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The Ingenious Design of the Aluminum Beverage Can

100 Comments



Every year nearly a half trillion of these
cans are manufactured—that’s about 15,000 per second — so many that we overlook the
can’s superb engineering. Let’s start with why the can is shaped like it is. Why
a cylinder? An engineer might like to make a spherical can: it has the smallest surface
area for a given volume and so it uses the least amount of material. And it also has no corners
and so no weak points because the pressure in the can uniformly stresses the walls. But
a sphere is not practical to manufacture. And, of course, it’ll roll off the table.
Also, when packed as closely as possible only 74% of the total volume is taken up by the
product. The other 26% is void space, which goes unused when transporting the cans or
in a store display. An engineer could solve this problem by making a cuboid-shaped can.
It sits on a table, but it’s uncomfortable to hold and awkward to drink from. And while
easier to manufacture than a sphere, these edges are weak points and require very thick
walls. But the cuboid surpasses the sphere in packing efficiently: it has almost no wasted
space, although at the sacrifice of using more surface area to contain the same volume
as the sphere. So, to create a can engineers use a cylinder, which has elements of both
shapes. From the top, it’s like a sphere, and from the side, it’s like a cuboid .A
cylinder has a maximum packing factor of about 91% — not as good as the cuboid, but better
than the sphere. Most important of all: the cylinder can be rapidly manufactured. The
can begins as this disk —called a “blank”— punched from an aluminum sheet about three-tenths
of a mm thick. The first step starts with a “drawing die,” on which sits the blank
and then a “blank holder” that rests on top. We’ll look at a slice of the die so
we can see what’s happening. A cylindrical punch presses down on the die, forming the
blank into a cup. This process is called “drawing.” This cup is about 88 mm in diameter—larger
than the final can — so it’s re-drawn. That process starts with this wide cup, and
uses another cylindrical punch, and a “redrawing die.” The punch presses the cup through
the redrawing die and transforms it into a cup with a narrower diameter, which is a bit
taller. This redrawn cup is now the final diameter of the can—65 mm—but it’s not
yet tall enough. A punch pushes this redrawn cup through an ironing ring. The cup stays
the same diameter, as it becomes taller and the walls thinner. If we watch this process
again up close, you see the initial thick wall, and then the thinner wall after it’s
ironed. Ironing occurs in three stages, each progressively making the walls thinner and
the can taller. After the cup is ironed, the dome on the bottom is formed. This requires
a convex doming tool and a punch with a matching concave indentation. As the punch presses
the cup downward onto the doming tool: the cup bottom then deforms into a dome. That
dome reduces the amount of metal needed to manufacture the can. The dome bottom
uses less material than if the bottom were flat. A dome is an arch, revolved around its
center. The curvature of the arch distributes some of the vertical load into horizontal
forces, allowing a dome to withstand greater pressure than a flat beam. On the dome you
might notice two large numbers. These debossed numbers are engraved on the doming tool. The
first number signifies the production line in the factory, and the second number signifies
the bodymaker number — the bodymaker is the machine that performs the redrawing, ironing
and doming processes. These numbers help troubleshoot production problems in the factory. In that
factory the manufacturing of a can takes place at a tremendous rate: these last three steps—
re-drawing, ironing and doming—all happen in one continuous stroke and in only a seventh
of a second. The punch moves at a maximum velocity of 11 meters per second and experiences
a maximum acceleration of 45 Gs. This process runs continuously for 6 months or around 100
million cycles before the machine needs servicing. Now, if you look closely at the top of the
can body, you see that the edges are wavy and uneven. These irregularities occur during
the forming. To get a nice even edge, about 6 mm is trimmed off of the top. With an
even top the can can now be sealed. But before that sealing occurs a colorful design is printed
on the outside—the term of art in the industry is “decoration.” The inside also gets
a treatment: a spray-coated epoxy lacquer separates the can’s contents from its aluminum
walls. This prevents the drink from acquiring a metallic taste, and also keeps acids in
the beverage from dissolving the aluminium. The next step forms the can’s neck — the
part of the can body that tapers inward. This “necking” requires eleven-stages. The
forming starts with a straight-walled can. The top is brought slightly inward. And then
this is repeated further up the can wall until the final diameter is reached. The change
in neck size at each stage is so subtle that you can barely tell a difference between one
stage and the next. Each one of these stages works by inserting an inner die into the can
body, then pushing an outer die—called the necking sleeve—around the outside. The necking
sleeve retracts, the inner die retracts, and the can moves to the next stage. The necking
is drawn out over many different stages to prevent wrinkling, or pleating, of the thin aluminum. Since the
1960’s, the diameter of the can end has become smaller by 6 mm — from 60 mm to 54
