© Siemens AG 2003 All Rights Reserved
SIMOTION Safety Unit (AP) - Edition 06.2003
5-39
5 Procedural functions of mechanical
presses
5.1 Cam evaluation
Definition
The system monitors the safety cams for operating and switching off the press to
ensure that they are operating correctly.
According to the current regulations, it is not sufficient to generate cam signals with
electronic components alone (proximity switches or shaft angle encoders).
Therefore, on mechanical presses, a mechanical limit switch must be used to query
the ramp up cam as late as possible in the TDC. The ramp up cam activates the
end of the hazardous closing movement and the press switch-off. In addition, the
over run cam, which also plays a part in monitoring the TDC switch-off and
monitors the overtravel distance of the clutch/brake combination, must be
mechanical in design.
Since presses capable of higher speed ranges are becoming more common, an
additional electronically designed dynamic cam that calculates the speed-
dependent brake engagement point can be looped into the TDC switch-off.
Example of a cam setting
up to 320°
10°
Overtravel cam
(mechanic)
Dynamic cam
(electronic)
up to 340°
170° to 180°
Run-up cam
(mechanical)
BDC
TDC
Switch-off time
Figure 5-1 Example of a cam setting
5
