bending 7075 T6 aluminium

[notger]

Hi there.

until now i was using mostly steel sheets for my project.
but for the next on id like to take some aluminium.

id like to bend 3mm 7075 T6 aluminium sheets by 90 degrees.
i know i could read bending radius from charts but id like to hear some real experiences.

does anyone know what would be a realistic minimal radius for 3mm aluminium sheets?
Without weakening the material too much.
or would "normal " 7075 be easier or better to ben and still stiff enough?

its about this part....


thanks in advance

Gernot

 

[Deafcat]

use a brake press? I don't know how 7075 bends though, I'd never recommend that alloy unless you know you need it. it cannot be anodized, and corrodes and stains easily... typically used for machined aircraft parts.

use 5052, it's the aluminum we typically use in fabrication and it can be bent properly even up to 1/4" sheet thicknesses. for a 1/8" sheet (3mm), typical inside bend radius is 1/8" (same radius as thickness is a good rule of thumb for bending aluminum)

If you don't have access to a full brake press, a hand brake could work, but it may be very difficult with something like 3mm aluminum. they are typically used with light guage steel.

 

[notger]

use a brake press? I don't know how 7075 bends though, I'd never recommend that alloy unless you know you need it. it cannot be anodized, and corrodes and stains easily... typically used for machined aircraft parts.

use 5052, it's the aluminum we typically use in fabrication and it can be bent properly even up to 1/4" sheet thicknesses. for a 1/8" sheet (3mm), typical inside bend radius is 1/8" (same radius as thickness is a good rule of thumb for bending aluminum)

hi, thanks for the quick answer.

but sure i will use a brake press,
still... a brake press can fore the material to any radius, but it might just destroy the stability of the marieal in the bend.

i guess you see wich part of a mid drive motor kit it will get (in my added file), so there is a lot of torque on it (up to 3000 electrical Watts )
will 5052 be strong/hard/stiff enough to not bend?

greets

Gernot

 

[speedmd]

Make sure what ever sheet AL alloy you use to bend across (90 degrees to) the grain direction. Much less likely to split or fail prematurely at the bend.

http://www.clintonaluminum.com/which-aluminum-alloy-bends-best/

 

[Deafcat]

if using the correct bend radius and bottom die, the aluminum should never fail at the bend *unless* the part is not engineered accordingly to the mechanical stresses**. if the material is bent with too tight a bottom die, you will be able to see visible small lines (crazing) following the bend, this would be a good sign that you have not allowed enough radius for the particular material... K-factors vary between different aluminum alloy sheets from different suppliers.

one alternative to consider: using aluminum extusion (angle), coupled with sheet sections with less aggressive bends, riveted or TIG welded together. we build a lot of stuff this way for heavy-load vehicles and it's typically preferred.

**it would be uncommon to find bent aluminum sheet components being used for structural elements, the method above is used.



note: grain direction is also often ignored for most aluminum bending, though it does make sense to follow it for material thickness above 3/16" and especially if the part will be subjected to greater stress.


edit: for that particular bracket you attached, if part is not strong enough in aluminum and thicker sheet can't be used, I would make it out of mild steel instead (as is the typical approach for such a part). 12 guage steel will be stronger than 3mm aluminum, and not much heavier (weight reduction cutouts can be incorporated if you know how to maintain the strength). or, you can use 10 guage which is similar thickness to 3mm, and have super strength

 

[speedmd]

+1 on the extruded angle or channel use.

 

[major]

I think it will crack at the bend due to the T6 temper. That's been my experience. I used normal (not tempered) for parts requiring bends.

 

[WoodlandHills]

+1 on the extruded angle or channel use.

Ditto, I built the ducting for the downdraft radiator on my Lotus 11 replica using just that technique, same with the storage area under the Le Mans tail. Works great for 90* angles, the rest you have to form yourself. If you have sufficient reserve strength in the part you could anneal it along the bend line using the torch and soot method to prevent cracking, but you won't be T6 anymore there. Forming the part will cold work it and put a bit of strength back in there though, how much is best left for the engineers to figure out

 

[Deafcat]

not only will annealing wipe out the temper of aluminum, it may weaken it considerably for its ability to handle mechanical stress in the long run. annealing is fine for cosmetic aluminum parts with aggressive forming operations, though.

Will also recommend not using *any* alloy of aluminum with T6 or T651 tempers in a process involving bends. very likely to crack, even with a minor angle bend it may weaken and embrittle the material in that area, ensuring it will fail eventually.

 

[Chalo]

Form it in T0 temper, then have it heat treated back to T6.

My experience suggests that 7075-T6 doesn't like to be bent even a little, let alone 90 degrees. That's a job for 5052 alloy.

 

[MrDude_1]

Alloys and structural choices aside, I bend sheet aluminum 90* by using angle iron in my press.

 

[notger]

ok, i think i leafe the 7075t6 idea.

anyone experiences with 5052 or 6061 (t? hardened) and bending 90 degrees with 3mm thickness with raius around 3mm ?

is 5052 t? still stiff enough for a bottom bracket like mine ? what do you think ??

i just do not want to give up on the idea with bended sheets so fast, cause of simplicity.
But sure extruded angels would be the best sollution.

Greets

Notger

 

[Miles]

is 5052 t? still stiff enough for a bottom bracket like mine ? what do you think ??

The difference in elastic modulus between 7075 and 5052 is hardly worth agonising over...

 

[Mikebergy]

If you want it from 7075, why not just get the part machined, and eliminate the bending? Have any any calculations been done to see what actual loads will be on the part?