Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 621)

Irregular Pocket Milling Cycles
Chapter 25
25-3
Prior to the G89.1 block, the tool should be positioned near the start/end
corner of the pocket and should be just above but not touching the part.
This position is referred to as the start-point of the cycle (A in figure
16.16). From the start-point the cutter must be able to move down into the
part and then directly over to the start/end corner of the pocket without
cutting into any wall of the pocket. The Z coordinate of this position
determines the initial Z level or top of the pocket.
Once the axes are positioned at the start-point, a plunge along the Z axis
takes place. If L is programmed, the tool plunges along the Z axis to the
incremental depth specified by the L parameter (B in Figure 25.1). If L is
not programmed, the tool plunges along the Z axis to the pocket depth
specified by the Z parameter (B in Figure 25.1). This move takes place at
the plunge feedrate specified by the E parameter. If E is not programmed,
the plunge takes place at the roughing feedrate specified by the F
parameter.
After the plunge, the control uses the active cutter compensation mode
(G41/G42) to offset the cutter one cutter radius perpendicular to the line
from the start-point to the start/end corner (C in Figure 25.1). The control
then moves the cutter from this offset position to a point where it is located
one cutter radius plus the finish allowance away from both the first wall of
the pocket and the line from the start-point to the start/end corner (D in
Figure 25.1). This move takes place at the roughing feedrate.