Circular interpolation in CNC milling is a critical process that allows the machining of arcs and circles. It is achieved through the G02 and G03 commands, which instruct the machine to move in a circular path around a defined center point.
Usage Format
The G02 and G03 commands follow this basic syntax:
 G02 for clockwise (CW) circular interpolation
 G03 for counterclockwise (CCW) circular interpolation
The commands can be used with either R or IJK parameters to define the circle’s radius or its center point, respectively.
Explanation
 G02 X_ Y_ R_ F_: Moves the tool in a CW arc to the end point (X_, Y_) with a specified radius (R_) at a certain feed rate (F_).
 G03 X_ Y_ I_ J_ F_: Moves the tool in a CCW arc to the end point (X_, Y_) with the arc’s center offset (I_, J_) from the starting point at a certain feed rate (F_).
Example
Here’s a simple example of a program using G02 and G03 with a text diagram:
% (Program Start)
N10 G17 G90 (Select XY plane and absolute positioning)
N20 G01 X0 Y0 F20 (Move to start point)
N30 G03 X2 Y2 R1 F10 (CCW arc to end point with radius)
N40 G02 X4 Y0 I2 J2 F10 (CW arc back to start point with center offset)
M30 (Program End)
Text Diagram:
Y+

 (2,2)
 / \
 / \
 / \
 / \
/ \
+ X+
/
/ 
(0,0) (4,0)
In this example, the tool moves from the origin (0,0) to (2,2) in a counterclockwise arc with a radius of 1 unit, then returns to (4,0) in a clockwise arc with the center of the arc located 2 units left and 2 units down from the end point.