force needed to bend tubing

[stephenjvb]

I'm an electronics / controls guy with a basic knowledge of mechanical engineering - possibly just enough to be dangerous. I want to bend some 3/4" aluminum 6061 tubing with a 35 or 49 mil wall. The resulting strength isn't an issue but the cost and bending force is. In some places Ive looked it seems that 49 mil tubing may be cheaper than 35 mill tubing but it will be harder to bend. Crutches are commonly made with 49 mil tubing so that may be the material to use.

It looks like I'm going to make my own bender to get the radius I need. This I can do. However I can't seem to understand the bending force calculations I would use to calculate the force I will need on the end of an arm for manual bends, important so I know how long an arm I'll need and what I need to mount the bender.

Are there any charts or simple calculations out there with even approximate calculations? I have seen the yield strength mentioned to be related to the bend force without saying exactly how they are related. I would think this is a common issue so I figure I'm just looking in the wrong place. Any help would be appreciated.

Thanks

[RWOLFEJR]

Hi and welcome to the forum,

Why 6061 aluminum tubing? I ask this because you say strength after being bent wasn't important. Unless you're buying a truckload or mill run at a time... you'll have to buy off the shelf at T6 temper and it won't appreciate being bent much. If you're putting a typical conduit bend on it which is pretty generous radius you might get away with it but I wouldn't go into this counting on it. It's likely to crack if you bend it too much. I've shattered some T6 temper aluminum a time or two...

If you don't need the strength then go with a cheaper flavor aluminum?

With a better idea of what you're doing with this I... or others here might be able to help you out.

Far as bending it goes... if it is indeed T6 temper it'll bend just a little bit harder than steel of the same cross section but will have more spring back and like I said... high likelihood of cracking. You could have it drawn back to T0 and it'd move like putty but then why bother paying for alloy if you don't need the strength?

Also... more of an F.Y.I. lighter wall material requires more processing to get it thin and that runs the cost per pound up. Unless you're buying a mill run you'll need to see what's readily available before you get too carried away.

Good Luck,
Bob

[PinkertonD]

Everything that Bob said and...

Thin wall tubing will probably require an inner mandrel to prevent it from crushing down on the inside radius. There are ways around it without a mandrel, but not simple and not always as effective. It may prove less costly to get a tube bending company to do it for you.

Again, as Bob says, if you can show and tell what you are trying to do then maybe we can give you more specific advice.