KEVOS® MAKEOS · Manufacturing
Inverse Time Feed Rate (G93)
What inverse-time F value programs this move at the feed I want?
Inverse time feed command (G93 F-word) for a linear, rotary or combined multi-axis move: the reciprocal of the move time, from the feed rate and the length or angle of the move, with the time per block and the surface speed of a rotary move at a radius.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Move | choice | Kind of move. |
| Linear length of the move | mm | Straight-line distance of the linear axes in the block. |
| Rotary angle of the move | ° | Angle turned by the rotary axis in the block. |
| Cutting radius on the rotary axis | mm | Radius from the rotary axis to the cutting point. |
| Wanted feed at the cutter | mm/min | Feed you want along the cutting path. |
Method and formulas
- Inverse time feed = feed rate ÷ distance moved = 1 ÷ time (in minutes) for the block.
- Rotary path at the cutter = π r × angle ÷ 180°; combined path ≈ √(linear² + arc²).
- Program G93 with F = 1 ÷ time on every block; return to G94 afterwards.
- Example: 90° at 40 mm radius at 300 mm/min needs F4.7746.
Limitations
- Combined path is approximated as straight in the developed plane; long blocks with large rotation should be split.
- Controls differ in G93 limits and decimal resolution.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Program feed for 4th- and 5th-axis moves
- Convert a target surface feed to an inverse-time F value
- Check block times in a multi-axis program
Who it is for
- Machinists
- CNC programmers
- Manufacturing engineers
What you get
- Inverse-time F value
- Time for the block
- Path length at the cutter
Interpreting the result
- Every G93 block needs its own F word; a missing F is an alarm on most controls.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1288–1289. Topic reference; no source tables or recommended settings are reproduced.
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