Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 609)

Using Hemisphere Milling Cycles
Chapter 24
24-3
Figure 24.1
Concave Hemisphere Roughing Using G88.5
Plunge Position
Y
X
D’
R
D D D
(X, Y)
INITIAL Z-LEVEL
Z
D’
CUSP
HEIGHT
(L)
L’
Important: The tool should be positioned near the center of the concave
hemisphere prior to the G88.5 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.
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 concave
hemisphere specified by the X and Y parameters. This simultaneous move
takes place at the rapid feedrate. The center of the concave hemisphere is
the plunge position, the position where the plunge to the programmed
depth takes place.