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FLEXO Magazine : January 2014
frequency of long run orders has decreased dramatically, while the number and frequency of many other types of or- ders have increased: • Private label • Innovation • Special event marketing • Low volume SKUs • End of life products The traditional packaging supply chain challenge has been to manage volume. The new challenge is to continue to manage volume, while at the same time managing shorter runs. Companies with an infrastructure tailored for volume typically have a difficult time handling shorter runs with flexibility and lower costs. This problem creates opportunities for companies that can more effectively manage the shorter runs, as well as produce the high volume orders profitably. Some companies are working to reengineer their businesses to better manage these shifts in order volume and frequency. MANUFACTURING ENVIRONMENT There appears to also be a shift, for many companies that went offshore several years ago, toward moving manufac- turing supplies closer to demand locations. The ability to meet their customers' demands for unique packages, rapid delivery and response times, as well as maintaining low inventories, has caused this return of manufacturing to the U.S. In an Accenture study, 61 percent of respondents said they were considering more closely matching supply location with demand location by on or near shoring manufacturing and supply. As offshoring of manufacturing and packaging shifts back to local supply chains, the cost for retooling locally and ROI becomes a major challenge in today's environment. Continu- ing structural changes in the packaging industry with consol- idation among converters and increased material costs has significantly added pressure on prices and margins. The cost of capital equipment and financing is an important consider- ation, coupled with shorter runs in today 's environment. SHORT RUN & MID WEB Over the years, a number of flexo press manufacturers have entered the market with a mid web central impression (CI) press, but these attempts failed to penetrate the market. Their approach was a low cost, lower speed press, based on the theory speed should not be an issue for short runs. This concept did not remain viable for the constantly changing market. High speed flexo has become a trend but has had its chal- lenges. Ink containment, slinging and ink misting together with proper ink release from anilox cells at higher speeds require special converter expertise. The wider and faster you go, the more plate and anilox sleeve accuracy becomes a problem, leading to critical print pressures and even bounce problems. Then there is the approach of a robotic press change that can pre store multiple jobs in a holding rack, ready for the next job change. This high speed press concept has met limited market acceptance, mainly with larger converters for longer runs which, as we have said, are decreasing each year. The high cost of this approach has also been a draw- back for most converters. Then came the approach of going wider with a combination of SKUs across a web, but this was never met with widespread acceptance from a practical point of view, due to the scheduling situation it can pose. GAME CHANGING ADVANCES It has been a well known fact that flexo printing requires a light impression setting for highlights and vignettes, whereas solid areas need pressure to transfer the ink and achieve proper ink densities. Conversely, gravure and offset printing requires more impression to transfer the ink properly. Pres- sure affects ink transfer differently with each print process. On a flexo press, too much pressure increases the possibility of bounce with certain images or printed bars across the web. Researchers at the DFTA-TZ (Technology Center of German FTA) at the Hochschule der Medien (Media University) in Stuttgart have done a lot of work on what they call "Planoflex" shallow relief plates of 100 μm. depth and how they relate to printing pressures of the anilox to plate versus plate to substrate. They found that increasing pressure between the anilox and plate had the most negative effect on print quality. They proved that a defined lower impression between the an- ilox and plate contributes more to sharp print than pressure between the plate and impression roller with substrate. Anilox to plate impressions need only to transfer the ink to the entire surface of the print area evenly and then the plate to impression roll is not as critical. DFTA-TZ found that with 100 μm. relief plates and a pressure between anilox and plate of only 60 μm., the plate impression to substrate could be up to 140 μm. with no detrimental effect on print quality. DFTA-TZ has applied for a patent based on this concept. The basis of this approach is: You cannot print what you do not ink. In addition, thinner relief plates can also reduce the likelihood of bounce caused by the plate images. Taking this approach that a deep relief plate is not needed, plate thickness can also be reduced. By combining: • Plate relief • Advances in plate surface structuring to improve ink transfer of solids to gain higher density ranges together • Lowering the highlight dot structure The resulting combination is a game changer. By altering the surface tension of the plate, more ink can be transferred with less pressure, yet still hold the highlights dots. A NEW CASE Mid web flexo can be defined several ways, but for this article we define it as 27 in. (670 mm.), 34 in. (870 mm.) or 42 in. (1,070 mm.) web widths. A mid web press can contribute great- ly to reduced print pressures. How does the TIR (total indicated run out) and printing pressure relate to a mid web press? If you have a printed area that is 42 in. wide and a print repeat of 28 in., this equals 1,176 sq. in. of printed area. A 62 in. wide press with the same 28 in. repeat equals 1,736 sq. in. It is logical that with a print area 32 percent larger there will be a greater TIR of the mounted plate on the sleeve to deal with and greater anilox TIR as well. Taking into consid- www.flexography.org JANUARY 2014 FLEXO 45