Rockwell Automation 8520 9/Series CNC Lathe - Manual (Page 443)

Programming Feedrates
Chapter 18
18-17
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 18.9, this problem is obvious when the
direction of cutting changes from the X axis to the Z axis. In this case, the
X axis decelerates as it completes its move, while the Z axis is at rest. As
soon as the X axis reaches the AMP defined in-position band, the Z axis
begins accelerating to make its commanded move. Since the Z axis begins
motions before the X axis finishes, a slight rounding results.
Figure 18.9
Rounding of Corners
Programmed tool path
Actual tool path
Z
Cutting tool
X
G09, G61
G64, G63
Use these G-codes to eliminate corner rounding:
Exact Stop (G09 - - non-modal)
If a programmed motion block includes a G09, the axis moves to the
commanded position, decelerates, and comes 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 it is active
only for the block in which it is programmed.
18.3.5
Precautions on Corner
Cutting