новости компании о Paper can packaging production process

01. Winding：
Along the roll direction, one side of the inner liner paper is folded, heated, and then heat-sealed together with the other side of the inner liner paper to form a closed heat-sealed tube. Outside the heat-sealed tube, the base material paper is spirally wound and glued to the inner liner layer. The inner liner layer and the base material layer overlap each other and move forward along the roll direction to form a continuous paper tube. Raised diagonal stripes are visible on both the inner and outer sides of the paper tube. The inner side consists of a heat-sealed section between one folded edge of the inner liner paper and the other side, providing a sealing and barrier effect. The outer side consists of a direct overlap between one and the other sides of the base material paper, acting as a reinforcing rib (diagonal stripes) to enhance the radial strength of the paper tube. To improve the smoothness and aesthetics of the outer surface of the tube, the paper overlap can be replaced with a butt joint, but this will result in some loss of strength.

02 Labeling：

There are two main methods for automated labeling. One is to directly wind the spiral label using a winding process, where a layer of label paper is wound on top of the substrate layer. The basic principle is the same as winding the substrate paper. This method results in a visible diagonal overlap on the outer surface, which may affect the integrity of the design. Therefore, the overlap requires high labeling precision and special design of the artwork. However, the winding process is relatively simple, does not require a separate labeling machine, and is faster. The other method requires a separate labeling machine. The label paper is applied parallel to the paper tube along its axial direction to a certain length of paper tube (a continuous paper tube from the winding machine, first cut, for example, 1 meter long). This labeling method results in high artwork integrity, with only one seam along the can's axial direction. However, due to the larger width of the label paper (around 1 meter), quality control during labeling is more difficult, and appearance problems such as bubbles, wrinkles, and curling edges are more likely to occur. Currently, the parallel labeling method is more common in the market.

03. Top and Bottom Flanging Forming:

After labeling, the paper tubes are cut to a fixed length (close to the finished can height). A large top flange and a small bottom flange are formed. The large top flange can be preheated or formed in several stages to create a closed, circular flange, which is then covered with a top film and heat-sealed. Flanging formation is a crucial process, involving top and bottom flanges, heat-sealing the top film, and attaching the plastic cap (optional). The top flange and top film heat sealing directly determine the top seal; therefore, the top flange must be free of cracks, and the top film must be aligned with the can's center. The shape and size of the bottom flange need to be coordinated with the subsequent bottom sealing process, requiring structural matching.

04. Bottom Sealing:

Taking the commonly used metal bottom as an example, the metal bottom shape needs to match well with the can bottom flange. The metal bottom's hardness cannot be too high, and the bottom sealing machine mold shape needs to be properly designed to avoid under-forming and insufficient pressing, or over-pressing and causing the metal bottom to burr.