First, the principle and characteristics of gravure printing 1. Gravure printing principle Gravure printing plate layout and seal similar, the printing method is similar to rubbing or printing.
Earlier seals were usually carved letters that had been carved into text and were printed on dirt or paper (called mud). After the method of writing or painting, they formed the text of the negative writing. If the image of the seal is engraved into the positive image of the anti-body (the figure is highlighted), the method of the extension or the embarrassment is the positive figure written to the right.
The surface of the stone (stone) engraved with a concave image (an overcast image) is coated with a wet, soft tissue paper, and then a slight pressure is applied to the surface of the paper (slight brushing) to engrave the paper. In the recessed graphic part, after the paper is dried slightly, brush it with a soft-bristle brush (or use a soft cloth) evenly. Due to the fact that the indented part of the text does not contain ink, the white-on-black-on-white (Yin-Yi-Wen-wen) extension, commonly known as the Rubbing inscription, is obtained. If the image on the stone tablet is engraved into positive writing (part of the graphic and text is highlighted), the rubbing of the positive image (black text on white) can be obtained in the same way.
Gravure printing uses the principle of rubbing. The text is carved on a cylindrical metal surface to make a gravure plate. Then, the printing plate is coated with ink, and then the ink layer on the surface of the printing plate is scraped off, the printed matter is then spread, the printing pressure is applied, the ink layer embedded in the graphic is transferred to the surface of the printing object, and the gravure printing product is obtained.
With different depths of concaves and concaves, the depth of the ink layer can be accommodated. When transferred to the surface of the printed matter, thick and vivid printed images are obtained.
2. Gravure printing features The gravure printing plate layout is contrary to the relief plate layout. The graphic part is concave and the blank part remains the original plane. The graphic part is concave and receives the ink layer. After the pressure of the impression cylinder, the ink layer is transferred to the surface of the printed matter and is reproduced as a printed matter.
Compared with other printing methods, gravure printing has the following features:
1 thicker ink layer. The thickness of the gravure ink layer is 1-50μm, second only to screen printing (15-100μm), and much higher than the embossed (2-6μm) and flatprint (1-4μm). Therefore, the density of printed matter varies greatly, and the layers are rich. Thick and thick lines of ink are thick and glossy; thin lines, though fine, are clearly distinguishable;
2 The area between the dots of other printing methods is blank, and a thin layer of ink is coated between the dots of the gravure printing. This is due to the strong fluidity of the gravure ink. Therefore, the gravure layer is delicate and suitable for continuous tone.
3 The gravure printing uses the detachable roller, the circumference of the printing roller is allowed to change, and it can adapt to different finished product sizes;
After chrome plated on the 4th edition roller surface, the plate surface is smooth, the texture is hard, its printing rate is higher than other printing methods, suitable for large-volume printing and reprint printing, and the printing roller can be stored for a long time;
5 a wide range of applications. By selecting different inks, printing can be performed on various materials such as paper, plastic films, textiles, aluminum foils, and cellophane;
6 The plate making process is complicated, with many unstable factors, long cycle and high cost. Corrosion and chrome plating liquids can cause public hazards;
7 The printing ink solvent is volatile and pollutes the environment.
3. Gravure Printing Gravure Printing There are mainly two types of gravure, gravure and electronic engraving gravure. According to different plate-making processes, the photogravure is divided into two types: ordinary gravure and dot gravure.
(1) Ordinary gravure plate The so-called gravure gravure plate refers to the gravure made by exposing the image of the continuously adjusted film to a sensitized and carbonized carbon paper, and then printing it onto the surface of a copper cylinder and developing and etching it. . It expresses the tone level of the manuscript by means of the cells with the same area and different depth on the plate (ie, different ink layer thicknesses).
The original manuscript used in photogravure is a positive manuscript manuscript. The whole process of plate making includes four parts, namely the production of positive manuscript manuscripts, the pretreatment of carbon paper, the pre-processing of rollers, and the production of intaglio, as shown in Figure 1-45.
Carbon Paper Core Processing ↓ ↓
Photographic coating copper ↓ ↓
Photographic original sun mesh grinding ↓ ↓ ↓
Text Manuscript→Continuously Adjusting Yang Picture→Sun Positive Image→Transferring→Developing→Apply Corrosion Inhibitor→Chromium Plating→Correction→Inspection Figure 1-45 Ordinary Photogravure Production Process The so-called continuous involution manuscript refers to a manuscript whose tone value is continuous and gradual. , It can be a monochrome or original document. The production of positive manuscript manuscripts mainly includes the following contents: the production of image-positive pictures, the production of text-positive pictures, and the arrangement of positive pictures. The quality of the printing depends mainly on the quality of the positive image, because the positive images are printed directly to make the carbon paper and then transferred to the surface of the plate cylinder. If there is a certain defect in the positive picture, it must be reflected on the plate, and it is difficult to make corrections. Therefore, the correction of the Yang picture is very important.
Ordinary photogravure still occupies a certain proportion in the current color gravure platemaking, and it does not require high printing quality, or it can print on a narrow-width polyethylene printing material. This type of gravure is acceptable if there are no seams or joints are few. of. However, from the overall trend of development, ordinary gravure should gradually be eliminated.
