Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 612)

Using Hemisphere Milling Cycles
Chapter 24
24-6
Figure 24.2
Convex Hemisphere Roughing Using G88.5
Y
X
D’
R
(X, Y)
TR D D D
Z R
INITIAL Z-LEVEL
TOOL DIA
D’
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 convex
hemisphere specified by the X and Y parameters. This simultaneous move
takes place at the rapid feedrate. The center of the convex hemisphere is
the plunge position, the position where the plunge to the programmed
depth takes place.
Prior to each plunge, the control computes a delta rough cut thickness, D’,
and a delta plunge depth, L’. These computations are based on the cusp
height (L parameter) and the hemisphere radius (R parameter) programmed
in the G88.5 block, and the tool radius programmed prior to the G88.5
block.