Corrugated board printing process

Color corrugated cartons (boxes) occupy an important position in product packaging. Due to the non-pollution of paper packaging, environmental protection requirements, and low cost, they are increasingly favored by businesses.
The prosperity of commodity economy and fierce competition in the market have promoted the improvement of the quality of product packaging. Landscaping has become an important means of marketing and propaganda. The printing quality of corrugated boxes has been increasingly valued by commodity producers and consumers.
With the advancement of carton processing and packaging machinery, the scope of corrugated carton packaging is getting bigger and bigger. It can not only pack mechanical parts and electrical components, but also package motorcycles, washing machines, refrigerators, and pianos. As the demand for packaging of goods above 50KG will increase substantially, the demand for heavy corrugated packaging boxes such as five-story, seven-story and nine-storey will increase significantly.
First, the printing method of corrugated board (1) Post-printing process, that is, the use of light pressure flexographic printing in the forming corrugated board.
(2) Face-to-face processing: Fine color screen printing is performed on the surface of 150 g/m2 coated paper or offset paper, and the printed matter and corrugated paperboard are then bonded with an adhesive.
(3) Pre-printing process: A web-type web flexographic printing is performed on the cardboard material of corrugated cardboard, and then the web printing surface paper is placed on a production corrugated cardboard production line to produce corrugated cardboard.
The above-mentioned first process is currently used in China, accounting for about 70%, this process is in line with the principle of rapid, convenient, environmentally friendly, economical, but it is difficult to avoid the emergence of product "washboard" stripes. Since the second and third processes are not directly printed on the corrugated board, there is no possibility of reducing the strength of the corrugated board. The effect of printing area on the compressive strength of the carton is shown in Figure 1. (slightly)
The second pairing process, high production costs, suitable for a small number of high-definition requirements, special-shaped corrugated boxes, fine corrugated box production.
The third pre-printing method is suitable for the production of large-volume products and is rarely used in China.
Second, corrugated board flexo process points 1. Corrugated board printing plate corrugated box printing plate thickness of 3 to 7mm, the hardness of Shore hardness (HS) 25 ~ 50. When the quality of corrugated paper is poor, a thicker plate with a lower hardness should be used. When the corrugated paper is of good quality and needs to be printed in small prints or screens, thin plates with high hardness should be selected.
2. As shown in Fig. 2 (slightly), with thick printing, if the printing pressure is too low, the printed substrate is likely to produce corrugated and “sawboard”-like patterns, and it will affect the field and fine lines; when the printing pressure is too large, the printing base The material is easily deformed or even damaged. At the same time, the resin plate is deformed and the printing dots are enlarged.
When the printing pressure is too low, the printed substrate is susceptible to corrugated and washboard-like patterns, as well as affecting field and fine line printing.
When the printing pressure is too high, the printed substrate is easily deformed or even damaged. At the same time, the tree finger printing plate is deformed and the printing dot is enlarged.
At the same printing plate thickness and the same printing speed, the flexographic printing pressure distribution with different hardness is different from the imprinting condition. The plate with higher hardness has no obvious expansion of the imprint, but the imprint of the edge parallel to the edge parallel to the corrugated sheet is less realistic. On the contrary, the soft imprint is imprinted with strong imprinting, but the edge is expanded. The reason is that the flexibility of the flexographic plate is different, resulting in a difference in elasticity, high hardness, and low elasticity, that is, the deformation of the surface layer of the printing plate is small, whereas the deformation of the printing plate surface layer is large, and the fidelity of the imprinting is poor. In order to complement each other with two different hardness plates, a two-layer flexographic version emerged, consisting of two types: 1 overall structure. That is divided into two layers, the surface layer after the hardness in the Shore hardness of about 55, the middle and lower plate hardness in the Shore hardness of 35 to 45 or so. Carton B version of the market product "GS flexo". 2 binder. That is to take a thick 2.5 ~ 3mm thin carton flexo (such as listed in Table 1), in the back of a layer thickness of 3 ~ 4mm foam rubber plate.

Table 1 DuPont Xili corrugated carton printing thin TDR series double-layer flexo printing surface deformation is small, most of the deformation is absorbed by the softer middle, lower layer or foam rubber, from the actual effect, the overall effect The structure is better than the bond type because the relief is deep and the cushioning is good, but from the economic point of view, the bond type price is low and easy to promote.
