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The traditional method for making metal packaging cans is as follows: first, sheet steel blank plates are cut into rectangular pieces. Then the blanks are rolled into cylinders (known as the can body), and the resulting longitudinal seam is soldered to form the side seal. One end of the cylinder (the can bottom) and the circular end cap are mechanically flanged and double-seamed by rolling, forming the can body. After filling the product, the other end is sealed with a lid. Since the container is composed of three parts—the bottom, the body, and the lid—it is called a “three-piece can.” Over the past 150 years, this method has remained largely unchanged, except that automation and machining precision have greatly improved. In recent years, the side seam welding has been switched from soldering to fusion welding.
Manufacturing Three‑Piece Cans
In the early 1970s, a new can-making principle emerged. According to this, the can body and bottom are formed from a single circular blank by stamping; after filling the product, the can is sealed. This is known as a "two-piece can." There are two forming methods: stamping–ironed drawing (drawing) and stamping–redrawing (deep drawing). These techniques are not entirely new—drawing was already used during World War I for shell casings. The difference with can-making lies in the use of ultra-thin metal and extremely high production speeds (annual output can reach several hundred million units).
Process steps:
▼ Cut coil stock into rectangular plates using a shear
▼ Apply coating and apply printing
▼ Cut into long strips
▼ Roll into cylinders and weld side seams
▼ Touch-up seams and coating
▼ Cut the can bodies
▼ Form beads or corrugations
▼ Flange both ends
▼ Roll-bead and seal the bottom
▼ Inspect and stack on pallets
① Can‑Body Fabrication
The key operations are rolling/forming and side‑seam sealing. There are three sealing methods: soldering, fusion welding, and adhesive bonding.
Soldered seam cans: The solder is usually made of 98% lead and 2% tin. The cylinder-forming machine works in tandem with the soldering/seam sealer. Edges of the blank are cleaned and hooked, aiding in securing during cylinder formation. The cylinder then passes through a side-seam machine: solvent and solder are applied, the seam region is preheated by a gas torch, then a longitudinal soldering roller further heats it, allowing the solder to flow fully into the seam. Excess solder is then removed by a rotating scraper roller.
Fusion welding: This uses a self-consuming wire-electrode principle and resistance welding. Earlier systems used wide lap joints with steel heated to melting point under lower roller pressure. Newest welders employ small lap overlaps (0.3–0.5 mm), heating the metal just below its melting point, but increasing roller pressure to forge the overlap together.
The weld seam disrupts the original smooth or coated inner surface, exposing iron, iron oxide, and tin on both sides. To prevent product contamination or corrosion at the seam, most cans require protective coatings at the side seal.
Adhesive bonding: Used for packaging dry products. A nylon strip is applied to the longitudinal seam, melting and solidifying after cylinder formation. Its advantage is full edge protection but it can only be used with tin-free steel (TFS), since tin's melting point is close to that of the adhesive.
② Post‑Processing of the Can Body
Both ends of the body must be flanged to attach end caps. For food cans, during processing the can may undergo external pressure or internal vacuum. To enhance strength, stiffening ribs may be added to the body in a process called corrugation.
To increase production efficiency for shallow containers, cylinders are made long enough for two to three cans. The first step is cutting the cylinder. Traditionally, the blank was cut on a cutting/creasing machine before forming. But recently, trimming-shearing machines developed for two-piece can production have emerged.
Chengdu Changtai Intelligent Equipment Co., Ltd.- A automatic can equipment Manufacturer and Exporter, provides all the solutions for Tin can making. To know the latest news of metal packing industry, Find new tin can making production line, and get the prices about Machine For Can Making,Choose Quality Can Making Machine At Changtai.
Contact us for details of machinery:
Tel:+86 138 0801 1206
Whatsapp:+86 138 0801 1206
Email:Neo@ctcanmachine.com CEO@ctcanmachine.com
Plan to set up a new and cost low can making line?
A: Cause we have leading edge technology for giving the best machines for a wonderful can.
A: That's a big convenience for buyer to come to our factory to get machines cause our products all don't need commodity inspection certificate and it will be easy for export.
Our engineers will come to your site, help to build up your metal can production line, till it works perfect!
The machinery parts well be provide a life long with your plant.
Aftersales provided, addressing problems in the way.
A: Yes! We can supply free quick-wear parts for 1 year, just rest assure to use our machines and themselves are very durable.
Post time: Jul-21-2025