3 Fundamentals of press design

Sheet metal forming lines
(Fig. 4.4.8). Once correction is completed, the bed plate is precisely
clamped in its new position by releasing the hydraulics.
Universal presses with modified top drive system
If an operating sequence involves a wide variety of work processes such
as drawing, blanking, bending, stamping or reducing, it is rarely possible
to achieve ideal working conditions for the respective forming
process when using conventional press drive systems.
The modified knuckle-joint system used in mechanical presses offers
considerable benefits (Fig. 4.4.9)when it is necessary to satisfy the widely
differing demands made on the optimum forming velocity for universal
operating sequences. By actuating the press drive and slide in this
special way, it is possible to alter the movement and velocity profile of
the slide (Fig. 4.4.10). A velocity reduction is achieved over a relatively
large slide stroke in the working area, while the idle strokes for forward
and return travel are conducted at increased speed (compared to eccentric
and knuckle-joint drive system) (cf. Fig. 3.2.3).
This drive system provides power transmission from the drive to the
slide, allowing to achieve high press forces and nominal force-displacement
curves with a relatively small drive torque. As a result, the gearbox
with clutch and brake can be produced in a compact and cost effective
way.
slide velocity V St [mm/s]
400
300
200
100
0
– 100
– 200
– 300
– 400
slide displacement h
slide velocity V St
TDC BDC
TDC
0 90 180 270 360
crank angle [°]
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998
200
150
100
50
0
slide displacement h [mm]
Fig. 4.4.7
Slide displacement and
velocity versus crank angle
of a hybrid press
205