Second, the use of gravure printing carton preprinted this production method features
1, high production efficiency. Gravure printing web printing speeds up to 150-200 m/min, basically matching many corrugated board production lines in China, shorter than traditional flat-sheet offset printing and veneer lapping, low labor cost and high efficiency.
2. The color carton produced by gravure preprinting can get high quality ink prints. Due to the high accuracy of gravure printing, it is not more than 0.2mm. The gravure printing can also be completed by printing and varnishing once, and the printed wire after general gravure printing Up to 300 lines, gravure printing ink than other printing methods, up to 4.5-6g/m2, India ink full, soft, bright, solid, and gravure printing after each color has a full drying system, Therefore, under the premise of choosing the paper with higher surface smoothness for printing, gravure printing can obtain high printing quality of ink and ink. Most cigarette packs are made from paper gravure printing. At present, the domestic production of paper gravure printing inks has been relatively mature, domestic has been able to meet the corrugated board line preprinted with water-based paper gravure ink, can fully meet the corrugated board production line 180 Â°C high temperature and hot plate friction.
3. Large-format, multi-color printing can be performed. The maximum size of traditional color offset printing is generally up to 1.2mÃ—0.9m (encyclopedia), and most of them are four-color printing. The maximum printing material width of the gravure printing machine for carton preprinting is 2.5 meters (Shaanxi Beiren Printing Machine Co., Ltd.) At present, it has produced a variety of preprinting machines, including 1300mm, 1650mm, 1800mm, 2000mm, 2200mm, and 2500mm, and it runs well. The number of printing colors can reach 4-10 color groups, and gold ink, silver ink, etc. can also be produced. Special ink printing.
4, more suitable for large-scale long-run printing. The preprinted plates are all made of steel chrome-plated electrogravure. The number of prints resistant to printing is 3 million to 4 million times, which reduces the time for changing plates and is particularly suitable for printing long lived prints.
5. The strength of the corrugated boxes produced is higher. Since preprinted corrugated cartons are produced on the production line, there is a certain amount of heat-forming time during the production, and the final production of corrugated cartons is high in strength and can avoid uneven coating and carton creases when the laminator is produced. , cardboard warping and so on.
Third, the carton preprinted production equipment and technology
1. The main equipment used for the preprinting of cartons is a large-sized group-type gravure printing press. Its auxiliary equipment is a computer-controlled cross-cut and slitting of a corrugated paper production line. The pre-printed face paper is placed on the noodle station of the corrugated board line, and after sizing, veneering, flattening, drying, cutting and other processes, the colored cardboard is finally made, and the post-passage is obtained through die-cutting, sticking, and the like. The production process completes the production of the carton.
2. Carton pre-printing requirements for corrugated cardboard lines.
The important configuration of the gravure printing carton preprinting production line is the computer cross cutting of the corrugated cardboard production line, that is, a crosscutting control function must be installed on the cross cutting knife of the corrugated board production line. Its main control principle is to identify the corrugated cardboard by the photoelectric eyes. The cross-cut logo on the printed pattern transmits the time when the cross-cut mark reaches the photo-electric eye to the control computer, and then the control computer controls the cross-cutting time, thereby accurately cutting the corrugated cardboard at the border of the pattern. At present, cross-cutting machine manufacturers at home and abroad can install this function for the carton factory, and the cross-cutting accuracy can be controlled within 0.5mm. At present, China's current production of corrugated board production lines can be installed according to customer requirements computer cross-cutting device.
3, the choice of ink and varnish.
The ink used in the preprinted gravure printing machine is mainly based on alcohol-soluble inks or water-based paper-specific gravure inks.
