Out of the misunderstanding of the folding machine
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When customers complain about the quality of binding of certain folding products, folding is one of the important processes in the binding process, and it is often easy to become the focus of criticism. In fact, the defects and shortcomings of the products in the binding process are not entirely the responsibility of the folding department, and sometimes they are completely irrelevant. The following quality faults seem to be related to the quality of the folds. In fact, they are all “false and wrong cases”.
The line position does not coincide with the color line
The effect of paper thickness on the quality of the fold must be taken into account when designing the folding product. In general, in multiple folds, the size of the page folded inside must be slightly smaller than the external page, that is, the design department must give a certain amount of cropping compensation to increase the actual cutting amount. If the amount of compensation is too small. The internal page will interfere with other pages due to the size being too large. The collision between the pages causes the external page to be arched and the entire book is flat. Therefore, for multiple folds, it is best to explicitly give the amount of compensation in the design process. Otherwise, once the document with this design defect is sent out, as the final defense department, the binding department has to compensate the page cutting amount during the folding process. In this case, if the product's polyline position is just the same as the color division. If the boundaries overlap, the actual misalignment will result from the cropping compensation.
The inner fold page size is too small
Under normal circumstances, the standard cropping compensation amount for a single page is 1.5 to 3 mm. However, if multi-layer paper or thick paper is used, it is necessary to appropriately increase the amount of cropping compensation for the in-fold page. However, if the amount of compensation is too large, the actual size of the in-fold page will be small due to the large amount of actual cutting. In reality, we often see the practice that the design department does not specify or set the amount of cropping compensation in the design sheet. Instead, it is tempted to save trouble and directly ask the binding department to solve the problem of crop compensation. This type of practice is especially common in some simple folding operations. For example, when designing a direct mail envelope for sending a bank statement, the shorter page should be about 2mm smaller than the other two long pages. However, most of the practice is to bypass the design process. Cut the size of the third page directly to a relatively short length. In order to fundamentally prevent the problem that the in-fold page is too small due to the excessive amount of actual cutting. It is best to specify the amount of cutting compensation directly in the design sheet. In general, it should be stated that it should not exceed 3mm.
Paper cracked at the fold line
When the fibers of the paper are stretched too far apart. Paper cracking will occur. If this happens in the field, the result is especially bad. There are many reasons for paper cracking, such as no indentation before folding; the water content of the paper is too low; the setting of the folding roller is incorrect. Among them, the first reason is the most common. No matter what kind of printed product. Customers want the cost to be as low as possible, and the added value of the product can be as high as possible. In the case of the customer's recognition of the added value of the product and the importance of the appearance, it is necessary for the relevant departments of the printing and processing unit to advise the customer to carry out the indentation processing before the folding, so that the customer willingly increase the cost. Under normal circumstances, if the folding direction of the paper is perpendicular to the direction of the silk thread, the area where the fold line passes through the thicker ink layer such as the ground, the amount of paper is large, or the cover of the book, etc., the fold line must be indented beforehand. Get clear, accurate fold lines.
Paper wrinkles at the corners
In multiple vertical folding. The corners of the page (near the intersection of the fold lines) are easily wrinkled. To avoid this kind of phenomenon. It is necessary to take appropriate preventive measures. Common reasons are:
The order of 1 folds is unreasonable, so that the folding pressure is too high, so that the paper at the corners is wrinkled.
The 2 fold process is unreasonable. The air is trapped inside the book sticker and cannot be discharged smoothly, thus affecting the folding effect. For example, if the page is folded twice in parallel and then paralleled twice in the vertical direction, this solution can easily cause air retention inside the signature. But if you change the previous two parallel folds into fan folds, you can get out of trouble.
The 3 fold speed is too high, which increases the pressure on the paper during the folding process. Generally speaking. Both the heavier and lighter papers must have a lower folding speed.
4 Replace the paper type and sometimes get better results. For example, recycled paper has short fibers and low strength. It is more likely to wrinkle at the corners, if it is replaced with a paper of better quality. This can greatly improve the folding effect.
The finished page margin is too small or part of the graphic is cropped
When binding. Sometimes the finished page margin is too small and part of the graphic is cropped. If the folding edge is straight and tidy, the cutting amount and the finished product size are correct, then this situation should be a cutting failure, regardless of the folding quality. In order to ensure the cutting quality, at least one centimeter distance should be left from the cutting edge during design. If it cannot be guaranteed, the phenomenon that the margin of the finished product is too small and the part of the graphic is cut is inevitable.
Finished product thickness is too large or too small
When selecting the specification model of the paper. Sometimes people just take a cursory look at the samples provided by the customer and easily determine them. Some even choose directly based on the verbal suggestions of others. However, the type of paper is differentiated based on the basis weight, and the actual thickness of the same amount of paper is not the same. It is not difficult to understand why it is sometimes clear that standard quantitative paper is used, but the actual thickness of the final product does not meet the standard. In order to prevent the thickness of the finished product from not meeting the requirements, the customer should be required to provide the correct pattern at the beginning of the operation.
Folding of digital prints
The folding effect of digital prints is often not comparable to offset prints.
First, the toner is solidified on the paper surface by heat when it is fixed, thereby forming a graphic. These cured toners only stay on the surface of the paper (the ink is mainly osmotic in the offset printing), and it is easy to fall off due to friction when folding. This phenomenon is achieved by continuous paper feeding with high paper feeding. The page machine is especially serious.
Secondly, because the paper is subjected to high-temperature baking, the water content is decreased, the brittleness is increased, the strength is lowered, and the folding is easily broken.
Third, the electrostatic phenomenon of digital prints is more serious, which is not conducive to correct folding.
With the improvement of the toner formula in digital printing technology, the first problem has been solved. For the second problem, there are two measures: 1 Before the folding, the indentation treatment is performed at the fold line to increase the toughness; 2 The print after the salt image is placed indoors, and the paper is adjusted by the natural humidity in the air. Wet processing and then folding. Of course, in the case of on-demand printing, the delivery cycle is often tight. The feasibility of the second option will be limited to a large extent. For the third problem, the static problem, many folding machines use an ionized airflow system. To neutralize the static electricity carried by the paper, to ensure that the folding is smooth.
Through the above analysis, it is known that the defects and deficiencies reflected in the folding process are not entirely the responsibility of the folding department. In order to achieve perfect folding and avoid various failures, it is necessary to start from the pre-press design, and the three departments of pre-press, printing and post-press work together to strictly enforce the operating standards.