Aside from sizing, it’s important to understand how the cans you purchase are produced
From a manufacturing standpoint, food cans can be assembled from two or three pieces of metal, and they are classified as either made from aluminium or steel, depending on the can-body material.
Two-piece metal food cans consist of:
1. a body integrated with a bottom lid and
2. a lid with a lip
These types of cans are made using a drawing process, in which a coil of coated rolled steel or aluminium is fed into a press and formed into a cup shape object, complete with a flat, round bottom and cylindrical side walls.
The cups then go through another drawing phase (the redraw) to achieve the final shape (DRD, draw and redraw cans), or they may go through a wall ironing phase (DWI, draw and wall ironing cans), which results in the cup walls being stretched and ironed to a predetermined height. Regardless of the can being redrawn or ironed, the final step is to trim the cup into a finished container before filling and sealing on the top lid via “double seaming”.
Three-piece metal food cans feature:
1. a bottom lid,
2. a cylindrical body, and
3. a top lid
These cans are made with a rectangular, flat sheet of food-grade steel that’s shaped into a cylinder and closed with a vertical side seam. The bottom end is then attached via “double seaming” to create a hermetic seal. Once filled, the can is sealed closed at the top with a similar seal to the bottom. Three-piece cans can either be assembled via soldering or welding, depending on the manufacturer.
