The WEKO DigiCon was developed for high-performance inkjet printing systems and restores moisture withdrawn in the drying process to the paper.
Moisture restoration has such a positive effect on the quality of the finished product for the following reasons:
Paper is a natural 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% when absorbing moisture. In the same way, fibres shrink under the effect of heat when losing 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.
Challenges for digital printing
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 then lost. Only 15 to 20% residual moisture remains in the paper. The fibres shrink and undesirable effects such as paper curl, waviness and electrostatic charges occur. These 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 such as the WEKO DigiCon are based on the WEKO RFDi conditioning unit for high-performance printing systems working with toner. 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,' said Thomas Laissle, product manager at WEKO. 'Because of the printing process, this technology is especially appreciated for pages with high ink application and paperbacks.'
In addition to the development of the WEKO DigiCon, the WEKO WebCon for the HP T-series was developed in close cooperation with HP. This conditioning unit specifically follows the evolution of the HP high-performance endless printing systems with regard to high speed, high colour resolution and a wide range of papers and grammages.
The WEKO DigiCon will be presented during drupa 2016.
