Gravure printing is mainly used in a wide range of fields such as food packaging, human leather, cigarette packaging, building home decoration materials, flooring materials, and fabrics. Intaglio printing ink has high gloss, strong coloring power, vivid color, good transfer printing and overprinting performance, high printing density, large contrast, enlarged balance of halftone dots, high printing plate resistance, and high printing speed. Many gravure printing factories in China use a lot of plate making methods, but with the rapid improvement of printing plate making technology in recent years, digital plate making gradually occupied the mainstream of the market. According to the actual situation in China, gravure digital platemaking has three methods: 1 electronic engraving machine mode; 2 laser engraving and post-etching treatment; 3 electroplating alloy laser direct ablation plate making.
First, the electronic engraving machine type electronic engraving machine is a modern machine with integrated automation and control, and has a high-quality and stable precision machinery. Taking the German Hell machine as an example, engraving frequency 4000Hz-8000Hz network cable range: 40-140 lines / cm, after the manuscript is produced by color separation, through the RIP after 1-BitTiff graphics format or bill unit to the electric engraving machine workstation, through the digital The signal-driven diamond engraving needle vibrates on the surface of the copper plate cylinder to sculpt the pit. The diamond carving head has a quadrangular pyramid shape. The v-shaped pits produced by the electric head not only changed in depth, but also changed in size, thus completing the halftone reproduction of the graphic and text. All electric production data are collected in digital form and can be used in subsequent jobs with high reliability. The manuscript becomes a digital signal from being scanned and sent to the software for color separation and then transmitted to an electric engraving machine or a color proofing machine. This is very favorable for the standardization and standardization of the production process, and thus the quality of the printed matter is more assured. Moreover, the electric carving workstation uses TIFF graphic data for transmission, after HelioLight version workstation for convenient integration and setting the working parameter configuration, the engraving software generates electric carving curves, records the electric carving parameters and shows the engraving status until the disc is saved. (Convenient for multiple use and revision).
The electric carving process is relatively mature, simple in control and realistic in level reduction. The disadvantage is that the amount of ink on the ground is limited, and the ink layer does not have enough hiding power for some rough substrates; due to the mesh wall partition between the mechanically engraved network points and the net points, the occurrence of sawtooth edges on the edge of the lines formed by the net holes is inevitable. , Small text is not clear when printing and it is easy to break or paste. However, Germany's Haier recently introduced the Xtreme engraving technology. It can reproduce the finest parts with extremely fine lines of up to 400 lines/cm. Fine text can be independently selected for recording resolution without depending on the number of engraving lines. The flow of ink smooths the outline and creates the outline. Both conventional sites and FM screening can be implemented. In addition to the mature products of electric engraving equipment manufacturers in the United States, Ohio, Germany, Haier, Japan screen and Switzerland mdc, there are also domestic manufacturers have developed products with similar performance.
Second, laser-engraved film and post-etching process Laser-engraved film and post-corrosion process is an advanced digital plate-making method after the electric carving. It accepts the color-processed image files through the interface as well as the electric sculpture. The image signal is sent to the laser modulator. The laser acts on the protective layer precoated on the surface of the drum to expose the bottom of copper or iron. After different times of corrosion, pits of different sizes are formed on the drum. Take the West Bass Ohio SCHEPERS laser machine in Germany as an example. It uses a neodymium-doped yttrium aluminum garnet (Nd3+:YAG) solid-state laser. The laser power is not higher than 50W, and the lens is focused to a spot of 20μ. The laser breaks up the black glue on the surface of the drum, and the residue is discharged into the collection bag from the suction pipe. The retained black glue forms a corrosion-resistant protective layer on the surface of the drum. Finally, the concentration of the FeCL3 liquid and the spraying time are controlled in the corrosion tank in the copper. Layers or iron roll surfaces produce mesh dots of uniform depth and size. The laser engraved film process overcomes the weaknesses of electrograined texts and thin hairlines and hairlines, highlights the characteristics of high ink content, thick colors, clear writing, and durability. Compared with traditional gravure platemaking, it has high screening accuracy. , Arbitrary editing mesh, no seams and other advantages. It is applicable to printing plates with particularly small texts, but with high definition, such as smoke plate, anti-counterfeiting printing, and is widely used in high-precision security printing such as currency, securities, ticketing, and high-grade tobacco and wine packaging, and in the production of fine embossing rollers and coated rollers. The process has more advantages. There is also a sensitizer laser method that utilizes a violet laser to expose and irradiate the photosensitive layer of the graphic portion. The other processes are basically the same as the laser engraving.
Third, the electroplating alloy laser direct ablation plate making method Currently used in the market is DÅwyler's DLS (Direct-Laser-System) system, high-power YAG pulsed laser galvanizing roller surface zinc gas in a non-contact manner of irradiation The formation of dots, followed by hard chrome plating completes the entire process. Zinc is selected because its physical properties (melting point, boiling point, hardness) and reflective properties are more suitable for laser ablation than copper. The DLS system supports universal PS, PDF, and TIFF data formats. By adjusting the energy and focus point diameter of each laser pulse point to generate dots of different sizes and different depths, the current maximum dot size is 140μ, and the depth is 35μ. It is mainly suitable for cigarette packets and anti-counterfeiting. print. The extensive application of laser ablation technology in gravure will rapidly spread with the development of laser technology. It does not require mechanical adjustment, clear lines and text, and is easier to control than corrosion. At present, the German company HELL has launched a new laser engraving machine, the Cu-Diretlaser system. It uses a high-resolution laser to perform fine engraving directly on the surface of the copper drum. The contour, dot distribution, and depth of the sculpted information can be arbitrarily changed so as to achieve the output effect that can only be achieved by the laser image-setter.
The Advantages of Digital Platemaking Technology Digital platemaking is the transmission of color information in the form of digital signals as the original is copied onto the plate. Its main advantages are: 1It simplifies the plate making process. The well-made graphic and text files can be printed and controlled by the computer; 2 It reduces the direct cost of plate making and eliminates the use cost of the film; 3 It reduces the signal in the process of color reproduction. Loss, more conducive to color management; 4 to solve the continuous seamless stitching of the graphics on the roller, for the decoration, textile and other fields of practicality greatly enhanced; 5 format size changes more freely, the current domestic can produce 2800mm × 2000mm format printing plate No need to limit the output film of the photofinisher. 6 It can provide precise positioning for multiple processes on the same roller. There can be dots with different line numbers and different screen angles on the same plate.