In offset printing, when the paper enters the cylinder under pressure, it forms curved or irregular irregular folding marks on the surface of the paper, which is called paper crease deformation, also called paper arching or discounting. The wrinkles appearing after drum embossing is a common process failure, which not only causes troubles for the process, but also seriously affects the accuracy of the overprinting and destroys the complete structure and appearance of the entire situation. In the upper grade product, if there is a wrinkle pattern on the printed sheet, it is an unqualified product.
Paper from the wrinkle distribution by state, can be divided into large fold, small fold, straight fold and branch folds and other types. The main reason is due to the mechanical and paper itself, especially when printing thin paper, wrinkles often occur.
First, the paper itself causes analysis
Mainly from the paper appears flounces and tight edges, they are caused by the paper wrinkles are not the same, the wrinkles caused by the lotus leaf around the paper, mainly to the tip position, the tight edge caused by the fold in the middle of the paper, Generally do not leave.
Second, the imprinting roller uneven teeth cause paper crease
If the impression roller bite uneven force, will make the paper's imprinting process can not be balanced, resulting in partial forced stretch paper wrinkles, this kind of wrinkle is related to the elasticity of the teeth, when the pressure on both sides of the impression cylinder loose or loose on both sides of the teeth The wrinkles in different positions will appear when the middle is tight or when one side is tight, that is, the position of the wrinkles corresponds to the side where the teeth are loosened.
In order to prevent paper creases, the flatness of the impression cylinder teeth is absolutely necessary. After calibration, the teeth of the drum teeth can easily be changed. Otherwise, not only is paper crease prone to occur, but also paper that cannot be bitten, paper breaks, etc. , sometimes it can cause other failures.
The above two reasons will also lead to the occurrence of wrinkles, which should be analyzed according to specific circumstances. The following points are discussed in detail.
1. Paper moisture distribution is not uniform. If the water content on the four sides is greater than the middle, ie, the phenomenon of “foliage†occurs, the wrinkles on the dragging part will be generated. If the water content on the four sides is smaller than the middle part, the “tight edge†phenomenon of the paper will produce the wrinkles in the middle part.
2. The pressure on the transfer roller is uneven. The platen roller is a device that controls the leveling, constant speed, and positioning of the conveying paper. Due to the unequal pressure adjustment of each wheel, the paper is affected by the axial force in the conveying process, causing the paper to bulge in the middle of the conveying, and still maintain the middle bulging state in the front specified position. After the printing, the bulging cannot be achieved. Eliminated, causing wrinkles in the trailing area.
3. The biting force of the impression cylinder bite paper teeth is not equal. The biting paper force of the roller biting paper teeth should be strong and strong, and the force of each biting paper should be equal. If the biting force of the two teeth is insufficient, the paper will produce dragging and wrinkling. If the bite bite is insufficient, the corresponding drag The wrinkle is generated at the tip of the tip, and if the bite force is insufficient in the middle, the middle tip causes wrinkles. If the middle is severely lacking (biting force) and the speed difference between the printing rollers is large, the trailing portion may be damaged.
4. Paper is improperly handed over. If the length of the paper edge is changed (decreased) during the proximity of the paper before it is imprinted, it is prone to wrinkle or even chipping.
5. There is a big difference in the level of the tooth pad. When the paper is bitten, the edge of the paper is uneven (bite) but wavy, resulting in short crease deformation closer to the nip portion.
6. Knock paper marks too deep. Because the paper cannot be punched with force, the paper traces are deep and dense. As a result, the paper creases on the creases of the knocked paper.
7. The edge of the paper is in the half tooth position. After the paper is positioned, the corners of the paper are bitten by the teeth of the roller by half or less, so that the corners of the paper are often uneven, and paper crumpled calendars are printed on the edges of the paper.
8. Excessive thick deposits on the impression cylinder. The ink on the surface of the embossing cylinder is too thick, so that the paper is imprinted unevenly, resulting in short-distance wrinkle deformation of the mouth.
9. Paper fibers are aligned. When the paper enters the machine imprinting, the direction of the fibers is straight and the paper tends to cause wrinkles.
10. Paper moisture content is too large, the paper own fiber fat fertilizer album printing, in the pressure, fat fertilizer fiber from the narrower tend to produce a bite mouth stretched to the tip of the corrugated wrinkle deformation.
The above is the main reason for paper creases. However, how to judge whether it is due to the paper itself or because of mechanical reasons is also critical for discount wrinkling. It determines the direction for us to resolve quality accidents.
In general, mechanical reasons are as follows:
1. Wrinkle paper due to improper mechanical adjustment. However, the mechanical causes of the wrinkles are generally the same. The wrinkles are in the middle or on the edge, or face outward. The position is fixed.
2. The frequency of wrinkles. Printing is now wrinkled, some are Zhang Zhang; sometimes there are several, there are not a few; some are larger, some are smaller; if Zhang Zhang repeated, and the size of the fold is basically the same, most of the mechanical folds .
3. The wrinkled paper will be turned or turned over. No matter how you turn your head or turn over, the paper will not wrinkle. In the same area, it is usually a mechanical wrinkle.
4. With another paper test of the same type, if the single-sheet printing is still creased on the same part, it is basically a mechanical problem.
