Digital printing film, binding, cutting attention
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With the popularization and application of digitalization, intelligence and networking in the printing field, the printing process has gradually developed from analog to digital, thus opening the prelude to digital printing. Today, fast-growing digital printing is not only integrated into all areas of printing, but also continues to expand its market share. According to statistics, the current digital printing business in the United States has accounted for more than half of the total printing capacity, and this trend is still evolving. According to the British Paper Printing and Packaging Technology Research Association, global digital printing will account for more than 25% of the printing business by 2010. In addition, the standard file format based on XML is released, and the same program can be used to complete the job without being limited to the file type. The maturity and wide application of PDF files as an international standard guarantees the consistency of cross-platform operations, which lays the foundation for the development of digital printing. According to China's development of the "pre-press digital, network, printing multi-color, high-efficiency, post-press exquisite, automated, high-quality equipment, serialization" development of the 28-word policy, indicating that digital printing is now and in the future printing technology A focus of development. In digital printing, how to make post-press processing compatible with pre-press and printing is one of the keys to fully perfecting and developing digital printing.
Digital printing is a fully digital production system that runs through the entire production process, from information input to printing and even binding output. Digital printing combines prepress, print and postpress. From a system control point of view, it is a seamless all-digital system.
However, in order to make digital printing truly reflect its superiority, in addition to pre-press and printing processes, it also requires better matching of post-press processing. Therefore, attention should be paid to the cooperation of post-press processing of digital printing. Let's talk about the issues that should be paid attention to such as laminating, binding, and cutting, which are closely related to digital printing and post-processing.
Laminating problem
Laminating is a commonly used post-press finishing method for printed materials such as books and magazines. It has a wide range of adaptability and is suitable for digital printing products. Laminating the surface of digital prints, especially after printing a large area of the ground, will help to protect the printed matter during post-press processing, especially during cutting or packaging. The product is more beautiful and durable. However, it is not necessarily advantageous to carry out the single-sided coating on the double-sided printed matter, because the uncoated side may be prone to peeling off of the printing color due to the frictional force in the subsequent processing. Many printed products are covered with various bright films, matt films and matting films to achieve distinctive effects. However, digital printing is more suitable for hot film coating. This method is convenient to use and low in price. The film used for the thermal coating mainly includes a polyester film and a polypropylene film. Generally, a polypropylene film is required for coating a thin film, and a thick polyester film may be used for a printing product requiring additional protection. The price of the polyester film is higher than that of the polypropylene film, but the strength is high, and the printing product can be better protected. If the two sides of the print need to be coated, it is best to use a polyester film. In the film coating of digital printing products, it is mainly necessary to avoid failures such as curling of the printed product after lamination. Therefore, when conditions permit, the film is coated on both sides of the substrate as much as possible; if only one side of the paper is coated and the other side is not covered, curling is very likely to occur. However, it should be noted that the cover of the wireless binding book can only be coated on one side. Do not cover the cover and seal three, otherwise the book block and the cover cannot be firmly bonded. In addition, when the laminating machine is selected, it is also possible to select a rod for preventing curling of the coated printing product, so as to ensure that the product after lamination is flat and not curled. Avoiding foaming of the product after lamination is also a problem that should be paid attention to in the film. When hot stamping the printed product, first ensure that the surface of the printed product to be coated is clean and dust-free. Secondly, the temperature must be suitable. If the temperature is too high, the toner will melt and cause foaming of the film. In addition, in order to prevent wrinkles after the film is folded, the OPP film can be used. For the selection of the coating material, the film may affect the color reproduction of the digital printing, mainly because the film used in the film is not necessarily 100% transparent film, so it will affect the color balance. Therefore, for the sake of insurance, you can try to cover a few samples to the customer to see if the color of the printed product after the film meets the requirements of the customer, and then formally process the film.
2. Binding problem
Products that can be printed by digital printing include books, brochures, tenders, calendars, etc. Therefore, commonly used binding methods include wireless adhesive binding, saddle stitching, lock stitching, wire binding, spiral binding and ring binding. But be careful, be sure to decide which binding method to use before you start printing your work, rather than blindly waiting for the binding to be considered. Because different binding methods (such as perfect binding and saddle stitching) have different requirements in the page arrangement of the prepress typesetting stage. Deciding which binding method to use should be based primarily on the customer's requirements, the characteristics of the paper used, the direction of the paper, and the end use of the print.
