New technologies for the preparation of gravure printing cylinders
von Ansgar Wessendorf,
In Autumn 2021, representatives of the European gravure industry met at the ERA Annual & Packaging/Decorative Gravure Conference in Thessaloniki, Greece. Despite the ongoing Corona restrictions, more than 80 delegates accepted ERA’s invitation to discuss current challenges such as sustainability in packaging printing and alternative technologies in the field of electroplating.
The conference developed an encouraging future perspective for the gravure printing process. In this context, it was considered a success for ERA to finally obtain approval from the EU Commission for the continued use of chromium trioxide until 2024. To further secure the future of this type of chrome plating, the Kaspar Walter company submitted an application to the European Chemicals Agency regarding gravure and embossing cylinders.
In addition, promising alternatives to traditional cylinder preparation were presented by Rossini (Ecogravsystem), Contitech (Dynasurf) and Kaspar Walter (HelioChrome Neo and HelioPearl). Finally, press manufacturers Bobst and Uteco presented their enhancement solutions for the use of water-based inks, thus further increasing the sustainability of the gravure printing process.
Direct engraving into the functional layer
What is the state of gravure printing, whose future prospects for success are almost exclusively linked to further developments in printing cylinder preparation? Basically, however, the future of the process cannot be in bad shape if internationally leading printing industry suppliers become involved in the market segment of gravure cylinder preparation.
During the ERA conference, several companies presented their new, future-oriented technology concepts for single-layer gravure cylinders. This included Heliograph Holding (Helio Pearl), Rossini (Ecograv) and Continental (DynaSurf). What they all have in common is the complete elimination of the galvanic processes of copper and chrome plating. Continental utilises elastomer for the engraving layer, whose surface can be processed directly with a high-resolution fibre laser but also with traditional electromechanical processes.
In contrast, the engraving layers for the technologies introduced by Heliograph Holding and Rossini are made of a special polymer material. In this context, tt is worth mentioning that Helio Pearl is currently only available for direct laser engraving, while the Ecograv concept still relies on the electromechanical process.
All solutions have in common that they only require three process steps for the preparation of gravure cylinders:
Coating of the cylinder
Grinding/polishing of the monolayer
Imaging (engraving) of the coating.
Furthermore, all three companies come to almost the same conclusion regarding the status quo of their respective projects. The print tests with the monolayer gravure cylinders so far have been very satisfactory and in some respects even exceeded expectations, for example with regard to ink release properties. However, further field tests are still needed before achieving final market maturity. The prospects for success, however, seem extremely favourable. After all, the three protagonists mentioned have worked for about 10 years on the development of their single-layer direct-engravable gravure cylinders.
The success of these technologies would be an important evolutionary step for gravure printing and could herald an era of entirely new and very promising opportunities. Furthermore, it could also strengthen its competitive edge in regard to other printing processes.
More than an environmentally friendly alternative
HelioChrome NEO is an alternative developed by Kaspar Walter that has now reached market maturity and is intended to replace chromium trioxide with chromium (III) in the galvanic process of gravure cylinder preparation. With a Vickers hardness of about 1200 HV, this environmentally compatible technology can be used to achieve cylinder surfaces of equal quality compared to classic chrome plating with chromium (VI). Moreover, in principle there are no changes in the overall preparation process.
The energy requirement of HelioChrome NEO is relatively low at around 20 A/dm² at 40°C. The 20 °C lower bath temperature compared to traditional chrome plating also results in lower emissions and electricity costs, thus protecting the environment. Currently, chromium (III) coatings up to a thickness of 25 µm can be achieved. The build-up of a 6 to 8 µm thick layer, which is common in gravure printing, takes about 20 minutes and is thus similarly fast as the chromium (VI) coating. In addition, chromium (III) salts have been proven to be less of a concern for the environment and health than chromium (VI) salts and their toxicity is below the level of copper baths. However, it is not possible to use current chromium (VI) plating equipment for the HelioChrome NEO process.
Awards for sustainable packaging
During the ERA conference, the winners of the „Gravure Award for Sustainable Packaging“ for 2021 were presented. In the category „Printed Products“, the Greek packaging printer Hatzopoulos, based in Thessaloniki, received an award for a mono-material coffee packaging printed exclusively on PP film. In addition, the Vietnamese packaging printer Thành Phú was awarded for its stand-up pouch for dog food, which is built on a mono-material PE/PE structure. In the „Innovation“ category, Bobst Italia was awarded for the development of a gravure press that facilitates the use of water-based inks. The Swiss company Rheonics received a certificate in the „Emerging Technology“ category for a new inline viscometer for measuring ink viscosity in the press.