The cups are then forced though a series of rings to iron out and form a full-length can and to form the bottom dome.
Subsequent operations include trimming the can to a specified length, washing to remove drawing lubricants, decorating the exterior of the can with the desired brand level and applying coating to prevent contact of the food or beverage product with the metal substrate.
The product at this stage is a container with sides and a bottom representing one of the pieces of a two-piece can. The lid, secured and sealed after filling, is the second piece.
Since 1970, through the conversion of three to two piece cans and subsequent lightweighting, the weight of a 350 mL tinplate soft drink can has been reduced by 50% to 30g, and that of the inherently lighter two-piece aluminum can by 39% to 13 g.
It is evident that two-piece steel can would eliminate the long seam and one double seam and thus preclude two sources of potential leakage.
Steel is a cheaper metal than aluminum, but it is far more difficult to form. A two –piece steel can could offer the advantages of a two piece aluminum can, but at a lower price.
The two piece can has no side seam and only one double seam, which is more easily formed and controlled because of the absence of a side seam lap juncture.
Seaming by the filler at the top end is considerably easier owing to the absence of a junction of the side seam and the end seam.
Two piece cans
