Analysis of capillary transfer printing technology for ink

Ink is transferred from the ink holes to the surface of the substrate through capillary action (in some cases, the proofing machine also uses an electrostatic assisted ink transfer device). The large drum rolls to the end position of its circumference to obtain a large printed sheet. After the rolling is completed, the large cylinder leaves the surface of the plate cylinder, and the plate cylinder can be cleaned and disassembled at this time. The sampling of each color after the second color should be repeated after the previous color has dried, following the same process as described above.  
Soft packaging materials can cause stretching and shrinking of printing materials during printing. Printing companies require an increase in the number of color group plate rollers when making plate rollers, which can pose certain challenges for sampling. Experienced operators can use the drop in dots to produce samples with high registration accuracy.
The ink transfer of Japanese machines is achieved by using pressure to drive the embossing cylinder to roll and transfer ink onto the substrate. The machine speed is generally around 30m/min, but the separation speed between the embossing cylinder and the gravure cylinder is different from the start to the end because the substrate is tightly wrapped on the surface of the printing cylinder. Under the inertia of the cylinder, the speed increases, and the second round of sampling speed will be faster than the first round. The British machine completes ink transfer by using pressure to drive the plate cylinder to roll. The speed of the impression cylinder itself is kept constant, and the speed of the substrate tightly wrapped around the impression cylinder is the same from beginning to end. This solves the problem of inconsistent rolling speed in Japanese machines. When making samples, first tightly wrap the substrate on the impression cylinder, and then make samples according to the printing order based on the inner and outer printing characteristics of the plate cylinder.
The substrate for printing plates is usually transparent. When making samples, a dark color is first printed, and then a light color is printed on top of the previous color. For example, for prints with only four-color electric separation images and white plates, a black plate is usually made first, followed by a green plate, a magenta plate, a yellow plate, and finally a white plate based on these four colors. The sampling sequence of the printing plate is opposite to that of the inner printing plate. The substrate of the printing plate is mostly opaque, so the sample should be made in the order from light to dark. When making samples, it is also necessary to pay attention to the important factor of sample ink.
The gravure proofing machine does not have an ink tank component. When the embossing cylinder is in close contact with the gravure printing plate cylinder during proofing, the prepared ink is manually poured onto the gravure printing plate cylinder. Because the speed of the sampling machine is not high, it determines that the viscosity of the ink used for sampling cannot be too low, otherwise it will lead to paste. Under normal circumstances, the high-speed gravure printer can be driven to 160m/min, with an ink viscosity of around 16s. However, the ink viscosity used for gravure sampling should be adjusted to around 20s. Slow sampling speed, high ink viscosity, and low rubber hardness on the impression cylinder are all beneficial for the full transfer of ink to the substrate, resulting in a more vibrant color of the sample.
If the ink is not diluted with ink blending oil during sampling, it will also cause great trouble for the printing company, as it is difficult for them to print very bright and lively color effects. It is necessary for plate making companies to dilute the ink when making samples, so that printing companies can easily adjust the color and make samples based on gravure printing samples. In the entire process of intaglio plate making where no soft film carving has been achieved in electric engraving, the most human influenced factor is the intaglio proofing workshop. The dilution of the sample ink, the degree of dilution, the pressure between the gravure printing plate cylinder and the embossing cylinder, the angle and installation method of the scraper and its pressure, and the unequal spacing between the scraper and the embossing point can all affect the effect of the concave sample.