3. Corrugated flexo inks should use a new generation of water-based inks, such as water-repellent inks or flexographic UV inks with good acrylic copolymer resins as the bonding agent.
4. Ink system Anilox roller is the key component of flexo printing machine, the heart of flexo printing machine. Compared with the CO2 laser-engraved ceramic anilox roller, the new YIG laser-engraved ceramic anilox roller has a higher effective ink transfer capacity, and it is estimated that the 1200-line/inch anilox roller volume is the same as the conventional 700 line/inch, which can meet the requirements for fine and high-intensity products. Production requirements. Select the number of anilox roller lines should consider the level of the number of lines. The number of general screen lines: the number of anilox roller lines = 1:4 to 1:5. Should use reverse (reverse) squeegee ink system, (see Figure 3, omitted) The installation direction of the squeegee of this system is opposite to the direction of rotation of the anilox roller. Compared with the conventional angle, the pressure between the squeegee and the anilox roller during working is lighter, the loss is smaller, and the ink can be more accurately transferred and controlled to meet the requirements of high-quality printing.
Third, the corrugated paper paper printing process after the printing process points printed surface paper and corrugated board affixed to the coating process shown in Figure 4 (slightly). The troubles and analysis of the cover worker Rui Yi appear as follows.
(1) In the production of color box, the "sawboard" fault is fused to single-faced corrugated paper. Sometimes, color-printed face papers appear as indentations in the shape of the sampan plates (as shown in Fig. 4). This type of failure has the effect of affecting the appearance of the finished product and the impact on the strength and thickness of the carton.
1-Reel print; 2-reel paperboard; 3-finished product; 4-coat roll;5- Reason for dry box formation: Noodles and single-sided corrugated paperboard Excessive amount of binder squeezed on both sides of the top of the crucible will cause the topsheet to shrink at the top of the crucible in the process of binding and drying to form a “seesaw”. Need to see the amount of adhesive coating in front of the paste, if there is a very thin line on the paper, then it shows a good state of glue (Figure 5a), there will be no seesaw phenomenon; if there are heavy double lines, indicating If the amount of glue applied is too large (as shown in Figure 5b), the see-saw phenomenon will occur, especially if it is more severe.
Solution: 1 Change the amount of dough paper. The easiest way is to replace the low-quality tissue paper with high-quality tissue paper, which can significantly eliminate the see-saw phenomenon, but this will increase the production cost. 2 To increase the adhesive viscosity of corn flour to 100ml 60s, the viscosity of corn flour adhesive is increased by 100ml for 70-90s, so as to reduce the amount of glue applied on the back of the peak and to significantly reduce the phenomenon of seepage. 3 Wetting method (hanging, humidifying, etc.) can be used after the paper absorbs a certain amount of water, so as to avoid the phenomenon that the dry tissue paper absorbs too much amount of glue to cause the seesaw phenomenon. 4 Adjust and control the parallelism and clearance between the glue roller and the pressure roller. The gap between the squeegee roller and the pressure roller is based on the corrugated paper, and the pressure between the pressure rollers is strictly controlled so as to reduce the occurrence of the sag plate phenomenon. 5 Make full use of paper. The longitudinal filaments of the tissue paper should be aligned perpendicular to the direction of the corrugated fiber paperboard to eliminate the phenomenon of jaws. This is the most basic and most effective method, but sometimes it wastes paper due to the width of the web not matching the size of the carton, increasing the cost.
(2) Collapse failure Collapse refers to the expansion of the corrugated paper on both sides of the corrugating after 2 min. In the case of a good adhesive, both sides can be bonded. If the quality of the adhesive is not good, the two ends of the surface will be severe. Open plastic.
The main cause of this failure: 1 The direction of the corrugation is not parallel to the direction of the crepe. 2 The corrugated paper sizing is not enough and the elongation is large. As a result, the glue has not penetrated into the fibers of the paper without forming a film on the crucible, causing the fibers to elongate, causing them to collapse and form a large amount of glue.
Corrugated paper can be checked for quality before use by tapping on the corrugated paper with a finger and a little water to observe its penetration rate and repeat it several times. After 6s, the infiltrated corrugated paper was proved to be qualified by practice. (Jin Yinhe, Beijing Institute of Graphic Communication) ("Packaging Special Paper Packaging")