(2) Mesh photogravure dot photogravure, also known as direct corrosion gravure or sprayed gravure gravure, is a gravure made by directly printing photo resist on the gravure copper drum and printing and etching. Its characteristic is to use the size of the dots to represent different tones and levels, as shown in Figure 1-46.
Yang pictures
Drum pre-processing → coating photosensitive solution → printing plate → developing, washing → painting → corrosion → washing → chrome plating → gravure Figure 1-46 dot gravure production process This plate making method has been widely used. The plate making point is that after the plate cylinder is pre-processed, the photosensitive liquid is coated on the surface of the roller, and the positive image is printed with a screen, then the solvent is used to develop and rinse the hard film, and after it is dried, it is etched with a ferric chloride solution. The drum pre-processing is the same as ordinary gravure.
(3) Electronic engraving The gravure electronic engraving gravure is a novel gravure making process. The so-called electronic engraving gravure refers to the gravure made by electronically controlling the carving knife on the surface of the copper drum according to the principle of photoelectricity.
In 1967, the German company Haier completed the development of the world's first electronic engraving machine. In 1977, the Ohio Electronic Engraving Machine came out. In 1992, the Ohio company launched a new model, the OEE electronic engraving system, which expanded the capabilities of the OEE electronic engraving machine, thus realizing the so-called non-film-making process.
Compared with other intaglio plates, electronic engraving gravure has the following main features:
a. Platemaking process is more simplified, easy to control the quality of the plate; b. The quality of the plate is stable, the engraving quality is excellent; c. Has a variety of functions, can achieve seamless plate making; d. No engraving corrosion pollution, improve the working environment; e. The price of engraving equipment is higher, and the cost of plate making is higher. f. The carving knife is a part that is easy to wear, and the plate making cost is higher; g. The engraving speed is higher than that of the generation.
In the production of the electronic engraving gravure, the pre-processing of the drum is the same as that of the gravure, and the whole process of the plate making process is shown in Figure 1-47.
Make original film → paste film → install plate roller → test → electronic engraving → chrome plated
Drum pre-processing Figure 1-47 Electronic Engraving Intaglio Making Process The original used in the electronic engraving machine is a color-screened positive/negative film, which is generally made of a small, stretchable, opaque polyester film. The negative film should be flat and firm when pasted. Before engraving, the surface of the pre-processed plate cylinder is cleaned to remove foreign matter such as oil, dust, and oxide on the surface of the copper, and then mounted on an electronic engraving machine. In addition, prior to engraving, the various levels of highlights and darkness of the original document should be tested to determine the number of screen lines and the shape of the dots. When engraving, when scanning, the engraving knife that moves synchronously with the scanning head performs automatic engraving on the surface of the printing plate cylinder. Finally, in order to increase the printing durability of the printing plate, chrome plating should be performed after engraving.
Second, gravure printing equipment Modern gravure printing machine is divided into two types according to the form of substrate, namely, sheet-fed gravure printing machine and web gravure printing machine.
(1) Sheet-fed gravure printing machine Sheet-fed gravure printing machine refers to a machine for gravure printing using a single sheet of paper.
1. Basic structure and main equipment The basic structure of a typical model of a gravure printing machine is shown in Figure 1-48. It consists of a paper feeding device, a printing device, an inking device, and a delivery device.
The plate cylinder (P) is generally 1/2 the diameter of the impression cylinder (I). The surface of the impression cylinder is wrapped with a certain thickness of liner, and the plate cylinder is directly immersed in the ink fountain. The excess ink is scraped off with a squeegee during printing, and the ink is transferred from the impression cylinder to the plate cylinder to complete the ink transfer. After printing, it is output by the delivery device and the paper is delivered.
(1) Feeding device The feeding device is basically the same as other types of sheet-fed printing presses. The paper is positioned and accelerated by the input register device of the automatic paper feeder, and then the paper is pressed by the impression cylinder to bite the paper for printing.
(2) Drum parts The drum parts are mainly composed of a plate cylinder and an impression cylinder. The arrangement of the two rollers has three types of vertical arrangement, horizontal arrangement, and arrangement of overseas Chinese. Generally, they are arranged vertically or obliquely. According to the different diameters of the two rollers, there are the following two types, that is, 1:1 type and 1:2 type, as shown in Figure 1-49.
21:2 type. The diameter of the plate cylinder is 1/2 of the diameter of the impression cylinder. The smaller the diameter of the plate cylinder, is conducive to the gravure plating process. In addition, the impression cylinder rotates for 1 week, and the plate cylinder rotates for 2 weeks. The ink is also applied and the ink is scraped twice. The effect of ink is better. Moreover, the entire circumference of the plate cylinder can be used as a layout. Therefore, this model is widely used.
1 basic form. There are mainly three types of short ink inking devices, namely, immersion, ink fountain roller, and ink jet.
About 1/3 of the lower half of the plate cylinder is directly immersed in the ink fountain, and the inking process is completed by the rotation of the plate cylinder. Excess ink is scraped off with a squeegee. This form is a standard form of gravure printing machine inking device.
b. Ink roller roller inking device. The ink of the plate cylinder is completed by the ink fountain roller and its basic
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