Gravure printing is one of the four major printing methods today. Intaglio printing is the opposite of letterpress printing. The image and text on the layout are lower than the printing plane, and the shades on the surface of the printing plate are used to show the varying shades of the original. If the graphic part is deeply recessed and the amount of ink filled is large, the ink layer left on the surface of the substrate after imprinting is thick; the concave part of the graphic part is shallow and the amount of ink contained is small. The ink layer left on the substrate is thin. The amount of ink on the printing plate corresponds to the light and dark levels of the original graphic. When printing, first let the plate cylinder pass through the ink tank or use the ink transfer stick to fill the ink with the entire plate, then use a doctor blade to scrape off the ink attached to the blank part, and fill the ink in the hollow cavity, Under the appropriate printing pressure, it is transferred to the surface of the substrate. Gravure printing has fast speed (up to 300m / min or more), high printing plate durability (up to 3 ~ 4 million prints), thick ink, rich color, clear and bright, moderate contrast, realistic image, and diverse product specifications Etc. Can be printed on paper, aluminum foil, plastic flexible packaging, thick paper containers, liquid paper containers, trademarks and other substrates. With the development of science and technology, the range of gravure printing at home and abroad is becoming larger and larger. It is suitable for the printing of various materials, such as the preprinting of color packaging boxes. The carton produced by gravure preprinting is of better quality than the carton produced by traditional methods. High strength and low cost; and multi-color (up to 12 colors), high speed (above 300m / min), automation (registration automatic control and strong control, etc.), online (continuous process of gravure printing and printing are carried out continuously ) And other directions. Gravure printing mainly includes: plate making, printing and quality control. 1. Gravure plate making At present, gravure plate making mainly includes: direct corrosion gravure, electronic engraving intaglio, laser engraving intaglio, electron beam engraving intaglio, etc. Direct etching of the gravure is to print the gravure grid on the dichromate-sensitized carbon paper, then the continuous sun-shading image, and then transfer the image on the carbon paper to the roller, through The printing plate is prepared by developing, filling and etching. Direct corrosion gravure is mainly controlled directly by humans, so the plate-making stability, field density uniformity, reprint repeatability, and text clarity are poor. Generally, it is only used for ordinary plastic flexible packaging printing. Electronic engraving gravure is to engrave the gravure cylinder directly with an electronic engraving machine. It scans the manuscript through the scanning head to obtain the density light signal, which is converted into an electrical signal after photoelectric conversion. After a series of processing by the electronic computer, it is transmitted to the output end, driving the electronic engraving head, and engraving on the copper drum. And made into gravure printing plate. Laser engraving intaglio uses a laser engraving machine to engrave the intaglio cylinder; while electron beam engraving intaglio uses an electron beam intaglio engraving machine to engrave the intaglio cylinder. Electronic engraving intaglio, according to the depth of the original, the scanning head of the intaglio engraving machine converts it into electrical signals of different sizes one by one, and the strength of the vibration of the diamond engraving needle is engraved to engrave the dots of different depths on the surface of the drum, corresponding to The dots of the light part of the original are light and small, while the dots corresponding to the dark part of the original are deep and large. Because the gradation reproduction of the image is achieved through the change of the size and depth of the dots, the electronic engraving gravure can truly reflect the gradation of the original. Its plate-making stability, field density uniformity, and reprint repeatability are excellent, and the printed graphics are very clear. Laser engraving intaglio and electron beam engraving intaglio have increased the cost of plate-making due to the high equipment cost. Although these two methods engrave the plate quality is very high. However, it is still used in a small amount, and the majority of gravure is still mainly based on electronic engraving. In order to ensure the quality of electronic engraving intaglio, the size and depth of engraving mesh holes are specified in industry standards (see Table 1). However, the size and depth of the mesh holes are random (products of different companies), the number of wire lines, the old and new degree of the cutter, the angle of the cutter, the thickness of the copper layer (the hardness of the copper layer is 180 to 210 Vickers), and the product quality The influence has many variable factors. The industry standard only takes 70 lines / cm, 130 ° cutter angle