Output methods
| Method | FANUC-type | SINUMERIK | Best for |
|---|---|---|---|
| Indexed C | C.. + brake | C.. / SPOS | Holes at fixed angles |
| Polar interpolation | G12.1 / G13.1 | TRANSMIT | Face contours: flats, hexes, slots on the face |
| Cylindrical interpolation | G07.1 C.. | TRACYL(d) | Grooves and slots on the diameter |
| Y-axis milling | G17/G19 with Y | Y moves | Off-centre flats and pockets (Y-axis machines) |
| Direct XZC | Post-calculated C moves | Same | When interpolation modes aren't available |
Example: cylindrical interpolation
(Slot on 40 mm diameter - FANUC-type)
M* (C-axis on)
G00 C0.
G19 G98
G07.1 C20. (radius of the cylinder)
G01 Z-10. C0. F200.
Z-30. C90.
G07.1 C0.
M* (C-axis off)Inside G07.1, C is still commanded in degrees, but the controller uses the programmed radius to interpolate as if the cylinder surface were unrolled flat. Plane selection and exact behaviour depend on the controller.
How the post chooses
- Machine capability: Y-axis, interpolation options available.
- Feature geometry: face vs diameter, centred vs off-centre.
- Accuracy: polar interpolation near centre can limit C speed.
- Programmer preference via CAM settings or post properties.
Feed and spindle details
- Switch from feed per rev (turning) to feed per minute (milling).
- Start live tool spindle with its own M-code and speed.
- Keep main spindle stopped and C engaged throughout.
The same feature can be posted four ways; the right one depends on the machine.
C-axis and live tooling posts
See our CNC post processor development service and live tooling posts.