In the production of aluminum can lid, the core of the sealing process is the double roll sealing technology, which combines the can body and the can lid closely by mechanical rolling and pressing. For instance, drink cans. The speed of sealing of the production line can reach 2,000 to 3,000 cans per minute. Sealing pressure has to be kept very tightly in the range of 2,000 to 2,500 Newtons so that the aluminum alloy sealing surface material (about 0.2 millimeters thick) can form a perfect structure with the can body (0.28 millimeters thick). Temperature control in this process is of utmost importance. As a principle, after can lid formation through stamping, it should be cooled to less than 25°C to prevent thermal expansion of the material causing the seal to fail. According to Anheuser-Bush InBev’s 2021 report, its production line uses servo motor-driven winding equipment, conserving energy by 15%, increasing the sealing qualification rate to 99.98%, and reducing leakage loss by approximately 1.2 million US dollars annually.
In the sealing quality inspection stage, the industry commonly uses eddy current testing systems, which examine the junction between the can lid and the can body with high-frequency electromagnetic fields. For example, the detector tool of Ball Corporation in America scans at a speed of 200 scans per second, and has a recognition rate of 0.05 millimeters, and can detect pore defects whose diameter is less than 50 micrometers. According to a study in the journal “Packaging Technology” of 2022, use of such systems can reduce the leakage rate from 0.1% to 0.003%, and reduce the cost of manual quality checking by approximately 30%. Take the example of the Red Bull manufacturing line. Its sealing humidity should be controlled between 40% and 60% to prevent the corrosion of the aluminum alloy oxide film and impact the sealing strength. Excessive humidity can elevate the risk of corrosion due to the penetration of water molecules into the aluminum oxide layer on the can cover surface (about 5 nanometers thick).
In terms of saving cost, aluminum can lid sealing rings can save 12%-15% of the production cost. Taking the example from the data of Coca-Cola in 2023, one production line will consume around 1.2 tons of sealant yearly. The viscosity of glue needs to be maintained at a range of 3000-3500 mPa·s in order to obtain a uniform coating in sealing procedure. If the glue coating deviation is greater than ±5 microns, then it will have a chance of 0.5% for seal failure. Other than that, reprocessing and sealing of recycled aluminum cans is also of utmost importance. For instance, the recycled aluminum can line constructed by Japan’s Daito Can utilizes laser cleaning technology to remove surface impurities on used can LIDS (residue concentration <0.01%), enabling the sealing strength of recycled aluminum to reach up to 98% of virgin materials and reducing carbon emissions by 45%.
In the innovation industry, Carlsberg Group launched in 2023 the “Infinite Circulation Tank” with the application of glue-free sealing technology. Through the use of the self-locking property of the aluminum alloy nanostructure (grain size <10 microns), the winding pressure decreased to 1800 Newtons, and the production energy consumption was lowered by 20%. This technology has lightened the weight of the can lid from 2.2 grams to 1.9 grams, saving about 180,000 US dollars in aluminum material expenses for one production line annually. Based on figures from the International Aluminium Institute, over 400 billion aluminum can LIDS are manufactured worldwide every year. Among them, the optimization of the sealing process can advance the achievement of the industry’s overall carbon reduction target 3 to 5 years earlier than planned.