G30 is a G-code that instructs the CNC machine to move the tool to the 2nd, 3rd, or 4th zero return position. The zero return position is a predefined location where the tool can be safely parked or changed. The zero return position is also known as the home position or the reference position.

Usage Format

The general format of G30 is:

G30 Pn

where n is an integer from 1 to 4 that specifies which zero return position to use. For example, G30 P1 moves the tool to the 1st zero return position, G30 P2 moves the tool to the 2nd zero return position, and so on.

Explanation

G30 is useful for several purposes, such as:

• Moving the tool away from the workpiece to avoid collisions or interference.
• Moving the tool to a convenient location for tool change or measurement.
• Moving the tool to a known position for calibration or alignment.
• Moving the tool to a position that corresponds to the machine origin or the work offset origin.

G30 can be used with or without a modal group. A modal group is a set of G-codes that affect the same function and remain active until another code from the same group is called. For example, G90 and G91 are in the same modal group that controls the distance mode (absolute or incremental).

If G30 is used without a modal group, it will move the tool to the specified zero return position in the current distance mode. For example, if the distance mode is absolute (G90), then G30 P2 will move the tool to the absolute coordinates of the 2nd zero return position. If the distance mode is incremental (G91), then G30 P2 will move the tool by the incremental amount of the 2nd zero return position from the current position.

If G30 is used with a modal group, it will move the tool to the specified zero return position in the distance mode of the modal group, regardless of the current distance mode. For example, if the current distance mode is absolute (G90), then G91 G30 P2 will move the tool by the incremental amount of the 2nd zero return position from the current position. Similarly, if the current distance mode is incremental (G91), then G90 G30 P2 will move the tool to the absolute coordinates of the 2nd zero return position.

Example

Here is an example of using G30 in a CNC program:

N10 G90 G54 G00 X0 Y0 Z0 ; Set distance mode to absolute, work offset to G54, and move tool to origin
N20 G01 Z-10 F100 ; Perform a linear feed to Z-10 at feed rate 100
N30 G03 X10 Y10 R5 F200 ; Perform a circular interpolation to X10 Y10 with radius 5 at feed rate 200
N40 G30 P3 ; Move tool to 3rd zero return position in absolute mode
N50 M06 T2 ; Perform a tool change to tool 2
N60 G30 P2 ; Move tool to 2nd zero return position in absolute mode
N70 G91 G30 P1 ; Move tool by the incremental amount of the 1st zero return position from the current position
N80 M30 ; End of program