The wrinkles of the paper exclude the cause of the machine. Then it is the fault of the paper. The wrinkles appear on the paper itself. The main reason is that the paper itself is uneven and should be analyzed and resolved according to the specific circumstances.
Paper from the wrinkle distribution by state, can be divided into large fold, small fold, straight fold and branch folds and other types. The main reason is due to the mechanical and paper itself, especially when printing thin paper, wrinkles often occur.
First, the paper itself causes analysis
Mainly from the paper appears flounces and tight edges, they are caused by the paper wrinkles are not the same, the wrinkles caused by the lotus leaf around the paper, mainly to the tip position, the tight edge caused by the fold in the middle of the paper, Generally do not leave.
Second, the imprinting roller uneven teeth cause paper crease
If the impression roller bite uneven force, will make the paper's imprinting process can not be balanced, resulting in partial forced stretch paper wrinkles, this kind of wrinkle is related to the elasticity of the teeth, when the pressure on both sides of the impression cylinder loose or loose on both sides of the teeth The wrinkles in different positions will appear when the middle is tight or when one side is tight, that is, the position of the wrinkles corresponds to the side where the teeth are loosened.
In order to prevent paper creases, the flatness of the impression cylinder teeth is absolutely necessary. After calibration, the teeth of the drum teeth can easily be changed. Otherwise, not only is paper crease prone to occur, but also paper that cannot be bitten, paper breaks, etc. , sometimes it can cause other failures.
The above two reasons will also lead to the occurrence of wrinkles, which should be analyzed according to specific circumstances. The following points are discussed in detail.
1. Paper moisture distribution is not uniform. If the water content on the four sides is greater than the middle, ie, the phenomenon of “foliage†occurs, the wrinkles on the dragging part will be generated. If the water content on the four sides is smaller than the middle part, the “tight edge†phenomenon of the paper will produce the wrinkles in the middle part.
2. The pressure on the transfer roller is uneven. The platen roller is a device that controls the leveling, constant speed, and positioning of the conveying paper. Due to the unequal pressure adjustment of each wheel, the paper is affected by the axial force in the conveying process, causing the paper to bulge in the middle of the conveying, and still maintain the middle bulging state in the front specified position. After the printing, the bulging cannot be achieved. Eliminated, causing wrinkles in the trailing area.
3. The biting force of the impression cylinder bite paper teeth is not equal. The biting paper force of the roller biting paper teeth should be strong and strong, and the force of each biting paper should be equal. If the biting force of the two teeth is insufficient, the paper will produce dragging and wrinkling. If the bite bite is insufficient, the corresponding drag The wrinkle is generated at the tip of the tip, and if the bite force is insufficient in the middle, the middle tip causes wrinkles. If the middle is severely lacking (biting force) and the speed difference between the printing rollers is large, the trailing portion may be damaged.
4. Paper is improperly handed over. If the length of the paper edge is changed (decreased) during the proximity of the paper before it is imprinted, it is prone to wrinkle or even chipping.
5. There is a big difference in the level of the tooth pad. When the paper is bitten, the edge of the paper is uneven (bite) but wavy, resulting in short crease deformation closer to the nip portion.
6. Knock paper marks too deep. Because the paper cannot be punched with force, the paper traces are deep and dense. As a result, the paper creases on the creases of the knocked paper.
7. The edge of the paper is in the half tooth position. After the paper is positioned, the corners of the paper are bitten by the teeth of the roller by half or less, so that the corners of the paper are often uneven, and paper crumpled calendars are printed on the edges of the paper.
8. Excessive thick deposits on the impression cylinder. The ink on the surface of the embossing cylinder is too thick, so that the paper is imprinted unevenly, resulting in short-distance wrinkle deformation of the mouth.
9. Paper fibers are aligned. When the paper enters the machine imprinting, the direction of the fibers is straight and the paper tends to cause wrinkles.
10. Paper moisture content is too large, the paper own fiber fat fertilizer album printing, in the pressure, fat fertilizer fiber from the narrower tend to produce a bite mouth stretched to the tip of the corrugated wrinkle deformation.
The above is the main reason for paper creases. However, how to judge whether it is due to the paper itself or because of mechanical reasons is also critical for discount wrinkling. It determines the direction for us to resolve quality accidents.
In general, mechanical reasons are as follows:
1. Wrinkle paper due to improper mechanical adjustment. However, the mechanical causes of the wrinkles are generally the same. The wrinkles are in the middle or on the edge, or face outward. The position is fixed.
2. The frequency of wrinkles. Printing is now wrinkled, some are Zhang Zhang; sometimes there are several, there are not a few; some are larger, some are smaller; if Zhang Zhang repeated, and the size of the fold is basically the same, most of the mechanical folds .
3. The wrinkled paper will be turned or turned over. No matter how you turn your head or turn over, the paper will not wrinkle. In the same area, it is usually a mechanical wrinkle.
4. With another paper test of the same type, if the single-sheet printing is still creased on the same part, it is basically a mechanical problem.
The wrinkles of the paper exclude the cause of the machine. Then it is the fault of the paper. The wrinkles appear on the paper itself. The main reason is that the paper itself is uneven and should be analyzed and resolved according to the specific circumstances.
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