The Fanuc G94 Facing Cycle is a fundamental G-code used in CNC programming for lathes. It allows for efficient and precise facing operations, which are essential for creating a flat surface at the beginning or end of a cylindrical part.

Usage Format

The basic syntax for the G94 Facing Cycle is as follows:

G94 X... Z... F...

• X specifies the end point in the X-axis (diameter).
• Z specifies the end point in the Z-axis (length).
• F denotes the feed rate per revolution.

Explanation

When the G94 code is executed, the tool moves to the specified X and Z coordinates at the defined feed rate. The cycle is modal, meaning it will remain active until canceled by a rapid movement command (G00).

Example

Consider a scenario where we need to face a blank size of 65mm in diameter and 85mm long to a final size of 65mm in diameter and 82mm long. Here’s how the G94 cycle can be used:

(Start with a blank size of 65mm by 85mm)
N10 G50 S2500 (Set max spindle speed)
N20 G96 S180 M03 (Start spindle with constant surface speed)
N30 T0100 (Select tool)
N40 G00 X66.0 Z3.0 (Rapid move to starting position)
N50 G94 X-1.6 Z0 F0.2 (Facing cycle to centerline with feed rate)
N60 G00 X200.0 Z200.0 (Rapid move to safe position)
N70 M30 (End of program)

Text Diagram

Here’s a text representation of the facing operation:

Starting Point
|
|   /-----------------\
|  /                   \
| /                     \
| \                     /
|  \                   /
|   \-----------------/
|
End Point (after facing)

In this diagram, the slashes represent the tool path as it faces the workpiece from the starting point to the end point.