Industrielösungen Für Digitaldruck Und Leichtbau
Industrial digital printing made by Wemhöner
Wemhöner MasterDigital® with perfection to precision
Digital printing in the furniture and flooring industry and other sectors is the topic. Wemhöner Surface Technologies concentrates the development with waterbased printing inks since 2008. Today Wemhöner is one of the technology leaders in performing surface decoration.
Developments are going also with waterbased inks on PP, PVC and PC or other substrates. Full line, customised solution with or without pre-treatment, developed to the need of specific projects. From feeding to stacking or roll to roll solutions, Wemhöner supplied the complete system. In some projects the digital printing technology has replaced previous applications. The pre-treatment is crucial for the subsequent digital printing, as surface and ground colour must have a high quality.
Wemhöner digital printing with Multipass
The printing unit with the print heads moves repeatedly across the workpiece. In a 4 pass order, for example, the print heads run over the surface to be printed four times, while printing the surface to 25 percent each time, until after the final printing run the 100% image is achieved. This not only provides a great depth of colour, but also eliminates possible nozzle errors. The flexibility of the quality of the printed design is a very big advantage of the Multipass System from Wemhöner. Printing in 2 – 3 – 4 or maybe 6 passes give the customer a bigger range in process safety for medium to high end quality production.
The image composition can be carried out both uni as bi-directional. The bi-directional printing makes the printing process not only faster but also more homogeneous in image building. On the one hand printing units mounted on the infrared dryer have the function to preheat the material to be printed and on the other to dry the ink immediately after application and to fix it. The intensity of the drying can be varied according to requirements.
Wemhöner digital printing with Singlepass
The print heads are installed over the substrate, which is running under the digital print heads. The substrate can be an endless substrate like paper or PVC or a board product like MDF, HDF or PVC panels. It is a running through process. The difference to the multipass technology is the much higher output. Working width up to 2.250 mm is already designed with a speed of 80m/min with waterbased printing inks. This development is done with the newest generation of 1.200 x 1.200 dpi sideshooter printheads.
600 x 600 dpi or 1.200 x 1.200 dpi natural pitch
The print heads used by Wemhöner are among the highest performing products on the market. With 2.560 nozzles per unit at 600 x 600 dpi and 5.312 nozzles at 1.200 x 1.200 dpi they generate a physical print resolution, the so-called natural pitch. Higher resolutions are possible, but they reduce the production output. So the number of printheads and the working width can give an output between 100 – 1.000 m²/h at 600 x 600 dpi.
To create a natural as possible printed image Wemhöner works with three different droplet sizes. A special algorithm controls the applied quantity in dependence of decor and colour so that no repetition pictures can be created and the human eye perceives an absolutely natural and authentic picture.
CMYK+ 2 special colour print with water-based inks
The print is generated in the CMYK-process that is with the primary colours cyan, magenta and yellow and black. With CMYK “only” are coming some limitation in the full colour cloud. That is the reason, that we can additional place 2 more colours into the digital printing machine. Optionally, leading tones such as gray or red are possible as well, if more halftones or gradients are needed. Wemhöner only uses water-based inks. These inks have the advantage that they are absolutely lightfast and keep compressible after printing the printed surface. Thus, after digital printing there is not only the possibility of sealing by means of an UV protective lacquer; the printed substrate may also be pressed, for example, in a short-cycle press with a melamine overlay. An UV ink would not stand the required temperatures of over 160 °C, whereas for water-based inks these temperatures were no problem. In addition, due to the lack of solvent water-based inks are more environmentally friendly and therefore more versatile.
Concerning the inks Wemhöner works closely with the ink manufacturers and the supplier of the printheads, Kyocera. Kyocera has given its approval for certain applications of ink. Thus the user has the security that his ink meets his application requirements to 100%.
Quality made by Wemhöner
Except from the printheads, the MasterDigital printing machines are completely self-producted by Wemhöner. The base is a particularly heavy machine stand out of steel. It absorbs the strengths arising at the accelerations by the linear drive of the printer unit so that this can drive over the substrate free from vibrations. This high-precision component is not only responsible for the precise movement of the printhead, but it is designed in a way that the vertical distance between the printheads and the substrate is always the same. In specifically defined acceleration and deceleration areas, the acceleration and deceleration of the printing unit takes place before the change of direction. The real printing begins only after reaching the final speed. Depending on the requirements, the printing speed is up to 2.4 m/sec.
Tolerance range less than 1/100 mm
For the precision of the pressure, at least as important is the positioning of the conveyor belt on which the materials to be printed are carried according to a well-defined program. Owing to this vacuum transport, the material is held in the track absolutely precisely, the deviations are less than 1/100 mm. Moreover, the vacuum can be adjusted to variable widths of material as well as to different materials, which must be sucked sometimes more, sometimes less. The result of all this engineering technicalities is a perfect repeatability.
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