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Bending Alu Tube to Tight Radius?

Dr. Rob

Hot Rolled
Joined
Nov 25, 2002
Location
Sweden
Got a thing on the agenda here..

Bending aluminum tube of the 6061 variety, OD 30 mm with a 5 mm wall, 90 degree bend... with a radius of two inches. Not sure if that radius spec is inside, outside or center line. Say it is inside for the time being.

What say you?

We need to do a few of them; say a dozen. And we have a Euromac bender, it works on a principle similar to a Hossfeldt. Can use shoe or rollers; that's not a problem.

Whaddya figger... will it crack? Best to do hot? Or filled with that low-temp melt alloy stuff?

Hmm.

.
 

Jeff D.

Aluminum
Joined
Jul 11, 2007
Location
Spanish Fort, AL
6061 aluminum derives some of its strength from a heat treating and tempering process. I am sure that it can be "warmed" safey up to some point without considerably affecting its strength, but I know that welding leaves it considerably softer.
 

powerglider

Stainless
Joined
Oct 13, 2006
Location
Mediapolis, Iowa
I say you have a good chance at not cracking since the wall thickness is pretty good.

It will distort quite a bit, won't look like a round tube in the bent area.

I bend 3/4" OD, .058 wall aluminum tubing, 6061-T6, in 2" CLR with my Diacro #3 bender and it distorts a bit, but no cracks.

I use a die and follow block, is that the same for your bender?
 

Limy Sami

Diamond
Joined
Jan 7, 2007
Location
Norfolk, UK
30mm tube at say 50mm inside rad, makes that 65mm centre rad?

With compression bending, ie former & guide/shoe, normally a radius of 3 X D (=90mm) is considered the minimum, so IME you're in mandrel bending country and more than likely with heat treat issues.
 

biometrics

Cast Iron
Joined
Apr 22, 2008
Location
Northern VA
Fill the tubes with water and freeze solid until the bend operation. The ice will help prevent tube collapse and will drain itself with no watching necessary as soon as the tubes reach room temperature... leaves no residue.
 

scojen

Stainless
Joined
May 21, 2004
Location
Zellwood, Fl.
Freezing the tube would probably work as long as you can get it in the freezer :angry: barring that fill it with wet sand, cap off the ends with caps and tape and bend away. Yes the cap is going to come off but will contain the sand until you finish the bend. You may still get some distortion in the tube but not as bad as a empty tube.

Scott
 

Doug S.

Cast Iron
Joined
Apr 1, 2007
Location
West Michigan
Be careful with the heat. I split some similar tubing just last week, giving it a little too much heat. ( Believe it or not! ) I wanted a little more bend, but was waiting to let the heat spread a bit, and the CRaCKola magically formed. I will also admit I was bending in a tri-stand. =)

Doug S.
 

huntinguy

Cast Iron
Joined
Dec 17, 2006
Location
Washington
Iirc

If I recall. Aluminum is make workable by heating... can't remember the temperature off hand... 700- 900F... and then quenching.... I think the water should be 62....

I am getting old...........:bawling:
 

metlmunchr

Diamond
Joined
Jul 25, 2004
Location
Asheville NC USA
On a 2" CLR you're going to get subtantial flattening of the OD in a compression type bender. But if the tubing is T6 temper then you may run into cracking on the OD. That'll be hard to overcome unless you can soften the tube by overaging it. 400*F for an hour will substantially soften the tube, but the problem then is that the only way the hardness can be recovered is via a complete rerun of the solution heat treatment / aging process.

I stuck a piece of 1/2 x 3 6061-T6 flat bar in the press brake yesterday to get a rough setup for some 1100-0 flat a customer is bringing tomorrow for me to bend. The 6061 cracked all the way across at less than a 15 degree bend. Upper die had a 1/2" radius on the nose and lower was a 3" opening, so it wasn't as if I was pinching it to failure. Its worse to crack when bent "across the grain" as I was doing, and a bend in your tube will be in the same across-the-grain direction as well.
 

Doug

Diamond
Joined
Dec 16, 2002
Location
Pacific NW
.............................

400*F for an hour will substantially soften the tube, but the problem then is that the only way the hardness can be recovered is via a complete rerun of the solution heat treatment / aging process.

...................................................

Low temp heating of aluminum eases forming.

One of my aluminum handbooks has a chart showing degrees of heat versus time increments for aluminum while maintaining acceptable hardness.

The chart goes something like this (these are not the actual numbers)....300 degrees for 1/2 hour, or 400 degrees for 10 minutes, etc, etc. The higher the heat the shorter time it's allowed at that temp. As long as the heating/time conditions are not exceeded there is no appreciable long term effect of the softening.

Dimpling machines for aircraft skins use this principle to create countersunk rivet settings.
 

surplusjohn

Diamond
Joined
Apr 11, 2002
Location
Syracuse, NY USA
a crush bend will help here, that is where you dent in the tube on the inside of the radius, like the old fashioned lawn chairs, allows a tighter bend, but of course is a restriction if you are using the tube as a duct of some sort.
 

CMLbend

Plastic
Joined
Jun 17, 2009
Location
Davenport IA
What does your material finish need to look like, A crush bend is possible but will look awful. I would suggest a Mandrel bend on something that tight with that rigid of a material.
 








 
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