They really do exist: uncompromising professional users who place the highest store by exact bending
results simply because this is what their projects need. Jorns, the Swiss manufacturer of bending machines
and double bending machines, developed the dynamic positioning (DP) function for them years
ago and has now taken things to the next level. Dynamic positioning compensates deformations at the
ends of profiles during the bending and closing of parallel open hems. This is only possible because Jorns
uses a control technology that allows you to measure, control and position clamping arms individually,
and to keep them in position during bending. The clamping force exerted on the part remains even during
the bending process: this reduces, or even completely eliminates significant over bending at the
ends of profiles.
A remedy for inaccurate and tedious makeshift solutions
Long bending machines, unlike shorter swivel bending machines, have several clamping arms that are
driven directly or via control shafts distributed over the entire bending length; when bending profiles,
these exert a uniform pressing force on the sheet – over the complete bending length.
In practice, the problems usually start at higher sheet thicknesses and when the bending profile is two
to three metres shorter than the machine’s maximum bending length – so that the outermost clamping
arms do not grip the material. Until recently, there was only one solution to achieve an accurate
bending angle to the very ends of the sheet, no matter whether the clamping arms are driven individually
or via a control shaft: insert the sheet strip to keep the upper clamping tool parallel during
bending.
Previously, accurate parallel open hems could only be achieved through mechanical hem milling
that allowed immutable opening dimensions; or by inserting a sheet strip that had to be laboriously
removed again after closing. Even precise positioning of the clamping tool across the entire bending
length did not allow for a parallel open hem, as the material in the centre of the profile springs back
more than at the profile ends.
Improvement with dynamic positioning
Dynamic positioning allows the uniform closure of a hem over the entire length of the profile; the pretension
is simply programmed in the control system and lets the clamping arms exert more pressure in
the middle of the profile, up to the maximum clamping pressure if needs be. Thanks to the modular design
of the machines, Jorns bending machines can also be retrofitted with this function; dynamic positioning
can be integrated as an option when ordering new machines. The ‘wow’ effect for the bending
accuracy comes for free.
Watch the dynamic positioning function in action with an animated 3D visualisation: