Minimum bending radius in aluminum 2

[Lepetit]

Hello everybody,

I need to know how can I calculate the minimun bending radius in a aluminum sheet? The sheet has a thickness of 2mm and the radius I want to bend is 90 degrees. Can someone help me?

Thank you

 

[KENAT]

Talk to a sheet metal shop?

Or assuming you know what grade of Aluminium you can look it up in machineries hand book or similar - there are even online resources if you care to google for them such as

http://www.precisionsheetmetal.com/home/materials.htm.

I'll say this though, individual sheet metal shops will often have values that don't exactly match the text book values so I'd talk to whoever is going to be making it for you.

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[btrueblood]

What Kenat said. And, different benders (more specifically, different bending processes) can achieve radii that others can't.

 

[berkshire]

Wait a minute, the minimum bending radius is a function of the type and temper of the aluminum, not the machine it is bent on.

For example bending 3003 h14 .100" thick to an inside radius of .07" is no problem. Bending 7075 T6 of the same thickness to the the same rad will result in instant breakage.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[KENAT]

Well it can also vary with the grain direction and probably some other factors that don't spring to mind right now.

I only said individual shops values didn't exactly match the text book values, not that they were way off.

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[btrueblood]

"Wait a minute, the minimum bending radius is a function of the type and temper of the aluminum, not the machine it is bent on."

Yes to first half of statement, no to the last.

I can air bend 1/8" thick 5052 H32 to a 1/4" inside radius, but any tighter and it wants to crack. But a punch press can give me clean bends with 1/32" inside radius.

With a hydroforming process, I could go even tighter.

With a hot forming process, tighter even more so.

With blast forming...

etc.

 

[btrueblood]

Oh, and you would probably want to start with O temper 7075, and post heat treat, but I've been told it is formable with care and attention.

 

[KENAT]

Well I was thinking hydroforming, super plastic forming etc. aren't really still in conventional 'sheet metal forming' arena that I assumed the OP was asking about. However, you know what assuming does.

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[berkshire]

trueblood wrote"" I can air bend 1/8" thick 5052 H32 to a 1/4" inside radius, but any tighter and it wants to crack. But a punch press can give me clean bends with 1/32" inside radius.""

That does not compute - One: 5052 h32 will airbend to less than a 1/4" inside rad with no problem. At 1/8" inside radius it will be showing some orange peel on the outside of the bend.
Two: to do a 1/32' inside rad on a press brake you would have to be coining the part, which would close up and hide any incipient cracking in the part.
B.E.


The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[berkshire]

This may help the OP. This is a reprint from Alcoa table 4 .

http://www.aircraftstamping.com/radii4coldbend.htm

I am doing this before this post degenerates into a war of opinions.

B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[KENAT]

You've got me thinking though berkshire, for a structural application such as I suspect you're typically involved in any cracks or similar surface deformities would need to be avoided for functional reasons.

However, for many of my designs this would be less critical as I don't have much loading or fatigue etc. If this is what my sheet metal shop is used to then maybe that's why they'll quote smaller radii.

Hmm, nice link, a bit more detailed than mine!

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[btrueblood]

My point was that the process can dictate capability. Your ability to air bend I will not debate. Your assertion that cracks can be generated by and then hidden by compressive forces I will also not debate.

 

[berkshire]

Actually Ken your table and mine complement each other.
And you are right about cracks being avoided for structural reasons. The latter part of my career was making structural aluminum panels for the outside of buildings. If these things crack when forming, they tend to fall off in high winds much to the dismay of pedestrians. So it was imperative that product quality be maintained. This used to cause conflicts between architects who wanted sharp corners and sheet metal shops that could not produce them.
B.E.


The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[Lepetit]

Thank you everybody for your fast answer. I will check that links and also I would ask to the workshop where I am going to make the aluminium profiles.

By the way, it's possible to obtain a approximate value using a formula? I'd like to know due to I want to be sure of my design.

Thanks again!

 

[KENAT]

berkshire - the table I posted isn't from my manufacturer, it's actually one I used for other information than the bend table - but it was to hand to answer the OP's question.

Lepetit, does berkshires link not have your case. I think machineries has some tables & formula related to this. However as you can see from berkshire and my links - it's not a simple linear relationship between thickness and bend radii.

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[berkshire]

Ken I am guilty of the same thing. The table I posted is Table 4 from Alcoa's book "forming Alcoa aluminum", I did not want to be guilty of plagiarizing So I went on line and found somebody who had already done that, and used their link.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor