Gravure Printing Carton Preprinting New Process Introduction

The preprinting of gravure printing carton is to pre-print the corrugated carton on the wide web (carton paper) with the required fine pattern before making the corrugated cardboard, and then printing the good paper in roll shape. The upper corrugated board production line is made of corrugated boxboard, and then die-cut by a die-cutting machine into a box type.

At present, 30% of the total output of corrugated boxes in some developed countries such as Europe and the United States adopts preprinted new technologies. With the rapid development of China's paper product packaging industry, many customers have stable cartons such as Mengniu, Budweiser and Qingdao in recent years. Beer, etc. have turned their eyes to new pre-printing technologies. With the packaging and packaging of beverages, beer, home appliances and foodstuffs in the design and usage of corrugated boxes, the use of web pre-printing to produce high-grade colored corrugated boxes will become a future package. Industry development trend.

Web preprinting is better than flat offset preprinting

At present, the vast majority of domestic color cartons use flat sheet offset printing preprinting methods. The process flow is: cutting webs into single sheets, offset printing, single sheet printing, and single-sided roll-rolling. Paperboard → Face Paper and Single-faced Corrugated Paperboard on the Backing or Veneer Laminate → Die Cut Indentation Molding → Nail Box / Sticky Box

The technical process of web printing gravure printing preprinting technology is: gravure printing machine printing surface layer paper roll → cardboard line production cut into three layers (or five layers) cardboard → die-cutting indentation molding → nail box/glue box

So why do you need gravure preprinting? There are two main reasons. First, gravure printing can easily provide high-quality color prints. Second, electronic engraving technology can significantly reduce the production cycle and cost of metal plate rollers, which is close to or even lower than that of flexographic plates. Moreover, the domestic Shaanxi Beiren has produced a high-speed wide-format paper concave machine, the price is only one-third of the imported flexographic printing press, and the gravure pre-printing method may be more suitable for the actual situation of packaging companies in China.

In comparison, people often refer to the commonly used printing process as “post-printing”. Pre-printing has some obvious advantages over post-printing:

- Get higher print quality and adaptability. The pre-printing is performed on a smooth paper surface using a gravure printing machine or a flexographic printing plate. Compared with the printing after printing using a printing slotting machine to print on uneven paperboard surfaces, it is possible to perform fine color printing with richer layers and brighter colors. Printing quality will also be more stable and reliable.

- The highest strength of corrugated board can be achieved, because the pre-printing does not need to imprint the board after it is formed, thus avoiding the deformation of the corrugated board and weakening of the board strength. After printing with corrugated board printing slot machine, each color printing will cause more or less deformation of corrugated board, and the more color number, the greater the effect on the deformation of corrugated board.

- High production efficiency, ease of production management, low scrap rate, etc. Preprinting has become an important trend in the printing of corrugated board, especially the printing of high-grade cartons (including large and special-shaped cartons). The use of intaglio printing carton preprinting has the following salient features compared to traditional color offset printing:

--high productivity. 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.

- Color carton produced by gravure pre-printing can get high-quality ink prints. Due to the high accuracy of gravure printing, it is not more than 0.2mm. Gravure printing can also finish printing and varnishing once. General gravure printed wire after 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 °C high temperature and hot plate friction.

- Large-format, multi-color printing is possible. The maximum size of traditional color offset printing is generally up to 1.2×0.9m (pancake sheet), and most of them are four-color printing. The maximum printing material width of the group-type 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 of 1300mm, 1650mm, 1800mm, 2000mm, 2200mm, and 2500mm in various specifications and operates well. The number of printing colors can reach 4-10 color groups, and special inks such as gold ink and silver ink can also be produced. print.

- It is more suitable for large-scale long-run printing. The pre-printed plates are all made of steel chrome-plated electrogravure, and the number of prints resistant to printing is 300-400 thousand Indian, which reduces the time for changing plates, and is particularly suitable for large-volume long-lived printing.

- The corrugated box produced has a higher strength. 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.

Carton preprinted production equipment and process

- The main equipment used for preprinting cartons is a large-sized group-type gravure printing press. Its auxiliary equipment is a computer-controlled cross-cut and slitting of corrugated paper production lines. 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.

——Carton preprinting 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.

The same principle applies to computer slitting and computer crosscutting.

- Inks and Varnishes: The inks used in the preprinted intaglio printing machines are mainly 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 180°C. -250°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, and some domestic brands have also been widely adopted. The effect is also very good.

- Printing plate: The preprinted plate is made of steel chrome-plated electrogravure. The number of gravure lines can reach more than 300 lines. It can be used for dot printing of dot printing on the ground and tone transition, but the gravure ratio of paper printing General gravure printed in gravure is more deeply carved in the sculpting, and the price of gravure plate has dropped from 0.7 yuan/cm2 to about 0.35 yuan/cm2, which is close to the flexographic version, and the number of gravure prints is 3-4 of the flexographic version. Times, up to 300-400 million printed, glazing roller can use a fixed number of line 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.

- Paper: Intaglio preprinted substrates must use coated white paper with good surface smoothness, strong printability, 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.

Problems and Solutions

The paper concave machine's printing products include preprinted paper rolls such as decorative paper, bubble gum paper, beer drink boxes, cigarette cases, medicine boxes, milk boxes, and fruit boxes, household appliances and daily necessities. The features are exquisitely designed, colorful, and demanding. The following solutions are available for reference for some common problems in the application process of the current paper concave machine.

Wrinkling: high gram preprinted paper roll tension is about 50kg, more difficult to control than the film (10kg) and thin paper (25kg). When the water is uneven and the thickness is uneven, greater tension changes will cause the paper to swing laterally. Form the surface creases of printed products. 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.

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.

Lubai: mainly due to the dust on the surface of the paper roll and blocked by the ink. The dust and explosion-proof electrostatic ink-absorbing devices installed in the field printing group can separate the air from the dust, improve the ink repellent effect, and reduce the dot loss.

Spiral rewinding: Preprinted gravure printing presses should use a closed-loop control system to ensure tension taper control.

Incomplete edges: The edges of the cross section are not uniform, and the backup roller (receiving rubber roller) can be added to remove air from the paper roll and eliminate static electricity on the surface. When the paper roll receives the material, the roller device is tightened to reduce the 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.

Roll overlap: If the roll is improperly overlapped during printing, 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.

At present, the gravure presses for preprinting of carton produced by our company mainly have the following features:

(1) High printing speed and high overlay accuracy

This series of models printing speed is 150-200 meters / minute, overprint accuracy ± 0.2mm longitudinal (automatic tracking system tracking, normal printing) ± 0.2mm horizontal (manual control)

(2) The printing format is large and the quality of printed products is good.

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

(3) Printing and painting are completed once

This series of models can achieve 4-10 color ink printing, and painted once and finished. The coating unit is driven by a separate motor and can use a different coating roller than the printing plate roller diameter, which saves money.

(4) Use alcohol-soluble environmental ink or environmental ink printing

The series models are equipped with an independent intelligent drying system. The fully-enclosed oven and heat source can be used for secondary air return. The ink can be fully dried and cured to ensure that the printing surface does not fade when it enters the corrugated paper production line and the backing plate. "Fetching flowers", automatic ink circulation system and ink stir bar enable mass production of printed products, ink color