The reason and processing of binding center offset in imposition

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In the printing process of books and periodicals, the phenomenon of misplaced front pages and misprinted versions often occurs after the inner pages are folded. That is, the inner pages of the pages are gradually pushed outwards, and the inner pages of the pages are shifted toward the front. In order to ensure that the entire book version of the heart and page number consistent, imposition, in addition to minimize the error, to ensure that the folding accurate to the outside, should intentionally the inside pages of the book, saddle stitching products in the layout of the center of the layout of the mouth to allow 1 ~ 2mm, In the imposition of this, the position of certain pages in certain posts or posts will be adjusted to ensure the consistency of the pages and pages of the finished books and editions. This can also avoid the appearance of misplaced copies and incorrect editions.

It is one of the standards to measure the quality of books and periodicals. The National Press and Publication Administration publishes the test data for high-quality books and publications published by the State Administration of Press and Publications. The error of excellent books is ≤4mm, and the associated page error is ≤2mm. Version of the heart skew ≤ 0.5mm, image plate error ≤ 0.5mm. The style of books and journals has become more and more active. Designs such as cross-page, bleeding, and border lines are frequently used in designing. Although these practices can improve the quality of books and magazines and maintain their own characteristics, they also impose higher requirements on binding and cutting. . For example: cross-page map design, not only requires that the hue of the patchwork area during printing be consistent, and the imposition, folding, and other procedures must also be accurate: the front edge of the eyebrow, the page number of the product with text, to ensure that the front port line ink uniform, wide and narrow Consistent with the content and so on. When this type of product is put into production, it needs more attention. Because it involves paper thickness, machine performance and other uncertainties, the imposition operation will have a certain degree of difficulty. Specific analysis should be made on specific issues.

The reason why the finished book's heart offset

There are many reasons for the deviation and distortion of finished books, such as the deformation of printing paper, improper control of printing pressure and water consumption, inaccurate folding, incomplete stitching, and so on. The offsets associated with inequality and revision are simply summarized as follows.

1. Offset due to paper thickness

(Figure 1 is not coincident after the setting of the folds)
It can be seen from the analysis that the edition-centered deviation exists between every page from the outside to the inside of the signature. Therefore, in principle, every page should be corrected during the imposition. The thicker the paper is, the larger the scale that needs to be biased, and the more the closer it is to the Ritsui Nei page, the more it will be required. The correction amount should be determined based on the thickness of the printing paper, and a paper thickness should be added every other page in the signature. For cases where the folds are not tight, an empirical value can be added to each page to correct the errors. In actual production, generally, page-by-page correction is not performed, but from the perspective of operability, according to the requirements for product accuracy, each page is subjected to a graded bias distribution processing with four pages and eight pages. For example: general saddle-stitched product version 2 overall version of the heart to set the direction of the mouth to allow 0.5-lmm, the third edition of the overall version of the direction of the mouth to the direction of the mouth so that 1-2mm and so on; using WD-B550 book rotation offset press In the large set of pages printed by other types of printing presses (two sheets per post), the overall 8 pages of the pages are offset to the order of 0.5-1 mm, and special treatment is required for special products. Such as the factory has printed "Mao Zedong Collection" and other high-quality classics, according to the factory's older generation memories, although the use of lead printing process, but the error produced by the front of the mouth in the up and down, right and left directions through repeated proofing , folding and other means to do a page by page correction correction.

2. Correcting Page Numbers

Different prescriptions and different folding styles are different in the relative position of each page on the large version. It is important to correctly correct the relative position of each page on the large version. Skilled imposition operators can accurately make impositions on different models, different celestial bodies, and ground rules. However, in order not to make mistakes, they should fold out small samples, draw sketches, and clear page numbers before making up. It will not be confused when processing, as shown in Figure 3.

