Gravure printing adopts direct printing. The structure of the printing press is simpler than the offset printing press, and the operation and maintenance are also simple. The printing speed is fast, and the printing plate cylinder is very resistant to printing force and surpasses all other kinds of printing.
Gravure presses have different sizes of printing presses, as well as sheet-fed gravure presses and web-fed gravure presses. They are gravure plates. In terms of classification, printing presses are divided into photogravure printing machines and gravure printing machines. Photogravure printing machines are used more often than gravure printing machines. Most gravure printing machines are rotary printing machines.
(A) Photogravure printing machine
1. Kind
In addition to the usual classification of photographic gravure printing presses, depending on the purpose of printing, the gravure printing press is also attached with some ancillary equipment to improve the printing and post-processing functions.
1 Book printing: For printed books, magazines, and catalogs, a folding device is attached to the delivery section.
2 paper container printing: used to print thick cardboard, it is attached with the post-processing equipment for punching the carton.
3 Flexible Packaging: For printing flexible film materials such as plastic film, cellophane, etc., a rewinding device is provided at the delivery section to rewind the printed flexible packaging material.
4 building materials used for printing: for printing grainy paper, decorative paper, etc., requires a large paper web wide printing machine, also in the receiving part is also attached to the rewinding device, roll the paper roll into the user.
2. structure
The structure of the gravure printing press is similar to that of the letterpress rotary printing machine and the offset printing rotary printing machine and consists of a paper feeding portion, an ink printing portion, a printing portion, a delivery portion, and a drying portion. There are special requirements for the impression cylinder, the version of the cylinder, the inking device, and the drying device.
(1) The impression cylinder
Since the plate cylinder is cylindrical, the image is directly formed on the surface of the cylinder. If the diameter of the plate cylinder is different or uneven, it cannot be adjusted like the relief plate or the lithographic plate. Therefore, the pressure surface of the impression cylinder of the gravure printing machine is increased. To have a 3.5 mm lining, the outermost lining is a blanket, the inner layer is a paper and wool, when the surface diameter of the plate cylinder is different, in order to ensure a uniform and sufficient pressure, it is necessary to adjust the lining All or part.
Since the plate cylinder is a cylinder, the bite teeth on the impression cylinder are also different from plain printing and embossing. There are two kinds of pressure control and spring pressing using a convex plate. Reliable, easy to adjust, so more applications.
(2) Plate cylinder
The images and texts are directly formed on the plate cylinders. Each time the plate is changed, the plate cylinders need to be changed. Therefore, each gravure printing machine is provided with a larger number of plate cylinders for circulation, and the plate cylinders are also loaded and unloaded. Conveniently, it can be moved radially. When the plate cylinder idles, it is disengaged from the platen roller due to the displacement of the plate cylinder. The embossing roller still runs along the fixed axis.
The plate cylinder and the impression cylinder are arranged vertically. Tilt and horizontal, plate cylinders are all below. The ratio of plate cylinder to impression cylinder diameter is 1:2 and 1:1.
The plate cylinder and the impression cylinder have a 1:2 structure. The plate cylinder can be made smaller. The entire circumference is a layout. The impression cylinder can be printed one revolution and the plate cylinder must be rotated for two weeks. Squeegeeing is also performed twice, which has a large wear on the layout and is limited by the force resistance.
The printing roller with a 1:1 structure of the plate cylinder and the impression cylinder, because the impression cylinder needs to have the position of the fixed lining device, the surface of the plate cylinder can not be used for producing the graphic, but the two rollers rotate at the same speed. , high resistance to India.
(3) Inking device
The inking device of the gravure printing machine is totally different from the inking device of the letterpress and lithographic printing machine. The gravure printing ink is in the form of a liquid and is contained in the ink tank. The ink is transmitted to the printing cylinder in two ways: open type and closed type. The open style is further divided into direct inking and indirect transfer, as shown in Figure 5-23.
One-third of the direct transfer printing plate cylinder is directly immersed in the ink tank. When the printing plate cylinder rotates, the ink sticking on the roller is taken out, and the excess ink is then added by the upper doctor. Scrape off and print once after embossing with the paper.
The indirect transfer printing plate cylinder is in contact with the transfer roller, and the transfer roller transfers the ink sticking from the ink tank to the printing plate cylinder. The excess ink is scraped off by the squeegee on the upper side of the plate cylinder. Finish printing after imprinting.
2 Closed ink
The plate cylinder is placed in a closed container, and the ink is sprayed onto the cylinder by the bite. The ink scraped by the layout is recycled. This method can prevent solvent evaporation, reduce pollution, and reduce costs.
The squeegee is made of 0.15 to 0.30 mm spring steel. The position of the blade and the pressure angle of the plate are both
The use of a squeegee to scrape off excess ink is a traditional old method. At present, the high-speed gravure printing machine is changed to a chemical wiping method, and a special wipe roller is used instead of a squeegee.
(B) Engraving gravure printing machine
Compared with gravure printing and gravure printing, the gravure printing and photogravure printing machines have deeper and larger lines and dots in graphic parts, and require strong printing pressure during printing. The general pressure is 150-200 kg/cm3. Therefore, engraving and gravure printing machines are The structure should have high stiffness
Figure 5-24 Squeegee
In the past, in order to improve the printability, increase the transfer rate of ink, give a certain amount of moisture to the paper on the imprint, for the wet method
The types of structures that are carved into gravure printing presses include: hand gravure printing presses, gravure printing presses, and gravure printing presses.
Hand-type gravure printing presses were early gravure printing presses, and now some proofing machines use this form.
Rotary gravure printing presses have different forms of motion, which are divided into two types: double-table and double-circular type. The characteristics of double-format version are similar to that of a round-press type letterpress printer. As shown in Fig. 5-25, the platen circulation type is shown in Fig. 5-25. The plate is loaded with four printing plates on the platen table, and the printing plates are connected by a chain during the printing and are circulated and moved on the quadrilateral guide path. In the fixed position of the moving device, there are an inking device 1, an ink wiping device 2, an auxiliary wiping device 3, and an impression cylinder I. The printing plate is inked in one place, two inks are wiped, three inks are assisted, and four are given. Paper, through the impression cylinder I, to 5 to receive paper, plate table along the four sides
Figure 5-25 Plate Rotary Gravure Printing Machine
Rotary gravure printing machine commonly used multi-color engraved gravure rotary machine (Figure 5-26), in the vicinity of the plate cylinder, there are four automatic clutch inking device, plate cylinder P mounted two identical gravure A, B Contact with the impression cylinder I, complete the imprinting, printing, swatch roller P1 ~ p4, first by the respective inking device swatch stencil inking, then the swatch roller roller on the ink transferred to the elastic plastic roller S, and then by The elastic plastic roller applies the ink of different colors to the printing plates A and B, wipes the excess ink on the plate through the wiping device C, and finally, the multi-color printing is completed by one rotation of the printing plate cylinder. This printing method The ability to change colors between pattern lines is conducive to anti-counterfeiting, so it is most suitable for printing valuable securities.
Gravure printing presses automatically
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