Flexo graduates to CI UV presses

Flexographic printing with UV curable inks on in-line, narrow web presses is now a common technology. Developing the technology for wider web, central impression (CI) presses has been slower due to the press design and amount of heat generated from the UV lamp. UV systems manufacturer GEW and press manufacturer, SOMA Engineering have been at the forefront in refining recent UV flexo technology on CI presses and six such lines have been installed in Central and Eastern Europe during the last few years.

Miroslaw Bohdan, M.Eng. (Food Technology) has carried out an in depth study of CI UV flexo technology sourcing empirical data and technical information from both the press and UV systems manufacturer and consumables suppliers as well as from traditional, wide web flexible packaging printers with new installations that have opted for the technology.

Flexographic printing using conventional solvent or water-based inks still has limitations despite progress over the past 10 years. These include problems in obtaining high-quality and consistent print, due to the limited ability of transferring halftone dots above 50 lines/cm (127 lines/inch) plus the significant effects and costs of solvent emission. Water-based inks for example can contain from 5 to 15% organic solvents. The development of UV curable flexographic (flexo) inks for central impression (CI) printing presses with printing widths of 800 to 1300 mm (31.5 to 51 inches) has significantly advanced print technology in this field and the results obtained.

Flexographic printing with UV curable inks on in-line, narrow web presses has been around for almost 30 years. This is now such a common technique that almost 80% of all narrow web presses sold worldwide are UV equipped presses using UV curable inks while the remaining 20% are designed for water and/or solvent based inks. Developing the technology of printing with UV inks on central impression cylinder presses with a width over 800 mm (31.5 inches) was not an easy task for several reasons. One being the difficulty of removing the high amount of heat created during the operation of the UV lamps (nearly 60% of the UV lamp output is IR). UV versions of CI presses are currently manufactured by only a few companies globally, but the results and benefits obtained indicate unequivocally that the future of flexographic printing will centre around this technology. Czech Republic based CI press manufacturer SOMA Engineering for example confirms having supplied six 800 mm wide, eight colour presses in central and Eastern Europe in the last three years with demand growing. This demand is also confirmed by the extraordinary progress that has been made in developing new generations of UV cured inks as well as the fact that their prices are consistently decreasing.

The popularity of the technology has been limited to some extent by the widely held belief that the price of UV inks is high. This is not actually the case as detailed analysis can clearly establish that the costs of UV inks are similar to those seen when printing with solvent based inks.