The quality of the fold will directly affect the quality of the book. Whether it is a manual folding or machine folding, the entire folded signature should meet the following requirements.
The page number and page layout of the signature are correct. The center of the page number shall prevail. The allowable error of the position of the page number between two pages shall be ≤ 4.0mm. The allowable error of the position of the entire page shall be ≤ 7.0mm, and the allowable error of the screen connection shall be ≤ 1.5mm.
The signatures are neat and tidy, with no obvious wrinkles, dead folds, folded corners, scraps, placards, and dirty spots.
More than three fold and more than three fold, should be excluded from the air.
Up to 40% off for papers above 59g/m2; Up to 30% off for papers between 60g/m2 and 80g/m2; Up to 30% off for papers above 81g/m2.
In order to check the quality of the folded pages, the black folds in the folds of the finished folds are centered. After the signature of the book, the mark forms a step-like mark on the back of the book block.
Knife hole should be properly marked in the middle of the crease, and the break should be well-drawn and scratched to avoid page breaks.
The signature of the line that is locked by the automatic sewing machine should comply with the requirements of Figure 2-25.
The signature must be clean, oil-free, undamaged, and free from corners. The folds should be flat and have no wrinkles.
Figure 2-25 Book folding requirement for automatic sewing machine lock line
From the above requirements, it can be seen that the accuracy of the folds of the signature and the degree of crease compaction are important aspects of the quality of the crease, because it directly affects the production efficiency of the next-step equipment and the quality of the book block. In the process of folding, the factors that affect the accuracy of folding and the degree of folding of the book's folds are mainly two aspects: one is the pressure and extrusion time between the folding rollers when the folds are formed; the second is the degree of influencing the folding Process technology factors.
As the pressure between the folding rollers increases, the more the booklet creases. The pressure between the folding rollers can be adjusted by changing the gap between the folding rollers. As the thickness of the paper and the signature increases, the gap between the folding rollers also increases with this thickness, but it cannot be too large or too large. small. If the gap is too large, the paper conveying speed will be slowed down, and if the gap is too large, the conveying speed between the two rollers will increase, and wrinkles and tears will occur.
The time during which the folding roller presses the crease has a direct relationship with the circumferential speed of the folding roller, the width of the contact band, and the like. In the folding process, although the effect of the crease extrusion is proportional to the time it passes through the folding roller, this time cannot be greatly changed in actual production.
The technological factors affecting the degree of crease compaction include: paper thickness, moisture content of the paper, ash content of the paper, crease direction, number of folds, and folding method. Paper thickness. For thin paper, after folding into a signature, the elastic recovery force at the crease is smaller, so the crease is more easily compacted.
The ash content of the paper. The greater the amount of filler in the paper, the weaker the bonds between the fibers in the paper, and this connection is significantly destroyed at the creases. Therefore, in the case of folding, the paper with high ash content has a significantly lower breaking strength and elasticity than paper with a low ash content, so that the creases are easily compacted.
The moisture content of the paper. As the water content in the paper increases, the plasticity of the paper increases. When the water content of the paper is increased, a more realistic crease can be obtained with less pressure, and the damage of the molecular chains between the fibers is small. Therefore, in order to obtain a more realistic crease, the water content of the paper is preferably between 10% and 12%.
Folding direction. When the alignment direction of the paper fibers and the crease direction are the same, the creases are not easily compacted and are easily restored (the upper half of the signatures bounces up at a certain angle). When the orientation of the paper fibers and the creases are vertical, the creases are easily compacted. Therefore, in the case of folding in the latter case, there is no need for much pressure between the folding rollers, because if the pressure is too great, the paper may be broken at the creases, which ultimately reduces the life of the publication.
Number of folds. As the number of folds increases, the thickness of the signature increases. In order to make the crease pressed. The gap between the folds and the rollers should be adjusted according to the thickness of each folded signature to increase the pressure between the next folding rollers.
Folding method. When other conditions are the same, the use of parallel folding method folds, the reality of the book folds is better than the mixed folding method; the use of mixed folding method folding; the reality of the book folds than vertical folding The way is good. Therefore, when adjusting the folding machine, for the parallel folding mode, the pressure between the folding rollers in the mixed rear folding mode should be increased, and the pressure between the folding rollers in the vertical folding mode should be larger.
