There are two folding methods: manual folding and machine folding. Large-format printed sheets printed on a single sheet of paper need to go through manual or folding machine pages to become a signature. The web book rotary printing machine has a special folding mechanism, so printing and folding are completed continuously on one machine.
1. Manual folding
Manually fold the printed sheets into a signature according to the page number sequence and the prescribed format, which is called manual folding. With the improvement of the mechanization of binding, manual folding is used less and less in book printing plants. At present, only books with few prints, fractional pages, mantissa recovery, rework, and some special folding signatures are required. Finish it by hand. The tools for manual folding are a folding table and a folding board. According to the trial folding, arrange the printed pages, as shown in Figure 2-14, and then make two, three, and four folds. After folding a post, check whether the page number sequence is accurate, whether the page number and the crease are neat, whether the fold label folded into the signature is centered on the crease, etc., and then fold and fold the folded signature.
Second, the machine folding
Machine folding is to fold the printed sheets to be folded into book signatures by machine according to the page number sequence and the prescribed format?
At present, the commonly used folding machine is composed of three parts: a paper feeding device, a folding mechanism and a post-receiving mechanism.
The paper feeding device is mainly responsible for the task of separating and conveying paper, and can accurately convey the printed page to the folding part.
The folding mechanism is to fold the printed pages fed by the paper feeding device into book signatures in the order of page numbers according to the format of the format.
The paper collection mechanism is to stack the folded signatures regularly.
1. Folding preparation. The folding mechanism is the most important part of the folding machine. Its assembly accuracy and adjustment accuracy directly affect the quality of the folding. Therefore, before the folding machine is turned on, it is necessary to check and adjust each part of the folding machine. The main inspection and adjustment parts are:
â‘ Check the printed sheets for errors before loading the paper. When using the ring-wrap paper loading mode, the printed sheets should be evenly staggered by 1.5 to 2 mm in a stepped manner on the paper feeding table. The minimum page number on the printed sheet should be On the top, the folding label is facing up. When using the platform-type paper feeding format, the printed sheets should be placed on the stacking table neatly, with the minimum page number facing down, and the paper loading should be timely without affecting the paper feeding speed to ensure the smooth folding;
â‘¡Check the side gauge and block gauge (the position of the front gauge to ensure the horizontal and vertical positioning of the printed sheet;
â‘¢When using the fence type folding machine, according to different folding requirements, use or close each fence to complete one or several folds of multiple folding methods and folds;
④Adjust the distance between the folding rollers and the position of the center line according to the folding method, the thickness of the paper and the number of pages per fold, so that the printed sheet is pressed into the two folding rollers and the gap between the two ends is the same to ensure the conveyance The speed of the folding makes the folding stable, avoiding the skewed or torn wrinkles of the printed sheet; ⑤According to the adjusted spacing of the folding roller, adjust the correct position of the folding knife, etc.
The folding machine is also equipped with a cutting and punching device. The function of the cutting device is to divide the full-page printed page into two in a folding process. From the point of view of the performance of the full-sheet knife folding machine, its second folding part has two sets of folding devices. After the first folding, only the second folding can be carried out, otherwise the folding cannot be carried out. In addition, after the printed sheet is cut, the thickness of the book sheet is reduced after folding into a signature, thereby improving the accuracy of folding. The edge of the edge of the paper after cutting should be smooth, otherwise the separation knife should be checked or replaced. The function of the punching device is to make a row of long holes in advance on the crease line of the next fold, in order to facilitate the discharge of the air in the paper when folding, and to prevent wrinkles during folding. The position of the punching knife must be consistent with the crease, and the crease of the signature should be cut through, but it must not be cut off to avoid loose pages and falling pages. The punching device on the four-fold line is used for the punching of wireless binding. During binding, the glue liquid penetrates into each page of the signature opening through the cut edge, so that each book page is stuck to each other.
2. Folding process. Due to the difference between the size of the printed sheet and the book format, especially the thickness of the printing paper, the requirements for the number of folding (the number of pages in the signature) are also different. Generally it is two-fold page, three-fold page, and at most four-fold page. 8-sided / post, that is, two-fold pages, generally used in thick paper or scrap pages; 16-sided / post, that is, three-fold pages, used in general bookmarks, which are basic posts; 32-sided / post, which is four-fold pages, Apply to the pages of thin paper or general signatures.
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At present, the commonly used ZY102 and ZY104 full-sheet knife folding machines can fold the full-page printed pages into the desired format. The two folding folds are two-fold, positive and negative three-fold, four-fold, double Joint pages, etc. Their folding knife sequence is shown in Figure 2-8. The process of opening the folding of the ZY102 full-sheet knife folding machine 32 is shown in Figure 2-15: 1 in the figure is the full-page printed sheet entering the folding machine in the direction of the arrow, AA is the first folding line; 2 is the first Folded size of the folding knife, where BB is the cutting line and CC is the second folding line; 3 is the two 8-fold pages of the same size folded by the second folding knife, DD is the third folding; 4 is the third folding Folded by the knife into two identical 16-page book pages, EE is the fourth folding line; 5 is folded by the fourth folding knife into two 32-fold single-page book signatures.
If we say that the quality of books and periodicals printed 10 years ago is still in terms of whether there is inaccurate overprinting, pasting and dirty spots on the page printing. Nowadays, with the use of a large number of advanced offset presses, the printing quality is a comprehensive , New concept. The process design of any link in the processing of a book cannot be ignored. Folding is a very important process in post-press processing, and the quality of folding directly affects the overall quality of books and periodicals.
Almost all prints that need to be booked have folding links, such as corporate product brochures, saddle stitched books, wireless perfect binding products, picture albums, etc. For processing such products, the usual folding problems focus on the following two aspects:
1. When imposition, the page numbers of the upper and lower versions can not exactly match. After folding, there will be errors in the page numbers of the front and back pages and the position of the center of the page, and sometimes the errors will be very large;
2. The printed sheet passes through the folding machine, and sometimes it may be scratched, and sometimes "8" wrinkle marks appear.
When looking for the causes of such failures, many people often arbitrarily blame the improper operation of the folding machine master, and let them repeatedly adjust the machine to try to correct and reduce errors. However, if we analyze from the process point of view, the cause of this type of error is often due to the insufficient understanding of the suitability between the paper and the machine by the process designer of the production department, resulting in poor final folding quality.
Shijiazhuang Asa Technology Co., Ltd. , https://www.asaantiwrinkle.com