Before the binding, the printed matter is generally to be folded. When the printed paper has a basis weight of more than 120g, the creases can be easily made before folding, and the folded sheets are more flat and the effect is more beautiful. In fact, no matter which kind of paper, if you fold the crease before folding, you can get good results. The creases can be made on a special crease machine, which has a desktop machine and a larger crease and perforated type. If there is an indentation mold, the work of creases can also be done on the flat press. In addition, some folding machines themselves have the function of creases. Cracks in the printed image of the printed sheet after the indentation or folding may be caused by the drying of the paper, and the higher the basis weight, the more likely the paper is to be broken. Therefore, to avoid cracking, the paper should be kept at a proper humidity and not too dry. In addition, folding the paper in the direction of the paper thread when folding, can also avoid breakage at the crease. In the case of processing books and digital printing, the direction of the silk of the paper should be parallel to the direction of the spine of the final finished book. Of course, the filming of the printed paper can also prevent cracks from appearing at the printed page. Attention should also be paid to the depth of the indentation when indentation. If using a creasing machine, be careful not to drive too fast.
At present, domestic digital printing shops use more or more flat, especially in the way of wireless adhesive binding. The glued book is not only beautiful, but also strong. When designing a booklet, first of all, pay attention to leave enough room for binding between the booklet and the body. For example, when the O-spiral wire-to-hole ratio is 3:1 (referring to 3 holes per inch), Leave at least 3/8 inch of blank; and when the line-to-hole ratio is 2:1, leave at least 1/2 inch of blank. This blank refers to the distance between the booked edge and the nearest hole. In order to clarify the specific location of the processing, it is best for the designer to understand the changes of the actual printed paper after digital printing before the digital printing process, which is especially important for digital printing. Most computer design programs do not take into account small changes in the thickness of the printed paper. In digital printing, the color printed on the surface of the paper causes a change in the thickness of the printed sheet. When binding dozens of pages of digitally printed sheets, the cumulative thickness Changes may make the size of the binding calculated by the computer meaningless. Therefore, it is necessary to grasp the sample variation parameters of the actual production paper after digital printing, in order to accurately measure the thickness of the book during the printing design, and to ensure a suitable binding size for post-press processing. As with the offset gluing of offset printing, the wireless adhesive binding of digital prints also takes into account the amount of cut that is stapled. In addition to leaving a 1/8 inch milling back allowance on the back of the book, a 1/8 inch cut is also required on the other three sides of the book. In addition, a 1/4 inch rubberized area should be left in the lower part of the book cover to prevent the glue from seeping into the next book during binding. The wireless adhesive binding process also requires that the print cover should be larger than the size of the text. Wireless adhesive binding finishing is also an important post-press processing method in digital printing and binding. The key to the hardcover process is how to firmly bond the book block to the hard book case to produce a book that can be stored for a long time. Although the cost and time required for wireless adhesive finishing is somewhat inconsistent with digital printing for the short-run printing market, some post-press binding companies have pre-made different colors, styles and different colors commonly used in digital printing hardcover. The size of the hardcover book case is used by digital printers. Therefore, the wireless adhesive binding hardcover is also a commonly used binding method for digital printing.
In the wireless adhesive binding, some books or booklets sometimes have a page drop phenomenon. There are many reasons for this phenomenon, the reason for the glue, and the reason for the machine.
The wireless perfect binding machine used by digital printers generally includes several steps of milling back, gluing and covering the cover. Some cheap binding machines have no milling process at all; some binding machines have milling function. However, the milling back processing of the spine is not in place, which will affect the firmness of the binding. In addition, the type and quality of the glue also have an effect on the fastness of the binding. If the temperature is improperly controlled during the binding process, the book can be loosened or dropped. In the binding process, opening time is an important parameter, which refers to the time required for the glue to bond the cover of the book to the book. When the book or booklet is glued on the machine, the glue will take some time to continue to solidify, sometimes for hours. Therefore, do not flip through the books as soon as they are bound on the perfect binding machine. At least 15 minutes later, they should be reviewed and checked.
