New process for carton pre-printing - gravure pre-printing
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Gravure printing carton pre-printing is to pre-print a multi-color printing on a wide white card web (carton paper) with a gravure press before making corrugated paper, and then print it on a beautifully printed roll paper. The corrugated board production line is made of corrugated cardboard with a printed pattern, and the die-cutting is indented into a corrugated box.
At present, 30% of the total output of corrugated boxes in some developed countries such as Europe and the United States adopts pre-printing new technology. With the rapid development of China's paper product packaging industry, in recent years, many stable carton factories such as Mengniu, Budweiser, and Tsingtao Brewery have turned their attention to pre-printing new technologies. With the stability of the design and consumption of corrugated boxes for beverages, beer, home appliances and food products, the production of high-grade color corrugated boxes by web preprinting will become the development trend of the packaging industry in the future.
1 roll of paper gravure preprinting is better than sheetfed offset preprint
The traditional color carton uses a pre-printed offset sheet. The process flow is: cutting the web into a single sheet of paper → printing a single sheet of paper on the offset press → simultaneously forming a two-layer corrugated board on a single-sided machine roll → and the paper and the single-faced corrugated cardboard are slanted or affixed on the veneer. Machine veneer → die cutting and indentation molding → nail box / sticky box
This approach has the following disadvantages:
1 pattern color number is small, generally more than 4 colors, and gravure preprint can meet 4-10 colors;
2There are many processes, which affect the strength of corrugated paper. During the process of offset printing of single-faced paper and corrugated cardboard, the veneer uses cold glue to pressurize the paperboard by pressure roller to bond the paper and paperboard, which will destroy the corrugated spike. Reduce the strength of the corrugated box;
3 printed solid ink is not thick enough compared to gravure;
4 low production efficiency, suitable for single or small batch printing;
5There are many equipments required, the process is complicated, and the scrap rate is high.
The process of web gravure pre-printing technology is: gravure printing machine multi-color printing paper → upper corrugated board production line veneer cut into 3 layers (or 5 layers) cardboard → die-cutting indentation molding → nail box / sticky box
So why do you need gravure pre-printing? There are two main reasons: one is that the gravure can easily complete the multi-color color printing of high-quality drying at one time; the other is that the electronic engraving technology greatly reduces the manufacturing cycle and cost of the metal plate roller, which is close to or even lower than the softness. Version, and the printing durability is high. At present, people in northwestern Shaanxi have produced gravure printing machines for high-speed wide-format carton preprinting. The price is only one third of the imported flexo press. The use of gravure preprinting will be more suitable for the reality of packaging companies in China.
The production process using gravure printing carton preprinting has the following remarkable features compared with the traditional color offset printing method:
1 High production efficiency. The printing speed of gravure printing web reaches 150-200m/min, which can basically match the domestic corrugated board production line. It has the advantages of short process, low labor cost and high efficiency compared with traditional sheetfed offset printing and veneer tile. .
2 Gravure printing Pre-printed color carton for high quality ink prints. Due to the high precision of gravure printing, no more than 0.2mm, gravure printing can also complete printing and varnishing at one time. Generally, the printing network after gravure printing can reach 300 lines. The amount of ink on gravure printing is larger than other printing methods. Up to 4.5~6g/m2, the printed ink is full, soft, bright and firm, and there is a sufficient drying system for each color after gravure printing. Therefore, under the premise of printing on paper with high surface smoothness, gravure printing High ink printing quality is obtained. At present, domestically produced paper gravure printing inks are relatively mature, and have already produced water-based paper gravure inks that can meet the pre-printing of corrugated paperboard lines, and can fully withstand the high temperature of 180 ° C and the friction of hot plates on the corrugated board production line.
3 Large-format multi-color printing can be carried out. The traditional color offset printing can be up to 1.2 x 0.9m (large sheet) from the large surface, and most of them are printed in 4 colors. The maximum printing of the unit type gravure printing machine for carton pre-printing The width of the material is 2.5m, the printing color can meet 4-10 sets, and special inks such as gold ink and silver ink can also be printed.
4 is more suitable for large-scale long-run printing. The pre-printed plates are made of steel chrome-plated electric gravure. The number of times of printing is 3 to 4 million impressions, which reduces the time for changing plates, and is especially suitable for printing in large quantities of long-running.
5 Corrugated boxes produced are stronger. The production of corrugated boxes by pre-printing process is completed on the production line. There is a certain heating and forming time during the production, and the final production of corrugated boxes is high. Moreover, it is possible to avoid the uneven glue coating, the hull lifting of the carton, and the warpage of the cardboard generated during the production of the veneer.
