I am designing a part that needs a 10in radius bend in 11ga mild steel. Due to the nature of the part I cannot roll it. To increase speed of manufacture and bend surface quality, I would like to try and bend this part in one shot. So I would rather not bump form if I can avoid it. I am having troubles finding any calculations to calculate sprinback and final radius of such a large bend. I need this so I can design a die with the correct initial radius to result in a final 10in radius. Any of the equations I have used do not give me an answer I am confident will work. Can anyone point me to a calculation for very large profound radius bends?
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Very Large Radius Bending
- Thread starter LGSwensen
- Start date
- Replies 15
- Views 3,392
azmachining
Cast Iron
- Joined
- Dec 26, 2014
- Location
- Central Valley, AZ
The Fabricator has it, I can't tell you exactly where, but that's where I think I found it when I needed it awhile ago.
SteveBausch
Stainless
- Joined
- Jan 11, 2010
- Location
- Indianapolis
You might investigate magnetic sheet metal brakes, and you may end up creating an adjustable radius brake.
I’m thinking the production variations of the metal will drive you nuts, unless the item has flanges.
A Hossfield bender won’t work?
Bending Basics: The hows and whys of springback and springforward - The Fabricator
I’m thinking the production variations of the metal will drive you nuts, unless the item has flanges.
A Hossfield bender won’t work?
Bending Basics: The hows and whys of springback and springforward - The Fabricator
My neighbor got a job making mini excavator buckets.
He scaled up a Hossfield to 36" wide.
He used the bucket side burnouts as a starting point, added some Kentucky windage,
and still came up wrong. Final form had allot of shims tacked to it.
At our shop we have a 150 ton CNC pressbrake. And we are going to be making a lot of these parts so I need to be able to use that press. A Hossfield bender would not suit our needs. The part will have flanges welded to it so it does not need to be spot on every time, just close enough so that our welder won't kill me.
I have read all the material I can find on The Fabricator but all of their equations are for large radius, not really really large radius bends. The general equations stop being applicable after 4" or 5" radius as far as I can tell. I need something specific to very large radius bending.
You are going to have to make something and try it.
I designed a complex part with large radius springs made from 4130. Same situation, could not be bump formed. I have been around press brakes a bit and have a feel for how material behaves. I took the part drawing and drew my "best guess" of what the punch and die needed to look like to make the part I needed. The tools I made did not have simple radii. They had some complex curves in them so the part came out right. First shot I got exactly what I needed with 4130. I tried it with mild steel first and the part came out wrong! Mild steel has very little spring to it.
The way I thought about it was the larger radius needed more overbend than the smaller radius areas. Does that make any sense?
I designed a complex part with large radius springs made from 4130. Same situation, could not be bump formed. I have been around press brakes a bit and have a feel for how material behaves. I took the part drawing and drew my "best guess" of what the punch and die needed to look like to make the part I needed. The tools I made did not have simple radii. They had some complex curves in them so the part came out right. First shot I got exactly what I needed with 4130. I tried it with mild steel first and the part came out wrong! Mild steel has very little spring to it.
The way I thought about it was the larger radius needed more overbend than the smaller radius areas. Does that make any sense?
timopen
Plastic
- Joined
- Apr 23, 2013
- Location
- Finland, Kouvola
Well... it might be that there is no specific equation for large radius bending.
I know something about plate work, but not so much...
But, if read correctly... you didn't give information about bending width and angle. Width, well I was thinking about tooling costs... You said that you are going to do these lot, but if you are bending some 1" width bar, it will be very cheap to iterate to needed tooling... and if we assume that it will work with wider parts you can just do the test pieces with some narrow stuff and plasma or oxyfuel cut tooling for testing the right bending radius.
If you want to calculate you might try to use equation that combines pure bending moment to bending radius (this is working at the elastic zone)(I don't remember it right now) and try to figure how it would be applied when some of the material has been already at the plastic zone... well I'm really not sure if you can calculate it analytically or does it need FEA.
I would just make narrow dies for test bend and figure it that way.
If you find the equation from internet... You will trust it to be right?
Best regards.
I know something about plate work, but not so much...
