Corrugated carton printing method overview (below)

(2) The characteristics of gravure preprinting

a. The advantages of gravure preprinting

1The color carton produced by gravure preprinting can get high-quality, green ink and ink prints. The amount of gravure printing ink is larger than other printing methods. The gravure printing ink is full, the ink layer is thick, there is a three-dimensional sense; colorful and rich layers. High definition. Among various printing methods, the printing quality is best, and the printing quality is stable. The tension control system of the gravure printing machine controls the stable operation of the machine, and the automatic color registration control system can ensure that the overlay accuracy reaches 0.1 mm. The gravure printing is fully dried after each color printing, and the printed products are more firm. After the gravure printing, the number of printed screens can reach 200L/in. Even with the use of paper with high surface smoothness, gravure printing can achieve high printing quality. Preprinted water-based gravure printing ink is used for printing, which is non-toxic and non-polluting and meets the requirements of environmental protection. At present, the domestic production of gravure printing paper, ink, etc. are already relatively mature, can withstand corrugated paper production line 200 °C high temperature and hot plate friction requirements. Gravure printing can also print and polish once.
2 Gravure Preprinted Plates High print resistance and suitability for large-volume production of cartons Since the gravure plate is a steel chrome-plated electrogravure, the entire plate is protected by a hard layer of metallic chrome, so even when printing With the non-stop contact with the layout, it still maintains a high resistance to printing force, generally up to 300 to 4 million impressions, which is suitable for high-quality, large-volume printing production requirements of cartons.
3 Gravure Preprinting A printed offset suitable for a continuous stretch of pattern is to wrap the prepared plate on the plate cylinder. Therefore, there is always an area on the surface of the plate roller for fixing the plate. The gravure printing plate is different because the plate making operation of the gravure printing plate is directly performed on the cylinder body. Therefore, as long as the image on the cylinder is seamlessly spliced, a continuous continuous pattern can be obtained on the substrate.
4 The corrugated box produced by gravure preprinting has higher strength. Because the preprinted corrugated box is produced on the production line, when the corrugated board is made, it has a certain heating and forming time, so it is better than the traditional method using a veneer machine. The corrugated box has higher strength and can avoid direct printing damage to the carton and improve and improve the strength and stamping strength of the corrugated box.
5 Gravure preprinting has high printing speed and high production efficiency. Because the preprinted printing method uses the web gravure printing machine to print, there is a drying device after each color is printed, and it is not necessary to spray powder to enter the next process. The printing speed can reach 150 meters/minute. In the high-speed gravure printing process, a roll of material can be printed in a short period of time. The use of a non-stop automatic roll changer to replace the roll can greatly increase the printing efficiency. After printing, the upper corrugated paper production line is made of corrugated cardboard, which is much faster than the traditional veneer machine.

b. Insufficiency of gravure preprinting: gravure platemaking is complicated, and the cycle of making a steel chrome-plated electric gravure cylinder is generally 5 to 10 days, and the price is higher, which is 8 to 10 times that of the flexographic plate; gravure The technology is relatively complicated, the processes are relatively large, and the investment in the entire production line is relatively large.

(3) Characteristics of flexo preprinting

a. Advantages of flexo preprinting:

1 Non-toxic, non-polluting and conducive to environmental protection. It is a green printing method and has great advantages in the printing of food cartons, medicine boxes and other green cartons.
2 can print large-format multi-color, high-quality color crates. The web width of flexographic printing presses in foreign countries can reach a maximum width of 1.8 meters, and satellite-type flexographic printing units can make 6 colors. A wide format can be printed, and a multi-color, high-quality, high-precision color carton 3 has a low cost. The low cost of flexo printing has formed a broad consensus in foreign countries and there are different opinions in the country. The main reason is that most of the current domestic flexographic presses and flexo printing plates rely on imports, resulting in higher costs. Offset printing and gravure printing are relatively inexpensive in this regard. With the flexographic equipment and its plates and local production in China, its cost will gradually decrease.
4 Printed using different lines, fine prints, and strong print consistency. Can use 100L/in, 133L/in, 175L/in performance patterns, delicate dots, colorful eye-catching.
5 In the corrugated paper production line, the surface paper and the corrugated board are re-bonded one at a time to improve and improve the strength and the stamping strength of the corrugated box.
6 printing speed, high output. The speed of the satellite flexographic printing machine can reach 250-300 m/min, which can meet the needs of multiple automatic corrugated production lines.
7 A wide range of printing materials can be printed from 80 to 400 g/m2.

b. Insufficient flexo printing

1 In the process of plate making during the process of plate making, the highlights of the pattern are markedly polarized, or small dots (below 8% of dots) have been lost during the printing and become an absolute net; Big, it is an outlet that is already close to the middle. In the dark tone, the network will be leveled at approximately 85% and will be in the field. It can be seen that the scope of the gradation that can be copied when the flexographic printing uses the amplitude modulation dot for copying the manuscript is relatively narrow, about 8% to 85%. In other words, when printing more than 85% of the area, due to the increase in the number of outlets, there will be a parallel level phenomenon, so that the dark tone area will be dead and non-hierarchy; when the area is printed below 8%, the dots are too small to be printed on the plate. On the "stop." Less than 8% of the dots in the design do not show up in the actual printing process. Therefore, it is difficult for some rich manuscripts to present their rich layers and colors with a flexible version.

