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FLEXO Magazine : October 2013
was a big problem because some pressrooms were run with minimum personnel. Today’s sleeves are back savers and time savers for most operations. Not many operators in the printing industry were able to lift a solid steel cylinder without developing spinal issues or needing a hoist system. By comparison, moving a sleeve in and out of a mounter is easily done—safely—by a single person. Just like a press station, mounters have a sta- tionary mandrel on which one person can easily load sleeves. In the past with older printing presses, buying steel cylin- ders for every size repeat print job was the only option. Most printers, due to storage and cost concerns, would opt not to buy any spare cylinders of the same size. The person doing the scheduling had to take this into account, because of the poten- tial downtime incurred while waiting for a job to be mounted. While today’s sleeves are still a sizable investment, they are cheaper than a steel base, especially if a printer can utilize a thin-walled printing sleeve. This means a converter can afford a larger inventory of sleeves. No longer are presses left idling, waiting on same-size cylinders for the next job to be mounted. eArLY ProbLeMs & soLutions Much like smartphones have done to communication today, the newest printing sleeves have revolutionized the flexo industry. And much like cellphones of yesterday, when they were first introduced, printing sleeve technology had a lot of refining to do. When sleeves first started making their footprint in flexo- graphic printing, I remember lots of trial and error. First, we did not have a gearless press and were sleeving steel cylin- ders outside of the press and then transferring them to press stations. Old steel cylinders were cut back for the thicker .105-in.-thick plate and with thinner plates we had to use build up to continue their use. Even though cumbersome, sleeving steel cylinders was a necessity due to plate technology and the fact that a lot of converters were switching from 0.105-in. thick plates to 0.065-in. plates. We had many different thicknesses of sleeves and also had bridge sleeves (repeat builders), which cut our floor space for storing steel cylinders. Print sleeves could be stored tighter together and didn’t require big heavy metal steel racks and hoists. Nevertheless, we still got a good workout sleeving cylinders and prepping them for the press. One of the biggest mistakes was to push a sleeve beyond the air holes on a steel cylinder or bridge sleeve that had no stops on the end. When this occurred, we had to use our ingenuity to try and get them off without causing any damage to the sleeve. cutting sLeeves Another initial obstacle to proper sleeve use, which we still see today, is a lack of proper training. One example is the use of a razor blade to trim back mounting tape. Cutting sleeves with razor blades will cause print defects and weaken their rigidity and stability. Using a Stanley knife or razor blade on a sleeve is not recommended, but in the real world sometimes there is no other option. In this case, it all comes down to train- ing how and what to use to trim mounting tape or plate edges. If possible, look at a sleeve supplier that offers a mounting tape cutline on sleeves. Sleeves cannot be sanded down for razor blade cuts like a steel cylinder can. This will end up changing the Total Indicated Runout (TIR) and diameter toler- ances. Using a pre-made cut line on a print sleeve will help make sleeve inventory last longer and maintain print quality. KeePing cLeAn Residue or ink buildup on sleeve ends is another common issue. Inks and solvents can migrate through a sleeve’s com- position and start to weaken the edges. A dirty sleeve will be a lot more difficult to put on and take off a mandrel. Of course, this increases setup time and that’s exactly why it’s imperative that any debris gets cleaned off. Sleeves are very easy to clean. Implement cleaning pro- cedures and you will see a long life and performance from sleeves. This includes any tooling the sleeve comes in contact with—the mandrel and splash guards, for example. Press deck mandrels need to be cleaned and properly maintained to consistently accept the mounting of the sleeve; periodical checks of the mandrels should be done to ensure this. Make sure air holes get cleaned and PSI is set to the OEM’s recom- mended settings. Often, splash guards will become misaligned or ink will build up on them and when this happens, both the plate and anilox sleeve can be damaged. Ensure any other guards near or next to a sleeve never come in contact with it, as this can cause irreparable damage. When it comes to cleaning a sleeve through a machine, it is imperative that the ends of sleeves get sealed off to avoid any cleaner migrating through a layer. This is especially critical when it comes to anilox sleeves—these have an aluminum cladding and most clean- ing chemicals are caustic to aluminum. storAge, sPAce & setuP When a sleeve is going to be put away for storage, whether a plate is still mounted or not, it is recommended that it is stored standing on its end (vertically). When it is stored hori- zontally, suspended by a pipe from the inside, the positioning can eventually cause the sleeve to lose its round shape. This is especially critical for an anilox sleeve, due to the inner expansion layer that can be flattened over time. When unloading a sleeve from a horizontal position, it is also very common for the sleeve to drop and collide with those stored below it. These collisions will typically cause dings on a ceramic anilox face and lead to future corrosion or scoring issues. Because sleeves are so lightweight and easy to maneu- ver, this is another potential issue in the pressroom. Often sleeves get end damage from being placed down too hard on concrete floors or not having a rubber mat on their stor- age rack. Sleeves are a lot more susceptible to getting dam- aged due to their being lightweight and as such, they cannot be treated as steel cylinders. Unlike steel cylinders, sleeves cannot be repaired; only replaced. One step that I always see is the rocking of sleeves up and down or side-to-side to get them started on a mandrel. If this becomes an issue, check the cleanliness of the sleeve bore and the mandrel. When mounting a sleeve onto a mandrel, line them up and make sure the air is properly set to OEM specification. Push and twist the sleeve to get through and over the mandrel air holes. Rocking the sleeve to get it started The Most Accurate in The World FTA’s2013FallConferenceandTabletopExhibit#143 Forget Tape Use Twinlock Polymount US LLC • 126 West Bledsoe Road • Newnan, GA 30265 • T: 770 683 2629 ww w.polymount-int.com Sales offices in: France • Germany • Hong Kong • Latin America • Sweden • United Kingdom Production and sales in: Czech Republic • United States 102 FLeXo OCTOBER 2013 www.flexography.org www.flexography.org OCTOBER 2013 FLeXo 103 Deep cut lines throughout the entire face of a plate sleeve will affect print quality and render the sleeve useless.