Canned beverages have become so commonplace, that people often neglect the awesome engineering behind it. Before you open and take a sip of your favorite canned soda, why don’t you take some time to learn something about the standard aluminum can?
Bill Hammack, the Engineer Guy from the University of Illinois, shared this comprehensive video about how an aluminum can is made and what design elements make this rather common object so ingenious.
Personally, I was in awe of how much engineering takes place in the manufacture of a single aluminum can. Wow!
Here are some of the aluminum can’s design highlights as explained in the video:
Why is the aluminum can cylindrical?
Engineers could have made it spherical for the least amount of aluminum and the absence of weak pressure points, but it’s difficult to make and it will roll off the surface. Plus, it wastes storage space because of the voids between the spheres. In the case of a rectangular / cuboid shape, it may be efficient for storage. However, it’s difficult to drink from, and the corners are considered weak points
To merge the advantages of the sphere and the cuboid, engineers decided that a cylindrical shape works best. From the top, it looks circular, and it looks rectangular from the side.
How is an aluminum can created?
- The can starts out from an aluminum sheet about 0.3 mm thick. It is clamped between a drawing die and a blank holder, from which the sheet takes its cylindrical shape using a punch pressed down on the aluminum.
- The drawn cup is passed through a redrawing die to reduce its diameter and increase its height.
- The redrawn cup passes three times through an ironing ring that stretches the can height by making the aluminum walls thinner.
- The can base is pushed inward to a concave shape using a convex doming tool and a concave punch with a similar shape as the doming tool. The base is shaped into a concave dome because it can withstand more pressure than a flat base. Amazingly, in a standard aluminum can manufacturing plant, the first four steps happens in one-seventh of a second for every can!
- The top portion of the can will have an irregular edge, so about 6 mm is chopped off from the top
- The can design is printed on the outer walls. Meanwhile, the inside walls are sprayed with epoxy lacquer to prevent the aluminum from mixing with the beverage.
- The top of the can undergoes a process called necking, which curves the can’s top inward to give it a smaller diameter from the rest of the can.
- The top is flanged outward, and the seal is affixed to the can by double seaming. This process doesn’t use welding to attach the seal to the can, but rather uses a tight curl to bind the two pieces together. A liquid sealing compound is applied to the curl, and hardens to a gasket.
Why is an aluminum beverage can pressurized?
The pressure strengthens the filled beverage can in spite of its thin walls. This is in contrast to canned fruits, wherein the walls of the can are corrugated to increase strength.
Why is the can opening tab designed that way?
Earlier cans did not have tabs to open the top, so a can opener is needed. By the 1960s, the pull-tab was invented to allow people to enjoy the drink even without a can opener. However, this pulled-out tab got separated from the can, leading people to throw it carelessly. In response to environmental and safety concerns, the beverage can industry invented the stay-on tab so that you can open the can and the tab stays in place.