User Manual

Motion control is easy
10.6 Operation of motion control for S7-1200
Easy Book
Manual, 03/2014, A5E02486774-AF
247
Use additional hardware limit switches if a mechanical endstop is located after the software
limit switches and there is a risk of mechanical damage.
Additional information
Your user program can override the hardware or software position limits by enabling or
disabling both hardware and software limits functionality. The selection is made from the
Axis DB.
● To enable or disable the hardware limit functionality, access the "Active" tag (Bool) in the
DB path "<axis name>/Config/
PositonLimits_HW
". The state of the "Active" tag enables
or disables the use of hardware position limits.
● To enable or disable software position limit functionality, access "Active" tag (Bool) in the
DB path "<axis name>/Config/
Position Limits_SW
". The state of this "Active" tag enables
or disables the software position limits.
You can also modify the software position limits with your user program (for example, to add
flexibility for machine setup or to shorten machine change-over time). Your user program can
write new values to the " MinPosition " and " MaxPosition " tags (engineering units in Real
format) in the DB "<axis name>/Config/
PositionLimits_SW
".
10.6.3
Homing
10.6.3.1
Homing the axis
Homing refers to the matching of the axis coordinates to the real, physical drive position. (If
the drive is currently at position x, the axis will be adjusted to be in position x.) For position-
controlled axes, the entries and displays for the position refer exactly to these axis
coordinates.
Note
The agreement between the axis coordinates and the real situation is extremely important.
This step is necess
ary to ensure that the absolute target position of the axis is also achieved
exactly with the drive.
The MC_Home instruction initiates the homing of the axis.