The pre-printing of gravure printing carton is to make multi-color printing on wide-width white card roll paper (carton face paper) with gravure printing machine before making corrugated cardboard, and then print the roll-shaped face paper with beautiful patterns The corrugated cardboard production line is made into corrugated cardboard with printed patterns, and finally die-cut and crimped into corrugated cardboard boxes.

Currently, 30% of the total output of corrugated paper boxes in some developed countries such as Europe and the United States uses pre-printed new technology. With the rapid development of China's paper product packaging industry, many carton factories with stable output in recent years, such as Mengniu, Budweiser and Tsingtao Brewery, have set their sights on new preprint technologies. With the stable design and consumption of corrugated cardboard boxes for beverages, beer, home appliances and food, the production of high-end color corrugated cardboard boxes by web preprinting will become the future development trend of the packaging industry.

1 roll of simple paper gravure preprinting is better than sheetfed offset printing

The traditional color carton adopts the method of pre-printing with sheet-fed offset printing. The process is as follows: cutting the roll paper into a single sheet of paper → printing a single sheet of offset paper with an offset press → two-layer corrugated cardboard rolled by the single-sided machine at the same time → and the paper and single-sided corrugated cardboard are mounted on the surface Machine veneer → die cutting and creasing forming → nail box / sticking box

This method has the following disadvantages:

â‘  The number of pattern colors is small, generally 4 colors, and gravure pre-printing can meet 4-10 colors;
â‘¡Many processes affect the strength of corrugated paper. In the process of laminating offset sheet and corrugated cardboard, the laminating machine uses cold glue to press the cardboard through the pressure roller to bond the tissue and cardboard, which will damage the corrugated peak. Reduce the strength of corrugated boxes;
â‘¢ The solid ink color printed is not thick enough compared with gravure printing;
â‘£Low production efficiency, suitable for single piece or small batch printing;
⑤Many equipments are required, the process is complex, and the scrap rate is high.

The process flow of web gravure pre-printing technology is: multi-color printing surface paper of gravure printing machine → upper corrugated cardboard production line is cut into 3 layers (or 5 layers) of cardboard → die cutting and indentation molding → nail box / stick box

So why do you need gravure preprinting? There are two main reasons: one is that gravure printing can easily complete high-quality multicolor color printing at a time; the second is that electronic engraving technology has greatly reduced the manufacturing cycle and cost of metal plate rollers, close to or even lower than the soft Version, and high print resistance. At present, Shaanxi Beiren has produced high-speed wide-format carton gravure printing presses for pre-printing. The price is only one third of the imported flexo printing machine. The use of gravure pre-printing will be more suitable for the actual situation of China's packaging enterprises.

Compared with the traditional color offset printing method, the production process using gravure printing carton pre-printing has the following significant features:

â‘  High production efficiency. The printing speed of gravure printing roll paper reaches 150-200m / min, which can basically be matched with many domestic corrugated cardboard production lines. It has the characteristics of short process, low labor cost and high efficiency compared with the traditional sheet-fed offset printing and veneer mounting tile. .
② The color carton produced by gravure printing pre-printing can obtain high-quality ink-and-print products. Due to the high precision of gravure printing overprinting, no more than 0.2mm, gravure printing can also be completed by printing and varnishing at one time. The general printing line of gravure printing can reach 300 lines, and the amount of inking is larger than other printing methods, the highest It can reach 4.5 ~ 6g / ?, the ink color of the printed product is full, soft, bright and firm, and there is a sufficient drying system for each color after gravure printing, so under the premise of selecting paper with a high surface smoothness for printing, gravure printing Can get very high ink-print quality. At present, domestically produced paper gravure printing inks are relatively mature. We have manufactured water-based paper gravure printing inks that can meet the pre-printing requirements of corrugated cardboard lines, and can withstand the high temperature of 180 ℃ and the friction of hot plates on the corrugated cardboard production line.
â‘¢ It can carry out large-format multi-color printing. The traditional color offset printing is generally from a large radial surface, up to 1.2 x0.9m (completion sheet), and most of them are 4-color printing. The material width is 2.5m, the printing color number can meet 4-10 groups, and it can also print special inks such as gold ink and silver ink.
â‘£It is more suitable for long batch printing in large quantities. The pre-printed plates are made of steel chrome-plated electrogravure gravure. The printing durability is 3 to 4 million prints, which reduces the time for plate change, and is especially suitable for printing large batches of long-form jobs.
⑤ The corrugated cardboard box produced has higher strength. The pre-printing process is used to produce corrugated boxes on the production line. There is a certain heating and forming time during the production, and the final corrugated boxes are produced with high strength. In addition, it can avoid uneven glue, carton ribs, cardboard warpage and other phenomena generated during the production of the veneer.
â‘¥ Gravure printing with higher cost performance is direct embossing, the printed ink layer is thick, fine dots, fine patterns, and the quality of the printing is high; after pre-printing of the gravure, the corrugated cardboard line is produced by rolling on the corrugated cardboard line It will damage the corrugated, and will not form "washboard" stripes to ensure the strength of the corrugated cardboard; when the sheet is offset and the paper is mounted on the corrugated board, the veneer presses the cardboard with a pressure roller to bond the paper And corrugated cardboard, this will damage the peaks of corrugated cardboard, reduce the strength of corrugated cardboard, experiments show that under the same conditions. The fourth edition preprint is 10% stronger than the offset preprinted carton. Therefore, when the carton strength is constant. Pre-printing with gravure printing can reduce the weight of the paper to maintain the required strength, and lowering the weight can reduce the cost of 10%, but the method of reducing the weight is limited on the offset press, and the whiteboard paper below 200g is used After the offset printing is applied to the box, there will be obvious "washing board" phenomenon. In addition, the efficiency of gravure pre-printing will be transferred to the cost, and the total cost of the carton will also be greatly reduced