When preprinted paper is subjected to flattening and drying processes on a corrugated paper production line, the ink used requires high temperature and abrasion resistance, otherwise the colored surface will be pulled or dragged. At present, the "Tianshi" brand ink produced by the Tianjin Toyo Ink Factory can meet the requirements of water-based paper gravure printing. The cost is low, no pollution and meets the national environmental protection requirements. The gravure carton preprinted inks produced by Shanxi Essence Industry & Trade Co., Ltd. are based on cellulose. The main solvents are alcohols and esters. Compared with water-based inks and offset inks, this kind of ink has bright color, high gloss and abrasion resistance, and is resistant to 180Â°C. -250Â°C high temperature, good printing adaptability, clear printing pattern, delicate color, etc., and excellent adhesion to most printing surfaces. Some domestic manufacturers of Varnish use high-temperature Varnish from Cprecision & In Technology of the United States. Some domestic brands have also been widely adopted and the results are very good.
4, the choice of printing plate.
The preprinted plate is made of steel chrome-plated electric gravure, and the number of gravure lines can reach more than 300 lines. It can be completely suitable for dot-printing and dot-tone printing of the ground printing and tone transition, but the gravure of paper printing is more intaglio than the general plastic printing. During carving, the deeper of the cave carvings, the price of the gravure plate has dropped from 0.7 yuan/cm2 to about 0.35 yuan/cm2, which is close to the flexographic version, and the gravure printing is 3-4 times that of the flexographic plate, up to 300 Million - 4 million printing, glazing roller can use a fixed number of wire roller, using a shaftless drive. At present, there are more domestic plate-making manufacturers, such as the electric engravings produced by the shipping companies, the Southern platemaking industry and Sanmenxia Blue Snow, etc., which have reached the international advanced level.
5, the choice of paper.
Gravure preprinted printing materials must use coated white paper with good surface smoothness, strong printing adaptability, and stable moisture content (6%-7%). Imported coated cattle card and domestic gray board can meet the high-end color corrugated cardboard paper distribution requirements. Finland's M-REAL Forestry Company is world-renowned for producing coated paper with high hygiene standards. 185g of coated paper has been widely used in domestic preprinting machines. The paper's quantitative range is 150g-350g/m2, and the US Mead Paper Industry has been using it. 500 grams of raw wood pulp coated bovine card gravure printing cartons and canned beer cartons are stronger than corrugated cartons.
Fourth, common problems and solutions
The common problems in carton pre-printing are as follows: The solutions are as follows:
1. Wrinkle: Pre-printed paper roll tension of high gram weight is about 50kg, which is more difficult to control than film (10kg) and thin paper (25kg). When the moisture is uneven and the thickness is not uniform, greater tension changes will cause the paper to transverse Swing to form a wrinkle on the printed surface. The preheating device of the paper concave machine can help reduce the tension change caused by moisture loss (when the moisture content is too low, install the humidifier); if you add a flattening roller, you can help the paper roll as far as possible The swing is reduced.
2. Ink draw: In addition to the above-mentioned temperature-resistant ink and varnish, the latest air-cushion heating plate heat conduction control system can reduce the heating temperature and stress strength of the cardboard through the hot end. The process is that an air spray channel is arranged at the gap between the heating plate and the cardboard, and air can be sprayed in an instant to form a gas film to hold the cardboard, so as to avoid defects such as scratches, inks and the like caused by overheated pressure of the cardboard.
3, Lubai: mainly due to the surface of the paper roll dust and ink blocked version, in the field printing group installed dust and explosion-proof electrostatic suction device can be blown dust, improve the ink effect, reduce network loss.
4, spiral type winding: prepress gravure printing press should use a closed-loop control system to ensure the tension and taper tension control.
5, uneven edges: cross-cutting edges, can increase the pressure roller (receiving rubber roller), the air out of the paper roll, eliminate the static surface, take up the roll when the roller closes the device, reduce Edge swing.
The installation of a PLC correction device also helps to alleviate uneven edges. Another solution to the problem of missing edges is offline rewinding.
6. Paper lap: If the paper roll is improperly lapped in the printing process, it will cause downtime and affect the consistency of the printed product. Zero-butt connection can be used to pick up the paper without interrupting the printing process.
Nan Jingsheng Information Source: China Packaging
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