Determining A Reference Point; Determining A Reference Point With Separate Switch - Siemens SIMATIC S5 Manual

Notes on Operation
5.4

Determining a Reference Point

Reference points calibrate the drive system and determine a system zero point
for the following positioning jobs. To calculate the reference point, you can
install a separate switch (position switch, BERO, etc.) within the traversing range
that will send a signal to the REF reference input when triggered. You can,
however, also use one of the limit switches for this purpose. In this case, the REF
input remains unassigned. The IP 267 evaluates a REF signal only if the RPA bit in
the positioning message frame is set. A reference point will exactly be
reproduced each time it is approached from the same direction. The direction
need only be laid down once.
The reference point approach must always be executed during commissioning,
after power failure or after operation of the emergency limit switch (PD).
The reference point approach is calculated in three steps:
• Search for reference switch
• Overtravel reference switch
• Approach reference switch (slowly)
5.4.1

Determining a Reference Point with Separate Switch

To calculate the reference point start by initiating a positioning job in any
direction. Set, for example, "Start forwards" mode with high velocity. The RPA bit
is set and the maximum path is transferred.
When the module detects the reference switch (REF input activated), it stops with
a slight delay. If the reference point is not found in this direction, the traversing
path ends for the time being at limit switch I+.
In both cases, you must then assign a positioning job with the same parameters
but with "Start backwards". This traversing movement is aborted with the
reference switch. The contact of the reference switch should not be blocked at
the end of the traversing movement. You will otherwise have to program an
auxiliary approach section with the same direction of travel and RPA = 0 to
enable the switch contact again ( 6.4.1).
5-8
IP 267
EWA 4NEB 812 6061-02a