The effect of mixed wetting device on the offset ink-water balance
The mixing and wetting device is also called a water and ink flushing device. Its main feature is that the same plate is used to wet the printing plate, and water and ink are supplied to the printing plate at the same time. Heidelberg, Manroland, KBA and many other well-known brand printers have adopted this device, which is easy to achieve water-ink balance.
Offset water-ink balance refers to the use of the minimum amount of ink and water under the premise of ensuring that color reproduction, gray balance, color density and tone values ​​meet customer requirements under certain printing speed and printing pressure.
According to the actual situation of water and ink balance, in order to prevent the increase of the dots and protect the blank part, the water consumption in the printing area where the amount of ink is large is also large. The ink and water of the form roller that transfers ink and water before the pressure is combined Consistent. After a few turns of the platen roller, the amount of ink on the roller will change, as shown in Figure 4. According to the principle of oil-water incompatibility, where the ink on the rubber roller is rich, the water absorption is poor, and the amount of water absorption is small; on the contrary, the place where the ink is small is the amount of water absorption. Therefore, the left end of the plate roller absorbs a large amount of water, and the left end of the printing plate is also a region with a large amount of ink supply, so that the water-ink balance required for printing is achieved.
The mixing and wetting device is easy to form proper ink emulsification, and the blank part is also easy to be dirty. In fact, the graphic part of the printing plate used in offset printing is on the same plane as the blank part. , So when the platen roller is in contact with the printing plate, the blank part absorbs water, and the graphic part absorbs ink, and the blank part will not be dirty. Due to the force of the ink in the transmission process, the ink will be slightly emulsified. This emulsification is also required for printing and will not cause emulsification failures because the content of water (foaming solution) in the ink is low and will not exceed the threshold. value.
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