Effectively compensate for irregularities in the bound version during the imposition process

During the printing of books and periodicals, when the inner text is folded, there is often a phenomenon of uneven front mouth and incorrect center of the page, that is, the inner page of the signature is gradually squeezed out, and the center of the inner page is shifted toward the front of the mouth. In order to ensure that the book center and page number of the whole book are consistent, in addition to minimizing errors and ensuring accurate folding in place during imposition, the center of the inner page of the book signature and the inner page of the saddle stitching product should be deliberately offset by 1 to 2mm towards the stapling direction. This method of adjusting the position of the center of a certain post or some pages in the post during imposition to ensure the consistency of the center and page number of the finished book can also avoid the phenomenon of uneven front mouth and incorrect center of the page.

Whether the center of the book and the page number of the finished book are aligned is one of the standards for measuring the quality of books and periodicals. The test data requirements for high-quality books and periodicals published by the State Administration of Press and Publication: the page error of the whole book of superior products≤4mm, the error of the associated page≤2mm The center of the plate is skewed ≤0.5mm, and the image connection error is ≤0.5mm. The style of paragraph books and journals is becoming more and more lively. The design often uses spreading, bleeding, fringing and fringing, etc. Although these methods can improve the quality of books and periodicals and maintain their own characteristics, they also put forward higher requirements for binding and cutting. . For example, cross-page design, not only requires the hue of the jigsaw area to be consistent during printing, but also the process of imposition and folding must be accurate: the front eyebrow, the page number of the product with net line text, to ensure that the front port net line ink color is uniform and wide Consistent with the content. This type of product needs more attention when imposition, because of uncertain factors such as paper thickness and machine performance, imposition operation will be difficult, and specific problems should be analyzed.

The reason for the deviation of the center of the finished book version

There are many reasons for the deviation and skew of the center of the finished book, such as the expansion and contraction of printing paper, improper control of printing pressure and water consumption, inaccurate folding, uneven binding and so on. The misalignment of the alignment of the Qi and the version can be simply summarized as the following points.

1. Offset due to substrate paper thickness

Figure 1 The stitching in the imposition does not overlap after folding

Ignoring the thickness of the printing paper during assembly and layout will often cause the offset of the center of the finished book. If printing with thinner paper (such as 50g / m2 or less), if you use stacking binding, you can generally ignore the effect of the paper thickness. . But when printing with thicker paper or in saddle-stitched products, the effect of paper thickness on the offset of the plate center appears. The specific performance is as follows: the inner post of the finished book is closer to the front than the outer post, and the center of the inner page of the post is closer to the front mouth than the outer page. The thicker the paper, the more the saddle stitched posts, the more obvious the performance. In the conventional layout, the elements of each page are the same, and the positioning of the center of the plate is treated uniformly according to the requirements of the distance of the stapling, incision, head and foot. With the existence of the thickness of the paper, after the actual folding, each page of the stapling cannot completely coincide with the center of the positioning relative to the stapling position during imposition. Taking the saddle stitching product of 70g / m2 paper and 4 printed sheets as an example, the gap between the center page and the outer page can be up to 3-4mm. As shown in Figure 1, this deviation is not only in the direction of the stitching and front opening, the sky, The direction of the footing also exists, but relatively speaking, the folding hands in the direction of the sky and the footing are one fold less than the direction of the cut, so the total deviation in this direction is small.

2. Deviation caused by too many folding times

The printing paper is the same. If there are too many folding times, the center of the inner and outer pages of the signature will also shift significantly. This deviation is ultimately caused by the thickness of the paper, but it can be controlled by controlling the number of folds. The folding limit of book printing is clearly defined in the industry standard CY / J28-1999: the maximum paper consumption is 59g / m2 or less Fold four hands, at most 60-80g / m2, at most three hands, 81g / m2 or more, at most two hands. The main reason for this limitation is that there are too many folds, and the signature will have a fold, which affects the quality of the binding. Strictly enforced according to this standard, the irregularity of the front of the signature and the malformation of the version can also be controlled within a certain range. However, in actual production, it is sometimes based on other considerations. The printing paper around 70g / mZ is folded in four hands, and the printing paper at 105g / m2 or even 157g / m2 is folded in three hands. Seriously, the problem of splayed pleats can be solved by the method of deflating or folding the folding machine, and then the center deviation caused by the unevenness of the front mouth needs to be solved.

