Discussion on the manufacturing process of metal packaging cans (1)

The traditional method for manufacturing metal cans is to first cut the sheet metal blank into a square business card printing machine, then roll the blank into a cylinder (ie, a cylinder), and then solder the formed vertical welding wire to form a side seal, and a round One end of the can (ie, the bottom of the can) and the round end cap are mechanically flanged and rolled (ie, double crimped seams) to form the can body; the other end is sealed after the product is loaded. Can lid. As the container is composed of three parts: the bottom of the tank, the body of the tank, and the lid of the tank, it is called a three-piece tank. This canning method has been printing in South China for more than 150 years. Basically, there has been little change. Only the degree of automation and processing accuracy have been greatly improved. In recent years, the welding of side sealing has been replaced by welding.

In the early 1970s, a new canning principle emerged. According to this principle, the can body and the bottom of the can is a whole, which is stamped and printed by a circular flat blank, and sealed after being filled into the product, namely, two-piece cans. There are two types of molding methods for such cans: stamping - thinning stretching (ie drawing and drawing) and stamping - re-stamping (ie deep drawing). These technologies are not new in themselves. Drawbacks were used to make shells as early as World War I. The difference between canning is the use of ultra-thin metals and the high production speed (the annual output can reach hundreds of millions).

1 Three-piece can manufacturing

The production process is: cutting the coil into rectangular plates with a shearing machine; painting and mounting printing; cutting a length of billet; rolling into a cylinder and welding side seams; repairing the joints and coating; cutting the barrel; forming a recess Slots or corrugations; flanges are pressed at both ends; rolled back; check and code on pallets.

1 cylinder processing. The key process is coil forming and welding side seams. Side sealing methods are soldering, welding and bonding three. Beiren Printing

Solder tin solders typically consist of 98% lead and 2% tin. The cylinder forming machine for rolling the flat blank into a cylinder is used in pairs with a side seam sealing machine for soldering. In the cylinder maker, the edge of the slab is cleaned and bent into a hook shape, which facilitates fixing when the cylinder is formed. Then the cylinder passes the side sealing machine word
Printing, adding solvent and solder, preheating the sealing zone with a gas torch, further heating the solder through a longitudinal soldering roller, and then using a rotating scraping roller to remove the excess solder, which is mainly in the form of a droplet.

Welding is the use of consumable electrode principle a3
Printing, using resistance welding process. The earlier welding systems used large laps to increase the temperature of the steel to the melting point and weld it at a lower roller pressure. The latest welding machine uses a small overlap (0.3 to 0.5mm), the metal temperature is just below the melting point, but the welding pressurization roller dek press is to be increased and the two overlapping surfaces are forged together.

The weld breaks the original or painted smooth surface of the inner surface so that exposed iron, iron oxide, and tin are present on both sides of the weld. In order to prevent the product from being contaminated and the weld seam from being eroded by the product, in most cases the side seals need to be coated.

Side seals for tanks containing only dry products can be glued. That is, the longitudinal seam is pasted with a nylon belt, and the nylon belt melts and condenses after the cylinder is formed. The advantage is that the original edge can be completely protected, but it can only be used for printing on TSF rice paper because the melting point of tin is close to the melting temperature of the plastic.

2 simplified post processing. Flanges must also be machined at both ends of the Simplified to install the end caps. For processed food cans, the cans may be subjected to external pressure during processing or may be internally vacuumed during storage. In order to increase the strength of the tank, the simplified surface may also need to make ribs. This process is called crimping. In order to improve the production efficiency of the printing body, the length of the round container made of shallow containers is usually two to three can lengths. At this time, the first procedure is to cut the cylinder. The traditional method is to form the front blank on the cutting machine (notch Machine) on the cutting. However, the recent development of the tank trim shears developed for two-piece can production.

2 Manufacture of two-piece cans

Both methods of forming two-piece cans are formed using sheet metal forming methods. This method is based on the “fluidity” of the metal that is displayed under the action of the composite stress under the printing stress and rearranged through the crystal structure, and the material should not break during this process.

1 stamping molding. That is, a punch is used to punch a flat plate into a cylindrical die to deform the flat plate into a cylinder. The diameter of the cup formed after the initial stamping can be reduced by applying a re-punching process. The re-punching process replaces the die with a stamped sleeve and is mounted between the punch and the inner diameter of the cup. The equal-area rule determines that the increase in process color is accompanied by a reduction in the diameter. The re-pressing process can be repeated once more. The diameter of the book is gradually reduced within a certain limit and the metal is prevented from breaking.
2 cups of thinning stretch. The stamped cylindrical cup is set on the punch to print the manager. The punch is extruded into a mold along the axial direction. The clearance between the mold and the punch is smaller than the thickness of the cup wall, so that the diameter remains unchanged. The wall thickness is reduced. After thinning, the metal volume of the barrel is equal to the metal volume of the cup during thinning and is also equal to the metal volume of the original slab. In the manufacture of cans in Beijing silk screen printing, this process is repeated two or three times. The punch with the cup passes through a series of molds one after another through one mold. The most convenient method for installing the stamped forest on the punch is to perform a re-pressing operation before the first thinning.