2 Carton pre-printing production equipment and consumables

Production equipment: The main equipment for carton pre-printing is a large-unit printing plate printing machine, and its auxiliary equipment is a corrugated paper production line computer-controlled cross-cutting and slitting. The pre-printed paper is installed on the hanging station of the corrugated cardboard line, after sizing, pasting, flattening, drying, cutting and other processes, and finally made into colored cardboard, which is die-cut, glued, etc. The manufacturing process completes the carton production.

Ink and Varnish: The ink used in the pre-printed gravure printing machine is mainly alcohol-soluble ink or water-based paper special gravure ink.

When the pre-printed paper is flattened and dried in the corrugated paper production line, the ink used is required to have high temperature resistance and friction resistance, otherwise the color surface will appear to be squeezed or dragged. At present, the "Tianshi" brand ink produced by Tianjin Toyo Ink Factory can meet the gravure printing of water-based paper. Its cost is low and pollution-free, and it meets the national environmental protection requirements. The pre-printing ink for gravure carton produced by Shanxi Jingke Industry and Trade is based on cellulose, and the main solvents are alcohol and phenol. Compared with water-based inks and offset printing inks, this ink has bright color, high gloss, abrasion resistance and 180 resistance. ℃ ~ 250 ℃ high temperature, good printing adaptability, clear printing pattern, delicate color performance, etc. At the same time, it has excellent adhesion to most printed surface. Some domestic manufacturers of varnish use the high temperature resistant varnish of American Cprecision In & Technology Company, and some domestic brands are also widely used, and the effect is also very good.

Printing plate: The pre-printed printing plate is made of steel chrome-plated electrogravure gravure, and the number of screen lines of the gravure plate can reach more than 300 lines. It is completely suitable for field plate printing and halftone dot printing with color transition, but the paper printing plate is better than ordinary plastic printing When engraving with a plate roller, the net hole carving is deeper. The price of gravure plate-making has been reduced from 0.7 yuan / square centimeter to about 0.35 yuan / square centimeter, which is close to flexo, and the number of gravure printing is 3-4 of flexo. Times, up to 3-4 million printed. The glazing roller can use a fixed number of screen rollers and adopt shaftless transmission. At present, there are many domestic plate-making manufacturers, such as Shanghai Ocean City, Southern Plate-making, Sanmenxia Lanxue and other manufacturers have reached the international advanced level.

Paper: The gravure preprinted printing material must use coated white paper with good surface smoothness, strong printing adaptability, and stable moisture content (6% -7%). Imported coated cow board paper and domestic gray bottom whiteboard paper can meet the paper matching requirements of high-grade color corrugated box face paper. The Finnish M-REAL forestry company is well-known in the world for producing coated paper with high hygiene standards. 185g of coated paper has been widely used in domestic pre-printing machines. The quantitative range of paper is 150g-350g / m2. The Mead industry in the United States has always used 500g of raw wood pulp to coat cattle cardboard gravure printing cartons and canned beer carrying cartons. The strength exceeds that of corrugated boxes.

3 Problems and solutions in the process of gravure pre-printing

The printing products of the paper concave machine include decorative paper, bubble gum paper, beer beverage boxes, cigarette boxes, medicine boxes, milk boxes and fruit boxes, household appliances and other preprinted paper rolls. They are characterized by exquisite design, bright colors and large demand. In view of some common problems in the current application process of paper concave machine, there are the following solutions for reference.

l) Problems and solutions of preprinted facial paper:

Lu Bai: Mainly due to the dust on the surface of the paper roll and the ink blocking plate. Install the dust removal and explosion-proof electrostatic ink absorption devices in the field printing group respectively to achieve the dust suction by blowing, reduce the loss of dots, and improve the ink effect.