and new cutter as examples. two. Gravure printing process The gravure printing adopts the direct printing method of the rotary press of the garden. Its features are: simple printing machine structure, high printing plate durability, fast printing speed, thick ink color, rich levels, and low cost when printing in large quantities. There are many types of gravure printing, which can be divided into three types according to the purpose: book gravure printing machine, flexible packaging gravure printing machine, hard packaging gravure printing machine. The book gravure printing machine is used to print magazines, books, pictorials, etc., and the back is equipped with a folding device; the flexible packaging gravure printing machine is used to print packaging materials such as cellophane, plastic film, aluminum foil and paper, and the back can be equipped with compound, glazing, mold Cut and other devices. According to the plastic method, it can be divided into two types: sheet-fed gravure printing machine and web-fed gravure printing machine, most of which are web-fed gravure printing machine. According to the classification of printing color, it can be divided into monochrome gravure printing machine and multi-color gravure printing machine. According to the arrangement position of printing color group, it can be divided into satellite gravure printing machine and combined gravure printing machine. Several color groups of the satellite gravure printing machine share an impression cylinder, and each color group of the combined gravure printing machine is arranged horizontally into a pipeline. Gravure printing, according to the requirements of the work order and sample to receive ink and substrate; then install the printing cylinder; adjust the liner on the impression cylinder to make the pressure on each part of the printing plate consistent; and adjust the doctor blade to print The angle and distance of the version, trial printing after starting. After the trial printing sample is qualified, it can be formally printed after being signed by the workshop supervisor and the customer. The following is a brief introduction to the printing process using the combined gravure printing machine as an example: 1. Unwinding device and adjustment 1) Roll paper holder The roll paper holder installs the roll paper or plastic film roll with a conical tip on the printing machine. When the paper roll is nearly used up, the automatic paper receiving device automatically bonds the new paper roll or plastic film roll. Go to the running paper belt and cut the old paper tail at the same time to complete the roll change without stopping. 2) The paper or film of the tension automatic control system needs to maintain a certain tension during the unwinding process before printing, the multi-color printing process or the post-printing paper collection process. If the tension is too large, it will cause longitudinal wrinkles, and if the tension is too small, it will produce horizontal wrinkles. In short, the fluctuation of tension will affect the accuracy of overprinting. Table 2 lists the tension values ​​of several web printing materials in different parts of the printing press. 3) Paper tape lateral regulation deviation device In order to ensure that the lateral regulation of the printing material web enters the printing part or rewinds, the lateral regulation remains consistent, and lateral deviation regulation is required. The lateral deviation can be adjusted by air (liquid) pressure cylinder or by the lateral regulation roller. 2. Squeegee and impression cylinder adjustment 1) Squeegee adjustment The sum of the pressure required to scrape off the ink on the surface of the printing plate and the pressure required to resist the impact force of the ink. The pressure is proportional to the printing speed. Generally, the speed is fast and the pressure is correspondingly large. In addition, the selection of the angle between the blade and the printing plate is generally 30 ° to 70 °. This keeps the knife edge from damaging the layout, and also makes the quality of the printed product ideal. 2) Adjust the impression cylinder After the plate cylinder is installed, you can adjust the impression cylinder. For different substrates, the printing pressure of the impression cylinder is different. Example: Cellophane, plastic film, printing pressure is 1 ~ 5Pa. Bond paper, thin cardboard, the printing pressure is 8 ~ 15Pa. The printing pressure for whiteboard paper is 20-30Pa. 2. Adjustment of ink drying temperature At present, gravure inks are basically solvent inks. When printing, the operator should adjust the drying temperature of each unit according to the type of printing material, printing speed, graphic area, and ink layer thickness. Drying temperature is not easy to be too high, generally should be controlled below 80 ℃, the highest should not exceed 100 ℃. Otherwise, it will cause shrinkage of the printing material and affect the registration. If it is too low, the ink will dry poorly. 