Gravure Printing Process (1)

(Basic Gravure Printing) Part 1 Introduction Gravure Printing is a simple, flexible, and versatile process. The range of applicable substrates is very wide, and the prints are bright in color, moderate in contrast, vivid in image, strong in three-dimensional, and of high quality. They are often used. Printing of magazines and newspaper supplements. In addition, compounding and glazing can also be performed after printing. In simple terms, the gravure printing machine is mainly composed of the following components (as shown in Figure 1): 1. Plate cylinder 2, rubber impression cylinder 3, ink tank 4, ink scraper 5, ink drying device Figure 1 Gravure The main part of the printing part of the second part of the gravure printing cylinder First, the composition of the gravure printing drum and processing version of the gravure printing version of the drum is mainly composed of the following components: 1, the roller body, also known as the roller core, is the version of the drum support . 2. Electroplated copper layer, which has a great influence on the service life and performance of the plate cylinder. 3, the surface of the chrome plating layer: greatly enhance the printing surface hardness, wear resistance, chemical stability and other printability, thereby enhancing the resistance to printing force. Otherwise, the plate cylinder is liable to cause damage during the printing process. Figure 2 If the ink and squeegee used are compatible with the drum, the desired effect will be obtained after printing. In today's gravure printing industry, there are basically two types of drum engraving methods: chemical etching and electronic engraving. Among them, the most commonly used chemical etching method is the direct transfer method, but with the development of electronic engraving technology, this method has gradually withdrawn from the stage of history. Regardless of which of the above engraving methods is used, the same roller body is used. After the steel or aluminum alloy roll body is polished and polished, it must be plated with copper, chrome plated, and then polished, and then it is ground to a predetermined size. People always hope that the same batch of drums will be 100% identical in size, but in reality this is difficult to achieve, and there will always be an error of a few thousandths of an inch. Therefore, it is easy to see that the diameter of the roller is a very important parameter. If the two rollers are not the same size, for example, a difference of 0.0002 inches, then the circumference of the two rollers will be almost different by 0.0006 inches. In a gravure printing machine, if a larger sized cylinder is placed in the former color group and a smaller sized cylinder is placed in the rear color group, the printing stroke traveled by each large sized cylinder is smaller than the small size. The drums are longer, and this will inevitably result in overprinting. Second, the arrangement of printing color order In the gravure printing of roll material, the registration between different colors depends on the linear speed of the roller and the size of the tension. In theory, the diameter of all platens should be exactly the same, and it is entirely possible to use a modern polishing device. If the diameter of the plate cylinder is deviated, the operator should place the plate with the smallest diameter in the first color group, and the plate with the largest diameter should be placed in the last color group. That is to say, the first color is printed first with a roller having the smallest diameter, and the last color is printed with the roller having the largest diameter, and the two are arranged in ascending order. It should be noted that the error we are talking about here is an error of a few thousandths of an inch. The printing color sequence used for surface printing is generally from light to dark, that is, according to the order of the colors from light to dark, the printing color sequence is arranged, the light color is printed first, and then the printing is dark color, basically yellow (Y)è magenta ( M)è Cyan (C)è Black (K) order. In the printing process, the color sequence of the printing is the opposite. The dark color is printed first and then the light color is printed. That is, black (C) è magenta (M) è yellow (Y). Third, the version of the engraving drum Figure 3 Electronic engraving diagram attached to the original document attached to the scanning roller, the scanning head of the original scanning, at the same time, the scanning head sends a pulse signal to the computer, the computer drives and controls a hexagonal pyramid in a certain order Shaped engraving heads sculpt the dots at the corresponding positions on the copper plated roller. The hexagonal pyramid-shaped carving knives sculpt an inverted-pyramid shape on the surface of the plate cylinder. The opening of the cell can reach a maximum of 200 microns (0.008 inches) and a maximum depth of 50 microns (0.002 inches). The actual volume of the electronically-engraved net hole is about 30% smaller than the volume of the net hole formed by the chemical etching method. However, there are other factors, such as the greater the opening degree of the electronic engraving net hole, the release property of the ink. The better, so that it can compensate for the lack of network space to a certain extent. Figure 4 Comparison of the shape of electronically engraved cells and chemically etched cells In the field of the image, the electronic engraving machine can also sculpt channels between the cells to improve the fluidity of the ink in the cells and enable the ink transfer performance of the plate cylinder. Significantly improved, resulting in a smooth ink film in the field area.