Why don't we make beer cans out of Granite?

[Ranger Mike]

Seriously...Granite is 2% heavier than aluminum and takes considerably more time to change with ambient temperature. I value your input. all suggestions welcome.

 

[mfb]

How strong is granite in a layer as thick as aluminium beer cans?

 

[William White]

seriously...imagine how difficult to form it is.rolling and forming thin sheets of metal is a piece of cake...stone, not so much

Then consider its tendency to brittle fracture when thin (what happens when you drop it?)

there are millions of practical reasons why aluminium is used.

you need to check out some information on

"thin walled pressure vessels"

and see why certain materials are favoured.

 

[Merlin3189]

What manufacturing process would you use?
What raw material? (I know it's granite, but are you mining rocks or do you have some other source in mind?)
Alumnium takes a fair bit of energy to extract, so you're in with a chance, but do you know how much energy would be needed to melt and cast granite or to machine solid lumps into cylinders or whatever.My own can holder is a cylinder of neoprene that slides over the can. Probably the same extra weight as your 1%, but no loss in strength and much greater insulation (time to change with ambient temp?)

 

[Ranger Mike]

good points all... i know aluminum has much more elasticity than granite. i think granite has zero modulus of elasticity as it breaks when under excess load.
i know that due to varying content of mica, granite is a natural sound deadening material. Aluminum is subject to resonance at some point is any kind of friction is applied.
believe me fellow posters ..there is a reason i ask this question.

 

[William White]

okay, so you need to look up thin walled pressure vessels like I said

work out the axial and radial stresses due to the contents.

work out what is more suitable - ally or stone.

then consider dropping it so the can lands on corner (which is a natural stress raiser anyway). Work out the stress there. Is the granite going to fracture?

 

[Baluncore]

Granite is strong in compression but not in tension. The internal beer is under pressure.
The closest thing we have to granite is ceramic materials. It was once used for beer bottles but had thick walls.

 

[Nidum]

Beer can thickness granite is likely to be both porous and semi-transparent .

 

[jlefevre76]

Yeah, ditto to what all of the others have said above. Brittle materials are not easy or even possible to form using some processes (like drawing/deep drawing that would be used to make a steel or aluminum can). Also, brittle materials don't absorb energy (high Young's modulus, and they don't deform plastically), so a dropped soda can would break into tiny pieces. Also note, the strength often quoted on ceramics is their compressive strength. They are usually far weaker in tensile strength (that's why they usually undergo flexural strength tests to find their failure stress on the tensile loaded side).

 

[Merlin3189]

So what we have to figure really, is why he's asking this question.

 

[DaveC426913]

So what we have to figure really, is why he's asking this question.

I'd bet a good sum of your paycheque he's thinking he can invent a new product that would keep beer cooler.

 

[Ranger Mike]

Actually the reason for asking is more mundane and a lot less enjoyable than drinking beer. I sell Cmms. Coordinate Measuring Machines. These are X,Y and Z axis servo driven machines of the traditional bridge design. Since invented in 1959 these Cmms have been made with granite. Almost all Cmms made today still use a granite table for the base. But unlike the ones I sell, todays competitors use aluminum or ceramic coated aluminum for the bridge and Z axis quill. From strictly a marketing point of view the reason for asking why we don’t make beer cans from granite could be answered with” for the same reason new don’t make gage blocks from Aluminum”.

The only advantage of using aluminum is that it weighs 2% less than granite. The air bearings on an aluminum Cmm are held on using Belleville cone washers. This , to me, is not a good method for the long term due to cyclical failure. They are used to counter thermal expansion which is a real problem for the aluminum bridge and Z axis as these are covered with bellows to keep the machined ways clean. The DC motors under these covers generate heat. And aluminum does not like heat. In fact , the scales must be mounted to stainless steel scale mounts and these are bolted on the aluminum structure on one end and the scale housing “Floats”. On my granite Cmms the scales are taped on to the hand lapped granite itself.
The major marketing ploy my competition uses is the CMM maximum acceleration of 1200 mm/sec. My CMM max acceleration is 800 mm/second. They tout the faster speed means higher thru put of measurement. Strictly bogus bunk since no one measures the apart at that speed.

My countering points are that granite Cmms accuracy comes from quality of components and quality of assembly. All Cmms have 21 errors of geometry . Flatness, straightness, Squareness yaw, pitch and roll and scale count in XYZ axis = 21. These errors are resolved by hand lapping or computer compensation. Granite Cmms are intrinsically accurate and the only compensation is to calibrate the scale count to true linearity with a laser interferometer. The Squareness is compensated as well (this is a static compensation). All other parameters are hand lapped to make the CMM intrinsically accurate. Granite cmms end up having volumetric accuracy of 2 to 3 micron uncertainty.
Aluminum Cmms use a computer error map to provide accuracy. The volumetric accuracy without the error map would be 50 micron. They market the compensated accuracy as the same as granite cmms.
Hence my odd questions these past year about digital scales, Belleville washers and granite beer cans..
I thank you for your valued input and will stick with race car suspensions in future...it’s a lot simpler!

