Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 623)

Irregular Pocket Milling Cycles
Chapter 25
25-5
These two passes cut a channel around the inside perimeter of the pocket
that provides clearance for the cutter to be raised and lowered as necessary
at the beginning and end of the rest of the roughing passes. While cutting
this channel, the control automatically adjusts the roughing feedrate so that
the volume of material being removed per unit time is the same as will be
removed later during normal roughing passes.
Figure 25.2
Irregular Pocket Initial Roughing Passes
TOP
VIEW
Start/end corner
X
Y
H
K
G F
J/N
M
E/I D
H
L
After the initial roughing passes are complete, the cutter is near the pocket
corner that corresponds to the endpoint of the block that follows the block
specified by the P parameter in the G89.1 block (point N in Figure 25.3).
The control analyzes the remaining pocket area to be machined-out and
determines which area to machine first. Any undone area within one cutter
radius of the current cutter position will be machined-out first.
The area within one cutter radius of the current cutter position will be
machined-out in a series of straight-line step-over roughing passes. The
orientation of these passes, either parallel to the X or the Y axis, is
dependent upon the pocket contour. The control determines whether
passes parallel to the X or to the Y axis will machine-out the most material
in the fewest amount of passes and orients the passes accordingly (N
through Z in Figure 25.3).