Is the folding of digital printed materials prone to cracking and deformation? It‘s actually quite easy to solve
Time:2024-08-13
Views:102
Folding is the process of machine or manual folding of printed large format sheets into book stickers in the order of the page numbers marked on them and according to the specified size. It is the main task of bookbinding. Nowadays, folding is no longer just a process in the process of publishing books, it is already a separate product category, such as the promotional pages, maps, exhibition hall instruction pages, and so on that we can see everywhere.
Folding machine should be one of the essential post press binding equipment for all graphic and text fast printing shops and digital printing enterprises. The structure of a digital printing folding machine is not complicated, but various situations often occur during the later folding process.
How does the position of the image on the printed sheet affect the folding process?
Usually, many digital printed materials design images in the middle of the printed sheet, but it is only discovered during post printing processing that this wastes a lot of time and money. For example, when designing an image with dimensions of 210mm × 285mm on a sheet with dimensions of 450mm × 320mm, it is necessary to cut all four sides of the printed sheet during cutting; But if the image is placed in a certain corner (such as the upper left corner), only two sides need to be cropped, which saves post press processing time and reduces printing costs. But if the other two sides of the image are designed with bleeding, it is still necessary to cut all four sides of the printed sheet.
What are the specific folding issues in digital printing?
Due to the fact that ink pigments on digital printed materials only adhere to the surface of the paper, folding processing is prone to cracking. Therefore, it is best to press the creases before folding processing.
Cracks in the printed image after indentation or folding may be caused by the dryness of the paper, and the higher the weight of the paper, the more likely this fault is to occur. Therefore, to avoid cracking, the paper should be kept at an appropriate humidity and not too dry.
In addition, folding the paper along the direction of the paper strands during folding can also avoid breakage at the creases. In addition to the direction of the threads, high printing quantity, dry environment, and low temperature can also easily cause faults such as breakage at creases. It is necessary to analyze the causes and correctly eliminate them.
If it is processing books and periodicals, when digital printing, the direction of the paper strands should be parallel to the spine direction of the final finished book. Of course, laminating the printed paper can also prevent cracks from appearing at the folds of the printed product. The folding effect of digital printed products often cannot be compared to offset printed products for the following reasons.
Firstly, during fixation, the color powder solidifies on the paper surface due to heat melting, resulting in the formation of graphics and text. These solidified color powders only stay on the surface of the paper (ink mainly penetrates and dries in offset printing), and are easily dropped during folding due to friction. This phenomenon is particularly severe in continuous paper folding machines that use high platform paper feeding. Scratching of ink marks on the surface of printed materials. The process arrangement of first laminating and then folding can also effectively avoid this problem. With the improvement of color powder formula in digital printing technology, this problem has been well solved.
Paper is prone to breakage during folding due to reduced moisture content, increased brittleness, and decreased strength caused by high temperature baking. There are two measures for this problem: one is to perform indentation treatment at the fold line before folding to increase its toughness. The second is to place the imaged printed material indoors, use the natural humidity in the air to humidify the paper, and then fold it. Of course, in the case of on-demand printing, the delivery cycle is often tight. This measure is not feasible.
The static electricity phenomenon of digital printed materials is quite serious, which is not conducive to automatic folding machine folding. Many hybrid folding machines now use an ionized airflow system to neutralize the static electricity carried by the paper, ensuring smooth folding.
3. Why is paper prone to cracking at creases?
The main manifestation of poor origami is paper breakage, which is mainly due to the nature of the paper and the processing steps before folding. There are many reasons for paper cracking, such as not performing indentation treatment before folding; The moisture content of the paper is too low; Incorrect setting of folding rollers, etc.
If it is related to the properties of paper, unlike the ink penetration coloring in offset printing, the ink in digital printing adheres to the surface of the paper. After the ink dries, if the paper is too brittle, white marks will appear on the folds. Therefore, it is recommended to make an indentation before folding to enhance the paper‘s toughness.
Regarding the pre folding process, it is required that the folding direction and paper fibers be parallel. If they are perpendicular, it is recommended to cover the folded area with film to protect the crease.
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