Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 468)

Programming Feedrates
Chapter 18
18-20
When Acc/Dec is active, the control automatically performs Acc/Dec to
give a smooth acceleration/deceleration for cutting tool motion.
However, there are cases in which Acc/Dec can result in rounded corners
on a part during cutting. In Figure 18.10 this problem is most obvious
when the direction of cutting changes from the X axis to the Y axis. In
this case, the X axis decelerates as it completes its move while the Y axis is
at rest. As soon as the X axis reaches the AMP defined in-position band,
the Y axis begins accelerating to make its commanded move. Since the Y
axis begins motions before the X axis finishes, a slight rounding results.
Figure 18.10
Rounding of Corners
programmed tool path
actual tool path
X
Y Cutting tool
G09, G61
G64, G63
These two G codes can be used to eliminate corner rounding.
Exact Stop (G09 -- nonmodal)
If a programmed motion block includes a G09, the axis will move to the
commanded position, decelerate, and come to a complete stop before the
next axis motion block is executed. The G09 can be programmed in rapid
(G00), feedrate (G01), or circular (G02/G03) motion blocks, but is active
only for the block in which it is programmed.
Exact Stop Mode (G61 -- modal)
G61 establishes the exact stop mode. The axes move to the commanded
position, decelerate and come to a complete stop before the next motion
block is executed. Cancel this code by programming G61, G62 or G63.
18.4.5
Precautions on Corner
Cutting