Siemens SINUMERIK 840C Installation Instructions Manual page 227

6 NC Machine Data (NC MD), NC Setting Data (NC SD)
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
MD 1100*
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
Bit 1 = 1
Example of application
Reduction of the permissible traversing range with a retracted tailstock.
6–42
Software limit switch 1
MD 1100*
Hardware limit switch
. . . . . 1st switch for 1st axis
. . . . . 2nd switch for 2nd axis
©
Siemens AG 1992 All Rights Reserved
Mechanical limit
of travel
EMERGENCY STOP
6FC5197- AA50
SINUMERIK 840C (IA)
10.94