The page number and page layout of the signature are correct. The center of the page number shall prevail. The allowable error of the position of the page number between two pages shall be ≤ 4.0mm. The allowable error of the position of the entire page shall be ≤ 7.0mm, and the allowable error of the screen connection shall be ≤ 1.5mm.
The signatures are neat and tidy, with no obvious wrinkles, dead folds, folded corners, scraps, placards, and dirty spots.
More than three fold and more than three fold, should be excluded from the air.
Up to 40% off for papers above 59g/m2; Up to 30% off for papers between 60g/m2 and 80g/m2; Up to 30% off for papers above 81g/m2.
In order to check the quality of the folded pages, the black folds in the folds of the finished folds are centered. After the signature of the book, the mark forms a step-like mark on the back of the book block.
Knife hole should be properly marked in the middle of the crease, and the break should be well-drawn and scratched to avoid page breaks.
The signature of the line that is locked by the automatic sewing machine should comply with the requirements of Figure 2-25.
The signature must be clean, oil-free, undamaged, and free from corners. The folds should be flat and have no wrinkles.
Figure 2-25 Book folding requirement for automatic sewing machine lock line
From the above requirements, it can be seen that the accuracy of the folds of the signature and the degree of crease compaction are important aspects of the quality of the crease, because it directly affects the production efficiency of the next-step equipment and the quality of the book block. In the process of folding, the factors that affect the accuracy of folding and the degree of folding of the book's folds are mainly two aspects: one is the pressure and extrusion time between the folding rollers when the folds are formed; the second is the degree of influencing the folding Process technology factors.
As the pressure between the folding rollers increases, the more the booklet creases. The pressure between the folding rollers can be adjusted by changing the gap between the folding rollers. As the thickness of the paper and the signature increases, the gap between the folding rollers also increases with this thickness, but it cannot be too large or too large. small. If the gap is too large, the paper conveying speed will be slowed down, and if the gap is too large, the conveying speed between the two rollers will increase, and wrinkles and tears will occur.
The time during which the folding roller presses the crease has a direct relationship with the circumferential speed of the folding roller, the width of the contact band, and the like. In the folding process, although the effect of the crease extrusion is proportional to the time it passes through the folding roller, this time cannot be greatly changed in actual production.
The technological factors affecting the degree of crease compaction include: paper thickness, moisture content of the paper, ash content of the paper, crease direction, number of folds, and folding method. Paper thickness. For thin paper, after folding into a signature, the elastic recovery force at the crease is smaller, so the crease is more easily compacted.
The ash content of the paper. The greater the amount of filler in the paper, the weaker the bonds between the fibers in the paper, and this connection is significantly destroyed at the creases. Therefore, in the case of folding, the paper with high ash content has a significantly lower breaking strength and elasticity than paper with a low ash content, so that the creases are easily compacted.
The moisture content of the paper. As the water content in the paper increases, the plasticity of the paper increases. When the water content of the paper is increased, a more realistic crease can be obtained with less pressure, and the damage of the molecular chains between the fibers is small. Therefore, in order to obtain a more realistic crease, the water content of the paper is preferably between 10% and 12%.
Folding direction. When the alignment direction of the paper fibers and the crease direction are the same, the creases are not easily compacted and are easily restored (the upper half of the signatures bounces up at a certain angle). When the orientation of the paper fibers and the creases are vertical, the creases are easily compacted. Therefore, in the case of folding in the latter case, there is no need for much pressure between the folding rollers, because if the pressure is too great, the paper may be broken at the creases, which ultimately reduces the life of the publication.
Number of folds. As the number of folds increases, the thickness of the signature increases. In order to make the crease pressed. The gap between the folds and the rollers should be adjusted according to the thickness of each folded signature to increase the pressure between the next folding rollers.
Folding method. When other conditions are the same, the use of parallel folding method folds, the reality of the book folds is better than the mixed folding method; the use of mixed folding method folding; the reality of the book folds than vertical folding The way is good. Therefore, when adjusting the folding machine, for the parallel folding mode, the pressure between the folding rollers in the mixed rear folding mode should be increased, and the pressure between the folding rollers in the vertical folding mode should be larger.
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