Thickness of aluminum cans, part 2

Factual Questions
1

Dangit! I accidentally deleted Mr. J’s thread. Luckily I copied off my cache version the following:

Mr J. Speaking:
Well that didn’t quite work I will try again and then contact mr nick. (all sorts of strange stuf has been happening to me ever since i did NOT discover and did NOT go to the private forums,which do Not exist. Almost as if THEY{who also do NOT exist} are trying to discourage me.) Here we go:
Sorry to start another thread,but search’s WAGs are totally without foundation. i can’t find the original. here is an Email i sent to two engineers at alcoa. and the answer one of them sent.
Gentlemen;
It is a debate I am involved in. Given that soda cans are harder to crush than beer cans; Is there a difference in the wall thickness of a beer can and a soda pop can? Or another structural difference that would make a soda can harder to crush? If so why? My hypothesis is that soda cans are thicker due to more pressure from the carbonation. If you shoot me down I won’t mind. If either of you can help me, I promise to drink even more beer, thereby increasing the amount of aluminum recycled. In closing I would like to remind you of some words from the movie “The Graduate”, “Mrs. Robinson, you’re trying to seduce me…Aren’t you?” thanx, Al

Well, yes and no. (now that i see that in juxtaposition it seems real strange,mj)
Yes, soda has more carbonation than beer. Typically about 3.5 volumes of CO2 for soda (sprite is higher, Fanta is lower), and only 2.7 for beer.This means on a hot day in the back of a delivery truck soda cans will have higher pressure than beer cans, perhaps 90 psi compared with 60 psi.But the crush load of a can (resistance to standing on it) is a requirementof the necking and filling operations, not the product inside. Necking is the metal forming operation on the can to allow the lid diameter to be smaller.(So that’s what necking is.What were my parents so worried about?mj) Beer and soda cans have the same requirements in this regard.My guess is that you buy good quality beer and lousy quality soda. Lots of
soda bottlers buy cans strictly on price, and those outdated can designs and equipment have much higher performance (and in many cases performance requirements) than the newer, more highly-engineered cans.
Of course, these comments are my own and do not reflect the opinions of my gracious employer.
Cheers,
abt

Turns out every body was right and wrong. At least those of us on the more pop in pop were right, but the entire thick can theory was bogus. To paraphrase ,some cans are thick some are thin,some have wide necks some narrow but not because of the pressure.It’s because of the machine they use to pour the stuff in. At least the research involved in comparing neck sizes was interesting, even if it was a lot of work to empty all those (burp,'scuse) beer cans ,so i wouldn’t strain myself holding them against the soda cans.

“Pardon me while I have a strange interlude.”-Marx

pmh
Member posted 08-24-1999 02:04 AM

quote:

But the crush load of a can (resistance to standing on it) is a requirementof the necking and filling operations

Is that the answer? MechEs please translate. My statics class was a long time ago.

FTR, the original thread is at

http://www.straightdope.com/ubb/Forum3/HTML/001959.html

2

pmh, look at the top of a Coke can. Notice the taper from the body of a can to the mouth. That’s the neck. Now, assume a vertical load evenly distributed around the rim. This will result in bending + axial stresses in the neck which greatly exceed the compressive stresses in the body (P/A). Therefore, that’s where failure will initially occur. Once the neck fails, you’ll end up with an eccentrically applied load in the body, resulting in bending moments there, greatly increasing the stresses and resulting in can crush.

3

Hmmm, I have yet to do a buckling analysis using a finite element modeler (I just do static and thermal analyses), but I may just have to give it a shot with this. Stay tuned.

4

you done good nick. that’s what I wanted.
I have a reply from the other engineer now. These two guys are working on making the cans ever more thinner! They each received the same mail from me BTW the other guy is Andrew Trageser, I gotta go buy some more canned beer to pay them back. The letter;

Probably the biggest difference is that soft drink companies have a minimum
sidewall thickness specification whereas most beer companies do not. Thus beer cans tend to be lighter. Both still have minimum requirements for axial column strength. Thank you for the inquiry.

Bob Dick
Technical Specialist
Rigid Packaging Design and Development Division

me again’ Axial column strength’,‘crush load’ ain’t scientifical talk cool? I used to work in flexible package art design,we didn’t have no axial column strength, about the biggest problem we had was that we never did find a good substitute for real potato chips in a package mockup,specialy if there was a window. For cheeto type things styrofoam peanuts were great,if there was a window we just backed it up with a piece of amber tintscreen, looked like the real thing. ( Tasted like some of the products I designed for too) Iam still not satisied by all his technical jargon,I am going to buy another case of beer and continue the research. Maybe a bag of pretzels too, I always buy the ones in a package that I designed. I have no resistance to that subliminal stuff hidden all over them.

