What you should know about Rotogravure printing
Rotogravure printing is a negative-relief printing technique, characterized by a print form that is a metal cylinder in which the image is engraved. The imaged cylinder rotates in an ink tray with a very low-viscosity liquid ink. The engraved areas are refilled with ink during each rotation. The excess ink on the outside of the cylinder is completely removed by a doctor blade before entering the printing nip. In the printing nip, the ink is transferred onto the substrate at high pressure utilizing a hard rubber counter-pressure roller and sometimes with electrostatic support.
Rotogravure presses are typically equipped with eight to twelve print units allowing to print of the 4 process colours CMYK plus additional PMS colors, whites, varnish, cold seal, and release lacquers. In Europe and North America Rotogravure is the second most frequently used technology for printing flexible packaging after Flexo printing. In Asia Rotogravure is even the largest by volume and number of installed presses. However, this is due to change drastically in the near future.
Why is Rotogravure under pressure?
Rotogravure operations are characterized by high image costs, high energy consumption, health safety risks, and environmental pollution risks, and high Greenhouse gas emissions. This is caused by the characteristics of the Rotogravure image cylinders and also the solvent-based inks that are applied.
High image costs of Rotogravure cylinders
Operating a cylinder engraving facility cleanly and safely requires that strict environmental protection measures must be implemented. Due to the high cylinder engraving and production costs, Rotogravure is economically unattractive for print jobs with a short- or medium-run length.
Health safety and environmental pollution risks
The imaging and re-imaging of a gravure cylinder is a complicated and time-consuming process, involving cupper and chrome platting baths. The processes bear a high potential risk regarding human health and environmental pollution. The applied technology is under investigation by European and other National Authorities. A ban on the use of Chromium III is being prepared, but its entry into force has been postponed until 2032.
Energy consumption and carbon footprint due to solvent-based Inks
Inks and lacquers used for Rotogravure printing and application have a low viscosity. This implies that the content of solvents and VOCs has to be very high, in some cases even up to 80% solvent. A Rotogravure press has after each print unit a drying hood with controlled hot-air flow passing through to remove the solvents from the printed ink. The printed ink has to be almost completely dry before entering the next gravure printing unit. This requires huge quantities of hot air, and afterward the removal of the solvents and VOCs from the air by utilizing RTOs (Regenerative Thermal Oxidizers) or a solvent recovery installation. This adds up to Rotogravure’s already high carbon footprint.
DG press hybrid web-press configurations
DG press hybrid web presses replace Rotogravure presses by printing the image with Offset technology often in combination with Flexo for whites and varnishes. In addition, Rotogravure facilitates the application of some specialty inks and lacquers that cannot be applied with Offset. For this reason, the integration of one or more Rotogravure units inline in DG press’s web offset presses is common practice. Web offset press series DG-AUXO and DG-Vision can both be equipped with up- or down-stream Rotogravure units, for the application of lacquers, varnish, specialty inks/coatings, cold seal, or first- or last-down whites. The available drying technology is hot-air drying for solvent-based Rotogravure inks, lacquers, and coatings. The use of energy curing for the inks is not common in Rotogravure printing.