In the digital layout (abbreviated as layout) operation, the physical properties of PDF pages, such as bleeding mode and page size, are the key factors that affect the layout and positioning of PDF pages on the layout. A PDF page with a complete standardized page structure can adopt a unified and efficient layout and positioning method when it is laid out. A non-standard page structure requires the establishment of multiple processing schemes, which has high work intensity, low efficiency and error-prone. This paper analyzes the structure of PDF pages, and combines the signastation software to summarize the positioning methods of PDF pages of different structures in the layout, and finally puts forward strategies to improve the efficiency of layout operations from the aspects of standardizing PDF page design and standardizing page preprocessing. .
1. PDF page structure
The attributes of the PDF page composition, page bleeding mode, and page size are the main factors that affect the structure of the PDF page.
1. Composition of PDF pages
Generally speaking, when a PDF page is created with software such as Indesign, Illustrator or Acrobat, a complete PDF page consists of a Media Box, Trim Box, Crop Box, and Bleeding Box ( Bleed Box) and content box (Art Box) are composed of five physical boxes.
â‘ Media Box. The media box is the largest box on the page and contains all the objects of a page, including the text, pictures, and tags on the page. The media box defines the range of physical media that needs to be printed on the page. In addition to the graphic content, it also includes crop marks, color control strips, and so on.
â‘¡Trim Box. The finished cutting frame determines the final effective size of the page after printing and cutting. The finished cutting frame corresponds to the actual size of the page (finished size). If a PDF document contains a cutting frame, the size of the cutting frame is equal to the final finished size.
â‘¢Crop Box: It defines the part to be cropped after the page is displayed or printed. Different from other frames, it has no physical page geometric meaning, and the crop box (Crop Box) is smaller than the media box (Media Box).
â‘£Bleed Box. The bleed box is a size outside the range of the page's crop marks. All the parts of the page between the bleed box and the crop box are finally cut off.
⑤Art Box. If the PDF page is to be placed in an application, the content box (Art Box) will determine the area of ​​the page to be placed.
2. PDF page bleeding method
The bleeding method of the PDF page also differs according to the requirements and habits of the pre-press design. Generally, there are the following situations (take the 16 format of the finished product with a size of 210 × 285mm as an example, and the unilateral bleeding is 3mm.):
①bleeding on three sides. That is, the head, feet, and incisions each bleed 3mm, and if the stapling does not bleed, the PDF page size is 213 × 291mm.
② bleeding on all sides. That is, the head, foot, incision and stapling each bleed 3mm, and the PDF page size is 216 × 291mm.
③ No bleeding. This situation is generally the text of books and periodicals, leaving four sides blank, without bleeding, the single page size is 210 × 285mm.
3. PDF page size
â‘ Single-page document. At this time, the size of the PDF page is the finished size plus the bleeding size.
② Spread file. At this time, the size of the PDF page is twice the size of the single-page file, depending on the size of the finished product and the bleeding method. For example, if two 16-page pages with a finished size of 210 × 285mm are combined into a double-page file and the three-sided bleeding method is adopted, the file size is 426 × 291mm.
In pre-press production, the actual PDF page structure will vary depending on the knowledge, experience, habits and standardization of pre-press job management possessed by pre-press designers. Some PDF pages are very standardized, including the media box (Media Box), finished trim box (Trim Box), bleeding box (Bleed Box) and other structural boxes, and the bleeding method and size are uniform (such as single-sided 3mm bleeding sheets Page); some are not standardized, no structure frame is defined, and the bleeding size is not consistent with the method. Non-standard PDF page structure will increase the pre-press processing workload and error probability. [next]
Second, the layout positioning of PDF pages in the layout
1. Large layout structure
The large-format layout structure is determined according to many factors such as the size of the printing press, the size of the printing plate, the size of the paper, and the structure of the PDF page. The large-format layout structure defined in the Signastation software, including plate bite, paper bite, home page (PDF page), binding line, cutting line and various marks. The home page is used for the layout positioning of the PDF page on the large version, which is divided into a left home page and a right home page. The home page size is determined by the actual size (finished size) and bleeding size.
2. Positioning of PDF pages
According to the PDF page structure, define the type of homepage in the layout software and determine the page positioning method, including the setting of the homepage type, actual size (finished size) and bleeding size, page displacement size With directions etc.
For different PDF page structures, there are two page positioning solutions in Signastation: automatic and user-defined.
â‘ Automatic: The system will automatically place the pages into the large version file according to the PDF page structure. The rules are as follows:
If a Trim Box is included in the PDF page, align the lower left corner of the Trim Box with the lower left corner of the finished size of the homepage; if there is no Trim Box and there is a Crop Box ), Then align the bottom left corner of the Crop Box with the bottom left corner of the finished product of the homepage; for example, there is no Trim Box and Crop Box, but there is a Media Box, Then align the lower left corner of the media box with the lower left corner of the actual size of the home page.
â‘¡User definition: Allow users to accurately position PDF pages by setting page offsets. The most important parameter here is the offset (Offset). Offset refers to the offset of the origin of the PDF page relative to the origin of the homepage of the large version. There are three methods for setting.
