Unbeding of the conic vessel

[konstruktor2]

Hi everyone, i am new to this wonderfull site. I have a problem with unbending of the conic pressure vessel sheetmetal (see pics). I can create an unbend sheet but such a shape makes no sence since this i conical vessel. I made this within sheetmetal in ProE 4.0 first the lower ring and then the flanged wall (the S option). I just don´t understand why this happens. I solve the problem with hand calculating the full lenght of the cone, but i like to know how to solve this within ProE sheetmatl.

 

[konstruktor2]

Its seems that only one pic is in this thread of mine. So here is the unbend version of the vessel.