Glossary · Motion control and drives
Circular interpolation
Also known as: Circular path interpolation
German: Kreisinterpolation
In motion control and CNC, circular interpolation is the coordinated control of two axes so that the tool or load moves along a circular arc, defined by start point, end point and either the center point or the radius.
- Motion control
In one sentence
Circular interpolation coordinates two axes so a tool or load follows a circular arc between a start and an end point.
Example
A milling machine uses circular interpolation (G02/G03 in ISO 6983 G-code) to mill a round pocket.
How it applies
- Engineering: The interpolator in the CNC or motion controller calculates intermediate setpoints for both axes in every cycle so that the path stays on the arc at the programmed feed rate.
- Commissioning: Circularity tests (for example a ballbar test) reveal mismatched loop tuning, backlash or reversal errors between the axes.
- Operation: Path accuracy depends on the axes' dynamic behavior; at high feed rates small radii may be slowed down automatically.
- Documentation: In programming manuals, show the arc syntax with a drawing of direction (clockwise vs. counterclockwise, seen from which side) and the plane selection. Ambiguous direction conventions are a common source of crashes.
Circular vs. linear interpolation
Linear interpolation moves on a straight line between two points; circular interpolation moves on an arc. Complex contours are built from both, or from spline interpolation.