mm today. This seems a tiny amount, but the aluminum can industry produces over 100 billion
cans a year, so that 6 mm reduction saves at least 90 million kilograms of aluminum
annually. That amount would form a solid cube of aluminum 32 meters on a side—compare
that to a 787 dreamliner with a 60 meter wingspan. Now, after the neck has been formed the top
is flanged; that is, it flares out slightly and allows the end to be secured to the body,
which brings us to the next brilliant design feature: the double seam. On older steel cans
manufactures welded or soldered on the ends. This often contaminated the can’s contents.
In contrast, today’s cans use a hygienic “double seam,” which can also be made
faster. This can is cut in half so you can see the cross-section of the double seam.
To create this seam, a machine uses two basic operations. The first curls the end of the
can cover around the flange of the can body. The second operation presses the folds of
metal together to form an air-tight seal. While the operations themselves are simple,
they require high precision. Parts misaligned by a small fraction of a millimeter cause
the seam to fail. In addition to the clamping of the end and can body, a sealing compound
ensures that no gas escapes through the double seam. The compound is applied as a liquid,
then hardens to a form a gasket. The end, attached immediately after the cans is filled,
traps gases inside the can to create pressures of about 30 psi or 2 times atmospheric pressure.
In soda, carbon dioxide produces the pressure; in non-carbonated drinks, like juices, nitrogen
is added. So why is a beverage can pressurized? Because the internal pressure creates a strong
can despite its thin walls. Squeeze a closed, pressurized can—it barely gives. Then squeeze
an empty can—it flexes easily. The cans walls are thin—only 75 microns thick—and
they are flimsy, but the internal pressure of a sealed can pushes outwards equally, and
so keeps the wall in tension. This tension is key: the thin wall acts like a chain — in
compression it has no strength, but in tension it’s very strong. The internal pressure
strengthens the cans so that they can be safely stacked —a pressurized can easily supports
the weight of an average human adult. It also adds enough strength so that the can doesn’t
need the corrugations like in this unpressurized steel food can. While initially pressurized
to about 2 atmospheres, a can may experience up to 4 atmospheres of internal pressure in
its lifetime due to elevated temperatures; and so the can is designed to withstand up
to 6 atmospheres or 90 psi before the dome or the end will buckle. Why is there a tab
on the end of the can? It seems a silly question—how else would you open it? But originally cans
didn’t have tabs. Very early steel cans were called flat tops, for pretty obvious
reasons. You use a special opener to puncture a hole to drink from, and a hole to vent.
In the 1960’s, the pull-tab was invented so that no opener was needed. The tab worked
like this: you lift up this ring to vent the can, and pull the tab to create the opening.
Easy enough, but now you’ve got this loose tab. The cans ask you to “Please don’t
litter” but sadly, these pull tabs got tossed on the ground, where the sharp edges of the
tabs cut the barefeet of beachgoers—or they harmed wildlife. So, the beverage can industry
responded by inventing the modern stay-on tab. This little tab involved clever engineering.
The tab starts as a second class lever; this is like a wheelbarrow because tip of the tap
is the fulcrum and the rivet the load — the effort is being applied on the end. But here’s
the genius part: the moment the can vents the tab switches to a first class lever which
is like a seesaw: where the load is now at the tip and the fulcrum is the rivet. You
can see clearly how the tab, when working as a wheelbarrow, lifts the rivet. In fact,
part of the reason this clever design works is because the pressure inside the can helps
to force the rivet up, which in turn depresses the outer edge of the top until it vents the
can and then the tab changes to a seesaw lever. Looking from the inside of the can, you can
see how the tab first opens near the rivet. If you tried to simply force the scored metal
section into the can using the tab as a first class lever with the rivet as the fulcrum
throughout you’d be fighting the pressure inside the can: the tab would be enormous,
and expensive. If you’d like to learn more about the entire lifecycle of the aluminum
can, watch this animated video by Rexam that describes can manufacturing and recycling.
A typical aluminum can today contains about 70% recycled material. Also, Discovery’s
How It’s Made has some great footage of the manufacturing machinery. Here are two
different stepwise animations of the entire can forming process. And lastly, these are
two detailed animations of the cup drawing and redrawing processes. The aluminum beverage
can is so ubiquitous that it’s easy to take for granted. But the next time you take a
sip from one, consider the decades of ingenious design required to create this modern engineering
marvel. I’m Bill Hammack, the engineer guy. Thanks to Rexam for providing us with aluminum
cans in various stages of production. And thank you very much to the advanced viewers
who sent detailed and useful responses for this video. We read every single comment.
If you’d like you to help out as an advanced viewer check out www.engineerguy.com/preview.
You can see upcoming projects and behind-the-scene footage. For example, you can see a early
drafts of this beverage can video. And you can sign up there to become an advance viewer.
Thanks again.

