Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 614)

Using Hemisphere Milling Cycles
Chapter 24
24-8
The following subsections cover using the G88.6 finishing cycle for
concave or convex hemispheres.
Use the G88.6 concave milling finishing cycle to finish a concave pocket
in a workpiece. This cycle is typically used to remove the finish allowance
that was left on the sides of the concave hemisphere during the G88.5
roughing cycle.
The G88.6 block used to finish a concave pocket has this format:
G88.6 X__Y__Z__R__Q0_P__H__L__E__F__;
Where : Is :
X Y The coordinates that specify the center of the concave hemisphere in the
selected plane.
Z The coordinate (along the plunging axis) that specifies the bottom of the
hemispherical pocket. In incremental mode this parameter specifies the depth of
the pocket as measured from the start level to the pocket bottom. This
parameter must be programmed.
R Radius of the concave hemisphere.
Q0 Code specifying a concave hemisphere.
P Direction of finishing cut. This parameter determines whether the finishing cuts
are performed in a clockwise or counter-clockwise motion. P0 specifies
clockwise. P1 specifies counter-clockwise.
Important: If cutter compensation (G41/G42) was enabled prior to the
G88.6 block, it is disabled when G88.6 is enabled.
H The finish allowance that will be left on the sides of the concave hemisphere.
This is an optional parameter that is provided to allow for multiple finishing cuts.
L Finishing cusp height. This value of this parameter is a measurement that
corresponds to the height of the material left along the sides of the hemisphere
after each X-Z roughing plunge.
E Plunge feedrate. This parameter determines the feedrate of any Z axis moves. If
not programmed the roughing feedrate (F) will be used.
F Finishing feedrate. If not programmed the existing (modal) feedrate will be used.
If Q0 is programmed, the control makes a finish pass around the sides of a
concave hemisphere. The control makes multiple circular finish cuts at
each level of the concave hemisphere. The depth of the pocket increases
and the diameter of each level decreases until the bottom center of the
concave hemisphere is reached.
Prior to each finish plunge, the control computes a delta finish 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 G88.6 block, and the tool radius programmed prior to
the G88.6 block.
24.2.1
Concave Hemisphere
Finishing Using G88.6