But, if read correctly... you didn't give information about bending width and angle. Width, well I was thinking about tooling costs... You said that you are going to do these lot, but if you are bending some 1" width bar, it will be very cheap to iterate to needed tooling... and if we assume that it will work with wider parts you can just do the test pieces with some narrow stuff and plasma or oxyfuel cut tooling for testing the right bending radius.
If you want to calculate you might try to use equation that combines pure bending moment to bending radius (this is working at the elastic zone)(I don't remember it right now) and try to figure how it would be applied when some of the material has been already at the plastic zone... well I'm really not sure if you can calculate it analytically or does it need FEA.
I would just make narrow dies for test bend and figure it that way.
If you find the equation from internet... You will trust it to be right?
Best regards.
SteveBausch
Stainless
- Joined
- Jan 11, 2010
- Location
- Indianapolis
Find the right person/consultant, and they will be happy to let you get your hands dirty, while they are the brains of the project.
Yes, they don't get the profit from thousands of pieces, but they don't get the headache, either.
Good Luck
Yes, they don't get the profit from thousands of pieces, but they don't get the headache, either.
Good Luck
azmachining
Cast Iron
- Joined
- Dec 26, 2014
- Location
- Central Valley, AZ
One question is what is the width of the part your trying to bend? You may not have to go to all the effort of making a press brake die. Depending on width you may be able to do it in one shot on a tube bender, like a hydraulic diacro tube/bar power bender. You would still probably need to make dies, but it would be way easier going this route.
I have some bends that need to be 10in radius and range from 5in to 10in wide. I'm probably going to end up making a 2in section and give my best guess what radius to use. I'd rather be able to calculate it, but it looks like I'm going to have to do it the hard way.
Your missing the obvious, you don't even need to be at 2" wide, rough starting point i would go 8" radi but i would expect to go tighter than that not loser, theres a reason people roll large radius parts and it has nothing to do with easy and fast. Differences from one batch to another will significantly effect things at these radi too.
Auto guys get around it by effectively coining the part, but your not even close to the tonnage you need to contemplate that.
Post up some part pics and maybe we can tell you how to roll it, i roll a lot of odd sections you won't fit in or do with std rolls.
Other option is stretch forming, kinda like coining in reverse, used a lot in the aircraft world, again not the fastest, but a very usefull way to make some truly nasty curvy shit!
Auto guys get around it by effectively coining the part, but your not even close to the tonnage you need to contemplate that.
Post up some part pics and maybe we can tell you how to roll it, i roll a lot of odd sections you won't fit in or do with std rolls.
Other option is stretch forming, kinda like coining in reverse, used a lot in the aircraft world, again not the fastest, but a very usefull way to make some truly nasty curvy shit!
sfriedberg
Diamond
- Joined
- Oct 14, 2010
- Location
- Oregon, USA
I think this is prudent. And I think you better write into the contract with your supplier that they ship you material from the same source, in the same condition, else your dies will work differently everytime you get a new shipment in. (Your supplier will laugh at you, BTW.)
Seriously, this cannot be precalculated with any accuracy without a lot of info about material condition you do not possess. Best to prototype your dies on a less-expensive width, iterating until you get the results you want, as previously suggested, then scale up to the full-width dies only after you've got a proven die profile. I'd also suggest you test on a couple of material variations, so that when your full-width die suddenly starts producing a different part profile, you know how much is attributable to softer, stiffer, thicker, thinner, etc. material.
Jimmy_pop
Aluminum
- Joined
- Aug 25, 2012
- Location
- Sedona, AZ USA
I'd contact your local Wila tooling rep for custom making tooling. I'm sure they have seen alot more complicated jobs than a 10in radius. They might advise to switch to CR steel.
Fish On
Hot Rolled
- Joined
- Feb 23, 2014
- Location
- Foley, Alabama
And even then, once you switch from the 2" die to the 10" die, it'll still change.
SteveBausch
Stainless
- Joined
- Jan 11, 2010
- Location
- Indianapolis
Of course, if you bought the coil, had it stored at the shop that slits it, flattens it, shears it etc. your learning curve would be once every few miles.
You might pick the brains of Precision Strip...
You might pick the brains of Precision Strip...