From the crop box: The crop box here refers to the Trim Box. At this time, the origin of the coordinates of the PDF page is in the lower left corner of the cutting frame, and the origin of the home page is in the lower left corner of the finished size. The layout system can automatically identify the origin of the coordinates and align it without displacement. This method is equivalent to the "automatic" method.
Centered: The PDF page is placed on the home page in a centered form, which is suitable for PDF pages with consistent bleeding on all sides.
Custom: It is mainly used when the PDF page is not set with irregularities such as cropping frame and bleeding frame. Need to set the displacement in the X and Y directions to achieve the positioning of the PDF page.
Offset X: Offset distance of the origin of the PDF page relative to the origin of the homepage in the X direction (horizontal direction). Offset Y: The distance that the origin of the PDF page is offset from the origin of the homepage in the Y direction (horizontal direction).
3. Examples of page positioning
Take the spread-page file as an example. Assuming that the finished product size is 210 × 285mm, the PDF page is a spread file, and the single page is bleeding on three sides, each side is 3mm, then the PDF spread file size is 426 × 582mm, and the PDF page does not have a trim box (Trim Box) . There are two ways to deal with this type of page in the layout:
①Method one: Split the cross-page file into a single-page file, set the left and right home pages for the single-page file, and perform the displacement in the X and Y directions. The split page is bleeding on three sides, with a size of 213 × 291mm; the displacement of the left page is (X: -3 mm, Y: -3mm), and the displacement of the right page is (X: 0 mm, Y: -3mm) .
② Method two: Do ​​not split the cross-page file, use displacement to locate directly. At this time, the displacement value on the left page is (X: -3 mm, Y: -3 mm), and the displacement value on the right page is (X: -213 mm, Y: -3 mm).
For other PDF page structures, different page positioning methods need to be adopted, which increases the variability and complexity of the imposition job, reduces the reliability of the imposition job, and thus affects the normal progress of post-press processing operations. Therefore, how to standardize the structure of PDF pages, simplify layout work, and improve reliability and efficiency are issues that deserve attention in prepress operations. [next]
3. Strategies to regulate the structure of PDF pages and improve the efficiency of layout
1. Standardize the design of PDF pages
Formulate standard operation manuals on PDF page design, train employees, communicate with customers, and hope that employees and customers can design PDF pages in accordance with standardized requirements. There are:
â‘ In Indesign and Illustrator software, establish the page structure frame such as Media Box, Trim Box, Bleed Box for PDF pages.
â‘¡Set the four-sided bleeding for the PDF page when setting the page properties, and unify the bleeding size.
2. Use Acrobat and Pitstop software to regulate PDF page processing
For non-standard PDF pages, use Acrobat and Pitstop software to process them before the big version, mainly:
â‘ For pages with three-sided bleeding, the pages are treated as four-sided bleeding by increasing the page size in Acrobat.
â‘¡ For the spread file, the page should be split into a single page file before the layout work.
â‘¢In Pitstop, add media frame (Media Box), cut box (Trim Box), bleed box (Bleed Box) and other page structure frames. In this way, the software can automatically recognize the page structure frame when positioning the layout, and perform automatic positioning.
3. Standardize the use of layout software
For different PDF pages, a unified PDF page positioning template is established in the layout software to form an operation specification, so that different operators have the same operation method.
The fourth step is to fix the separator support bar on the rainbow printing device with the help of the round pin alignment system. In this way, even if the customer wants to use multiple support bars for repetitive work, there is no problem. It saves time because no adjustment is required. The fifth step, between the divider and the divider, and between the divider and the squeegee and ink fountain roller must be well sealed. It is worth mentioning that we use a special silicon sealing material. Therefore, there is no adjustment screw on the divider-no tools are needed, just insert it easily-this saves a lot of time and does not require other connection or adjustment work. In the sixth step, it is necessary to reduce the movement range of the ink-feeding roller. This task must be completed on the transmission side of the printing press--precision, stepless, reproducible, and fast. If necessary, the ink supply unit separation and short-path ink supply modes may also be used.
If waterless offset printing or dry offset printing is not required, the bridge roller of the dampening system must be replaced with a non-sloshing type. After the ink key setting is completed, the printing press is ready. The operator only needs a total of 5-10 minutes to prepare the rainbow printing system in place. Rainbow printing device is designed and developed according to the special needs of customers. When producing long-form jobs, such as over 10,000 prints, we recommend the use of special ink fountain rollers with circumferential grooves to avoid ink color migration.
Rainbow printing technology is now widely used in Heidelberg Speedmaster SM 52, SM 74, XL75, CD 102 and SM 102 series products. In 2007, the world's largest banknote printing company-China Banknote Printing and Minting Corporation-installed 12 Heidelberg Speedmaster CD 102 printing machines at its six branches on the mainland, all of which were equipped with rainbow printing system. In Europe and the United States, manufacturers specializing in anti-counterfeiting printing are also using Heidelberg rainbow printing technology. In July 2010, the 150th Heidelberg printing unit equipped with a rainbow device was set up with a Speedmaster SM 102 six-color UV offset press in a Russian security printing company. A Dutch printing house also recently started using their first Speedmaster XL 105 offset press equipped with a rainbow printing system.
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