Hello Sinha,
That is the case with a TypeI profile, but not so with a TypeII profile where the X moves are not monotonous in direction.
The following picture shows a profile with a concave feature being machined with a tool set as a Type 3 tool (the Leading Edge in Z and the point on the Insert closest to the machine centre line). In the picture:
1. The Part Profile is shown in White
2. The coordinates of the profile (those coordinates, X and Z, specified in the Profile Definition between the P and Q blocks) are shown in Light Blue.
3. The TNR is shown in Light Green
and
4. The material Left and Over-cut is shown in Magenta.
View attachment 243242
You can see clearly in the attached picture that material is severely Over-cut by the Trailing Edge of the Tool on first element (right most angled element) of the Concave feature.
Cutter Radius Comp on a mill is practically mandatory, as its via this function that the dimensions of features, cut with the periphery of an end mill, are adjusted. Although it can be said that TRC on a lathe is used to adjust the size of some elements of a profile, its mainly Tool Offsets in X and Z that are used to correct the dimensions of a turned component.
There are many versions of Fanuc G71 cycles that are not documented in the Operator Manual supplied with the machine. FST10, 11 and 12 controls handled TRN Comp quite well in a G71 Cycle, but the control before, and many after the aforementioned models, ignore TNR Comp in the G71 Cycle. Accordingly, the profile shown in the above attached picture would be ruined before the G70 cycle is called to finish the profile.
Regards,
Bill