 

[Baluncore]

The only advantage of using aluminum is that it weighs 2% less than granite.

You can roll aluminium into a very thin sheet. When you roll granite you end up with a gravel roadway made from crushed rock.

Thermal conduction and tensile stregth of Al is far greater than granite. If you place Al in direct sunlight, it does not fracture or exfoliate like granite subjected to daily heating and cooling cycles.

Al is homogeneous. Granite is characterised by very large grains of quarts, feldspar and mica. Rhyolite is a volcanic rock with the same composition, but with a much finer grain. If you built beer containers from rhyolite you end up with an opaque glass bottle.

 

[Ranger Mike]

Good points all, from the Master!
I would add that because Al is homogeneous it makes for a noisier CMM as at some point it has resonance. It becomes a tuning fork. Because Granite has varying content of mica it is naturally sound deadening and makes for the quietest drive train operation when measuring. One nice thing about granite is modulus of eleasticity is nil and it will fracture when excess load is applied. Al flexes and is springy. Accuracy and repeatability of measurement to the micron requires stiff structure that does not flex or distort.
Finally, test s show that it takes 8 hours for granite to grow thermally..not so with AL.

 

[SteamKing]

You are assuming that just because someone uses aluminum to fabricate a piece of a CMM which was formerly made of granite, you can use (or should use) granite to make something which is presently fabricated from aluminum.

A much better question to ask is "Why can't I make an airplane out of granite?"

 

[KSG4592]

I worked in a granite shop moving and cutting slabs for most of my young working life, and granite tends to break rather easily. It wouldn't hold up well as a drink holder. Not to mention it would easily shatter my glass tabletop.

 

[Baluncore]

Interesting things can happen when the acoustic impedance of all the discrete minerals in the matrix of a rock are matched. It can produce a rock called a “phonolite” that rings like a bell. See; https://en.wikipedia.org/wiki/Phonolite

Notice that the phonolites are at the opposite end of the SiO2 axis to rhyolite and granite, so are free of quartz crystals. For quiet metrology it could be said that granite has an internal [pun]scattering matrix[/pun].

 

[Ranger Mike]

ahh, Physics humor...
fyi...the granite we use is South African black granite , impervious to water absorbing and lowww crystal content unlike pink granite from USA
much mica..we hand lap to flatnesss better than 1 micro per meter

 

[DaveC426913]

Am I still missing something here?

Your selling point for granite talks about its density being comparable to aluminium. Which means, to compete, it'll have to be of similar mass and thus thickness.

Soda can walls are on the order of 100 micrometers. I can't tell you what the thickness tolerance of them must be, in order to prevent weak spots in a pressurized container but ... are you going to hand lap a (curved )- container down to 1/10 of a millimeter in thickness with a tolerance one or two orders of magnitudes smaller? Again, without factoring in granite's brittleness and lack of tensile strength...The primary job of the can is to keep the contents in - at an economical weight. Insulation is only an afterthought.

If you want to insulate, use a thin, light insulating layer, such as bubblewrap. How does granite compete?

 

[boneh3ad]

The only advantage of using aluminum is that it weighs 2% less than granite. The air bearings on an aluminum Cmm are held on using Belleville cone washers.

It is also cheaper, much easier to work, and more durable. That would reduce the price of manufacturing a CMM and the cost of maintenance over the life of the machine. It's strength to weight ratio is also substantially higher, though that wouldn't mean much for a CMM.

This , to me, is not a good method for the long term due to cyclical failure.

I don't know all that much about the loading on these machines, but granite is also prone to cyclical failure (as is any other material). An advantage of granite is that it is not likely to plastically deform much, so throughout its life, it will likely maintain very nearly the same shape and flatness as when it was first manufactured. The downside is that you don't know when it is going to fail until one day it just fractures abruptly. Of course, I couldn't begin to tell you the fatigue life of granite versus aluminum, so who knows if that is ever likely to be an issue.

I would add that because Al is homogeneous it makes for a noisier CMM as at some point it has resonance. It becomes a tuning fork.

I guarantee you that granite can also undergo resonance. It would be at entirely different frequencies and may be less of a problem, but it will definitely have a resonant frequency (or frequencies). I would definitely believe that a granite CMM is quieter, though.

 

[Ranger Mike]

My reason for this question is to develop features and benefits traditional granite vs aluminum in Cmms. The obsurd granite beer can was to generate exactly whet it did..great points all.

i think i am off on the % weight difference..ooops

 

[Nidum]

Have you looked at the epoxy concrete series of materials .

CNC machine structures have already been successfully designed and built using them .

 

[Ranger Mike]

yes, the company i sell for has a line of Horizontal Measurement machines using synthetic granite base. The accuracy is good enough for sheet metal automobile bodies but not for higher accuracy precision machine parts.