How to deal with digital plate making in gravure p

2022-06-23
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How to deal with the digital plate making of gravure printing gravure printing is mainly used in food packaging, human leather, cigarette packaging, building and home decoration materials, flooring materials, fabrics and other fields. Gravure printing has the advantages of high gloss, strong coloring power, bright color, good transfer and overprint performance, high printing density, large contrast, balanced dot and step expansion, high printing resistance and fast printing speed

many gravure printing manufacturers in China use many plate making methods, but with the rapid improvement of printing plate making technology in recent years, digital plate making has gradually occupied the mainstream of the market. Digital plate making refers to the transmission of color information in the form of digital signals in the process of copying the original to the printing plate. Its main advantages are as follows:

① it simplifies the plate making process, and the printed plates can be obtained from the produced graphic documents through computer control; ② The direct cost of plate making is reduced, and the use cost of film is exempted

③ the loss of signal in the process of color restoration is reduced, which is more conducive to color management

④ solve the continuous and seamless splicing of graphics on the roller, and greatly enhance the practicability in the fields of decoration, textile and so on

⑤ the format size changes more freely. At present, China can make 2800mm 2000mm printing plates, which are completely free from the restriction of the output film of the imagesetter; ⑥ It can provide precise positioning for the implementation of multiple processes on the same drum, and there can be points with different line numbers and different line angles on the same plate

according to the actual situation in China, there are three methods for gravure digital plate making:

① electronic engraving machine

② laser etching and post corrosion treatment

③ laser direct ablation plate making method for electroplating alloy

I. electronic engraving machine mode

electronic engraving machine is a precision machine with high quality stability, which applies modern technologies such as integrated automatic control. It is suitable for measuring the static friction coefficient and dynamic friction coefficient when plastic film, sheet, paper and other materials slide. Take the German hell machine as an example. The engraving frequency is 4000hz- 8000Hz. The line range is 40- 140 lines/cm. After the original is made by color separation, it is transmitted to the electric engraving machine workstation in 1- bit TIFF graphic format or bill unit through rip. The diamond engraving needle is driven by digital signals to vibrate on the surface of the printing plate copper roller to carve pits. The diamond carving head is in a pyramid shape. The V-shaped pit made by the electric carving head not only changes in depth, but also changes in area, thus completing the halftone reproduction of graphics and texts

all production data of electric carving are collected in digital form, which can be used in subsequent live parts with strong reliability. From the beginning of being scanned, the original becomes a digital signal, which is sent to the software for color separation and then transmitted to the electric engraving machine or color proofing machine. This is very beneficial to the standardization and standardization of the production process, thus ensuring the quality of the printed matter. In addition, the electric engraving workstation uses TIFF graphic data for transmission. It is convenient to integrate and set the working parameter configuration through heliolight edition workstation. The engraving software generates the electric engraving curve, records the electric engraving parameters and displays the engraving status until the disc is burned to save the file (so that it can be used and revised for many times)

the electric carving process is relatively mature, with simple control and realistic hierarchical restoration. The disadvantage is that the amount of ink on the field is limited, and the ink layer is insufficient to cover some rough substrates; Due to the wall partition between holes in mechanical carving, the edges of lines composed of holes are inevitably jagged, and small words are not clear and easy to break lines or paste plates during printing. However, Haier in Germany recently introduced Xtreme engraving technology, which can reproduce the most subtle part very finely under the number of lines up to 400 lines/cm. Fine text can independently select the recording resolution without depending on the number of engraving lines, and smooth the contour and generate contour lines by optimizing the ink flow. Both conventional points and FM plus copy can be realized

besides the mature products of Ohio, Haier, Japan and MDC in Switzerland, some domestic manufacturers have developed products with similar performance

II. Laser film engraving and post etching process

laser film engraving and post etching process is another advanced digital plate making method after relay engraving. Like electric engraving, it receives color separated image files through the interface, and sends the added picture and text signals to the laser modulator to excite the light on the pre coated protective layer on the surface of the drum, exposing the copper or iron bottom, After corrosion at different times, pits of different sizes are formed on the drum

take the Siemens 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 it is focused into a 20 spot through the lens. The laser smashes the black glue on the surface of the drum, and the residue is discharged into the collection bag through the suction pipe. The remaining black glue forms an anti-corrosion protective layer on the surface of the drum. Finally, the concentration and spraying time of FeCl3 solution are controlled in the corrosion tank, and points with the same depth but different sizes are generated on the surface of the copper layer or the iron roller

the laser film engraving process overcomes the weakness of electric engraving characters and thin lines. It highlights the characteristics of high ink content, thick color, clear handwriting and durability. Compared with the traditional gravure plate making, it also has the advantages of high accuracy, arbitrary shape and no seams. It is suitable for printing plates with particularly small text but high definition, such as cigarette plate and anti-counterfeiting printing. It is widely used in high-precision anti-counterfeiting printing of currency, securities, ticketing and high-grade tobacco and alcohol packaging. It has more advantages in the production process of fine embossing roller and coating roller

there is also a photosensitive laser mode, which uses a violet laser to expose and then rinse the photosensitive layer of the graphic part. Other processes are basically the same as laser film engraving

III. laser direct ablation plate making method of electroplated alloy ō In the DLS (direct laser system) system of Wyler company, the high-power YAG pulse laser vaporizes the zinc layer on the surface of the galvanizing roll to form points in a non-contact way, and then hard chromium plating is completed. In such cases, the whole process is completed. Zinc is selected because its physical properties (melting point, boiling point, hardness) and reflection characteristics are more suitable for laser ablation than copper. The DLS system supports general PS, PDF and TIFF data formats, and generates points of different sizes and depths by adjusting the energy and focal point diameter of each laser pulse point. At present, the maximum point is 140 and the depth is 35, which is mainly applicable to cigarette packets and anti-counterfeiting printing. This is also the most important and longest emerging laser ablation technology. The wide application of laser ablation technology in gravure will be rapidly popularized with the development of laser technology. It does not need mechanical adjustment, and the thin lines and words are clear, which is easier to control the level than corrosion

at present, German hall company has launched a new laser engraving machine, cu- diretlaser system. It uses high-resolution laser to engrave the surface of the copper drum. The contour, point distribution and depth of the engraved information can be changed arbitrarily, so as to achieve the output effect that only the laser Imagesetter can achieve before

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