Rockwell Automation 8520 9/Series CNC Lathe - Manual (Page 527)

Tool Tip Radius Compensation (TTRC)
Function
Chapter 21
21-43
If a tool becomes excessively worn, broken, or for any other reason
requires the changing of the programmed tool tip radius, TTRC should be
cancelled and re-initialized after the tool has been changed. See page
NO TAG on changing the tool offset and page on changing the active tool
offset number.
Important: Slight overcutting may occur during Cutter Compensation,
depending on the programmed path at the point where the change in cutter
radius was made. To avoid overcutting, we recommend that you use a
Mid--Start Program until the point of tool breakage.
Figure 21.39 through Figure 21.41 are representations of the resulting tool
paths after the programming of a change in the radius of the cutting tool.
Assume in these figures that the programmed change to the tool radius is
entered in block N11 which also contains the motion as described in the
figure.
The tool path taken when changing tool radius is dependant on the move
immediately before the change in radius was programmed, the move that
the change in radius was programmed in, and whether any generated
motion blocks were made between these tool paths.
Figure 21.39 gives a description of the tool path when the programmed
moves are linear-to-linear.
Example 21.15
Linear-to-Linear Change in Cutter Radius
When the control generates blocks When the control does not generate
blocks
N10 X10.Z5.G1T1; N10 X10.Z10.G1T1;
N11 X-5.Z3.T2; N11 Z20.T2;
N12 Z20.G42; N12 X0.Z30.;
21.6.4
Changing Cutter Radius
During Compensation