Three-piece canning is a manufacturing method of forming canoes

How to Can Cans for Production

Three-piece canning is a manufacturing method of forming canoes, vats and similar containers with at least three pieces of opposite ends to form a closed can with an air-tight seal. The most common three-piece commercial cans are three-piece steel sanitary cans that usually contain a metal body, a thin, stiff metal vial or both, and two end pieces which are joined together permanently to give a tight, air-tight seal. Three-pieces can be made in a variety of shapes and sizes depending on the manufacturing process used. Three-piece production has its roots in early twentieth century German metal processing and manufacturing and has since become widely accepted throughout the manufacturing world.

Although three-piece cans are considered to be high-quality, they must meet certain production requirements in order to meet government and industry specifications. Generally, three-piece cans have a thicker wall thickness than two-pieces and are much heavier because of the added material, such as the metal insert that forms a part of every can. The thickness of the wall is not the only consideration for three-piece production; other factors, such as the bottom of the can, the rim, the sealing surface, the acid level of the tincture and the manner in which the can is opened also play a role in the quality and efficiency of the finished product.

Tinted metal, which is the most popular option for the top surface of three-piece cans, provides protection from air, moisture and light. Tinted metal is typically galvanized or anodized to prevent the formation of corrosion. The anodized surface provides a clear window for ventilation, while galvanized prevents rust. Metal that is not galvanized is painted with an aluminum-zinc solution to provide adequate ventilation, as well as to protect the surface from airborne corrosion. A thin layer of polyester or acrylic is applied over the metal surface to further protect it from abrasion and moisture. Some manufacturers paint the top surface of the can using a stencil to create the desired pattern, although this is not necessary.

The thickness of the can affects the ease in which it can be filled with food or drink cans. The less thickness, the easier it is to fill. Two-piece food cans, which have an inner liner made of tin, are the easiest to fill. However, three-piece can be filled easily using a metal spoon. One advantage of using metal spoons is that they prevent the can from drying out between fills. If using tinplate cans, ensure that the tinplate is adequately heated prior to filling, as otherwise the cans may develop cracks during cooling.

Maintain a consistent temperature during canning to avoid overheating of the metal cans. Although the three-piece can has a defined shape, care must be taken to ensure that the same shape is not used for the lid as well as for the other parts of the can. It is not advisable to have three-piece cans with different lid shapes because the variation in the shape of the lid will cause the inner can liner to become unstable, leading to cracking. For most three-piece cans, the lids should be placed on a flat surface and can be removed easily to allow for inspection and cleaning.

After canning, the metal cans are packaged according to the type of their contents. Two and three-piece cans can be packed into standard dimensional can packaging or special die casting boxes depending on the final product's shape and weight. Food can be easily moved from one location to another if packaging is done properly; therefore, three-piece cans are preferred in production process. This means that three-piece canning is more convenient than two-piece manufacturing.