earth magnet to spot check areas suspected of contamination. Using rare-earth magnets in tandem with ink filters with 40-60 mesh screens will trap and contain metal fragments. However, these magnets need regularly scheduled cleaning to ensure they will hold onto the fragments and not let them back into the system. (See figures 9, 10 and 11.) To determine whether using a rare-earth magnet will reduce scoring on your particular press, see sidebar, “Will Magnets Help?”. Remember that there will be residual debris after you cor- rect what caused the scoring, so it is necessary to sanitize and purge the ink system. If the problem was massive, you may still see a score line here and there. This is the time to clean—and even back-flush—your inking system to get rid of all contamination. n About the Author: Bill Poulson is the northeast technical advisor for Harper Cororation of America. He has been with Harper for the past 12 years as a technical advisor. Poulson has more than 30 years of experience, including press opera- tion and pressroom management. Figure 9: Metal fragments clinging to magnet. Figure 10: Magnet-cleaning in progress. Figure 11: Clean magnet. 72 FLeXO June 2011 www.flexography.org Will Magnets Help? The following steps will help you determine whether using a rare-earth magnet will reduce scoring: 1. Select a roll for evaluation. A new roll with no scor- ing is best. 2. Purge the entire ink train, including the ink cham- ber, ink pumps, hoses, hose connectors, stirrers and anything else that comes into contact with the ink as the ink pumps through the chamber. Clean out all crevices in the ink chamber. 3. Install a canister filter and fit it with a strong, large, rare-earth magnet on the in-feed line of a pump. The magnet, filter and selected anilox then be- come inseparable: The key is to isolate the offend- ing particles, so when you use the chosen anilox, you will also use the magnet on the ink supply line. If it is not possible to combine a canister filter and magnet, a rare-earth, large-tank magnet posi- tioned under the return line discharge will work. If you do not pump your ink, try using a magnet in the fountain. Secure the magnet in a thin-walled plastic bag and set it in the tray. (The plastic bag will make clean-up easier.) If you use a tray liner, another option is to place the magnet underneath to keep it clean. 4. Review the issues concerning blade pressure and overhanging blade ends. Explain the reason for the test to supervisors and press crews. 5. Run the press. 6. Observe the roll for scoring and inspect the kinds of metal pieces collected on the magnet for a des- ignated period of time. 7. Service the filter and magnet every day. This will allow you to see the amount of contamination cap- tured by the magnet and whether the magnet and filter are effective.
Sustainable Spring 2011