3 Fundamentals of press design

388 Sheet metal forming and blanking
ing and support rollers are used in order to avoid damaging the sheet
surface. With the help of straightening rollers with crowning capability,
waviness at the edges and center of the material can be eliminated.
The first pair of rollers must cause plastic deformation of the material,
but a certain roller diameter must not be exceeded. The thickness of a
straightenable sheet metal is accordingly calculated from the maximum
straightening force and the torque, which in turn is determined by the
size of the cardan shafts between the gear and rollers and the roller
diameter. As neither the gear nor the cardan shafts can be enlarged at
will for space reasons, the sheet thickness range and accordingly also
the flexibility of straightening machines with rollers of equal size are
restricted. This range can be extended by approximately one and half
times if individual rollers can be disengaged. Using the further developed
roller system depicted in Fig. 4.8.29 with different roller diameters,
it is possible to straighten sheet metals from 0.5 to 20 mm in thickness.
liftcylinder
feedrolls
straightening
rollers with
different
diameters
feed spindle
Fig. 4.8.29 Roller straightening machine for larger sheet metal thickness range
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998
height display