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roll forming aluminum bar the hard way

DanielG

Stainless
Joined
Oct 22, 2014
Location
Maine
I have a set of parts I'm designing. They are 1/4 to 1/3 circle pieces with 23" inside radius. The cross section is 3.5" x 3". If I make them out of steel, I'd probably just have them burned out of 3" A36, and it will be cheap and easy, but heavy.

If I need to do them in aluminum, that's going to be very expensive. Is it feasible to roll form them (the hard way) out of 3.5"x3" rectangular stock? Alloy doesn't matter, I was guessing that a 5000-series would be the way to go as it's more formable.

Thanks,
Daniel
 
Definitely an option. Roll forming would eliminate a lot of material waste, hence my interest.
 
I would talk to a specialist tube bending outfit as they should be able to answer that very quickly. I'm probably over complicating but could this be done in tubing? Getting the right dimensions could be an issue but if scale is large enough you could do a custom extrusion. Heck at that point maybe you can do a curved extrusion like making a spring. Or robotically weld the parts out of two flat curves and two rolled pieces.
 
I would talk to a specialist tube bending outfit as they should be able to answer that very quickly.

Any suggestions? I have a call into one of my vendors, but haven't heard back yet.

I'm probably over complicating but could this be done in tubing? Getting the right dimensions could be an issue but if scale is large enough you could do a custom extrusion. Heck at that point maybe you can do a curved extrusion like making a spring.

Tubing would be great, but I haven't seen anything with thick enough walls, and the quantity is low. I only need 3 or 4 parts.

Or robotically weld the parts out of two flat curves and two rolled pieces.

I'd like to avoid welding. The NDT requirements on this project for welds are rather onerous.
 
It will be machined afterwards, so not great.

Keep in mind that if you machine a severely-bent thick section, all hell may break loose -- machine away parts of the outside material that is in tension and the inside material that is in compression, and the thing may go all wonky on you when you unclamp it.

Regards.

Mike
 
and the quantity is low. I only need 3 or 4 parts

Cut from plate, ''setting up'' bending machines is seldom plug and play AKA waste material, plus you will lock in stresses which will come out with machining, and don't forget modern CNC profiling programs can nest parts like most humans wouldn't even dream possible.
 
You don't mention how many you need to make, but an aluminum casting might be the most economical if you need more than a few of them. The pattern would be pretty simple, and you could nest two parts in 1 mold with the gates and risers between the two parts.
 
I only need 3 or 4 parts.

Aluminum shouldn't be that much more expensive than a36. More per pound, but a pound of aluminum takes
up 3 times more room..

I don't think having them bent is going to be much fun.. First, you have to find somebody with the equipment to
do it, then you have to find somebody that has the equipment to do it, that is WILLING to do it. Then you have
to find somebody that has the equipment to do it, and is willing to do it, and quotes a price that that doesn't
make you puke all over the floor.

Then when it comes in, it could be pretty ugly, I don't think you are going to end up with 2 nice flat surfaces
to play with. And like others have said, stresses..

I'm not 100% sure what the heck you are doing, but my first inclination would be to get them waterjet out of plate.
2nd would be to just buy the plate and hog it myself.


I hate jobs where material choice and cost is all over the place, and what is going to make it the easiest to machine
etc.... You can waste a ton of time chasing down the best option, sometimes you can lose a lot of sleep over it too.
 
Mill them or waterjet them. If you really want to bend them, do the stress numbers first on the OD and ID. I suspect the stresses will be too high and will cause cracking. Not to mention the thinning on the outside and thickening on the inside.

When there's only a few pieces required, it almost always seems to be cheaper to go the more wasteful but guaranteed results method.
 
Regarding specialist bending outfits, I assume they are pretty common as we have more than one here in Greater Vancouver. I use a shop in Langley BC called Aggressive Bending, as they are good and I like the name! I like the casting idea but if you're only making 3-4 parts, for sure plate. The waste material factor for a 1/4 or 1/3 turn isn't so bad as a whole ring either.
 
Over 20 years ago NASA wanted us to bend 3 X 6" 6061 T 651 the hard way with a much larger radius - like six feet

They sent over the material and the first piece thru the huge Bertch plate roll broke with a sound like a cannon shot that could be heard all over the 300 man shop. We cancelled.:D
 








 
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