For multi-computer roll paper commercial paper products, the first single-link printing is required, and holes, ridge lines, and zigzag-shaped folding papers are provided for the paper, and then the pages are assembled. In production, coding is the last step and it is done on the collating machine. In order to prevent the printed multi-finished bills from being misaligned in the collation, it is necessary to press the multiple bills together by the embossing teeth on the collator. Due to the web printing, the expansion and contraction rates of the multi-layer papers [encyclopedias] are not necessarily the same. Therefore, the change in the lengths of the individual webs after printing will cause many problems in the dosing, and even make the dosing impossible.
Factors affecting paper length changes
1. tension
Tension is the stretching force of the paper feeding system on the paper during the printing process. Excessive tension in the printing process will stretch the paper. After the printing, the tension is relieved. The paper will inevitably retract, causing the length of the paper to be shorter and shorter. Match page.
2. Paper moisture content
Different paper moisture content can also cause changes in the length of the paper. The greater the moisture content of the paper, the more severe the shrinkage of the printed paper.
3. Paper ration
Under the same tension, the greater the amount of paper used for printing (thicker paper), the shrinkage of the paper after printing is serious, but also take into account the factors of thick paper moisture content, under normal circumstances, thick paper should increase the tension.
Precautions
(1) During the printing process, a type of paper with the same brand and the same thickness should be used as much as possible so that the tension can be kept constant during printing.
(2) In actual production, even if the same brand, the same thickness of paper, the water content of the paper is also different, we must pay attention to its identification. The method of touching by hand may cause cold and astringent papers with high moisture content. The paper with the same width and cane paper will have a heavier moisture content. Therefore, the tension should be appropriately reduced. However, we must pay attention to the suitability of paper. We can put paper in the production workshop for a certain period of time to adapt to the temperature and humidity of the workshop, so as to solve the problem of paper moisture content.
(3) When encountering multiple orders of different quantitative or different types of paper, attention should be paid to the adjustment of tension. First, when printing a joint, measure it with a hole length of 3m or more, and release 2~4mm more than the standard length to make up for the paper shrinkage caused by water loss; secondly, use 3m when printing the second joint. The hole distance gauge measures the paper hole pitch. If the link paper is thick, it can be released 1~2mm more than the standard length. The paper has high water content and a large number of shrinkage systems. This will be based on the thickness of each paper in the United Nations to give different amount of increase in the spacing, so that each sheet of paper can be maintained at the same time.
In spite of the above problems, complex sizing problems are occasionally encountered in multi-single printing, such as thermal paper with a basis weight of 180 g/m2 + offset paper with a basis weight of 70 g/m2 + basis weight of 40 g/m. The back of m2 is coated with carbon dictionaries.
In this case, do not rush to do it. Use a hole gauge to measure the thickness of the paper layer by layer. Measure the water content. You can even take 3m each paper before printing, ventilate it and dry it, and count the shrinkage factor. After comparison, it was decided to apply different tensions. After each printing, it must be tightly wrapped with plastic film to prevent loss of waterproofing and cause difficulties in the matching.
Remedy
If there is a problem with the collation, you can take the following measures to remedy:
(1) The paper is longer and can be ventilated and dried to shorten it.
(2) When collating, a humidifier can be installed under a short joint to increase paper moisture and extend the paper.
(3) If the paper is shortened, it is possible to increase the paper resistance in the middle of the paper blank while using the humidifier. For example, add a sponge on the paper rod to increase the resistance and make the paper stretch.
If you use the above method to arrange pages, do not ventilate them. Pack them in plastic boxes and store them in pressure.
Commercial paper printing is very strict with respect to environmental humidity and humidity. In particular, it has a relatively high requirement for environmental humidity. Therefore, it must be controlled as far as possible without drastic changes. At the same time after printing should be immediately wrapped with pigment film, but can not rotate too long, should be allocated as soon as possible to prevent environmental changes in temperature and humidity caused by paper stretching and affect product quality.
