Siemens SINUMERIK 828D Function Manual page 446

H2: Auxiliary function outputs to PLC
8.13 Block-search response
Explanation of example
If the number of spindles is known, outputs of the same type can be written in one part program block to reduce
program runtime.
Output of $P_SEARCH_SDIR should be made in a separate part program block because spindle positioning or
switchover to axis mode in conjunction with the gear change can cause an alarm.
If the ASUB which has been started is ended with REPOSA, spindle 1 remains at position 111 degrees, while
spindle 2 is repositioned at position 77 degrees.
If a different response is required, the program sequence for block search (for example) "N05 M3 S..." and "N30
SPOS[2] = IC(...)" requires special treatment.
Whether block search is active can be ascertained in the ASUB via the system variable $P_SEARCH.
$P_SEARCH==1 ; Block search active
In the case of incremental positioning after speed control operation, the path to be traversed is defined but, in
some cases, the final position reached only becomes known during positioning. This is the case, for example,
during position calibration on crossing the zero mark when switching on position control. For this reason, the
distance programmed after the zero position is accepted as the REPOS position (REPOSA in the ASUB).
Boundary conditions
Collected S values
The meaning of an S value in the parts program depends on the feed type that is currently active:
G93, G94, G95, G97, G971:
G96, G961:
If the feed operation is changed (e.g. for a tool change) before output of the system variable $P_SEARCH_S, the
original setting from the target block in the parts program must be restored to avoid use of the wrong type of feed.
Collected direction of rotation
For output of the direction of rotation, the system variable $P_SEARCH_SDIR is assigned default value "-5" at
the start of the block search. This value has no effect on output.
This ensures that the last spindle operating mode is retained for a block search across program section in which
spindles are not programmed with a direction of rotation, positioning or axis mode.
The programming of M19, SPOS, and SPOSA is collected as "M-19" (internal M19) in the system variables
$P_SEARCH_SDIR as an alternative to M3, M4, M5, and M70.
For the output of "M-19", the positioning data is read internally from the system variables $P_SEARCH_SPOS
and $P_SEARCH_SPOSMODE. Both system variables can also be written to, in order, for example, to make
corrections.
Note
Because of the assignments described above (e.g. M[<n>] = $P_SEARCH_SDIR[<n>]), the
values "–5" and "–19" generally remain hidden from the user and only have to be observed in
the case of special evaluation of the system variables in the ASUB.
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The S value is interpreted as the speed
The S value is interpreted as a constant cutting rate
Function Manual, 09/2011, 6FC5397-0BP40-2BA0
Basic Functions