2 From the printing screen number, the highest number of lines for offset and gravure is higher than flexo. The ideal number of screens for flexo printing is generally less than 150L/in, and more than 175L/in will increase the difficulty of flexo plate making and shorten the service life of plates. 3 should not use too thin lines and small text. Because the flexographic plate will be deformed during the printing process, lines and text that are too thin may easily deform. If the small anti-white or anti-white lines, due to the shallow relief, it is very easy to cause paste death. So try to use a thicker line. The contrast between the decorative line and the main line should be larger. From the above analysis, we can see that pre-printing is an ideal way to produce high-quality, large-volume corrugated cartons.

2 kinds of special printing box way

2.1 Plastic Gravure Composite Carton Process

When a single-faced corrugated production line is used, if a glossy film needs to be applied after the printing of the facing paper and the production volume is large, the printing may not be performed on the surface paper, but the gravure printing may be performed on the plastic film by a gravure printing method. It is painted on white, and the printed plastic film is first compounded with the face paper, and then the box is formed according to the conventional carton forming process.

The characteristics of this process are:

1 Carton production costs are low. When the production volume is large, such a process can greatly reduce the printing cost of the tissue paper and the material cost of the tissue paper. Because the noodle paper does not need to be printed, non-coated white paper can be used, so that the cost of the noodle paper is greatly reduced.
2 beautifully printed. Because plastic gravure is used, the printing effect can be comparable to that of offset printing. It is necessary to pay special attention to the fact that in the process of plate making, it is necessary to fully consider the dimensional change and deformation of the plastic film. Otherwise, the carton face paper will be misaligned with the lower cardboard.

2.2 Coated paper gravure composite carton process

When the production volume is relatively large, the film is not required and the printing effect is good and the cost is low, this process can be adopted. The process is to use a paper gravure printing machine to print thin (60-90 g/m2) art paper, and then composite this finely-printed art paper with normal slag paper or cardboard, and use it as a carton and then proceed with Pairing and normal carton forming.

The characteristics of this process are:

1 Carton production costs are low. The main reason for the reduction in cost is to convert whiteboard paper to low-weight coated paper in combination with cheap linerboard, which reduces material costs.
2 beautifully printed. Paper gravure printing is very beautiful.
3 Gravure plates are more complicated and costly, and are not suitable for printing carton products that are often revised.
4 The operation and control methods of the printing process, such as paper compounding and box making, must be carefully explored, accumulated, and reasonably implemented. Otherwise, the waste product rate will easily increase.

2.3 Direct offset printing corrugated box process

Corrugated carton direct offset printing process is relatively mature in foreign countries. It is the corrugated board directly on a special offset press for printing, suitable for processing thin corrugated carton.

The process can not only ensure the good moldability of the carton, but also can complete the exquisite face paper printing, but the printing machine used is relatively expensive. In the next few years, this process may become the new direction for the development of high-end carton printing in China.

2.4 screen printing corrugated carton

The screen printing corrugated box process uses direct printing. Since the ink ratio of the screen printing plate is proportional to the hole pitch of the screen, the resolution of the screen printing is not high, the image accuracy is low, and the number of conventional screen lines is 60 to 80 lines/inch. Screen printing corrugated boxes have the following advantages:

1 The printing format can be large or small.
2 can be completed before the box into the printing, but also after the box into the printing.
3 The screen printing ink is thick, its color saturation is high, the visual effect is strong, especially the spot color prints the field, the effect is better.
4 Plate making is easy and the plate making cost is low.
5 The printing cost is low.
6 The printing quality is relatively stable. The disadvantage of the screen printing corrugated box is that it is not suitable for the linkage production line and the production efficiency is low.

3. Conclusion

It can be seen from the above analysis that there are many methods for carton printing. Each method has its advantages and disadvantages. It is necessary to select the appropriate printing method according to the characteristics of the carton produced. In particular, high-quality, high-volume production of corrugated boxes, pre-printing is undoubtedly the best way.

Source: Corrugated Box