6 The higher cost-effective gravure printing is direct imprinting, the printed ink layer is thick, the dot is fine, the pattern is fine, and the quality of the printed product is high; after the gravure pre-printing, the corrugated cardboard is made by roll-to-roll corrugated cardboard line, neither Will damage the corrugated, will not form a "washing board" stripe, to ensure the strength of the corrugated board; in the offset sheet and the paper and corrugated board paste, the veneer is pressed by the pressure roller to bond the paper and paper And corrugated cardboard, this will damage the spikes of corrugated cardboard and reduce the strength of corrugated cardboard. Experiments show that under the same conditions. The four-plate preprint is 10% stronger than the offset preprinted carton. Therefore, in the case of a certain strength of the carton. Pre-printing with gravure can maintain the required strength by lowering the weight of the paper, while lowering the weight can reduce the cost by 10%, but the method of reducing the weight is limited on the offset press, and less than 200g of whiteboard is used. After the offset printing is made into a box, there will be a noticeable "washing board" phenomenon. In addition, the efficiency of the gravure pre-printing is put into the cost, and the total cost of the carton will be greatly reduced.
2 Carton pre-printed production equipment and consumables
Production equipment: The main equipment for pre-printing of carton is large-scale printing press, and its auxiliary equipment is computerized cross-cutting of corrugated paper production line. After pre-printing, the paper is placed on the surface of the corrugated board line, after being glued, pasted, flattened, dried, cut, etc., and finally made into colored cardboard, after die-cutting, sticking, etc. The processing process completes the carton production.
Ink and varnish: The ink used in the pre-printed gravure printing machine is mainly alcohol-soluble ink or gravure ink for water-based paper.
When the pre-printed paper is flattened and dried on the corrugated paper production line, the ink to be used is required to have high temperature and abrasion resistance, otherwise the color surface may be pulled or dragged. At present, the “Tianshi” brand ink produced by Tianjin Toyo Ink Factory can meet the gravure printing of water-based paper, and its cost is low and pollution-free, which meets the national environmental protection requirements. The gravure carton preprinted ink produced by Shanxi Jingke Industry and Trade Co., Ltd. is based on cellulose. The main solvent is alcohol and phenol. Compared with water-based ink and offset ink, this ink has bright color, high gloss and abrasion resistance. °C～250°C high temperature, good printing adaptability, clear printing pattern, fine color performance, etc., and excellent adhesion to most printed surfaces. Some domestic manufacturers of glazing oil use high-temperature varnish of American Cprecision In&Technology Company, and some domestic brands are also widely used, and the effect is also very good.
Plate: The pre-printed plate is made of steel chrome-plated electric gravure and gravure. The number of mesh lines can reach more than 300 lines. It is suitable for dot-printing of solid printing and tone transition, but only for printing on paper. With the plate roll, the hole is carved deeper during engraving. The price of the gravure plate has been reduced from 0.7 yuan/cm2 to 0.35 yuan/cm2, which is close to the flexo, and the gravure print is 3-4. Double, up to 3 million to 4 million impressions. The glazing roller can be used with a fixed number of wire rollers and a shaftless drive. At present, there are many domestic plate-making manufacturers, such as the maritime city, the southern plate making, the electric engraving plate produced by Sanmenxia Lanxue and other manufacturers have reached the international advanced level.
Paper: Gravure preprinted substrates must use coated white paper with good surface smoothness, good printability, and stable moisture content (6%-7%). Imported coated cattle cardboard and domestic gray-bottom whiteboard paper can meet the paper-receiving requirements of high-grade color corrugated cardboard. Finnish M-REAL forestry company is famous for producing coated paper with high hygienic standards. 185g coated paper has been widely used in domestic preprinting machines, and the paper has a quantitative range of 150g-350g/m2. The Mead industry in the United States has been using 500g of wood pulp to coat cattle cardboard intaglio printing cartons and canned beer cartons. The strength exceeds the corrugated box.
3 Problems and solutions in the gravure pre-printing process
Paper printing machine printing products include decorative paper, bubble candy paper, beer beverage box, cigarette case, pill box, milk box and fruit box, household appliances and other pre-printed paper rolls, featuring beautiful design, bright colors and large demand. In view of some common problems that occur during the application of paper recesses, the following solutions are available for reference.
1) Problems and solutions for preprinted paper:
Dew: mainly due to the dust on the surface of the paper roll and the blocking of the ink. In the field printing group, dust removal and explosion-proof electrostatic ink absorption devices can be respectively installed to achieve air blowing, reduce dot loss and improve inking effect.
