Moog: The many advantages of sheet-fed gravure printing

The sheet-fed gravure printing process is generally the first choice when it comes to ultra-short to medium print runs. The ability to order the sheet format exactly to the required area for the respective packaging means that the printing area is utilised almost completely, which in turn drastically reduces the waste rate. Even when setting up the machine, only a few sheets are needed to adjust the lateral, circumferential and diagonal register. By pre-setting all variable parameters, the machine operator is able to produce good sheets fast and with minimal effort.

Sheet-fed gravure printing offers yet another advantage, which has a particular impact on achieving the highest print quality. This is because the colour and varnish immediately have the correct shade, as this is a direct printing process and does not have to be transported indirectly to the substrate via one or more rollers like it is the case with offset printing.

Drying in sheet-fed gravure

Today, IR/NIR/UV curing systems and hot air dryers are used in sheet-fed gravure printing. Sequenced in a row, they offer maximum flexibility without increasing waste. Such sequenced dryers are particularly advantageous for water-based coatings that are often used for pre-treatment, barrier formation and finishing. This is because a long, waste-free dryer section is generally the best choice for sheet-fed gravure printing. A typical configuration is a combination of IR + hot air + UV. This means that the print design can be realised with all kinds of ink systems and with the greatest possible flexibility.

Highly brilliant colour application

There is also the possibility of combination with other sheet-fed printing processes. A good example of this is the highly brilliant flat application of silver inks that can be achieved in sheet-fed gravure, which can also be overprinted with glazing inks in sheet-fed offset to achieve a coloured metallic impression. Unnecessary white areas can be left blank to save on opaque white printing or to facilitate the gluing of folding cartons. Sheet-fed gravure printing is also known for the ease with which inks and varnishes can be removed from the fibre, giving optimum deinking results.

An impressive mirror effect

After extensive development work and numerous test runs, Moog, the world’s leading manufacturer of sheet-fed gravure presses, and in close cooperation with its partners have succeeded in achieving a perfect print image for the two-dimensional transfer of mirror silver onto the sheet. The challenge was to apply the mirror silver on the Moog TBR-104 sheet-fed gravure press in such a way as to produce a mirror effect after transfer to the sheet. In this particular application, sheet-fed gravure printing is able to fully exploit its technical advantages over other printing processes.

Extensive barrier coating trials were also carried out on the TBR 104. Here too, sheet-fed gravure printing demonstrated its qualitative strengths by providing the required barrier properties through the transfer of a homogeneous and closed coating surface.

Ink transfer and sustainability

In gravure printing, inks can be transferred using cylinders with very different manufacturing processes. With this in mind, research is underway around the world to make the gravure printing cylinder and its production more sustainable. This starts with the base cylinder, which can be as durable as the press itself. It can be coated with a variety of materials such as copper, polyester, polymer or even elastomer. What all these materials have in common is that their surfaces can be further structured to create the typical gravure cells. It is possible to choose from coarse to fine screen resolution and from very small to large transfer quantities. A good example of this is water-based barrier coatings with high transfer quantities and so-called thin-film applications, where the amount to be transferred onto the sheet must always be exactly right.