4. Overprint After the machine is adjusted, it can be overprinted. First, the manual adjustment button is used to register the layout, and then the computer can be adjusted. The longitudinal error of overprinting depends on the tension adjustment, and the lateral error depends on the adjustment of the horizontal position control system of the paper tape and the push-pull plate cylinder. Table 3 shows the requirements for overprinting errors of plastic films. 5. Checking the prints in official printing During the official printing, the operator should constantly check the printed samples against the standard samples, check for errors, and make necessary adjustments. Second, gravure printing faults and troubleshooting In gravure printing, in addition to being prone to fire, there are various faults, among which the more common faults and troubleshooting methods are as follows: ①Ink overflow: The phenomenon is that spots and patterns occur on the full-print part of the ink. The main reason is that the viscosity of the ink is too low, the fluidity of the ink is too large, the printing speed is low, the ink drying is too slow or there is static electricity. The method of elimination is to add the original ink and adjusting agent to increase the viscosity of the ink and reduce the fluidity. It can also increase the printing speed or change the angle of the doctor blade. ②Ink is dried and embedded in the plate pattern: the drying speed of the ink is too fast, causing the ink to dry in the plate pattern. There are many reasons for imprinting, such as large ink pigment particles, foreign matter mixing, poor re-solubility of ink fixing agent, too high ink viscosity, and too shallow ink hole of printing plate. The exclusion method is to reduce the drying speed of the ink, increase the amount of solvent in the ink, improve the resolubility of the ink, remove foreign materials, and reduce the viscosity of the ink. At the same time, the hot air of the drying device should be prevented from blowing to the plate surface, causing the ink in the plate pattern to dry. ③ Blind fluffing of printed matter: mainly caused by static electricity, the static electricity of the printing material and ink should be removed to increase the humidity of the printing material, or polar solvents and adjusting agents should be added to the ink to increase the viscosity of the ink and the printing speed should be appropriately increased. The main part refers to the part on the screen that reflects the theme, such as patterns, text, signs, etc. ④The gloss of the printed product is not good: adding the proper amount of original ink can also increase the drying speed of the ink properly and replace the high-quality printing materials. ⑤ Poor color stacking: The ink film of the first printing ink has ink-discharging properties, which is caused by the mismatch of the viscosity of each ink of the color stack and the drying speed of the ink used for the color stack. Can reduce the viscosity of ink, slow down the drying speed of overlapping ink. ⑥Reverse printing and ink stacking: The reverse side of the printed matter is stuck with ink due to stacking. The reason is that the solvent in the ink contains a small amount of high-boiling components, which causes the solvent to evaporate too slowly. Plasticizer and plastic resin in the ink Too much, poor drying device, too deep ink hole on the printing plate, excessive relative humidity in the printing workshop, etc. The method of elimination is to select resins with good solvent detachment, reduce the content of plasticizers and plastic resins in the ink, add anti-printing inhibitors appropriately, and use solvents with a narrow boiling range as much as possible for the solvents used in the ink. Improve the drying device and increase the drying efficiency. Use rollers with shallow ink holes and improve environmental conditions. ⑦Scratches: The main causes of scratches on the printed matter are damage to the doctor blade, improper pressure of the doctor blade, incorrect angle of the doctor blade, foreign matter mixed into the ink, ink viscosity is too high, ink adhesion is too strong, The pigment particles are too rough, the printing plate cylinder has scratches, unevenness, poor correction, etc. The method of elimination is to use ink that does not contain foreign matter, filter before using the remaining ink, adjust the viscosity, dryness, and adhesion of the ink, use a high-quality doctor blade, adjust the pressure and angle of the doctor blade, and correct the plate cylinder. ⑧ Ink hydration: Moisture in the air enters the ink, causing sticking, resin precipitation, gelation, etc., which causes the disadvantages of ink gloss reduction, concentration reduction, poor transfer, and easy paste. To avoid hydration, it is best not to use excessively quick-drying solvents and reduce the chance of ink contact with air. ⑨Whitening: The ink transferred to the surface of the plastic film, the solvent volatilization is severely out of order, and the "resin whitening" phenomenon of resin insolubilization, white turbidity, and local gelation occurs. In order to prevent whitening, the printing speed can be increased, or the drying box can be brought close, or the drying solvent can be used to slow down the ink drying speed. Abs Frame Bag Filter,Pre Filter Bag,Pocket Pre Filter,Filter Bag Abs Frame Ningbo Ifilter Purification Equipment CO.,Ltd. , https://www.nbifiltor.com