Roll Forming - Straight between bends 1

[jmarkus]

I couldn't find a specific area to ask about roll forming, so I hope this forum has some expertise. I've read a lot that for a straight flange after a bend in roll forming the length should be at least 3 times the material thickness.

What I am wondering is what is the requirement for straight length between bends? If I have a complicated section profile with jogs here, there and everywhere, what is the best practice design requirement for how much space I need to keep between the bends.

Thanks,
Jeff

 

[berkshire]

If you are talking about the final flange on the edge of a roll formed part. Yes it should be at least that, or the forming roll will tend to shear off part of the edge.
The straight between bends will depend on your roller profile and the number of rollers you have on the machine.
I am presuming that we are discussing a Yoder or lockformer multiroll former here.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[rb1957]

i think your misinterpreting (or i'm misunderstanding) the 3*thickness rule of thumb. this is for the radius, not (as i think you're saying) the distance between bends.

remember too, it's very hard to create a bend across the curvature of a panel ... ie if you roll a sheet into a curved shape (like part of a cyclinder), it easy to bend a flange along the axis of the cyclinder, but it's very hard to form across teh cyclinder.

also, if you're forming a complex shape, it's probably better to do it in O condition material and heat treat later.

 

[jmarkus]

Just to be sure my question is clear, please see the attached image. The grey straight sections are what I am asking about (this is a cross section of the roll profile). Is there a rule of thumb for how short I can go between the bends.

Thanks,
Jeff

 

[rb1957]

no, i think it's limited by the machine and the material

 

[berkshire]

jmarkus,

For that profile rb1957 has it right. You can go back to back with your bends.
What I was talking about, was how short you could make what are your vertical legs on that part.
The radius of the bend of course will depend on the ductility of the part.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[mfgenggear]

This needs to hydro formed & not roll formed.
In my opinion it's to complicated for roll forming.
then the amount of straight between bends is not applicable.
an other option is to brake form.

generally the length of bend requires enough for the machine to grab at the ends.

simple for hydro forming, then maybe brake form, discuss it with your shop or vendor.

Mfgenggear

 

[jmarkus]

Another picture for clarification.

Jeff

 

[ornerynorsk]

What's the material? Roll forming should prove no difficulty with the right material. Aluminum would be best off extruded.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[jmarkus]

HSLA steel - 50 ksi.

Jeff

 

[ornerynorsk]

Grade 50 forms beautifully. As others have said, you can run the radii back to back, no need for tangents.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[mfgenggear]

Ornerynorsk

depends on the quantity. regardless of material.
are we talking about pinch roll forming or extruded roll forming.
if it's extruded, I would agree if the quantity would pay for the tooling.

jmararkus

are you making only 1 or 2?

I would still stick with my first answer.
Hydro form if it's low- to mid production.
for what ever reason I was thinking pinch roll forming.

Mfgenggear.

 

[berkshire]

jmarkus (Mechanical)
Are you roll forming this yourself, or are you sending this out.
For an experienced roll forming company with a good multi roll forming machine, this job is a no brainer.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[mfgenggear]

http://www.youtube.com/watch?v=Kke0_0okdlc

 

[mfgenggear]

http://www.youtube.com/watch?v=gUGJ_8uzcw8

 

[GregLocock]

Looks like a seat rail. How many thousand do you want a day?

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[berkshire]

mfgenggear,
The type of roller he needs looks like this.
B.E.

http://inv.nationalmachy.com/machpict/005700/109596.jpg

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[mfgenggear]

berkshire

yes you are right for long runs.

http://www.youtube.com/watch?NR=1&v=k6iODHla6qY&feature=endscreen

 

[mfgenggear]

I did this in my first job for five years

http://www.youtube.com/watch?v=2-1wbvuqEuA

 

[berkshire]

mfgenggear (Aerospace)
Damm that brings back memories, I played with one of those with an ETS2000 controller for about 3 years starting in 2001.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor