FANUC cylindrical interpolation: why rotation angle, cylinder radius and arc R are different quantities
The 0i-D manual distinguishes the cylinder radius, rotary-axis angle and developed-surface arc radius in G07.1. An arc-length calculation explains dimensional errors, followed by key restrictions on mode transitions.
Contents
When a contour machined on a cylindrical surface has a scale error, first check three easily confused quantities: cylinder radius, rotary-axis angle and contour arc radius. They contribute to the same path but represent different data.
G07.1 in the 0i-D manual
Section 4.5, printed pages 43–45, of the public mirror of the original FANUC B-64304EN/02 manual explains that cylindrical interpolation converts rotary angle into circumferential travel, combining it with a linear axis to form a path on the developed surface. This article applies to the 0i-D / 0i Mate-D with the relevant function and rotary axis configured. Other generations require their own manuals.
| Quantity or notation | Meaning in this edition |
|---|---|
| r in G07.1 IP r | Workpiece radius used for cylindrical interpolation; IP represents the rotary-axis address |
| Rotary-axis movement | An angle, not a directly entered arc length on the developed surface |
| R in an arc command on the developed surface | Contour arc radius in length units, not an angle |
These are meanings of symbols, not an executable program. Plane selection and the corresponding axes also depend on machine configuration.
An arc-length check reveals scale differences
For a cylinder of radius R, rotation through θ degrees corresponds to developed length s＝2πRθ÷360. Assume R＝50 mm and θ＝30°: s is approximately 26.18 mm. If R＝100 mm is used incorrectly, the same angle corresponds to about 52.36 mm. A factor-of-two radius error changes the scale of the angle-to-length conversion.
When the shape appears correct but circumferential dimensions are wrong, first confirm the cylinder radius and angular units, then compare circumferential travel generated by the postprocessor. Do not start by adjusting the origin to correct a scale error.
Restrictions inside and outside the mode also affect the result
The manual defines F as the feedrate along the cylinder circumference. Page 44 requires existing cutter radius / tool nose radius compensation to be canceled before entry; this compensation must be started and ended within cylindrical interpolation mode. Page 45 separately specifies that Tool offset must be established before entry and must not change within the mode. These requirements must not be combined into a claim that tool compensation can be reset inside the mode. Ordinary drilling canned cycles are also unavailable in this mode; check program transitions against the complete procedure for the machine.
Use the error pattern to set the checking order
- All features share an angular shift: check the circumferential start position, direction of rotation and coordinate reference.
- Circumferential dimensions change proportionally: check the conversion between cylinder radius, angle and developed length.
- A local arc is incorrect: check the units of contour arc R and the plane definition, then inspect the tool-center path.
These are priority checks, not the only possible causes. If the workpiece surface is not a constant-radius cylinder, reassess whether the model applies. Return to the OPTION resources.