Siemens SINUMERIK 840D Description Of Functions page 457

11.03
8.4 Safe cams at the modulo limit
Description
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For the rotary axis, the 90° position is to be safely detected. A cam signal is to
General position
detection (can be be generated for this purpose, that has a high signal level between 89.5° and
applied to linear axes) 90.5° (pulse).
These positions are entered into the machine data
36936 SAFE_CAM_POS_PLUS[0] :
36937 SAFE_CAM_POS_MINUS[0] : 89.5 degrees
36905 SAFE_MODULO_RANGE :
and are subsequently transferred into the FD/MSD machine data. The levels of
the safe cam signals change as follows:
Fig. 8-7
Safe cams SN1+ to SN4- are individual position signals with a signal change
from "low" to "high" at the saved position. The required cam signal is generated
by negating signal SN1+ and rounding it with signal SN1-.
© Siemens AG 2003 All Rights Reserved
SINUMERIK 840D/SIMODRIVE 611 digital SINUMERIK Safety Integrated (FBSI) - Edition 11.03
A problem frequently encountered with machine tools and production machines
is the reliable detection of the position of a drive. Safe cams (SN) are used for
this purpose, however it should be noted that the signal level of a safe cam
changes at the modulo limit of a rotary axis. The following spindle application
illustrates the problem:
89.5° 90° 90.5°
Safe cam signal characteristics
8 Application examples
8.4 Safe cams at the modulo limit
90.5 degrees
360 degrees
SN1+
SN1-
Position detection
to be implemented
8-457