Siemens Sinumerik 840D sl Function Manual page 592

Commissioning
9.6 Replacing a motor or encoder
Note
The error at a reference point approach is no more than one revolution of the
motor (difference between two zero marks). This offset is usually not critical for the
mechanical parts of the machine. If problems arise with the traversing limits
because of the type of reference point approach, then for example, set the offset
values in MD34080/34090 to non--critical values.
Alarms 27000/C01797 "Axis not safely referenced" are still present and indicate
that the functions "safe limit positions" and "safe cams" are not active in this state.
For example, if the "safe limit positions" are to be used as a substitute for
hardware limit switches, then they are not functioning at this time!
After completion of the reference point approach, the axis goes into the
"referenced" status. However, because of the zero mark offset between the
encoders, the reference position still has to be calibrated. This means that the
position reference with respect to the mechanical system must be re--established.
The system is calibrated after measuring the difference -- usually in MD34080
REFP_MOVE_DIST or MD34090 REFP_MOVE_DIST_CORR.
4. After the reference point has been re--calibrated, the reference point approach
must be re--initiated. The axis changes over into the "referenced'" state. At this
time, the reference point value is taken over as the safe actual value for the
axis and drive.
5. Finally, with the JOG/REF machine mode active, on the HMI the "user agree-
ment" softkey must be pressed and the user agreement for the axis involved
must be reset. Alarms 27000/C01797 disappear and the functions "safe limit
position" and "safe cams" are safely active again.
Comments about 2- -encoder systems
Case A
1st measuring system: Incremental motor measuring system
2nd measuring system: Absolute direct measuring system
As active measuring system via the axis interface, the 2nd position measuring
system (DBAx 1.5 = 0, DBAx 1.6 =1) is statically selected
In this case, motor replacement is straightforward because the NC reference point
position is only supplied with values from the 2nd measuring system (DMS). This
means that in this case, it is not necessary to recalibrate the motor measuring
system.
Case B
1st measuring system: Absolute motor measuring system
2nd measuring system: Incremental direct measuring system
As active measuring system via the axis interface, when booting, for monitoring
purposes, the 1st position measuring system (DBAx1.5 = 1, DBX 1.6 =0) is
selected, and then a switchover is subsequently made to the 2nd position
measuring system (DBAx 1.5 = 0, DBX 1.6 =1).
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SINUMERIK 840D sl/SINAMICS S120 SINUMERIK Safety Integrated (FBSI sl) - - 10.2015 Edition
© Siemens AG 2015 All Rights Reserved
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