Speed Monitor - Siemens Simotion TM 121C Applications Manual

Procedural functions of mechanical presses

5.2 Speed monitor

Definition
The safety cams are mounted on a shaft in the mechanical cam switchgear. During
rotation, the speed monitor at the end of this shaft generates pulses that are
monitored. Should the pulses cease, e.g. in the case of a shaft break or faulty
timing belt, the press comes to an immediate standstill.
The "Speed monitor" function can only be deselected if the safety cams are
mounted directly on the main drive shaft.
Operating principle of the monitor
A proximity switch at the cam controller (30 pulses per stroke) is used to monitor a
shaft break using an adjustable time interval. If the monitor does not detect at least
one pulse during this interval, the press is brought to a standstill.
Functional description of the monitor
An encoder that outputs 30 pulses per rotation is integrated in each cam
switchgear. These pulses are used to check whether the shaft or the cam
switchgear is defective. The encoder must be connected to the hardware counter
of the Safety Unit, terminal X9.
The cam switchgear expects to receive pulses when the press ram is moved. The
monitor checks whether at least one pulse is counted during the adjustable time
periods. If not, an error is output that causes the machine to be brought to an
immediate standstill.
The time intervals must be set to the working speed of the machine and must be
kept as small as possible for the slowest machine speed. The overtravel angle may
not exceed 90°.
Parameterization
Figure 5-4
5-42
Mechanical operation – Speed monitor
© Siemens AG 2003 All Rights Reserved
SIMOTION Safety Unit (AP) - Edition 06.2003