3 Fundamentals of press design

82 Fundamentals of press design
off center
die force
250 bar
opposing supporting torques exerted on the two sides counteract the
tilt moment. The maximum deviation measured at the parallel control
cylinders is between 0.6 and 0.8 mm during drawing, bending and
forming operations.
3.3.4 Stroke limitation and damping
Fig. 3.3.6
Full-stroke parallel control of the press slide
The deformation depth, which depends on the slide position, is determined
in hydraulic presses by the switchover point at the bottom dead
center (BDC) (Fig. 3.3.1). Depending on speed, the slide travels past this
switchover point by a few millimeters. However, repeatability remains
within close limits, meaning that the slide is reversed at the BDC with sufficient
accuracy for most forming operations. However, if a tolerance of
less than 1mm is required, a mechanical stroke limitation is called for. In
combination with a hydraulic damping system, this can achieve a marked
reduction in the blanking shock involved in presswork (Fig. 3.3.7). There
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998