Aluminium bending

[Jacktegla]

Question for all you clever bending folk out there, I had a sump guard o nrhe rally car that needed a slight tweek to the correct angle and when tried to be bent it cracked, so I'm after a new one now I've got a piece of 10mm aluminium and need to decide how to bend it to the corrent angle, angle is no more than 15degrees, I have access to pressbrake and a powered hydroform so I'm wondering which is more likely to be better for bending with less chance of cracking aluminium

Ps no idea on grades of Ali

 

[Shox Dr]

Grade of Aluminium will be factor, along with bend direction. It may also require annealing

 

[Jacktegla]

Grade of Aluminium will be factor, along with bend direction. It may also require annealing

No idea on grade unfortunately. Direction ? I presumed it would require annealing and I think this is what was missed on other one that cracked just trying to work out if there was and advantage of hydroforming over using a pressbrake

 

[Jacktegla]

For something like a sump guard that isn't structural I expect heating it along the bend area will be fine

Heating along line and just bending on bench ? Surely using some form of bending machine would be easier and would yiu not have to get ali very hot to just bend, or have I got wrong end of stick

 

[Shox Dr]

Direction

Rolled material will have a 'grain' in the direction of rolling. More of a probelm with Ali

 

[Jacktegla]

ahh ok which direction would be best to bend on following the grain with bend or other way cutting across the grain

 

[Shox Dr]

Across the grain

 

[bricol]

Needs annealing - heating to around 770F and then air cooling - rub soap over it and when it turns black, its hot enough. That's not full, proper annealing, but good enough for what you want. Bending it might restore some of the hardness, so don't be trying to bend it back. Annealing should also help with not cracking along the grain.

10mm thick ali sump guards isn't exactly going to be light - why not use some 3-4m steel, gain a tiny bit of ground clearance that might just clear some of the stuff you might shove into the ali one? Easer to weld mounting tabs on to as well.

I have a theory, totally unproven, a steel underguard slides easier over projections than an ali one.

 

[tom2207]

Id keep the 10mm plate for welding on or the likes , and get a bit of nice chquer plate , either alloy or stainless and bent it to suit , but put the chequer side to the inside , leaves an interesting pattern on the outside but not snaggy

 

[voipio]

Welding the cracks might be an option.

 

[Keith 66]

I was taught at college, to anneal aluminium paint a strip of soft soap on it, heat until soap goes dark brown then quench with water. Always worked for me.
Best one i did was a set of 4 volvo duo prop boat propellors, about 19" in diameter they had been driven over a concrete causeway at 40 knots & resembled something from an aeroplane crash. It must have been a very expensive noise!
It took a lot of beating & multiple anneals before i got them straightened out.
It won me a 50 quid bet with a local marine engineer who said it couldnt be done!
But they were not guarranteed afterwards!

 

[Munkul]

None of this advice is any good if the OP is using too small a press tool for bending. You need minimum 6x thickness for the V opening on a press brake, to avoid cracking the alloy, and sometimes bigger. That's a v60 minimum but ideally a v70 or 80.

 

[bricol]

I was taught at college, to anneal aluminium paint a strip of soft soap on it, heat until soap goes dark brown then quench with water. Always worked for me.

I reckon you can find as many references to quenching aluminium after annealing as for allowing it to cool slowly, or more controlled.

From my dimly remembered Metallurgy/Materials Science degree first year back in 1988, with quenching, the theory is it freezes the grain struture and stops/slows age hardening, but I think it also re-hardens to a good degree, even if it is softer than before.

Slower cooling creates a softer material more easily worked as the grain grows more.

I've only ever found a few references that the rate of cooling is irrelevant - which I suppose is what the many references to both quench/slow cool really proves

 

[500e]

6mm is plenty unless you have a big unsupported aeria. Never liked the cast ones on Escorts we used 5 or 6mm with wood bearers, never lost a sump
On the Midgets we used 3mm steel sheet on wood wood bearers, you don't get much lower than those