Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 597)

Using Post Milling Cycles
Chapter 23
23-3
Figure 23.1
Rectangular Post Roughing Using G88.3
Q
Q
Y
X
H + Tool Radius
D
Tool Radius
Plunge Position
POST
(X, Y)
J
I
Important: The tool should be positioned near the center of the post prior
to the G88.3 block. The Z coordinate of this position determines the initial
Z level or top of the pocket. This is the pre-cycle position of the tool. The
pre-cycle position must be at some depth other than the cycles
programmed final depth or an error is generated.
From the pre-cycle position, the control simultaneously raises the tool by
the clearance amount (AMP selectable, refer to the literature provided by
your system installer) while moving it to the center of the rectangular post
specified by the X and Y parameters. This simultaneous move takes place
at the rapid feedrate.
Depending on which axis intersects the longer side of the pocket, the tool
is moved along either the -X or the -Y axis to the outer perimeter of the
pocket to be machined around the post. This position is the plunge-
position of the cycle, the position where the plunge to the programmed
depth takes place.