Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 688)

Skip, Gauge, and Probing Cycles
Chapter 27
27-14
The control executes the G38.1 cycle in this manner:
1. When the G38.1 block is executed, the control initially moves only
the first axis in the G38.1 block to the coordinate position entered
with it. The approach feedrate (E) is used for this move.
2. The second axis in the G38.1 block is then moved to the coordinate
defined by the approach distance parameter, R. Again, the approach
feedrate (E) is used.
3. The feedrate is then reduced to the probe feedrate (F). The second
axis continues to move into the tolerance band (D) until the probe
triggers, signaling that contact has been made. If the probe triggers
before reaching the negative tolerance band (D) or does not trigger
after passing through the positive tolerance band (D), a PROBE
ERROR will occur. This error appears on the screen as a warning but
does not place the control in E-STOP. Instead the G38.1 block is
aborted, and program execution proceeds to the next block.
4. If the probe triggers within the tolerance band, the position is
recorded. The axis then reverses direction and retracts the distance
traveled in steps 2 and 3 above at the approach feedrate (E).
5. The first axis in the G38.1 block moves the incremental distance
entered with the I parameter. The approach feedrate (E) is used for
this move.
6. Steps 2, 3, and 4 above are repeated. Note that if the J parameter is
programmed, the value of J is added to the Y parameter for the
second probe hit. This will shift the location of the tolerance band
programmed with the D word.
At this point, the control calculates the amount that the workpiece or
fixture is out of parallel (with the first axis in the G38.1 block) using the
two recorded positions. Note that the probe tip radius is not a factor in
G38.1 parallel probing.
Table 27.B and Figure 27.5 show the values generated by this cycle and
stored by the control as paramacro system parameters. These values may
be viewed using the paramacro tables as discussed in chapter 28.
Table 27.B
Paramacro System Parameters for G38.1 Parallel Probing.
System Parameter Value this parameter holds
#5090 G38.1 run measurement (always equal to I)
#5091 G38.1 rise measurement