When the climate is dry, the problem of collapsing cracks (also known as “bend ribs†or “burstsâ€) that are plagued by users of coated paper will increase. To explain this issue, we must start with the composition of coated paper.
Coated paper is composed of wood pulp and paint. Wood pulp is what we call wood fiber (needle pulp/long fiber, broad-leaf pulp/staple fiber). Wood fiber has the characteristics of water hardness, brittleness and brittleness, and water absorption becomes soft and tough. This feature is well verified. We take a small tree branch from a living tree and perform a bending test. Generally the branches that have just been removed have a strong toughness at the time of bending and are difficult to break at one time. If the branches are dried, they are air-dried. Losing water can easily break it. The coated paper, which uses fibers as its main raw material, also inherits its characteristics. In China, summer temperatures are high and rainfall is high. The relative humidity of the environment is high, and the paper maintains its original toughness. However, in winter, the temperature and precipitation decrease, the relative temperature of the environment decreases, and the paper easily loses water and becomes brittle. This is the main problem in the production of crevice bursts. the reason.
After knowing the reasons, we can solve this problem when we solve the problem, that is, controlling the moisture content of the paper. The paper's moisture content is basically controlled at 4% to 6%. After production, it is quickly packed with Laminated Kraft paper to prevent water loss. During the processing of the printing plant, the temperature and humidity of the storage and processing plant environment were not controlled, and the moisture that would be lost when the unpacked paper was stored before printing was printed. In the process of printing and printing, printing inks, coating oils need to be accelerated by hot air, infrared, UV light and other methods. At this time, water in the paper is lost more and more, if the paper is not directly processed by folding, There will be a problem of collapsing bursts. The following is a brief introduction of several remedial methods after the problem has arisen for your reference.
Rewetting treatment: replenish paper before folding 1. Double-sided printing products. In the case of rotary printing, the temperature of the oven is adjusted during the drying process to prevent excessive loss of paper water. Another can be used to increase the humidity of the environment, such as water spray around the workshop and the paper roll, etc., to adjust the humidity of the paper, and spray near the sample at the same time, directly fill the water samples.
2. Single-sided printing products. You can use the back of the water, the effect is more obvious. Once there was a printing plant that used a gravure printing machine roll on one side of a copper plate paper, it was automatically bagged and automatically folded to make a small package bag. The problem of breakage occurred at the folds. After the back water treatment process, the finished product was used. The rate has increased dramatically.
3 boxes of products. After indentation, moisten the flaps with a damp cloth.
Folding, indentation process adjustment 1. Folding process to minimize the folding pressure, in order to ensure that the sample can be formed.
2. According to the requirements of the die-cutting process, different steel lines, different thicknesses of the bottom plate, and different bottom mold groove widths should be used for different papers. If the related process does not match, it is easy to cause a crack in the fold. The following is a common calculation method for your reference.
B=(C×1.5)+D
Among them, B-indentation bottom mold groove width; C-paper thickness; D-steel wire thickness. And D ≥ C; A ≤ C; A-bottom depth.
When indenting a thick paper or a box product, the width of the bottom mold groove is enlarged as much as possible, and the indentation pressure is appropriately reduced. Although the indentation line is not very clear, the molding will not be very clear and look good, but the problem of bursting can be avoided or mitigated.
The choice of paper orientation for paper folding is important. At present, many coated papers on the market are paper-laid high-speed paper machines. Paper has two directions (longitudinal: parallel to the paper, and horizontal: perpendicular to the paper). There are also certain differences in the properties of the paper. Relatively better than the landscape, it is recommended to select the folding line and the vertical direction of the paper in the folding direction.
The above is a summary of the author's brief analysis and processing methods for the cracks in the printing factory and the experts in work learning. In addition, different customers choose papers of different grades according to different requirements of their products, and it is also very important to avoid and mitigate such problems.
Coated paper is composed of wood pulp and paint. Wood pulp is what we call wood fiber (needle pulp/long fiber, broad-leaf pulp/staple fiber). Wood fiber has the characteristics of water hardness, brittleness and brittleness, and water absorption becomes soft and tough. This feature is well verified. We take a small tree branch from a living tree and perform a bending test. Generally the branches that have just been removed have a strong toughness at the time of bending and are difficult to break at one time. If the branches are dried, they are air-dried. Losing water can easily break it. The coated paper, which uses fibers as its main raw material, also inherits its characteristics. In China, summer temperatures are high and rainfall is high. The relative humidity of the environment is high, and the paper maintains its original toughness. However, in winter, the temperature and precipitation decrease, the relative temperature of the environment decreases, and the paper easily loses water and becomes brittle. This is the main problem in the production of crevice bursts. the reason.
After knowing the reasons, we can solve this problem when we solve the problem, that is, controlling the moisture content of the paper. The paper's moisture content is basically controlled at 4% to 6%. After production, it is quickly packed with Laminated Kraft paper to prevent water loss. During the processing of the printing plant, the temperature and humidity of the storage and processing plant environment were not controlled, and the moisture that would be lost when the unpacked paper was stored before printing was printed. In the process of printing and printing, printing inks, coating oils need to be accelerated by hot air, infrared, UV light and other methods. At this time, water in the paper is lost more and more, if the paper is not directly processed by folding, There will be a problem of collapsing bursts. The following is a brief introduction of several remedial methods after the problem has arisen for your reference.
Rewetting treatment: replenish paper before folding 1. Double-sided printing products. In the case of rotary printing, the temperature of the oven is adjusted during the drying process to prevent excessive loss of paper water. Another can be used to increase the humidity of the environment, such as water spray around the workshop and the paper roll, etc., to adjust the humidity of the paper, and spray near the sample at the same time, directly fill the water samples.
2. Single-sided printing products. You can use the back of the water, the effect is more obvious. Once there was a printing plant that used a gravure printing machine roll on one side of a copper plate paper, it was automatically bagged and automatically folded to make a small package bag. The problem of breakage occurred at the folds. After the back water treatment process, the finished product was used. The rate has increased dramatically.
3 boxes of products. After indentation, moisten the flaps with a damp cloth.
Folding, indentation process adjustment 1. Folding process to minimize the folding pressure, in order to ensure that the sample can be formed.
2. According to the requirements of the die-cutting process, different steel lines, different thicknesses of the bottom plate, and different bottom mold groove widths should be used for different papers. If the related process does not match, it is easy to cause a crack in the fold. The following is a common calculation method for your reference.
B=(C×1.5)+D
Among them, B-indentation bottom mold groove width; C-paper thickness; D-steel wire thickness. And D ≥ C; A ≤ C; A-bottom depth.
When indenting a thick paper or a box product, the width of the bottom mold groove is enlarged as much as possible, and the indentation pressure is appropriately reduced. Although the indentation line is not very clear, the molding will not be very clear and look good, but the problem of bursting can be avoided or mitigated.
The choice of paper orientation for paper folding is important. At present, many coated papers on the market are paper-laid high-speed paper machines. Paper has two directions (longitudinal: parallel to the paper, and horizontal: perpendicular to the paper). There are also certain differences in the properties of the paper. Relatively better than the landscape, it is recommended to select the folding line and the vertical direction of the paper in the folding direction.
The above is a summary of the author's brief analysis and processing methods for the cracks in the printing factory and the experts in work learning. In addition, different customers choose papers of different grades according to different requirements of their products, and it is also very important to avoid and mitigate such problems.
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