Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 568)

Cutter Diameter Compensation
(G40, G41, G42)
Chapter 21
21-50
If compensation is not cancelled using a G40 command, the control
automatically, temporarily cancels compensation for the change in work
coordinate system. This is done by using the last compensated move in the
current coordinate system as an exit move for compensation. The control
then automatically re-initializes cutter compensation after the new work
coordinate system is established. This is done by using the first move in
the new coordinate system that is in the compensation plane as a entry
move for compensation. This re-setup occurs even if the change to the
coordinate system is not in the active cutter compensation plane.
Figure 21.47 gives an example of programming a G92 offset to the work
coordinate system. The same figure, however, would apply to any change
in the work coordinate system.
Figure 21.47
Cutter Compensation During G92 Offset to Work Coordinate System
Temporary cancel of
compensation here
N10 N11
N12
N14
N15
G41
N13
r
Programmed
path
During normal program execution, the control is constantly scanning
blocks ahead to set up the necessary motions to correctly execute the
current block. This is called Block Look-Ahead.
The control has a total of 21 set-up buffers. Different features require the
use of some of these set-up buffers. One is always used for the currently
executing block. Cutter compensation requires at least 3 of these buffers;
other features also occasionally require the use of some of these buffers.
Any remaining set-up buffers are used for Block Look-Ahead, one buffer
for each block look-ahead.
21.6.8
Block Look-Ahead