Genetic Transfer Technology

Background

Last year Apex Group of Companies introduced a revolutionary type of metering roll for post-printing corrugated board, called UniCorr L manufactured by the Genetic Transfer Technology. The surface of this roll is no longer characterized by cells but has an open structure, which allows for a smooth ink transfer on solids, fine lines and screens with the same roll. The new roll technology is now further developed for flexible packaging and flexo coating units and presented at Drupa 2008.

The variety in anilox rolls is enormous and still growing. Rulings are getting finer and many rulings are available in a number of ink volumes. Every roll has its advantages for certain applications, but the margins for ‘better printing’ are getting smaller. Moreover, finer screen rulings have their own limitations, such as poorer cleaning properties. A critical flexo printer tries to choose his anilox rolls carefully, often a different one for each job and each color. However, the wide choice in anilox rolls is confusing and is not beneficial to the urgently needed standardization of the flexo printing process.

‘The development of the traditional anilox roll has virtually exhausted its potential for optimization’, observes Martien Hendriks, Technical Sales Director of Apex. ‘We felt that a new concept was needed. After two years of extensive research and development we are now ready to offer a complete new type of roll to the market. We no longer call it an anilox roll but a metering roll, because the roll is manufactured by means of the Genetic Transfer Technology and one of it’s characteristics is that the roll has no cells.’

The metering roll has a layer made of a mixture of chromium and titanium oxide with a number of fixed particle sizes. The surface profile has an open structure, which means that there are no screen rulings, cell depths or opening ratios to specify the roll.

To engrave the new surface structure, Apex developed a special low energy laser. What makes the metering roll so special is its ability to give each element of the printing plate the amount of ink that is needed for good printing. Solids, which require much ink, are heavily inked, while less ink is transferred to fine lines and halftones. It is no longer necessary to use separate plates and anilox rolls for the printing of solids and halftones. Moreover, the printing range of the metering roll is wider than the range of a conventional anilox roll. With the same roll, halftones of 40 l/cm and 60 l/cm can be printed.

Stressed inks

What is the secret of this characteristic? Martien Hendriks explains: ‘The wiping of an anilox roll with the doctor blade makes the ink move or stir in the cells. I call this “the ink has stress”. With the open and smooth structure of our new metering rolls, the ink film remains still after wiping and does not really move. The ink is stress less. As the solids are usually a bit higher on the plate, the pressure of the ink film on the roll is higher and so more ink is transferred to the solid. Other more open printing elements take less ink.

We have been inspired by the water management of the traditional Dutch flat lands. Here the water flows and is kept by an ingenious system of ditches and canals. The structure of our metering roll is comparable with that system.’ The metering roll is rather shallow, there are no deep cells. Therefore, the roll is less apt to plugging by dried ink remnants as happens in the cells of an anilox roll. Also the cleaning of the roll is much easier. The lifetime of the roll is probably longer than that of an anilox roll. Long-term practice has to prove this. It has already been proven that the doctor blades hold longer.

Three Types

The new metering rolls are available in three types: UniCorr for the Corrugated industry, UniFlex for flexible packaging and UniCoat for the coating and offset industry. Each type has a different structure adapted to its specific application. UniCorr was the first to enter the market and since more than 400 UniCorr rolls were produced in the past year, it is a successful product. It was extensively tested by a number of well-known corrugated printers, who showed great enthusiasm. Like mentioned in past articles, the prepress company Neuefeind GmbH in Ochtendung/Koblenz (Germany) developed a special test form. The testing proved that the UniCorr L was as good in printing solids as a 100 l/cm anilox roll and screens nearly as good as a 180 l/cm anilox roll.

One of the printers was able to print with one plate a solid combined with a screened illustration. A job that previously required two printing plates. The tests were so successful that since January this year, the UniCorr L roll is commercially available. It covers the printing range, which is traditionally served by anilox rolls with screen rulings from 100 up to 180 l/cm. The UniCorr M and S for smaller ink transfers are currently tested with several machine manufacturers and end-users.