In CNC machining, figure copy functions like G72.1 and G72.2 are used to replicate a pattern of operations at different coordinates. These are particularly useful for drilling or milling a circular pattern of holes, commonly known as a Bolt Hole Circle.

Usage Format

The format for G72.1 (circular pattern) and G72.2 (linear pattern) in Fanuc systems is:

G72.1 P_ Q_ (circular pattern)
G72.2 P_ Q_ (linear pattern)

• P is the start block number of the figure to be copied.
• Q is the end block number of the figure to be copied.

Explanation

G72.1 copies the figure defined between P and Q in a circular pattern around a center point, which is defined in the program. G72.2 does the same but in a linear pattern. The control repeats the operation at specified intervals or mirror images.

Example

For a Bolt Hole Circle pattern with 6 holes, 360° apart on a 50mm radius circle:

Text Diagram:

          O
      O       O
    O           O
      O       O
          O

G Code:

G17 G90 G40
G0 X0 Y0 (Move to circle center)
G72.1 P1 Q2 R50 L6 (Copy figure from P1 to Q2, 6 times on a radius of 50)
N1 G81 X20.0 Y0 Z-10 R5 F200 (Drilling cycle for first hole)
N2 G80 (Cancel drilling cycle)

This code sets up a circular pattern copy starting at block N1 and ending at N2, to be repeated 6 times at a radius of 50mm from the center of the circle.