Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 676)

Skip, Gauge, and Probing Cycles
Chapter 27
27-2
The control provides several means of triggering an external skip, gauge,
or probing block:
Discrete inputs on the I/O ring
Any one of the four available “High Speed inputs”
(not available on 9/230 CNCs)
A “Probe” input that directly latches the feedback counters.
These different inputs, each with different degrees of precision, may be
used to signal the control to store the current axes positions. Refer to
documentation prepared by your system installer for details on your
specific machine.
These conditions must be satisfied when an external skip, gauge, or probe
bock is executed:
Cutter compensation must be disabled (G40 mode) when the block is
executed.
The block that contains the external skip G code (excluding G04 as
external skip) must be a linear block.
CAUTION: We do not recommend using a skip block from any
fixed cycle block (such as drilling or pocket milling). If you do
choose to execute a skip block in a fixed cycle mode, be aware
that the block that is skipped when the trigger occurs can be a
cycle generated block. If this is the case the cycle will continue
normal execution skipping only the portion of the cycle that was
executing when the trigger occurred. If the generated block
skipped is a crucial portion of the cycle, damage to the part or
machine tool can occur.
Use external skip functions to terminate the execution of motion
commands in a block when the control receives a signal through PAL.
When the program block is terminated any remaining axis motion
generated by the block that has not been performed remains unexecuted
(other non-motion commands are still performed). The control continues
normal program execution at the beginning of the next block following the
skipped block.
The external skip function is controlled by G31, G31.1, G31.2, G31.3, and
G31.4. The system installer determines what signal (such as a touch probe,
manual switch, etc.) corresponds to each G31 code in PAL. The system
installer can choose different signals to correspond to G31.2, G31.3, and
G31.4. G31 and G31.1 are functionally the same, always using the same
external signal and the same AMP defined feedrate. With proper PAL
programming, a G04 dwell in seconds may also be used as an external
skip function.
27.2
External Skip
Functions (G31 codes)