Special Points To Be Noted - Siemens SINUMERIK 840D sl Function Manual

Safety Functions Integrated in the System/Drive
6.8 Safe software cams (SN)
Defining the cam positions
The cam positions for SN1+, SN2+, SN3+, SN4+ and SN1–, SN2– , SN3–, SN4–
are specified in the following machine data/parameters:
for 840D sl:
MD 36936: $MA_SAFE_CAM_POS_PLUS[n]
MD 36937: $MA_SAFE_CAM_POS_MINUS[n]
for SINAMICS S120:
p9536[n]: SI motion, SN plus cams position
p9537[n]: SI motion, SN minus cams position
6.8.1

Special points to be noted

Tolerance for SN
Owing to variations in the clock cycle and signal run times (signal propagation
times), the cam signals of the two monitoring channels do not switch simulta-
neously and not precisely at the same position. A tolerance bandwidth can there-
fore be specified for all cams using the following machine data/parameters. Within
this bandwidth, the signal states for the same cam may be different in the two mo-
nitoring channels.
for 840D sl:
MD 36940: $MA_SAFE_CAM_TOL
for SINAMICS S120:
p9540: SI motion, SN tolerance
Note
The lowest possible tolerance bandwidth (less than 5–10 mm) should be selected
for the "safe software cams" function. It makes sense to parameterize the cam
tolerance greater than or equal to the actual value tolerance.
Special case for SN
If the axis is positioned precisely at the parameterized cam position, the cam sig-
nals may have different states owing to system-related variations in the actual va-
lues between the two monitoring channels.
This must be taken into account when safely processing the cam signals, e.g. by
filtering the different signal states by means of a logic circuit (see "Synchronizing
cam signals").
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SINUMERIK 840D sl/SINAMICS S120 SINUMERIK Safety Integrated (FBSI sl) – 03.2006 Edition
© Siemens AG, 2006. All rights reserved
03.06