Spiral winding: The gravure printing machine for pre-printing should adopt a closed-loop control system to ensure the tension taper control of the rewinding and unwinding.
The edge is not aligned: the section is not aligned, the back pressure roller (receiving rubber roller) can be added to drive out the air from the paper roll to eliminate the surface static electricity. When the material is received, the pressure roller is pressed against the paper roll to reduce the edge swing. .
Installing the PLC computer correcting device can effectively alleviate the unevenness of the edge, and another way to solve the problem of uneven edge is offline rewinding.
Paper roll lap: If the paper roll is improperly overlapped during the printing process, the machine will be shut down, and the consistency of the printed product will be affected. The zero-speed docking method can be used to pick up the paper without interrupting the printing process.
2) Problems and solutions for facial tissue veneer:
Wrinkling: The high-gram preprinted paper roll has a tension of about 50 kg, which is more difficult to control than a film (1Okg) and a thin paper (25kg). When the water is uneven and the thickness is uneven, a large tension change causes the paper to oscillate laterally, forming a wrinkle on the surface of the printed product. The paper cupping machine is equipped with a preheating device to help reduce the tension change caused by water loss (the humidifier is installed when the moisture is too low); if the offset flattening roller is added, the flattening problem during the paper roll can be effectively solved. , reduce the swing.
Ink drawn flower: In addition to the aforementioned temperature-resistant ink and varnish, the latest air-cushion heating plate heat conduction control system can reduce the heating temperature and stress intensity of the cardboard when passing through the hot end. The process is that an air discharge channel is arranged at a gap between the heating plate and the paperboard, and the air can be ejected at an instant to form a gas film to lift the cardboard, thereby avoiding defects such as scratches and inks generated by excessive compression of the cardboard. In order to avoid the phenomenon of pulling flowers between the hot plate and the pre-printed paper on the corrugated board production line, Shaanxi Yinren Machine Co., Ltd. has a successful solution and has been adopted by many carton factories. Made a good result.
4 Carton preprinting requirements for corrugated board line
The important configuration of the gravure printing carton pre-printing production line is the cross-cutting of the corrugated board 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 board production line. Its main control principle is recognized by the photoelectric eye. Cross-cut logo on the corrugated board printing pattern. The time when the cross-cut mark reaches the photo-eye is transmitted to the control computer, and then the control computer controls the cross-cut time to accurately cut the corrugated cardboard at the boundary of the pattern. At present, the cross-cutting machine manufacturers at home and abroad can install this function for the carton factory. The cross-cutting precision can be controlled within 0.5mm. The corrugated board products produced in China can be installed according to customer requirements.
Computer slitting and computer crosscutting are the same principle.
5 Main features of gravure printing machine for pre-printing of carton produced by Shaanxi Yinyin Machine Company
This series of models can realize 4-10 color ink printing, and it can be completed once with the varnish, and the coating unit is driven by a separate motor. It can save the cost by using a coating different from the diameter of the printing plate.
(4) Printing with alcohol-soluble environmentally friendly ink or environmentally friendly ink
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. It can fully dry and solidify the ink, ensuring that the printing surface enters the corrugated paper production line and the pad is not faded. Pulling the flower", the ink automatic circulation system and the agitating ink stick can make the printing ink of the mass production uniform and no color difference.
(5) High-speed automatic non-stop refueling
This series of models can realize high-speed non-stop automatic reloading of coils, greatly improving the yield and saving working time.
(6) Automation control
This series of models adopts closed-loop tension control system, Japan Taiyang DT950M II photoelectric register device (or domestic register device), still picture observation system, computer automatic refueling system, and pneumatic non-axis mounted version. , pneumatic scraper, embossing, shaftless material, paper preheating, water cooling and other structures make the machine operation more convenient and reliable.
(1) High printing speed and high overprinting accuracy.
The series has a printing speed of 150-200m/min, an overprint accuracy of ±0.2 mm (automatic registration system tracking, normal printing), and lateral ±0.2mm (manual control).
(2) The printing format is large and the quality of the printed products is good.
The printing format of this series can be divided into the following specifications: 1300mm, 1650mm, 1800mm, 2000mm, 2200mm, 2500mm, which can be matched with corrugated board.
(3) Printing and oiling are completed once
5 Conclusion
The use of pre-printed production of cartons is still in the forefront in China. With the joint efforts of machinery manufacturers, ink, paper, printing plate suppliers and carton manufacturers, China's packaging carton grade will be raised to a new level.