Can making is an old
process that has remained almost the same for over a century with
improvements done to the choice of materials used and to the opening
mechanisms. Cans that are used nowadays for carrying various
items from corrosive liquids to food products can be classified
depending on their structure or through the choice of material from
which they are made.
A majority of the
quality cans made have three components namely, a bottom lid, a top
lid and a middle cylindrical body where these two parts are joined to
the body. These are known as three piece cans. Whereas the two piece
can only has the top lid and the bottom lid is integrated with the
body as the material used is more pliable to this structure.
The two piece can
technique uses a double seaming to attach the body of the can to the
lids to protect the contents from any kind of contamination from
external sources. While in the three piece can technique the lids are
sealed either with soldering or with electric welding. Electric
welding is the process now used as soldering used to use lead which
could be harmful to us humans.
Cans made of
aluminium and some varieties of steel mainly use the two piece method
where they are stretched, drawn and ironed into the desired shape
before the top lid is attached. While cans made of only steel use the
three piece method where the top and bottom lids are soldered or
welded to the body.
The can made from
the two piece method are better at resisting atmospheric pressure due
to a positive pressure inside by pressure filling making them
suitable to carry carbonated beverages including beer and soft
drinks. The three piece method is more used for cans that have to
carry items like paints that have a vacuum filling to remove all air
from the inside of the can to ensure their longevity and properties.
They are also used when the inside air is replaced with a non
reactive gas like nitrogen to preserve food items like juices.
Comments
Post a Comment