“Pardon me while I have a strange interlude.”-Marx

5

I have some empty pop cans at my desk, full beer cans in the fridge (Bud and MGD, left over from my b-day party. “Normally I drink out of bottles, but for this I’ll use cans, eh”), a knife, and access to a digital Vernier caliper. If y’all are interested, I’ll cut open some empties and measure the pop can wall thinknesses vs. the beer can wall thicknesses. All in the name of science. I need to see if the OP specified specific brands of pop and beer.

Sorry I’m so late posting, I haven’t been following this thread until today.

6

I was under the impression that higher internal pressure (from carbonization) actually made it possible for cans to be thinner. The main stress pop and beer cans are under is stacking weight- those cases stacked eight feet high at the supermarket. “Inflating” the cans with internal pressure helps them resist buckling under external loads. If this is not so, I stand corrected. But it does seem that products that aren’t carbonated (fruit juice, etc) still come in those thick sturdy cans.

7

Strainger, I know what the neck is, What I want to know is: What effect (if any) does the diameter of the top / angle of the neck (wrt vertical) have on the “crush load” of the can? (see the original thread for the argument)

I tried this in the original thread (and w/ 9 different beers and 11 different soda varieties since). Found they are the same (to within .0005"). But more data is always useful.

Please do! My attempts to figure it out with a bathroom scale and freeweights is pitiful.

Now? Now am I taking this too seriously?

WOTSB

8

pmh, after reading through the original thread, I realized that I had totally misunderstood your question. Sorry about that. A larger angle wrt vertical would be worse with regard to yield strength, but I admit I still have some things to learn about structural instability.

Sounds like you have plenty of data points. I’ll just measure the dimensions I need to create a FEM. samclem, was there a prevalent brand among the beers and pops? If so, let me know and I’ll model based on the dimensions of those cans.

Hey, it’s what us geeks consider “fun!”

9

Hello
I am working on a project, interested in the design details of beverage can lid. Hoping someone out there might know the answer.

When the lid is stamped, is the thickness of the can the same throughout, or does the thickness of the aluminum gradually reduce toward the center of the can lid. ??

Thanks
Cmod

10

I don’t know if you realize it, but you revived a conversation from 1999, and some of the participants aren’t even here any more.

11

zombie or no

so you’re saying the thread has fizzled?

12

The lid is made from a disc of metal the same thickness throughout - it is embossed, contoured and scored, but none of that significantly affects the thickness worth mentioning.

The can itself also starts off as a disc, drawn into an open topped cylinder by a series of pressings. This makes the thickness of the metal different in different places, but its complex, because as the edges are stretched upwards, they are also pulled into a smaller circumference.

13

Thanks for the quick help, and I had no idea this original string of messages was that old!! I’m new to this service, and liking it already.
For my project, I am looking for an aluminum “fin”, similar in size to a beer top, where the material is thicker on outside and gradually decreases toward the center. Can such a stamping be made?

14

Sure.
You use a convex punch.

15

My first factory job was making cans and lids for reynolds aluminum company. I have made millions of cans but cannot help with your question as it never crossed my mind to check. We used large D&I presses to create a cup from a disk, in one or two more presses it would become a can. At one point I worked quality control and measuring thickness was not part of our job.

The machines were very loud and the shifts were 12 hours, all we thought about was going home.

16

Im curious about what you’re actually trying to do with this component. Are you able to divulge any furter detail about the project?

If it’s a one off component, I’d suggest just getting a disc of aluminium and grinding it thinner in the middle with abrasives - coarse at first, then progressively finer.

17

Damn! I think the original thread that spawned this one was my first OP thread on the SDMB.

Searching says Aluminum can thickness.

I was musing on crushing my beer cans vs. my kid’s soda cans. I felt that the beer cans were thinner than pop cans.

18

Looking for an aluminum fin, similar to what’s found on a baseboard radiator element, but want the actual thickness of the fin to graduate from thicker to thinner. This is not a one off project, but high volume, which is why I was considering a can lid. They are made in the billions and are low cost. I guess I was hoping the can top was purposefully made thicker on outside/thinner inside in order to assist the operation of the pop top feature. Damn. I’m hearing from this forum that the top is uniform thickness. Bigger question: We want to move heat in a particular direction and having a thicker to thinner material will promote that conduction. Anyone know of a fin or product that is already stamped thicker-thinner? Otherwise I need a good tooling guy :wink:

19

How thick?
Extrusion is generally what is used to make these type of pieces, but I don’t know how thin an extruded piece can go.

(I had a case extruded by Minalex years ago).

20

Aluminum fin material now is 0.011" thick, so I assume we would use that thickness for the thin and grow thicker toward the outside edge. We use 100s of thousands of fins, so need high speed process to keep costs low.

Anyone out there confirm a beer can lid is uniform thickness?