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Metal Can Packaging and Process Overview
In our daily lives, a wide variety of beverages cater to diverse tastes, with beer and carbonated drinks consistently leading in sales. A closer look reveals that these beverages are commonly packaged in easy-open cans, which have become ubiquitous worldwide due to their popularity. Despite their small size, these cans embody remarkable ingenuity.
In 1940, stainless steel cans were first used for beer in Europe and the United States, marking a significant advancement with the introduction of aluminum cans. In 1963, the easy-open can was invented in the U.S., inheriting the design features of earlier cans but incorporating a pull-tab opening at the top. By 1980, aluminum cans had become the standard packaging for beer and carbonated drinks in Western markets. Over time, the manufacturing technology for easy-open cans has continuously improved, yet this invention remains highly practical and widely used today.
Modern aluminum easy-open cans consist of two parts: the can body and the lid, also known as “two-piece cans.” The bottom and sides of the can are formed as a single piece, and the lid is sealed to the body without seams or welding.
Manufacturing Process
Aluminum alloy coils, approximately 0.27–0.33 mm thick and 1.6–2.2 m wide, are used. The coils are unrolled using an uncoiler, and a thin layer of lubricant is applied to facilitate subsequent processing.
The aluminum sheet is fed into a cupping press, similar to a punch press, where the upper and lower molds work together under pressure to punch out circular cups from the sheet.
▶ Drawing: The punched cups are stretched by a drawing machine into the tall, cylindrical shape of aluminum cans.
▶ Deep Drawing: The cans are further drawn to thin the sidewalls, forming the tall, slender can body. This is typically done by passing the can through a series of progressively smaller molds in a single operation.
▶ Bottom Doming and Top Trimming: The bottom of the can is designed with a concave shape to distribute the internal pressure of carbonated beverages, preventing bulging or bursting. This is achieved by stamping with a doming tool. The uneven top edge is also trimmed for uniformity.
The cans are inverted and cleaned to remove oil and residues from the stamping process, ensuring hygiene. The cleaning process involves:Washing with 60°C hydrofluoric acid to remove the oxide film on the aluminum surface.
---Rinsing with 60°C neutral deionized water.
---Rinsing with 60°C neutral deionized water.
---After cleaning, the cans are dried in an oven to remove surface moisture.
- A layer of clear varnish is applied to prevent rapid oxidation of the aluminum in air.
- The can surface is printed using curved-surface printing (also known as dry offset printing).
- Another layer of varnish is applied to protect the printed surface.
- The cans pass through an oven to cure the ink and dry the varnish.
- A compound coating is sprayed on the inner wall to form a protective film, preventing corrosion by carbonated beverages and ensuring no metallic taste affects the drink.
The can’s neck is formed using a necking machine, reducing the diameter to approximately 5 cm. This process involves 11 gradual steps to gently shape the neck without excessive force, ensuring a smooth transition.
To prepare for lid attachment, the top edge is slightly flattened to create a protruding rim.
To prepare for lid attachment, the top edge is slightly flattened to create a protruding rim.
High-speed cameras and airflow systems work together to identify and remove defective cans, ensuring high quality.
- Coil Cleaning: Aluminum alloy coils (e.g., 5182 alloy) are cleaned to remove surface oil and impurities.
- Lid Punching and Crimping: A punch press forms the lids, and the edges are crimped for smooth sealing and opening.
- Coating: A layer of lacquer is applied to enhance corrosion resistance and aesthetics, followed by drying.
- Pull-Tab Assembly: Pull-tabs made from 5052 alloy are combined with the lid. A rivet is formed, and the tab is attached and secured, with a score line added to complete the lid.
Can manufacturers produce open-top cans, while beverage companies handle the filling and sealing processes. Before filling, the cans are rinsed and dried to ensure cleanliness, then filled with beverages and carbonation.
Beverage filling plants are highly automated, often requiring only one worker to place lids onto a conveyor, where machines automatically position them on the cans.
A specialized sealing machine curls the can body and lid together, pressing them tightly to form a double seam, ensuring an airtight seal that prevents air ingress or leakage.
A specialized sealing machine curls the can body and lid together, pressing them tightly to form a double seam, ensuring an airtight seal that prevents air ingress or leakage.
After these intricate steps, the easy-open can is complete. Isn’t it fascinating how much knowledge and technology go into creating this small yet ubiquitous can?
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Post time: Jul-08-2025