Pre-bend length of a Tube

[Anonymous]

Is there a way to find the Pre-bend length of a tube that I made using frame generator?

I read about various ways of calculating this from the bend angle and so on(though I would prefer a software based solution). I would like to know if there is any simple calculation and standard way of doing this?

My tube is pretty simple with just one bend and approximation might work. I just wanted a more universal solution.

Thanks...

[Lewis.Young]

Hi Paul,

If you want to find out the length of some tube before being bent then follow this equation.

(2π * R) * (X / 360) + A + B = Total Length

A & B are the straight lengths either side of the bent section.

X is the angle at which it's being bent.

R is the Bend Radius of the tube (make sure this is taken from the centre)

Using the example I've provided:

(2π * 40) * (90 / 360) + 110 + 160 = 332.8mm

If this is what you're looking for please accept it as a solution for anyone else who might also have this problem 🙂

[SBix26 · Accepted solution]

@Lewis.Young Your equation is correct, but the difficulty is knowing the exact value of R.  Material and bending method have a significant influence on the location of the neutral axis (where there is neither compression nor stretching), and for tubing it may get even more complicated than that, since wall collapse or folding are possible and may or may not be allowable.

But if the bend radius is pretty large compared to the tube diameter, your equation (assuming R is the centerline of the tube) should do the job.

Sam B

Inventor Professional 2017.3.1
Vault Workgroup 2017.0.1
Windows 7 Enterprise 64-bit, SP1
Inventor Certified Professional

[Jon.Dean]

Hi Paul,
If an approximation is good enough, then you can check the Loop length from the Inspect tab.
Jon.

[mpatchus]

If you are using frame generator than I can assume you have a skeleton model.

You can use the skeleton model to get your total unbent lengths.

if you just need to know the length, use the MEASURE LOOP tool on the sketch.

If you need the value for a drawing, you could create a parameter in your skeleton model to do the calculation for you.

Once this parameter has been created in the skeleton you can use it on your drawing with a LEADER TEXT.

If there are additional bends, simply adjust the parameter equation to include additional legs and bends i.e. LEG_3, LEG_4, ANG_2, RAD_2, etc.

[Anonymous]

After a small research, I came to a similar conclusion, that there are a lot of factors affecting the exact neutral axis position including material, bending radius, bending method etc. So the only way would be to go for an approximate calculation using your centreline.