Siemens SINUMERIK 840C - Manual (Page 227)

6 NC Machine Data (NC MD), NC Setting Data (NC SD) 10.94
6.4 Axis-specific MD 1 (axial data 1)
The software limit switches cannot fulfil their function correctly until the reference point has
been approached and NC MD 560 * 5 has been set to "1".
The software limit switches are always approached at the speed defined in NC MD 1 unless a
lower speed was selected in the current motion block. Deceleration to zero speed begins so
far ahead of the software limit switch that the limit switch is reached with absolute accuracy
but not overrun (in jog mode). The software limit switch can also be overrun under certain
conditions (see NC MD 1100*). (Traverse with handwheel, reference point approach mode)
Customary travel limits
Software limit switch 2
Hardware limit switch
EMERGENCY STOP
Mechanical limit
of travel
MD 1100*
MD 1100*
Software limit switch 1
Note
When axes are traversed with interpolation, all axes are shut down upon reaching the limit of
any one of the axes. Stopping without a contour violation, however, can be guaranteed only
when bit 7 of NC MD 5003 ("No deceleration at limit switch") is not set, i.e. when the
acceleration ramp is used for braking.
A second software limit switch position can be specified in a clockwise direction. The PLC
selects either software limit switch 1 or 2 on the basis of an interface signal (refer to Part 1 of
the Interface Description, DB32, DL m + 1, bit 1).
e. g. DB32 DL1 Bit 1 = 0 . . . . . 1st switch for 1st axis
Bit 1 = 1 . . . . . 2nd switch for 2nd axis
Example of application
Reduction of the permissible traversing range with a retracted tailstock.
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SINUMERIK 840C (IA)