In addition, for book and booklet binding, saddle stitching is a fast, efficient and economical way, and is also a good choice for most digital prints, especially for guides, brochures and brochures. Binding of thinner books. The binding method can be carried out online with other processing methods, and can perform post-press processing for collating, folding, stapling and in-line cutting at the same time, which can guarantee the fast delivery required for digital printing. However, the thickness of the saddle stitch is limited and generally cannot exceed 4 mm.
The lock stitching method is very good in binding, but the binding time is high and the cost is high. Therefore, it is necessary to make careful design and arrangement of the printing work at the beginning to ensure the harmony between printing and postpress processing. The following issues should be noted in binding and finishing. First, since the ink color on the digital print adheres only to the surface of the paper, the folding process is prone to cracking. Therefore, it is best to press the crease before the folding process.
Spiral binding and binding are also playing a role in the binding of digital printing products. Both spiral and ring stitching require first punching and then binding the printed book into a book. The spiral or loop wire used is available in a variety of sizes, both metallic and plastic; both monochromatic and colored. Spiral binding is to use a continuous plastic wire or wire to pass from the first hole of the printed product to the last hole; and the ring is stapled by a separate circular wire or plastic ring through the hole. Single page. Spiral binding and ring binding are characterized by low binding cost and good flattening. A manual small-sized perforated spiral binding or ringing machine (which can bind a booklet with a thickness of 20 to 28 mm) is bound to an A4 booklet. It takes 5 minutes. If the number of bindings is large, it is best to use a highly automated computer controlled punching and binding machine.
Digital printing products can also be selected by punching or drilling and binding. This binding method is more suitable for documents composed of bound sheets, and is suitable for students' materials or samples for sales personnel. Especially when you need to change some of the content, you only need to reprint one or more pages with changed content, then add the holes and replace the old ones. You don't have to reprint the entire document or sample. . When using the punching and binding method, be careful not to use too much paper and too thick, which will affect the quality of the punching. When drilling, the drill pin will heat up and cause the digitally printed image toner to melt. Care should be taken not to over-drill. When the polyester material is to be punched and bound, the punching process should be used as much as possible without drilling, because the heat generated by the drilling easily causes the polyester material to melt and stick.
3. Cutting problem
Cutting is also an important aspect of digital printing and finishing. The first is the cutting of paper. As with traditional printing, digital printing also uses a paper cutter to cut the paper or finished product into the desired size and shape. At present, there are various paper cutters on the market, both manual and computer-controlled automatic models. The cutting specifications of single-sided knife cutters are mostly 52-150cm. In general, digital printing is more suitable for a paper cutter with a cutting width of 78 cm. If possible, a computer-controlled paper cutter can better match digital printing because it can store a certain amount of data. When cutting a job that has been processed, simply transfer the original program from the computer, which can fully save the time of the adjustment. In the use of the paper cutter, in order to maintain the sharpness of the blade and prolong the service life of the paper cutter, the thickness of the paper to be cut at one time is preferably not more than 40 mm, and the pressure of the paper cutter on the paper should be appropriate, generally soft paper. The pressure required is greater, and the pressure required for harder materials is relatively small.
It is critical to keep the sharpness of the blade when using the paper cutter. Pay attention to proper maintenance and use of the blade. Once the blade is blunt, the blade should be reground, otherwise the cutting accuracy will be affected. In addition, care should be taken to maintain an ambient temperature of 19 to 23 ° C and a relative humidity of 50%. Under such conditions, the characteristics of the paper are relatively stable, which is conducive to the correct use and maintenance of the paper cutter, because the determination of many cutting parameters depends on the paper being processed.
Die-cutting of digital prints can make the final prints attract special attention with special shapes or outstanding features, which can increase the added value of the products. Whether digital printers need to add a die-cutting machine depends on how large the number of jobs they are processing. If there is not much activity, the die-cutting machine will be idle and waste. Select the die-cutting machine to pay attention to the processing requirements of the printed products. When die-cutting thick paper, you can use the platform die-cutting machine. For thin-cut paper, you can use the rotary die-cutting machine.