3. Folding pages into posts is too loose, causing misalignment of inner and outer pages

Figure 2 Hollow signatures also cause irregularities

In principle, the tighter the folded sheet is, the better. However, due to the limitation of paper tension, the phenomenon that the folded sheet is not tight has always existed. In addition, if the folding machine is not adjusted properly, the signatures will be not compact, inclined, hollow, etc. as shown in Figure 2. After loose binding, the pages will be dropped due to imperfect milling and sticking, which will also lead to the deviation of the center of the inner pages.

Unhealthy version

It is very difficult to completely solve the phenomenon of irregularities in the plate, but it is still possible to control the deviation within a certain range through proper processing when imposition. The processing method is very simple, that is, the deviations that may be produced by the center of the layout are confiscated in the opposite direction in advance, so as to offset the errors that may occur in the finished book. Correct and appropriate concessions need to solve the following problems.

1. Correction of one

16-open ground ruler folding version 16-open sky ruler folding version


Figure 3 Different folding methods result in different relative positions of each page on the large version

The analysis shows that the deviation of the edition center exists between every page from the outside to the inside of the signature, so in principle, every page should be corrected when imposition. The thicker the paper, the larger the scale to be biased, and the closer to the inner page of the post, the more to be biased. The determination of the amount of deviation correction should be based on the thickness of the printing paper as a base, and the thickness of the paper should be increased every other page in the signature. When the folding is not tight, an empirical value can be added to each page to correct the deviation. In actual production, it is generally not page-by-page correction, but from the operability point of view, according to the requirements of product accuracy, according to the requirements of the product accuracy, according to the inner 4 pages, inner 8 pages, etc., each grade of the sub-page is processed. For example: the general version of the saddle-stitching products, the second version of the overall version of the center is offset by 0.5-lmm, the third version of the overall version of the center of the book is offset by 1-2mm, and so on; using WD-B550 book offset offset press The large sets of pages printed by the same type of printing machine (two printed sheets per post) have a total deviation of 0.5-1mm toward the bookbinding port, and special treatment is required for special products. For example, the factory has printed classic works with high quality requirements such as "Selected Works of Mao Zedong". According to the older generations of the factory, although the printing process was adopted at the time, the errors caused by the unevenness of the front mouth were repeatedly proofed in the up and down, left and right directions , Folding and other methods have done page-by-page correction and correction.

2. Determination of page number

Different ordering methods, different folding methods, the relative position of each page on the large version is different, and it is important to correct the correct position of each page on the large version of the post. Skilled imposition operators can accurately imposition different models, different heads and feet rules, but in general, in order to make no mistakes, you should fold out a sample, draw a sketch, and standardize the page number before imposition, so that you are giving in There will be no confusion when processing, as shown in Figure 3.

3. Processing of cross-page graphs

The splicing requirements of cross-page diagrams are very high. The small errors of up, down, left and right will be obvious in the finished book, so correct stitching is very important. Before processing, it is necessary to carefully analyze the specific position of the two page numbers on the large page where the cross-page map is located. For flat-bound and bound-book products, the existence of milling and book-cutting should be considered when the cross-page map is imposition. When making large layouts, the cross-page diagram should be considered separately. Layouts with spread pages cannot simply deflect the entire page center to the direction of the booklet, but the spread pages should be separated from other version text. In the direction of the sky and the feet, the upper and lower corrections are performed together with the entire version of the center, to ensure that the left and right and the upper and lower of the mosaic after the book is completed.

Phenomenon such as uneven mouths and inaccurate version of the book are generally formed during the imposition process. Ignoring this problem will often result in product quality not reaching the standard, and sometimes will have more serious consequences. Therefore, you must take it seriously in your usual work .

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