Part I: Stamping of automotive components
BY ADAM GROSECLOSE
Editor’s Note: This article is Part I of a two-part
series that reviews applications for large servo-driven presses used to form automotive parts.
Part II, which will appear in the July issue, dis-cusses new technologies for servo-driven presses and die cushions.
During the last two years, presses with 2,500 to 3,000 tons’
capacity have been developed
to form large panels for automotive
applications. Toyota and Honda have
installed such large presses for automotive stamping in Japan. In
Germany, BMW is installing a large
servo press line in its Dresden plant.
conventional mechanical press.
In addition, the braking energy is
transferred back into the power system
during the dynamic braking operation
of the servomotors. It also is possible to
install an external energy storage capability to compensate for energy peaks
and reduce the nominal power drawn
from the local power supply system, if
it is economically justified.
One example of this energy storage is shown in Figure 2. The energy of deceleration is stored in an
external device and used when the
press motion requires more than
235 HP for each motor (two motors
= 470 HP). The stored energy—
maximum 470 HP—is used during
peak power requirements, so the
facility power load remains nearly
constant at about 70 HP.1
Production Comparisons
The best way to illustrate the cost-effective application of modern
servo-driven presses is to make
Cycle Time of Mechanical Press
Servo Press Capabilities
Figure 1 shows the difference between
the motion of mechanical and servo
presses. In addition to the flexibility of
controlling the slide motion, servo-driven presses also offer considerable energy savings, especially in large-capacity
presses. In these machines, the installed
motor power is larger than in compara-ble-capacity mechanical presses.
However, during a stamping operation
(deep drawing, blanking, coining), the
servomotor power is used only while
the press is moving, since there is no
continuously rotating flywheel and
clutch/brake mechanism as there is in a
Energy (k W vs. Time)
300
250
200
150
100
50
0
-50
-100
-150
-200
-250
-300
-350
Slide Position
Minimum
Stroke Length
(1) Variable
Stroke Length
Cycle Time of
Free-motion Press
Forming Length
( 6) Synchronize
With Feeder
( 2) Best
Speed
for Materials
Time
Standstill at BDC
( 5) Prevention
of Noise
and Shock
at Contact or
Breakaway
of Tools
( 3) Improve
Accuracy
by Dwelling
at BDC
( 4) Other
Process
at BDC
(Multiprocess)
Crank or Link Press - Fixed Motion
Figure 1
Free-motion Press
Servo-driven presses offer the flexibility of slide motion. 3
800
Stroke Height (mm)
700
600
500
400
300
200
100
150 mm
0
01
Output per
Main Motor Max.
235 HP (175 k W)
Identical Tool Impact
Velocity in Tool
Contact Area
Incoming Supply
From Network~
70 HP (50 k W)
Energy Storage
Output 470 HP
(350 k W)
2 3Time(s) 4 5
Cycle Time 3. 16 Sec. Cycle Time 4. 28 Sec
19 Parts/Min. 14 Parts/Min.
Servo Press HUQ 1,100 NC
Mechanical Press HUQ 1,100 With Draw Hipro
Figure 2
The main motor output can be supplied almost entirely by energy
storage. 4
Figure 3
Compared here are the slide motions of a 1,100-ton mechanical
and servo-driven press for identical slide velocity during forming.
Courtesy of Schuler-Weingarten.
