Can manufacturing is a large and complex industry, producing billions of units worldwide each year. The process involves extrusion, trimming, washing, annealing, coating, coloring, drying, and capping. The final step may include lactation for added protection and shelf life extension.
Cans are certainly one of the most common forms of product packaging known to man. From sodas to tennis balls and gunpowder, they’re all in cans. Can manufacturing is, therefore, one of the world’s most prolific industries, with billions of units produced worldwide each year. The average can production line is quite large and complex, consisting of a large number of stages, each facility geared towards producing a range of can types, but typically not all. For this reason it is difficult to describe a single definitive can manufacturing process, but a basic layout of an aluminum can plant will be able to detail the general procedure.
In most cases, a can production line starts with an extrusion section. Here, the raw aluminum stock is extracted to form a continuous cylinder of the correct diameter for the specific can. The cylinder is then dragged through a combined trimming and forming machine which cuts the cylinder into shorter pieces. The same machine can also be configured to cap the bottom of the can, form screw caps, and emboss custom patterns on the blank.
From the trimmer, the blanks are then transported via a conveyor belt to the washing section of the can production line. The blanks are then washed several times with a powerful alkaline solution to remove any contaminants that have built up during the extrusion and trimming stages. From the washing plant, the cans are transported again via conveyor belt to an annealing oven, which heats the cans to a specific temperature to remove any hardening and brittleness imparted by extrusion and trimming. Re-softening the cans in the annealing oven is an essential part of the process if the finished cans are to remain pliable.
After annealing, the cans are transported to an accumulator, which collects the cans so that they can be fed to the next two production steps in a controlled manner. These are the inner coating machine, which sprays a sterile coating on the inside surface of the cans, and a lacquer curing oven, which sets the coating. From the curing oven, the cans are passed to the first of the coloring processes. This process involves printing a special auto-sensing stripe onto the can which prevents the cans from ‘skipping’ the next steps in the process. This includes two base coat applications and a four, five or six color printing process that imparts the desired design onto the can.
Once the cans are dyed, they are transferred to a drying oven to fix the colouring. After the cans have cooled, they are sent to the last stage of the can production line where they are capped awaiting distribution. In some cases, the can production line may include an additional step, the lactation of the cans, upon request. In this step, a latex ring is added to the base of the can as an added measure of contents protection and shelf life extension.
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