A study conducted by the Leipzig University of Applied Sciences (HTWK) provides highly interesting answers to this central issue
How sustainable is the gravure printing process?
von Ansgar Wessendorf,
For branded companies and retailers with their own brands, the issue of “sustainability” is becoming increasingly important in the selection of the most suitable printing process. This means the detailed evaluation of production processes from an ecological point of view. However, these processes are always subject to a multitude of different influencing factors that need to be adequately assessed within the framework of such an evaluation.
In this context it is worth mentioning, that gravure printing offers current developments and innovations to further improve sustainability. This is now confirmed by a study presented by Professor Dr. Lutz Engisch at the 2022 annual conference of the European Rotogravure Association (ERA) in Baveno, Italy.
The framework conditions of the study
The study was carried out in the first half of 2022 under the supervision of Professor Lutz Engisch, Department of Materials and Materials Testing at the Leipzig University of Applied Sciences (HTWK). The corresponding data was collected on the basis of an online questionnaire and interviews with more than 116 industrial users of gravure printing. The entire workflow including upstream and downstream processes such as engraving and the transport of printing cylinders as well as recycling and deinking was recorded. With 53% participants from the prepress area (cylinder production) this was the largest group, followed by 33% from the area of printers/converters.
Depending on the respective group affiliation in the gravure industry, the participants were presented with a corresponding list of questions. The responses showed that the topic of “ecological sustainability within the rotogravure printing industry” is of equal relevance and importance for all groups. Thus, 43% of the study participants answered to be “very familiar” and 48% to be “familiar” with this issue.
Reusability and material recovery
Due to the nature of the process, gravure printing offers a potential for the circular economy that can hardly be underestimated. The almost endless reusability of the printing cylinders as well as the closed material cycles in cylinder preparation favours its sustainability compared to other printing processes. This is one of the most important results of the HTWK study. “According to the respondents, the greatest advantage of gravure printing is the reusability of the gravure cylinders. They can be used almost indefinitely beyond any individual job”, says Prof. Dr. Lutz Engisch.
In addition, the obvious strengths of the process, such as very consistent print run stability and exceptionally high print quality, contribute to minimal waste rates and thus to better sustainability. Above all, the combination of the finest screens and full tone areas on the same cylinder is an unbeatable advantage of gravure printing. Brilliant colours with high densities can be achieved by reproducing true halftones.
The sophisticated and precisely controllable technologies used (electroplating, engraving, surface treatment) for the fully automatic and standardised inline production of gravure cylinders are not only highly efficient but also save valuable resources. The low tolerances achieved in the entire production process allow for a high degree of reproducibility of the cylinders and thus of the printed image.
Another advantage of gravure printing in terms of sustainability is the reuse, recovery and recycling of all materials used in the cylinder preparation, such as steel blanks, copper and chrome. Other sustainability strengths identified in the study are the recovery of solvents and the use of water-based inks.
Reduced set-up times through automation
As an essential aspect to further improve sustainability, the respondents mentioned the reduction of set-up times through automation. In this respect, gravure has demonstrated a high capacity for innovation. The increasing use and interaction of artificial intelligent (AI) functions, fully automatic pre-register setting, fast-response register control systems, efficient drying technologies, short dryer sections and the associated short web lengths increase the level of automation of state-of-the-art gravure presses. This not only reduces set-up times and the number of press operators, but also substrate waste and residual ink quantities.
In this context, gravure printing benefits from the fact that the simple design of the inking units (printing cylinder/substrate/impression roller) makes press operation quite easy. The ability of gravure to print very long runs in consistently high quality is another element in the chain of sustainability benefits. The results of the study show that large jobs with run lengths of over 800,000 metres are still quite common in the market. Most of these jobs are printed on monolayer films, composites and paper. The thickness of the substrates used is predominantly less than 25 μm.
Ink savings with laser-engraved gravure cylinders
The application of thinnest ink films (ink savings) without compromising the usual high print quality (high ink density, good smoothness) proved to be a very important topic for the participants in the study. Here again, gravure printing offers the corresponding possibilities. This is because, that in contrast to the electromechanical engraving commonly used up to now, direct laser engraving in copper enables the generation of different cell geometries with individually adapted volumes (e.g. autotypical cells). They only transfer the amount of ink actually required and thus contribute to ink savings and therefore also to economic and ecological advantages.
The chromium problem is solved
Chromium trioxide is used to coat the gravure cylinder to ensure its hardness and prolong its service life. According to the results of the study, this is considered a major challenge for gravure printing, as the industrial use of chromium trioxide requires authorisation by the EU Commission in accordance with the REACH (Registration, Evaluation, Authorisation of Chemicals) regulation. “Although the EU Commission has granted authorisation until 2024, an extension beyond this point in time is most likely. This is due to the fact, that the ChromeExtend proposal issued by the European Rotogravure Association (ERA) together with the German company Kaspar Walter has been considered positively by the European Chemical Agency (ECHA)”, explains Professor Lutz Engisch.
In addition, the industry is developing promising alternatives to the traditional chromium trioxide coating, such as chromium (III) chloride or plastic coatings, which would further increase the sustainability of gravure printing. For example, chromium trioxide (chromium VI) can be replaced by chromium (III) chloride. After more than 10 years of development, this process reached industrial maturity in 2021 and is already being used successfully by some companies.
Another appealing alternative is the monolayer gravure cylinder, as offered by Continental with Dynasurf, Heliograph Holding with Helio Pearl or Rossini with Ecograv. It consists of a wear-resistant single-layer monolayer (polymer or elastomer) as a replacement for the conventional multi-layer structure of copper and chrome. The polymer or elastomer layer is directly imaged using laser technology or electromechanical engraving.
The entire cylinder preparation process now consists of only three steps:
Coating the gravure cylinder with polymer or elastomer in place of the previous copper and chrome coating,
Grinding the polymer or elastomer surface
Direct engraving by laser or electromechanical engraving.
Continental, Heliograph Holding and Rossini performed numerous and extensive print tests with their monolayer gravure cylinders, which have turned out very promising. However, due to the highly complex nature of this new process, there is still some development work to be done before it is ready for the market. In the future, monolayer gravure cylinders could also expand the range of possibilities in terms of high flexibility and fast responsiveness in cylinder preparation.
Particularly in the areas of logistics, transport, storage as well as supply, completely new ground could be opened up to reduce the high transport costs for gravure cylinders. Furthermore, this would facilitate the implementation of sustainable concepts in which, for example, in-house cylinder production could take place directly on compact, narrow-web gravure presses of the latest generation.
First approaches for a life cycle assessment
In addition to the surveys and interviews, first approaches for a life cycle assessment (LCA) were also developed. In this context, the first challenges and limitations were already identified. However, it is not possible to make general statements, because the wide range of parameters means that it would be very difficult to carry out general, holistic comparisons of different printing processes. Product-dependent individual decisions, supported by comparative life cycle assessments, could help to identify the most environmentally friendly printing process for the respective print jobs.
Improved communication and coordination
The interviews for the study also revealed a desire for better communication and coordination throughout the supply chain. This includes all participants including manufacturers of cylinders, machines and inks, design agencies and recyclers. This exchange could greatly facilitate the process of coordination and prioritisation of developments to improve sustainability in gravure printing.
For a successful communication and marketing strategy, the European Rotogravure Association (ERA), as a neutral platform, could pull all the strings together, whereby the high commitment of the ERA members would be of decisive importance.