Flexo EB & Its Evolution

Enrico Rimini – Uteco Project Manager

The arising key factors
The world is changing quickly and 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. Some of the new and critical key factors for flexible packaging include:

  • eco friendliness
  • reduction of carbon footprint
  • reduction of energy consumption
  • use of materials that are recyclable and/or inert to the environment
  • increase of safety in food packaging
  • increase of safety in manufacturing plants
  • high print quality
  • efficiency for short/medium print runs
  • user friendliness of the printing process

The advantages of Flexo EB
In printing plastic films for flexible packaging, 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 the latter, Flexo EB has lower operating costs in short and medium runs and can print flexible substrates. At the same time, compared to Flexo UV, 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 print run, high resolution, bright colors, very low dot gain, high opacity. Also, one sees excellent resistance to abrasion, aging, chemical agents as well as humidity and light – these characteristics that make it 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 setoff. Consequently, Flexo EB does not alter the organoleptic characteristics of the food packed, it gives no smells in the cured inks (vs. Flexo UV 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 (Flexo UV, UV offset) or with thermal drying (Rotogravure, Flexo solvent).

Is it the future of flexible packaging?
Printing & converting community expectations are high thanks to the potential benefits. Nevertheless a few early experiences were a bit disenchanting. For sure 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, vs. rotogravure and offset that are mature technologies without significant room to change and adapt to new needs. Flexo solvent and Flexo water-based are already gaining market share recently through better coping with the big shift towards short-medium print runs (but they still lack the edge of high print quality and eco-friendliness). However, in the current poor economic climate, the number of companies taking the challenge of a new technology is limited to dedicated new technology leaders and the trend to Flexo EB will be slower than it could have been in the 1980/90s. It will probably take a while to start up those niche markets that see the biggest advantages and then, step by step, to enlarge the base of installations under the pressure of environment constraints for pollution and energy reduction.

In Uteco a series of benchmarking press trials were run comparing Flexo EB, rotogravure and Roto-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 the Uteco product line. This analysis benefited from the input and feedback from experts by a leading food company. The conclusion was that ten years ago Flexography was so far from Rotogravure and Roto-offset that didn’t deserved attention from big companies for demanding markets, but that nowadays the quality gap is so narrow and there are so many advantages in other areas that the shift to Flexography is becoming a must. Besides, Flexo has room for improvement.

Variations on the same theme
Ink companies have had recurring nightmares, populated by variations on the theme of formulating and running Flexo EB. 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 WetFlexTM
  • Flexo EB ink with a small content of solvent – TechnosolutionsTM EZRad1TM
  • 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
  • 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, whereas many ink manufacturers are eagerly looking for new niche markets other than the continuously declining offset on paper for commercial printing, publishing printing, etc.


How to configure a standard or typical flexible packaging press for EB?

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 R&D approach in order to address similarities and differences between the various Flexo EB inks and to compare to the other Flexo technologies. Uteco built the current level of know-how about Flexo EB from the foundation of many years of work in the wide web Flexo UV, as well as the thorough competence on the Flexo solvent and Flexo water base processes.

    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 the ink correctly from anilox to plate to substrate
  • Handle the ink without damaging it, neither 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 get at the end “smart” solutions that are just what is needed (and not more than is needed).
Among the various solutions developed and introduced on the new Onyx EB press, the most significant is “ThermiloxTM”, a process for ink temperature control which is the subject of a patent filed by Uteco. We can say that ThermiloxTM simply preconditions the ink to bring it to correct operating temperature and, acting directly in the area of over-heating, it thereby maintains 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 an 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 towards press complexity. Uteco 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 keeping simplicity and user-friendliness.

The new patented ThermiloxTM inking and thermoregulating system and the new ThermowashTM automatic washing system (evolution of the smart SprintwashTM that is standard for most Uteco Flexo presses) makes life as easy for Flexo EB press operators as it is in solvent and water based technologies.

It would have not made sense to market a CI Flexo press for EB if that would not have been accepted by end users due to too much complexity. The Onyx EB is an easy press to understand, to use and to create high-quality flexible packaging.

Conclusions
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.

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