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# Roll bending forces6

## Roll bending forces

(OP)

I need to calculate the forces involved on a roll bending machine and components. I could find no documents or books on this regard

Any recommendation ?

The product is a 5mm thickness steel wheel, to be formed on a single roll (male and female, profiled to the final form), gradually pushing and rotating.
The wheel is already an enclosed cylinder, welded ends. All I need is to profile it.

### RE: Roll bending forces

I'm not really visualizing the problem, but not sure it would help if I could- anyway, a sketch would be informative.
If you assume that the entire cross-section involved is at yield stress, half in tension, half in compression, you'll have an idea of the bending moment required to form it. Note that some materials don't have a maximum yield strength, so you won't get too exact regardless.
It may also help to work from an energy approach, calculating the energy required to go from initial position to final deformed configuration.

### RE: Roll bending forces

Look up Roll swagers , roll formers.
B.E.

You are judged not by what you know, but by what you can do.

### RE: Roll bending forces

I have a book but in Italian : is it suitable ?

### RE: Roll bending forces

For the operation you are describing, the machine most often used is a 4 roll bender, but since you already have the cylinder, only two of the rollers are used. You are simultaneously shrinking and stretching the product by the roll forming operation so you have to mostly consider the yield strength of the material, since I do not know the grade of stainless you are using, I cannot offer advice on that, but you should be able to get that information from your material supplier

http://www.roundo.com/products/section-bending/4-r...

B.E.

You are judged not by what you know, but by what you can do.

### RE: Roll bending forces

The engineering equations for rolling processes (bulk deformation) are usually covered in any decent Manufacturing Processes textbook. Two authors I can think of are (1) Groover and (2) Kalpakjian. Usually those textbook chapters will reference even deeper technical reference books or other sources.

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering
www.bluetechnik.com

### RE: Roll bending forces

(OP)
Thank you all

I enjoy the idea offered by many here of calculating multiple simple bending stresses. That's probably what I'll do. My only fear is that the overall shape, which is full of curves, might interfere on each individual calculations. After all, if I don't neglect the radius of the wheel itself, the bending is 3D

I also enjoyed the books, authors and researches recommended. Some do cover deformations that resemble mine's. Yet, I'm still open to more specific material, if they exist.
BTW, a book in italian serves well, yes.

Here's an image to clarify my intent:

- The lower rolls are fixed, the upper one moves and rotates
- There are no guiding rolls yet.
Yet.
- These rolls are a sketch. I am yet to define their actual diameter, once I find a material that teaches that
- The steel is some AISI 1045

Documents I have so far:

Marciniak - Mechanics Of Sheet Metal Forming
Halmos - Roll Forming Handbook
Cadell - Metal Forming Mechanics And Metallurgy
ArcelorMittal - Guidelines For Plate Steel
Groover - Fundamentals Of Modern Manufacturing

Naturally, they don't cover 100% what I need

Again, Thank you all

### RE: Roll bending forces

LucasBS
Ok now that I know what you are up to,
I thought you might like to take a look at a production wheel rolling machine, they are all 4 roll machines in a gang, you will note that the roll operation is done in stages, not in one operation as your proposed machine does.

You are judged not by what you know, but by what you can do.

### RE: Roll bending forces

Here the Italian manual :

Later on I will try to post a video of a similar machine designed by me and suitable to shape steel plate 6 mm thick (shape not so complicate as Yours)

### RE: Roll bending forces

here the link for my video

https://mega.nz/#!9FE1DQ7R!06ZargvQPKaamu_8dGRVSU3...

My concern is : how much circular has to be Your item ? With a shaping machine probably You will manufacture something similar to a circle but oval, so You need to do an action to rectify the circular shape and probably to rectify the section too

### RE: Roll bending forces

(OP)
Thank you both

That book is probably the most adequate so far. Very specific

By berkshire's video I could count maybe two wheels per minute. Our market here absorbs 2 wheels per hour . For that reason, the machine must be economical (a single pass, low production)
I can see that the rolls are much larger. Helpful video

After the calandra (don't know the name in english) delivers the "round" ring, a press will round the joint and weld the seam at the same time.
If I'm not mistaken, berkshire's video show this step on the last machine (2:15)
Only after that, the profiling
If it's not enough, I'll apply your suggestion of expanding

### RE: Roll bending forces

LucasBS,
If you watch both videos , you will see that the wheel rim is delivered to the forming machine as a flat rolled blank, already electrically resistance butt welded .
The last step in the first film is punching a small flat for the valve stem. The rim then goes from there to meet up and get spot-welded to the center disc.
B.E.

You are judged not by what you know, but by what you can do.

### RE: Roll bending forces

What I have seen may be of interest and perhaps further investigation by you. I attended a week seminar by Cleaver Brooks in Lebanon, PA back in the 80's. Their process to manufacture corrugated furnaces entailed heating (red hot), section by section, a length of tube to form the convolution of a corrugated furnace with a similar contraption to your image. One of the benefit to red hot heating was the absence of ripples that would have developed during the forming process without heat.

### RE: Roll bending forces

(OP)
I'm putting thoughts on heating the thing. Not only because of the ripples, but to reduce stresses and ease the bending.
Thanks for the tip

And thank berkshire for the clarification. I've seen other videos where the only welding is on the beginning. Those wheels looked good enough

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