In the spotlight: The developed length in roll forming design
The developed length of each arc segment and with it the strip width normally is calculated dependent on sheet thickness, bend radius and angle. In reality, however, there are more dependencies. E.g. the material, the bending method and the bend angle sequence have influence. Anyway, this was the result of most recent research at the PtU of the Technical University of Darmstadt (Germany) and this insight meets the experience of the roll form designers.
This influence cannot be handled by a universally valid calculation method, but has to be defined individually and empirically. In the new release of the roll form design software UBECO PROFIL a separate calculation method can be applied to each arc segment. The user can select between a standard method like Oehler, DIN, centerline, or he defines user methods that can be equipped with empirical corrections. The latter are important in case larger angle increase is necessary because of limited count of stands and subsequently occurring deep drawing effects.
If the roll forming tools should be verified by using the FEA (Finite Element Analysis) simulation, the quite short sheet section must be threaded correctly into the roller stands.
In the new release of the roll form design software UBECO PROFIL the user can select between several options to enable correct threading: Guiding the nodes at the profile lead end forces safe threading of the profile into the next roller stands and prevents pushing against the rollers. Guiding the nodes at the profile tail end replaces the strip behind and prevents up and down oscillation. Alternatively, the sheet lead edges and be chamfered in width and in thickness direction. This improves threading. If precut blanks should be roll formed, guiding and chamfering can be switched off in order to simulate also this process correctly.
