The traditional method of making metal packaging cans is: first cut a flat iron sheet into a long square, and then cut the blank

The material is rolled into a cylinder (ie, the cylinder), and the longitudinal bonding wire formed is soldered to form a side seal. One end of the cylinder (ie, the bottom of the tank) and the circular end cover are mechanically formed into flanges and rolled. Press the seam (this is the double-hem seam) to form the body of the can; the other end is filled with product and then the can lid is closed. Because the container is composed of three parts: the bottom of the can, the body of the can, and the lid of the can, it is called a three-piece can. For more than 150 years, this can making method has basically not changed much, but the degree of automation and processing accuracy has been greatly improved. In recent years, the welding seam of the side seal has been changed to fusion welding.

In the early 1970s, a new canning principle emerged. According to this principle, the can body and the bottom of the can are a whole, stamped from a circular flat blank, and sealed after being loaded into the product, this is a two-piece can. There are two forming methods for this can: the stamping-thinning drawing method (ie punching method) and the stamping-re-stamping method (ie deep drawing method). The technologies themselves are not new. The punching method has been used to make cartridge cases as early as the First World War, and can making is different from the use of ultra-thin metal and the high speed of production (the annual output can reach hundreds of millions).

Both forming methods for making two-piece cans employ sheet metal forming. This approach is based on the "fluidity" of metals through rearrangement of their crystal structure under compound stress, and the material should not fracture during this process.

①Stamping and forming. That is to use a punch of a punching machine to punch a flat plate into a cylindrical die, thereby deforming the flat plate into a cylinder. The diameter of the cup formed after the initial stamping can be reduced by applying a re-stamping process. In the re-stamping process, a stamping sleeve is used instead of the die, which is installed between the punch and the inner diameter of the punching cup. The equal-area rule determines that the reduction in diameter is accompanied by an increase in height. The re-stamping process can be repeated again, and the diameter of the book is gradually reduced within a certain limit range, and the metal is prevented from breaking.

② Thinning and stretching of the cup wall. The punched cylindrical cup is sleeved on the punch, and the punch is extruded into a die along the axial direction. The gap between the die and the punch is smaller than the thickness of the cup wall so the wall thickness will be reduced when the diameter remains unchanged. get thinned. The metal volume of the cylinder after thinning is equal to the metal volume of the cup during the thinning and drawing process, which is also equal to the metal volume of the original slab. In the manufacture of cans, this process is repeated two or three times, with the punch with the cup passing through a series of dies, one stroke at a time. The most convenient way to install a stamped forest on a punch is to perform a re-stamping operation before the first thinning stretch.

③The manufacture of punching cupping. The manufacturing process of punching and cupping is generally as follows: unwinding ordinary strip coil; Xu lubricant; blanking and cup punching; re-stamping; thinning and drawing of cup sidewall; bottom forming; For dry beverage cans, outer surface coating, printing decoration, inner surface coating, open-end flange forming and closing are also performed.

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