CNC machines allow for precise control over cutting tools, enabling the creation of complex shapes and surfaces. Among the most common shapes produced are arcs and circles, which are programmed using G02 and G03 codes in G-code programming language.

Usage Format

The general format for these commands is as follows:

• G02 for clockwise arc movement
• G03 for counterclockwise arc movement

The syntax is:

G02/G03 X_ Y_ I_ J_

Where:

• X_ and Y_ denote the endpoint of the arc.
• I_ and J_ specify the distance from the starting point to the center of the arc along the X and Y axes, respectively.

Explanation

G02 and G03 commands are modal, meaning they remain active until changed. When programming an arc, the current point is considered the start point, and the X and Y values are the end point of the arc. The I and J values are used to determine the radius and position of the arc’s center relative to the start point.

Example

Let’s consider an example where we need to move the tool in a clockwise arc from the current position to a point 100 units to the right and 50 units up, with a radius of 75 units.

The text diagram below illustrates this scenario:

(Start)
   |
   |    (End)
   |     /
   |    /
   |   /
   |  /  <- Arc Path (G02)
   | /
   |/
(Current Position)

The G-code for this movement would be:

G02 X100 Y50 I25 J0

Here, I25 indicates that the center of the arc is 25 units to the right from the current position (since the radius is 75 and we’re moving 100 units to the right), and J0 means the center of the arc is along the same Y level as the current position.