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100 thoughts on “The Ingenious Design of the Aluminum Beverage Can”

  1. Alexandru Danciu says:

    Cool stuff and such a great explanation. Thanks.

  2. Dennis Germain says:

    back in about 1974 my Dad who worked in the Petrochemical industry said one evening that a fellow Engineer was working on a pull tab that stayed with the can, probably one of many, and I always remember that moment, he was looking for a solution to a problem I didn't know existed, it seems simple now, but you think back and ask yourself, how did Edison know electricity was the answer to the light bulb

  3. Cre Henge says:

    Amazing! You made me watch a full video on a can!!!

  4. Gregarious says:

    Why can't they make the diameter equal to the height and thereby minimize the amount of aluminum for a given volume?

  5. JG2201 and CG says:

    This is one of the greatest channel, I never cared about this before now!

  6. Better Run says:

    This was a pretty interesting video that’s a lot of work just to make fucking pop can crazy

  7. Vincit Veritas says:

    Why do aftershave/perfume companies have so much wasted space in box?

  8. Vids says:

    Superb video, love it.

  9. rich holloway says:

    Bill Nye the science guy look out!… Awesome vid once again.

  10. Martin Glastetter Jr says:

    wow, impressive stuff and awesome presentation, cheers!!

  11. Treece says:

    Im tooo high for this lmao

  12. Viruz jr says:

    If this explained by my teacher i would be put to a sleep in the first few minutes.

  13. David Hamilton says:

    There was also the Pop Top, two bubble like blisters you simply pushed…

  14. They’re great says:

    How did I go from watching a video about medieval plate armor to a video about why a soda can is the best

  15. Augustin Leonidas says:

    This guy is wow!

  16. Bill Shanks says:

    Human Biology 6:41

  17. tiberius staicu says:

    why did i rewatch this

  18. Happy Raccoon says:

    The pull tabs was an intentional act to maim millions at our beaches.
    Maybe I missed it but Plastic is what the beer touches the aluminum is the outer shell. Our cans are plastic and aluminum. He mentions spray paint at 4:40 ….but I have seen the plastic

  19. Bahadoor Abdool Nawaaz says:

    You should work as a teacher!!!

  20. Filter Taylor says:

    This forming process was invented by Ingersol Rand shop in Sherbrooke Quebec, Canada.

  21. WWTormentor says:

    You have a great gift of teaching engineering in a fun and understandable way. I can’t wait to see what other videos await us. Thank you sir.

  22. Abdullah Arif says:

    Did you all see what he did in the closing time hahahahha

  23. The Poet McTeagle says:

    Fantastic , as a 60 year old Plumber , I have always wondered how they are made , thanks !

  24. kargaroc386 says:

    A vessel that gets its rigidity from internal pressure is called a balloon tank

  25. Rando Plants says:

    This is everything I could ask for in an educational video. I love your set up with the wooden tables. Really ingenious!

  26. Kenneth Gundersen says:

    11:37 🙂

  27. mu99ins says:

    I am the last remaining human being that stands firmly against pull tabs. The can comes from a dirty factory, and shipped in a filthy truck, and unloaded by a sweaty truck driver, and presented to the public in refrigerated, glass door cases in the store, which is a happy home for mice and rats. The consumer takes these cans home and places them in the refrigerator, which is not a clean environment, as the microbes reproducer, some of those microbes may reside on the top of your can, which you never wash before drinking. Do you even wipe it with a napkin before drinking? No. Without the pull tab, the top of the can is smooth and quickly 'n' easily cleaned. Also, with the pull tab, there is unpleasant turbulence as the beverage flows into the mouth during drinking. Venting is through the top of the drinking hole. The aluminum beverage cans have more laminar flow when opened ( including a vent ) with a church key. The only can I drink out of is the small V8 juice cans, which I rinse at the sink, dry, and place in the refrigerator, upside down, on top of a fresh paper towel.

  28. Nate Ridgley says:

    Wow… never thought I would be amazed by a can. Awesome video!!! that was actually really fun to learn about.

  29. aquillae says:

    Are you related to alton brown?

  30. cgprecision says:

    I built dies for this industry for three years for stolle mfg. quite the undertaking, each die. And there were so very many dies, to produce something seemingly so simple. Thank you for breaking down the engineering behind all that tiring work. And now, psshht! (Beer taking its first breath) A toast to the human mind and its ingenuity. . . Cheers!

