Basic knowledge of back seal bags

Back-sealed bags are also called middle-sealed bags. Simply put, they are packaging bags with edges sealed on the back of the bag body. Back-seal bags have a wide range of applications. Generally, candy, bagged instant noodles, and bagged dairy products all use this packaging form. Compared with other packaging forms, back-sealed bags have no edges on both sides of the bag body, ensuring that the pattern on the front of the package is complete and more beautiful. At the same time, in terms of layout design, the bag pattern can be designed as a whole to maintain the coherence of the picture. Because the seal is on the back, the sides of the bag can withstand greater pressure, reducing the possibility of package breakage. Moreover, packaging bags of the same size are all sealed in the form of a back cover. The total length of the back cover is smaller, which in a certain sense also reduces the probability of cracking of the back cover.

   In terms of material, back-sealing bags are no different from ordinary heat-sealing bags. In addition, they are packaged in aluminum-plastic, aluminum-paper and other composite packaging. It is also widely used. Common packaging forms include bagged milk packaging and large bags of melon seeds. The difficulty in manufacturing and packaging back-seal bags lies in the heat sealing of the T-shaped opening. The heat sealing temperature of the "T"-shaped opening is difficult to control. If the temperature is too high, other parts will wrinkle due to the high temperature; if the temperature is too low, the "T"-shaped opening cannot be heat-sealed well.

   When designing the back-seal bag, attention should be paid to the fact that the front pattern should be slightly larger than the finished product size to prevent the front pattern from being too small after being made into a bag. At the same time, it is necessary to consider whether the top, bottom, left, and right needs to be seamless, and whether the light spot position setting meets the needs of cutting and making the bag. In addition, attention should also be paid to whether the finished unit pattern needs to be connected with transparent or the same color.

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