3 Fundamentals of press design

224 Sheet metal forming and blanking
force and force-displacement, a link-driven press can be loaded within
the work range considerably higher and further away from the BDC
than comparable eccentric presses, because the link-driven press has a
steeper force-displacement curve (torque characteristic).
Consequently, a link-driven press can achieve higher stroking rates
than an eccentric press depending on the drawing depth – the greater
the drawing depth, the greater the increase. If the stroking rate is not
increased, the lower impact speed results in improved drawing conditions.
Even low grade sheet metals can be successfully processed. In
addition, there is less wear and tear on the die and draw cushion, as
well as on the clutch and brake.
Under practical conditions, the motion curve of a link-driven press
with automatic part transport is configured so as to reduce the impact
speed. Therefore, and also due to the use of double-helical gears in the
drive system, noise is additionally reduced by up to 8 dB(A).
Number of presses
The number of presses which make up a line depends on the number of
operations required to process the part in question (cf.Sect. 4.1.1). In
general terms, an attempt is made to reduce the number of presses and
thus also the number of necessary dies.
Fig. 4.4.20 Hydraulic press line automated by robots
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998