In July 2016 KBA-Digital & Web in Würzburg signed a cooperation agreement with Dutch technology specialists Apex International regarding the coating and engraving of anilox rollers for its waterless KBA Cortina web offset press. The principal objective of this partnership is to guarantee the fast deliveries of newly coated and engraved anilox rollers to Cortina users when overhauling becomes necessary due to wear after several years of production. 

Twenty users have opted for the compact and waterless KBA Cortina so far, accounting for a total of 86 towers and 688 printing units. Nineteen of those presses, with 680 printing units and an identical number of anilox rollers, are in daily operation. The first press line was commissioned eleven years ago, and a certain degree of wear and need for anilox roller replacement is thus only to be expected. KBA estimates the lifetime of a Cortina anilox roller to be around 200 million cylinder revolutions, though many a roller has already been in service for considerably longer. Alongside the ink and the blade contact pressure, the nature of the ceramic coating and the type of engraving are essential factors influencing the life cycle.  

Extensive expertise on both sides 

As the world's leading manufacturer of anilox and metering rollers, Apex International possesses vast experience and know-how in the field. In fact, it holds patents for the so-called GTT anilox technology, an engraving geometry based on open, slalom-style channels, which are designed to achieve an extremely homogenous ink application while reducing wear to a minimum. The inner body of the double-walled Cortina anilox rollers, in turn, has been patented by KBA; here, the integrated temperature regulation permits fine control of the ink application. Accordingly, the anilox rollers for a Cortina press are more expensive than the standard film rollers of a conventional inking unit, as a result of which reconditioning with a new ceramic coating and laser engraving is a meaningful option.  

To date, the Cortina anilox rollers have been coated and engraved at the KBA-Sheetfed factory in Radebeul, which also manufactures and engraves hundreds of rollers for anilox coating units each year. The laser engraving machine used for the Cortina rollers, however, is starting to show its age and has become increasingly susceptible to disturbances and delays. After a thorough economic analysis and consideration of all conceivable alternatives, the KBA management has therefore decided to outsource its coating and engraving requirements rather than investing in new laser engraving equipment. Another aspect which clinched the decision in favour of Apex International was the latter's experience from its manufacturing of high-quality anilox rollers using the GTT technology; such rollers had already been used with good results on several Cortina installations before official announcement of the cooperation.   

No change in replacement procedures 

The patented GTT anilox technology developed by Apex uses an open, slalom-style engraving pattern to achieve homogeneous ink application without discernible lines or moiré effects, while at the same time reducing wear (3)For the Cortina user, there are no changes in the procedures for roller repairs and replacement. A worn roller must still be sent to the KBA factory in Radebeul, as before. The interior of the roller is there inspected thermographically for contamination. If necessary, any contamination is either flushed out or brush-cleaned, as appropriate. The roller is subsequently filled with nitrogen as corrosion protection and sent to Apex for renewal of the surface. At Apex, the roller is stripped, coated with a new ceramic layer and laser-engraved using the GTT technology. The warranty of at least 200 million cylinder revolutions given by KBA remains unaffected.   

KBA and Apex have committed to pooling their specific anilox roller know-how for the waterless offset process and plan to continue development of the existing solutions together. In addition, current users will benefit from the increased stability of the repair process, with high-quality results and short delivery times. The same naturally applies also in the case of new rollers, whether for a new or expanded Cortina installation or as replacement spares.