  31. Steve Skouson says:

    Margaritaville.

    Can a song really define a "soft" drink?

    steve

  32. TinyFoxTom says:

    I have this sudden craving for a Fanta.

  33. Adam Romanak says:

    Watched it third time now, still fascinates.

  34. PhillLsx Ga. says:

    The can got smaller and cheaper to produce now you get LESS product and it costs more!!
    Good old corporate greed at it's best!!!

  35. AlexTea says:

    I was never any good at physics and the thing about the way the pull tab works has literally never occurred to me. It's so obvious after it's pointed out, but I would never have realised it, was it not for this video… Thank you!

  36. HerdYa LikeGames says:

    Dude this video is great. He has a great informative, relaxing voice.

  37. Cableguy818 says:

    I triple dog dare one of my buddy’s to challenge me on aluminum cans.

  38. 544879 447360 says:

    Yet another American contribution to the everyday lives of human beings…

  39. Fleesaw The Vlogger says:

    11:37 wtf

  40. Keegan Pelton says:

    No one:

    YouTube recommendations: let’s learn about aluminum cans!

    Edit: wow that was a really good video! Thanks YouTube

  41. IronGemini says:

    Me: You’ve got class at 8am

    Also Me: Let’s watch this video about the cylindrical aluminum can and it’s history instead of sleeping

    Loved the video though, keep it up

  42. No says:

    At first I didn’t think I was even going to watch halfway through this video, and now here I sit at the end of the video having it entertained me the whole time.

  43. Nascar10100023 ! says:

    No one:

    Literally no one:

    This guy: Hey, wanna learn about cans?!

  44. dheepak g says:

    If college teaching is done like this , no one would fall asleep

  45. Francis Trayvilla says:

    That stay-on tab design is straight up mind blowing

  46. Virgelito Soon says:

    Plus one subscriber. You’re better than all of my Engineering professors combined.

  47. ocks says:

    I want to see a spherical and a cuboid can.

  48. Internal Medicine says:

    Great video. Thanks

  49. junk can says:

    Mr. Hammack's experience as a professor lends amazing well to his presentation method, delivery and performance. Amazing how decades of work can appear so effortless in the end. Wish some of my Cal professors were so good.

  50. rab woody says:

    All you need to know about cans but didn't know you wanted to know..cool!

  51. enterBJ40 says:

    Finally I CAN understand how it's made. 😉

  52. amadeusb4 says:

    Very well done, especially the pull tab description and explanation which is rarely provided. Thank you.

  53. Max Jacobi says:

    I always thought cans have stupid design. You're licking all the dirt from the top while drinking.

  54. Graham Kane says:

    Aluminum for foods, causes liver desease.

  55. Alex Abadi says:

    Thanks, very well made video, you actually did more than you can !

  56. DiyEm WatJay says:

    Great presentation but you forgot one more ingenious feature. The tab ring server as as STRAW holder. Please add that at the end.

  57. Texlith Graves says:

    For some reason when I hear him speaking at different points, I feel like I'm being given a lesson by Q from Star Trek.

  58. Sunny Islam says:

    Omg you did Phd on these can. Great

  59. Patty Daniels says:

    How do you save alluminum by reducing the size of the can? Don't you need more of them to store the same volume of liquid?

  60. Mike c says:

    Fantastic video…

  61. Ursine Warrior says:

    Man, these midnight youtube adventures are something else…

  62. Jorgi Petropov says:

    Fascinating.

  63. David Christopher says:

    Nice!

  64. s soldner says:

    can this guy lead a tour of the box factory?

  65. ** says:

    This was way more fascinating than it had any right to be

  66. Shmoe G. says:

    thank you YouTube for showing me this

  67. Pieter Kock says:

    Why people dont like this?

  68. Dreamster399 says:

    So great! Love this stuuff.

  69. Epic Johnny says:

    Love the video, and you Bill. WINK (call me)

  70. J A says:

    sounds like the plumbus if you squint

  71. glebeboi says:

    You left a can design category out. After the ring pull can there were the pop tops. The top of the can had 2 round disc/button shapes sealed in place by the pressure of the contents, 1 small & 1 large one directly opposite each other. To open you had to press the small one first which would break the seal and release the pressure so you could then press the second one to drink from.
    Also, you should have mentioned that the current stay on tab design was created to fulfil a dual purpose. Not only is it used to open the can with but the large open circle in the tab is for inserting and keeping hold of your straw in place. cheers

  72. God says:

    Thank you YouTube.

