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generating developed length


New member
we are developing a draft tube elbow of a hydro turbine and when we are trying to generate the developement lenght the results are not proper we would like to know the exact procedure for generating the developed length

component is modeled using swept blend and normal to origin trajectory


New member
Developed length is generated for simple bends, complex bends requiring forming the metal is not.

A tube elbow doesn't sound like it can use a regular unbend. If you have to use a cross section unbend then you are out of luck, Pro/E doesn't generate developed length for this.

Look at the Gaussian plot of the part to see where there is stress to determine if the part is formed or just bent.

If you can do a regular unbend then you can get a developed length. You will probably have to modify the bend table you use for the part to get better accuracy. If you don't have material specified in the part and in the bend table it will use the first of 3 bend tables which is for soft materials.

You can also specify to use the K-factor or neutral bend line which you add in and it will use a default formula which will get you close.



New member
Thanks for your reply.

We have done the work with the unbend--> xsection option.

Mr. jperkins can you give me more details about K factor.


New member
hi ankita,

u can do it with X section option in the unbend.

do it with specifying the deformed area .

i think this will solve ur problem .

do tell me the results after doing this



New member
The X-section unbend will not give you a developed length, it assumes you have to distort the material to make the part, usually in a forming die.

K factor is the neutral bend line, the metal on one side stretches and the other side it compresses. I varies depending on the material and temper, thickness to bend radii ratio and direction of the grain (rolling direction of the raw sheet) and the tooling and method used to make the bend. It is about centered when the bend radius is large, more than 3x to 4x thickness.

I usually have the sheetmetal shop modify it for their method of forming, that way they are responsible for the results.

When a complex bend is required, streaching or compressing the material in a forming die then you get the developed length from the die maker or by trial and error. Form it , measure it and make another piece with altered dimensions, or make it larger than needed and trim it to fit after the forming. Not very scientific but it works.

Just curious, how big is this elbow and how do you plan to have it made? Email direct [email protected]