Circular interpolation uses the G02 or G03 code word for the calculation of table positions required to produce a circular tool path. For the clockwise arc shown below the CNC controller must calculate thousands of positions along the path and correspondingly accelerate and decelerate the X and Y axes to achieve the smooth and constant motion required.
Example: G02 X0Y8 R8 (arcs are always begin at the current coordinate)
Where G02 is the code for clockwise arc, X0Y8 is the terminus of the arc, and R8 is the radius of the arc. G03 would be used for a counterclockwise arc.
Note that Y axis motor must start out at a pretty brisk speed while the X axis motor is barely moving. This changes throughout the arc until at completion the Y axis motor is barley moving and the X axis motor is running fast. Two G-codes use circular interpolation, G02, and G03.