Spiral winding: The gravure printing machine for pre-printing should adopt a closed-loop control system to ensure the tension taper control of winding and unwinding.

Uneven edge collection: uneven edge collection at the cross-section, a back pressure roller (receiving rubber roller) can be added to drive air out of the paper roll to eliminate surface static electricity. .

The installation of PLC computer correction device can effectively alleviate the phenomenon of uneven edge trimming, and another way to solve the uneven edge trimming is offline rewinding.

Paper roll overlap: Improper paper roll overlap during printing will cause downtime and downtime, and at the same time affect the consistency of the printed product. You can use the zero-speed docking method to pick up the paper without interrupting the printing process.

2) Problems and solutions of facial paper veneer:

Wrinkle: The tension of high-gram preprinted paper roll 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 uneven, a large tension change will cause the paper to swing laterally and form a wrinkle on the surface of the printed product. The pre-heating device installed in the paper concave machine helps reduce the tension change caused by water loss (moisture is installed if the water content is too low); if the flattening roller is added, it can effectively solve the problem of flattening the paper roll when feeding To reduce swing.

Ink drawing: In addition to the temperature-resistant ink and varnish mentioned above, the latest air-cushion heating plate heat conduction control system can reduce the heating temperature and the strength of the cardboard when it passes the hot end. The process is that an air discharge channel is provided in the gap between the heating plate and the cardboard, which can eject the air in an instant, forming an air film to support the cardboard, to avoid defects such as scratches and ink drawing caused by excessive heating and compression of the cardboard. In order to avoid the pulling phenomenon caused by friction between the hot plate on the corrugated board production line and the pre-printed facial paper, Shaanxi Beiren Printing Machine Co., Ltd. has a set of successful solutions, which are adopted by many carton factories. Very good results have been achieved.

4 Requirements of corrugated board line for pre-printing of carton

The important configuration of the gravure printing carton pre-printing production line is the computer cross-cutting of the corrugated cardboard production line, that is, the cross-cutting control function of the identification printing mark must be added to the cross-cutting knife of the corrugated cardboard production line. Its main control principle is recognized by the photoelectric eye Cross-cut logo on corrugated cardboard printed pattern. The time when the cross-cut mark reaches the photoelectric eye is transmitted to the control computer, and then the control computer controls the time of the cross-cut, thereby accurately cutting the corrugated cardboard at the boundary of the pattern. At present, domestic and foreign cross-cutting machine manufacturers can install this function for carton factories. The cross-cutting accuracy can be controlled within 0.5mm. Corrugated cardboard parts produced in China can be installed with computer cross-cutting devices according to customer requirements.

Computer longitudinal cutting and computer transverse cutting are the same principle.

5 Main features of gravure printing presses for carton pre-printing produced by Shaanxi Beiren Printing Machine Co., Ltd.

This series of models can realize 4-10 colors of ink printing, and can be completed at one time with varnish, and the coating unit is driven by a separate motor. It can use a coating reel different from the diameter of the printing plate roller, saving costs.

(4) Use alcohol-soluble environmentally friendly ink or environmentally friendly water-retaining ink for printing

This series of models is equipped with an independent intelligent drying system. The fully enclosed oven and heat source can be used for secondary air return, which can fully dry and solidify the ink, which can ensure that the printed surface enters the corrugated paper production line and the friction between the pad and the board does not fade or "Pulling flowers", automatic ink circulation system and ink stirring rod can make the ink color of mass-produced printed products even and no color difference.

(5) High-speed automatic non-stop pick-up

This series of models can realize high-speed automatic loading and unloading reel, which greatly improves the yield and saves working time.

(6) Automatic control

The whole machine of this series adopts closed-loop tension control system, DT950M II photoelectric registration device (or domestic registration device) of Japan Taiyo Co., Ltd., static picture observation system, computer automatic reloading system, and pneumatic shaftless version. , Pneumatic scraper, embossing, shaftless clamping, paper preheating, water cooling and other structures make the machine operation more convenient and reliable.

(1) High printing speed and high precision of overprinting.

The printing speed of this series is 150-200m / min, and the accuracy of overprint is ± 0.2 mm in the longitudinal direction (automatic registration system tracking, normal printing), and ± 0.2 mm in the horizontal direction (manual control).

(2) Large printing area and good printing quality.

The printing format of this series of models can be divided into the following specifications: 1300mm, 1650mm, 1800mm, 2000mm, 2200mm, 2500mm, which can be matched with corrugated cardboard line.

(3) Printing and oiling are completed at one time

5 Conclusion

The use of pre-printing to produce carton is still in the ascendant in China. With the joint efforts of machinery manufacturers, ink, paper, plate suppliers and the majority of carton manufacturers, China's packaging carton grade will be raised to a new level.

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