  73. ThrustFrom Behind says:

    I want a Cube Can, to finally finish the Illusion of living in Minecraft

  74. Joy Chapman says:

    Me: Hey google, what is this?
    holds up soda can
    Google: THAT IS A ALUMINUM BEVERAGE
    CAN.
    Me: uhhhhhhh ok.

  75. Pstain says:

    This guy really loves cans

  76. peter decordova says:

    I know full well that both spellings are correct, but I'm just saying the world would be a better place if you could just say aluminium…

  77. Ilya Liviz says:

    Brilliant!

  78. Electronic Music 2017 says:

    good science, but at the end of the day, if one can afford, would be better to drink only from glass containers. Coating or not, the taste is different!

  79. Fly house of truth says:

    But you have to drink it all at once or it goes flat. Do a video on 2litter plastic bottles. With screw on tops.

  80. Byte King says:

    Haven't you heard the word?

    can-shaped

  81. Ron Jay says:

    Look people is it natural that your drink comes in something made of metal know it isn't therefore for it is wrong or maybe cook something in aluminum this is all for the idiots that don't know any better

  82. Anonymous says:

    Quite an accomplishment! (Not the subject matter, but enthralling me enough to watch a video about engineering, manufacturing, and cans several times in a row!)

  83. Daniel says:

    Yes, we CAN – engineerguy

  84. Mr. T. says:

    Aluminum cans are dogshit

  85. Sheldon Bass says:

    Pleasantly inculcating. Thumbs up. I may be at the wrong venue for this question, but… Manufacturers of aluminum products, such as these cans—in what form do they purchase the aluminum for their products? I'd assume for cans it's bought in sheets. But what forms are available, like for making aircraft or engine parts—bricks, large slabs, or cubes, perhaps?

  86. m w says:

    Well, You learn something new every day.

  87. Christopher Meyer says:

    That's absolutely amazing

  88. Johnny W says:

    Brilliant.

  89. Ian Flanagan says:

    But do real question is do the illuminati drink out of pyramid shaped cans with the pull tab where the all seeing eye is supposed to be?

  90. Imustfly says:

    As a USAF 7 level tech. training instructor, Lowry AFB, CO (90-93), I taught quality assurance to NCO's from bases around the world, who'd come in for the course. We'd travel out to the Coors plant in Golden, Colorado to study (no kidding) their quality control processes. Right across the highway from the brewery, was Coors' own aluminum can plant,….I think the place was nearly a mile long. Long story short,….the 75 ton presses (many in a row) would put the smallest progressive scores on ribbons of aluminum,….that eventually became the sophisticated little pop top lid, that would eventually be attached to the can. The precision with which their presses worked was amazing,…so loud and powerful that you could feel the floor shake, but so precise as to put hair thin, progressively deeper and deeper scores in thin aluminum ribbons. Their process was so precise that the pop top was engineered to open at 3.5 pounds of force. They figured that amount was what would be tolerable to the average person. They would randomly take a stack of finished lids, put them on an articulated machine in a separate QC room, and digitally record the force that the machine used to pop the top. 3.5lbs, right on the mark,….with VERY little variation. Their cans were/are so good, that scores of manufacturers (and rival beer breweries) buy all their cans from COORS !!! We always finished with in the "hospitality center" for a taste of 29º Coors banquet beer that had just been filtered through 40 (FORTY) feet 2" thick, 18" diameter, cotton wafers filters. AMAZING PLACE.

  91. Ronnie G says:

    Such a shame that the streets and lanes of Britain and possibly the world are littered with this recyclable material.
    Many young people who protest about climate change are the culprits

  92. Don Webber says:

    Excellent video!

  93. Dadahabib says:

    I accidently cut myself by just look at those cut in half cans. The sides look fucking sharp

  94. Victor PONCE says:

    I am not an engineer. But i am always looking at packaging over the years how itnhas evolved. I notice subltle changes the average person will overlook. I always wonder who was the engineer that designed this, this maybe a plastic lid on a soft drink cup. Well now it seems an ENGINEER has made an interesting video on the complexity of an aluminum can. Its design is fascinating. Thank u sir. 🗽🔧🔩🔨

  95. Kalitoz says:

    This is one of the best YouTube channels out there, amazing, subscribing right now!

  96. smiley says:

    So many likes and views. And it was good.

  97. Sia LaterZ says:

    Better than How It’s Made

  98. CivilAviation1 says:

    If this guy had been a teacher at my school I now'd be a harvard graduate.

  99. flyswryan says:

    Kudos to my hero, Ed Escallon, for figuring this out, designing the tooling, and setting up the first line, back in the mid-70’s, all in Indiana!

  100. Dan Roberts says:

    OK, who knew there was such a thing as a cuboid before watching this video?

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