Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 683)

Skip, Gauge, and Probing Cycles
Chapter 27
27-9
They may be programmed directly in the G38 block. Values entered for
these parameters in the G38 block supercede both AMP values and
probe parameter table values.
Figure 27.2
Parameters for G38 Hole Probing Cycle
Probe
Hole
F feedrate
H
R D
D
E feedrate
E feedrate
+
Probe radius
(see section 27.5)
When the G38 code is executed, the probe must have previously been
positioned with the probe in the hole so that it will contact the sides of the
hole when axis motion takes place in the currently active plane. Ideally (to
maximize accuracy) the probe should be positioned near the center of the
hole.
The control executes the G38 cycle in the following manner:
1. When the G38 block is read during program execution, the control
starts axis motion in the positive direction of the second axis defining
the plane at the approach feedrate (E). If the plane is the XY plane,
then this would be the Y axis.
2. The axis continues on at the approach feedrate (E) until the approach
distance (R) is reached. Then the feedrate is reduced to the probe
feedrate (F).