Flexo EB & Its Evolution Presses Optimize Ink Control & Delivery

By Enrico Rimini
FLEXO Magazine
August 2012

The world is changing quickly. Through globalization, needs and key business drivers are spread openly. These factors deeply affect one of the main industrial applications linked with modern way of life: flexible packaging. Marketers and end-users are calling for and insisting on: eco friendliness, reduction of carbon footprint, reduction of energy consumption, use of materials that are recyclable and/or inert to the environment, increased safety in food packaging, increased safety in manufacturing plants, high print quality, efficiency for short/medium print runs, and of course, user friendliness of the printing process.

ADVANTAGE EB

  • Instant & full curing through power of emitted electrons
  • High resolution
  • Bright colors
  • Low dot gain
  • High opacity
  • Excellent resistance to abrasion, aging, chemical agents, humidity and light
  • Flexo EB does not contain substances that may migrate through the print substrate and/or by contact setoff
  • Flexo EB does not alter the organoleptic characteristics of the food packed, it gives no smells in the cured inks and does not release volatile organic compounds or other aerial pollutants, thus presenting itself as eco-friendly.

Comparing and contrasting the effects on ink between EB flexo, gravure and offset.

In printing plastic films for flexible packaging, electron beam flexo (Flexo EB) offers many advantages over traditional flexo using solvent inks. Flexo EB is now even possible to consider as an alternative to rotogravure and offset technologies. In particular, compared to offset, Flexo EB has lower operating costs in short and medium runs and can print flexible substrates. At the same time, compared to UV flexo, EB curing is, “by its very nature,” better suited for printing food packaging.

Flexo EB offers a number of advantages, enabled by the instant and full curing (through the power of the emitted electrons) of all ink layers deposited by the various printing units. This significantly reduces curing power consumption. Other advantages include graphics quality at the highest levels, which are very consistent throughout the entire printrun; high resolution, bright colors, very low dot gain and high opacity.

Also, one sees excellent resistance to abrasion, aging, chemical agents, as well as humidity and light. These characteristics make Flexo EB highly suitable even for the external printing of packaging to be stored in the open. One should also not forget an aspect of particular importance in the world of packaging: Flexo EB is particularly suitable for printing food packaging, thanks to the fact that Flexo EB does not contain substances that may migrate through the print substrate and/or by contact set off.

Consequently, Flexo EB does not alter the organoleptic characteristics of the food packed. It gives no smells in the cured inks (vs. UV flexo and offset) and does not release volatile organic compounds or other aerial pollutants (as is the case of rotogravure and flexo solvent), thus presenting itself as Eco-friendly.

In terms of safety and Eco-compatibility it, should also be noted that the EB work environment is explosion proof and therefore less hazardous, enabling a resulting reduction in insurance costs and disposal of dirty solvents. Likewise, abatement equipment for solvent released into the air from the machine is not required, and less energy is used than with UV (UV flexo, UV offset) or with thermal drying (rotogravure,solvent-based flexo).

FUTURE OF FLEXIBLE PACKAGING?

Printing and converting community expectations are high, thanks to the potential benefits. Nevertheless a few early experiences were a bit disenchanting. The learning curve is steep and it takes commitment and a methodical structured approach before there will be broad acceptance of the rather young Flexo EB technology.

On paper, Flexo EB has a leading edge and a capability to evolve, when compared to rotogravure and offset that are mature technologies without significant room to change and adapt to new needs. Solvent-based flexo and water-based flexo are already gaining market-share, given a big shift toward short and medium print runs. They still, however, lack the edge of high print quality and Eco-friendliness. Today, it’s the dedicated new technology leaders that have accepted the challenge of embracing Flexo EB. Currently, niche markets see the biggest advantages. Forecasters expect the installation base to grow larger, step by step, under the pressure of environmental constraints for pollution and energy reduction.

One leading press manufacturer, Uteco, recently conducted a series of benchmarking press trials comparing Flexo EB, rotogravure and offset, making use of the Onyx EB press (a Flexo EB platform developed over six years), and the E-Press Rotogravure and the Silver SIL Roto-offset presses from its product line. This analysis benefited from the input and feedback from experts by a leading food company. The conclusion was that 10 years ago flexography was so far from rotogravure and offset that it didn’t deserve attention from big companies for demanding markets, but nowadays the quality gap (See Table A) is so narrow, and there are so many advantages in other areas, that the shift to flexography is becoming a must.

A look at comparative plate characteristics between EB flexo, rotogravure and offset.

VARIATIONS ON THEME

Ink companies have had recurring nightmares, populated by variations on the theme of formulating and running Flexo EB. All kidding aside, the industry effort now is serious and more ideas and patents exist. It could even be that more than one will succeed in the medium-long term. Mainly we divide the Flexo EB group into three types:

  • Flexo EB ink with a small content of water – SunChemicalTM WetFlex™
  • Flexo EB ink with a small content of solvent – TechnosolutionsTM EZRad1™
  • Flexo EB without any volatile component, that is solid Flexo EB inks

All the variations turn on a couple of points: ink layers should trap over one another without inter-deck curing/drying; and all the ink layers should cure at the end of the line before rewinding. Many ink manufacturers’ expectations are that the future of flexible packaging will be mainly Flexo EB.

CONFIGURING THE PRESS

Different ink viscosities, different ink behavior, different ink operating ranges, different ink trapping mechanism, different
curing/drying ink mechanism, different ink transfer mechanism… Climbing the learning curve requires a methodical and structured research and development approach in order to address similarities and differences between the various Flexo EB inks and to compare to the other flexo technologies.

The main, even if not only, areas that needed to be addressed are: accurate temperature control in real time, optimization of chamber doctor blade, optimization of inking circuit, ink stirring without foaming, transfer of the ink from anilox, to plate, to substrate; and handling the ink without damaging it, either in the long run nor in the quick speed changes.

To understand the basics, to tell apart the solutions that work from those that don’t, to invent brand new solutions using
lateral thinking, to industrialize and validate the chosen solutions…you have to go through this circle in order to identify “smart” solutions that are just what is needed.

Among the various solutions developed and introduced on the new Onyx EB press, the most significant is “Thermilox™”, a process for ink temperature control which is the subject of a patent filed by Uteco. The technology simply preconditions the ink to bring it to correct operating temperature and maintain the optimum printing heat with accuracy and reactivity. In addition, the temperature set point can be independently controlled for each color group.

“Ergonomy” is not a simple goal when you have to design a press for the Flexo EB process. The concept is simple, but there are many subtleties that can lead one toward press complexity. Press manufacturers have approached the key topics of ink control and delivery (thermoregulation, viscosity control, circulation, metering) by redesigning from the ground up, in order to have good handling yet keep simplicity and user-friendliness.

Flexo paved the way to print on soft/elastic substrates by means of the CI drum configuration. It then stepped ahead with quick job changes through printing and anilox sleeves. Blending these pluses with EB curing is now leading to the next breakthrough in flexible packaging.

About the Author: Enrico Rimini is project manager for Uteco Converting S.p.A, headquartered in Verona, Italy. The firm, a leading manufacturer and supplier of equipment in the field of flexible packaging was established in 1985. Innovation has always been a key-point at Uteco, not only in the design and creation of leading edge equipment, but also with the ability to tailor machines to the specific needs of converters in any corner of the world. Its Onyx press line is now configured to facilitate electron beam curing that speeds packages to market and enhances barrier resistance properties while eliminating food migration concerns.

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