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FLEXO Magazine : July 2007
w w w . f l e x o g r a p h y . o r g J U LY 2 0 0 7 F L E X O 1 5 prOduct trEnd report Where Are We NoW? The result is that in-line flexo is growing. It’s making an impact in markets where only CI flexo and offset, as well as rotogravure and letterpress had been accepted. In-line flexo presses now print all types of unsupported film labels, wraps, sleeves and flexible packaging. The process continues to penetrate the paperboard packaging market (folding cartons, blister cards, paper cups). Flexible packaging producers see profit growth using in-line in short run production of stand-up pouches, candy wrappers and sachets. In-line converting such as die cutting and laminat- ing allows many of these products to be produced in a one step workflow. While web widths in machines used to print pressure sensitive labels are still generally less than 18 in., in-line printing machin- ery purchased for paperboard and unsupported film labels and packaging in recent years is typically 22 in. and 26 in. wide. The trend is to go wider yet; 32 in. will be common in flexible packag- ing. “Narrow web” isn’t narrow anymore. Risk of odor and taint from uncured photo initiators in UV inks makes the ability to print using water-based ink important for direct contact food packaging. Printing heavy laydowns of water- based opaque white ink on clear film created a very big drying challenge, but it is very desirable because cost is much less than with UV inks. With 10-in. long dryer tunnel designs of the past, 300 fpm was the maximum speed obtainable when printing on paper materials. To prevent material distortion with unsupported film air temperatures couldn’t be above 120 degrees. Run speeds were below 180 fpm. GettiNG the Speed Up Significant advances in press, ink, and drying technology now make it possible to reliably print at 1,000 fpm and more. Very high capacity dryers are mounted over large driven chill drums. Even very sensitive unsupported polypropylene and polyethylene materials are printed with UV, water base and solvent base inks with no loss of run speed. Keeping the web cool prevents web distortion. Web tension remains very stable. Innovations in impinged dryer nozzle technology make this happen economically. It is now possible to generate much higher air velocities (11,000 to 12,000 fpm) at the nozzle, which greatly improves drying effectiveness while also reducing air consump- tion by half compared to old impinged dryer designs. Combined with state-of-the-art heat recovery systems the energy efficiency more than doubled. FASter ChANGeoverS, LeSS WASte Fast machine changeovers are critical for efficient production of small orders. Innovative shuttle deck technology introduced in the 1990s allowed the operator to change plates, anilox and ink in machines of about 22 in. with the same ease that they could change a 10-in. machine with conventional design. By in- corporating light-weight sleeves for anilox and plates along with cantilevered mandrel technology that was first introduced for CI wide-web, in-line presses of 32 in. and wider change as fast and effortless as a 10-in. machine. Waste and makeready times are now cut by electronically sav- ing the print job’s settings in the machine computer for each job. This information is recalled the next time the order is produced. Among the most critical settings are web tension, plate cylinder register, dryer temperatures, repeat size, and print pressures. Alternative plate sleeve systems satisfy different performance and cost needs. Keeping sleeve wall thickness to a minimum is important in minimizing cost. Some printers have asked for quick change plate sleeve mandrels that can be easily removed and installed without having to use tools so they won’t experience the extra run-out tolerance issues which can result from bridge or build-up sleeves. Usually two or three different mandrel diam- eters cover the desired range of print repeats. Of course, many find that one mandrel size coupled with a few bridge sleeve sizes gives them the results they need. An innovative mandrel design eliminates a potentially trouble- some sleeve removal issue. When ink dries between the sleeve inner diameter and the mating mandrel surface, the sleeve can stick in place on the mandrel almost as if attached with a glue bond. Removal then becomes time consuming and difficult. By incorporating a powered sleeve removal mechanism, the bond is easily broken, and the sleeve readily slides off. State-of-the-art electronics and servo drive technology such as electronic line shaft play an important part in achieving higher quality and dramatically reducing waste. Because gears and other mechanical drive components have been eliminated, register variation and barring are greatly reduced. Precise print adjust- ments are made with specially programmed servo motor systems. Plates come into correct register in approximately one press length, automatically reducing waste. By using a printed mark for automatic registration control, the register scanner located at each station can see the printed regis- ter mark and make a correction right away. No longer do changes Various dryer design improvements have allowed in-line systems
Golden Anniversary Commemorative Journal