3 cross-page map processing

(Figure 2 hollow pages will also cause version of the heart)

Version misunderstanding

It is very difficult to completely resolve the issue of impulsive patterns, but it is still possible to control deviations within a certain range through appropriate processing during imposition. The processing method is very simple. The bias that may occur in the upcoming version will be biased in the opposite direction before the imposition, thus offsetting the errors that may occur in the finished book. The correct and appropriate bias needs to solve the following problems.

1. Correction of a correction

16 open plan machine folding plate format 16 open plan machine folding plate layout

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Printing paper is the same. If the number of foldings is too many, the hearts of the inner and outer pages of the signature will also be significantly shifted. In the final analysis, this offset is caused by the thickness of the paper, but it can be controlled by controlling the number of foldings. The folding limit of books and prints is stipulated in the industry standard CY/J28-1999: the maximum amount of paper is below 59g/m2. Four hands folded, 60-80g/m2 fold up to three hands, 81g/m2 up to two hands. The main reason for this limitation is the excessive number of folds. The signatures will produce pleats and affect the quality of the binding. Strict implementation of this standard, the front of the book is not uniform, the phenomenon of mindset can also be controlled within a certain range. However, in actual production, sometimes based on other considerations, printing paper of about 70 g/mZ is folded in four hands, and printing paper of 105 g/m2 or even 157 g/m2 is folded in three hands. At this time, there is a problem of pleat pleats and printing center offset. Severe, pleated pleats can be solved by folding the machine to deflate or discontinue the affixing of the posterior to solve the resulting census center offset.

3. Too loose sheet to cause inner and outer pages of the heart

Cross stitching requires very little up and down, left and right small errors will be obvious in the finished book, so the correct stitching is very important. Before processing, carefully analyze the specific position of the two-page code where the double-page image is located on the large-format version. For products that are flat-set and glue-stitched, the presence of milling and setting holes must be taken into consideration when composing a cross-page image. When making a layout, cross-page drawings should be considered separately. A layout with a spread sheet cannot simply offset the entire version of the layout to the orientation of the opening, but separate the spread pattern from other versions of the layout. In the direction of the sky and the foot, we work together with the entire version of the mind to make corrective corrections to ensure that the left and right sides of the mosaic are correct after writing.

Mistakes before the book is completed and the phenomenon of injustice is generally formed during the imposition process. Ignoring this problem will often lead to product quality that does not meet standards and sometimes results in more severe consequences. Therefore, it must be taken seriously in peacetime work. .

In principle, the tighter the flap is, the better, but because of the limitation of the paper tension, the phenomenon of insignificance has always existed. In addition, the folding machine adjustment is not in place, the signature will appear in the booklet, tilt, hollow and other situations as shown in Figure 2. Too loose a bookbinding will result in the phenomenon of page break due to imperfect milling and stickiness, and it will also lead to the deviation of the inner pages.

The thickness of the printing paper is often neglected in the group or the imposition. This often results in a shift in the center of the finished book. When printing in thin paper (for example, 50 g/m2 or less), the effect of paper thickness is generally negligible if the binding is used. . However, with thicker paper or in saddle-stitched products, the effect of paper thickness on the offset of the printing plate is revealed. The specific performance is as follows: the finished book has more inner posts than the outer posts, and the inner pages of the pages are closer to the front than the outer pages. The thicker the paper, the more the number of posts for horseback riding, the more obvious the performance. In the regular layout, each element of the page format is the same, and the position of the stencil is treated uniformly according to the requirements of the opening, incision, sky head, and foot distance. With the existence of the paper thickness, deviations are generated between the arbors positioned relative to the booklet when the booklet cannot be completely overlapped after the actual folding. For a saddle-stitched product with 70g/m2 paper and 4 sheets, the gap between the center page and the outer page can reach 3-4mm, as shown in Figure 1. This deviation is not only in the mouth and front mouth direction, The direction of the foot also exists, but relatively speaking, the sky-head and foot-bearers are one fold less than the direction of the cut, so the total deviation in this direction is small.