One of the most common types of metal containers is the metal can, which comes in two primary styles—two-piece and three-piece cans. So we have a two-piece can and a three-piece can. And so the difference is that a three-piece can, this body right here is a single piece. There's an end at the bottom and an end at the top. That's the three-piece can.

But in this lecture we're gonna talk about the two-piece can. The two-piece can is probably what you're familiar with. It's a solid body all the way through. And then just one end, making it two-pieces. There are several processes to manufacture two-piece cans—notably the redrawing and ironing processes. Each have their slight variations, enabling production in mere fractions of a second. So, let's dive into the details.

The process begins with a metal sheet, which historically was tin-plate steel, but is now predominantly aluminum. Circles are punched out from that sheet and are then formed into cups. You'll notice that the cup's diameter is much larger than the final can’s diameter. And so, depending on the method of manufacturing, we can draw and redraw, which means pushing this cup into different dyes ultimately resulting in this. But also the ironing process, which forces these shapes into rings and slowly moves the thickness of this metal up taller and taller and taller to, ultimately, get to our final can structure. 

But why a dome at the bottom of the can? In order to hold highly pressurized systems, an arc is formed into the bottom—the dome of the can. The dome of the can allows pressure to be distributed across that arc. And while I can deform this can very easily by pushing on it, there's not much I can do to deform that dome at the bottom. It's incredibly strong. Similarly, the internal pressure of carbonated beverages applies tension to the can's walls, reinforcing them. 

After sizing, the can is coated inside and out. The exterior receives a brand specific coating and printing. Once that happens, we'll have the final can print. So, this is your end graphics that are printed directly onto the canned, but you'll still see we haven't done anything with the top yet. 

And that'll begin the necking process—it tapers the top of each can, enhancing its structural integrity and reducing material use due to the smaller diameter. This process also creates a flange, which is essential for forming the double seam.

And then, our final can design here. So, we have the necking that has occurred and the taper, and you can see the flange on the very top. It's ready to be coated on the inside, which is a plastic coating that is ensuring that there will not be a reaction between the metal itself and the products that are being placed into it. And it'll be coated, filled with the product, and then, finally the end will be placed on it—right on top. And in this particular case, the flange and the end will match up, and then, the double seam will be made. And you can see here, the coating on the inside of the end that is used as a gasket. So, when that double seam is made, this coating is applied in there to ensure that none of the gases escape out of the can. 

And interestingly, cans carry a hidden code at the bottom revealing its manufacturing origin and method. So this aspect, among others, underscores the can’s fascinating history and its status as an infinitely recyclable product, produced in an instant.