No printing without WEKO! This textbook statement applies also to digital printing. Whether digital or conventional, many printing processes require drying processes. If the printing carrier is paper, it loses its original properties through drying. Electrostatic charges, waviness, paper curl or the break at the fold are effects that apparently belong to the daily work routine of a digital printer today.

Why does paper react so sensitively to physical impact? Are effective countermeasures available to maintain productivity and quality? These are questions Weitmann & Konrad GmbH & Co. KG, in brief, WEKO, has asked themselves. The experts from the Stuttgart area have specialised in the development and production of minimum application systems for moistening and powder-spraying of surfaces for over 60 years. The owner-managed company positions its products between printing and further processing thus bridging the gap between these two processing operations.

The latest development – the WEKO DigiCon – will be presented at the drupa 2016; it was developed for high-performance inkjet printing systems and restores the moisture withdrawn in the drying process to the paper. But why does this have such a positive effect on the quality of the finished product? Paper is a "living" product that cannot be standardised and its behaviour during diverse processing operations can never be completely anticipated, because paper essentially consists of plant fibres. They expand up to 25 per cent when absorbing moisture. In the same way, fibres shrink under the effect of heat when loosing moisture. Depending on the composition and manufacturing process, each paper has a defined moisture. Paper reacts to climate changes during printing and processing with changes of its properties, with dimensional fluctuations and paper curl.

Digital printing presses today work primarily either with toner-based electro-photography or high-performance inkjet technology. With both methods the print web runs through a process – fixing the toner or drying of the ink – where high temperatures act on the paper. The original moisture is lost then. Only 15 to 20 per cent residual moisture remain in the paper. The fibres shrink and the generally known and undesirable effects occur: Paper curl (the paper curls), waviness and electrostatic charges are the effects that significantly affect any kind of further processing and cause a quality reduction of the end product. In addition, the paper becomes brittle and breaks at the fold.

Paper conditioning through remoistening is an extremely effective measure of restoring the paper's original properties. The latest development of the WEKO experts – the WEKO DigiCon – are based on the WEKO RFDi conditioning unit for high-performance printing systems working with toner, proven for quite some time. The WEKO DigiCon is designed for the needs of high-performance inkjet printing systems and has been developed in close cooperation with the renowned digital printing machine manufacturers.

The special spray discs (rotors) are the core of these minimum application systems. They turn at a high speed generating a uniform stream of finest micro-droplets. Adjustable sliders regulate spray fans which border on each other seamlessly. In this manner, the WEKO DigiCon conditions the processed paper with an exactly metered liquid supply. It receives its original (positive) properties back and optimises running and stacking properties. The result are production runs free from malfunctions, less paper waste and markedly increased product quality.

"Paper conditioning through remoistening of the paper is an important step towards high-quality printing products", explains Thomas Laissle, product manager at WEKO. "Because of the printing process, this technology is especially appreciated for pages with high ink application and paperbacks", continues Laissle. The visitors or this year's drupa can see for themselves in detail. Numerous machine manufacturers will present printing lines at their booths equipped with the WEKO DigiCon conditioning unit. Furthermore, the WEKO experts provide consultation directly at their booth in hall 2 stand 2B54 under the motto "DON’T PLAY – WORK WITH PRECISION".

"The different installations also demonstrate how easily the unit can be integrated into all common printing lines and the advantages resulting from the application. The proven technology also requires very little maintenance and is highly energy-efficient. This makes it an economically and ecologically useful investment" emphasises Marcel Konrad, managing partner at WEKO.

In addition to the development of the WEKO DigiCon the WEKO WebCon for the HP T-series was developed in parallel in close cooperation with the digital printing machine manufacturer HP. This conditioning unit specifically follows the evolution of the HP high-performance endless printing systems in regard to high speed, high colour resolution and a wide range of papers and grammages. These attributes demand maximum flexibility and quantity variability of the conditioning unit. Again, the WEKO experts have outperformed themselves and can now cover the entire requirements profile of HP with the WEKO WebCon through innovative developments and without adaptations of system configurations.