Retract methods compared
| Method | Example | Notes |
|---|---|---|
| Reference return | G91 G28 Z0. | Goes to machine home Z; incremental form avoids intermediate point surprises |
| Machine coordinate move | G53 G00 Z0. | Direct move in machine coordinates, no intermediate point |
| Clearance plane | G00 Z50. | Fastest; only safe if clearance is truly clear of fixtures |
Watch out for G90 G28 Z0.: in absolute mode, the intermediate point is Z0 of the work offset, which can drive the tool into the part before it goes home.
When the post retracts
- Before and after tool changes.
- Before rotary axis moves (4-axis and 5-axis).
- Between setups and work offsets.
- At the end of the program.
- Optionally between operations with the same tool, to a clearance plane only.
Retracts on 5-axis machines
After a tilted operation, retracting straight up in machine Z may drag the tool through the part. Safer strategies retract along the tool axis first, then to machine Z, then rotate.
(Retract along tool axis in tilted plane)
G00 Z50. (tilted plane still active)
G69 (cancel tilted plane)
G53 G00 Z0. (machine Z home)
G00 A0. C0. (then rotate)Balancing safety and cycle time
Full home retracts everywhere are safe but slow. Good posts use full retracts where the risk is real (tool changes, rotary moves, setup changes) and clearance moves elsewhere, controlled by post properties.
A retract strategy should be safe by default and fast by design.
Safe post development
See our CNC post processor development service and tool change logic.