Fanuc’s G71 Turning Cycle and G74 Peck Drilling Cycle

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CNC lathe programming is a critical skill for precision machining. Fanuc’s G71 Turning Cycle and G74 Peck Drilling Cycle are essential for efficient and accurate internal machining operations.

Usage Format

  • G71 Turning Cycle: Used for rough turning operations.
    • Format: G71 P... Q... U... W... F...
  • G74 Peck Drilling Cycle: Employed for drilling operations with a pecking motion to break up chips.
    • Format: G74 X... Z... R... P... F...

Explanation

The G71 Turning Cycle is used to remove material in a rough turning operation. It requires defining a pattern for the tool to follow, which is specified in a separate part program.

The G74 Peck Drilling Cycle is designed for drilling or boring operations where the tool retracts slightly to break chips and prevent them from clogging the workpiece or damaging the tool.

Example

Here’s a simple text diagram and example of using both G71 and G74 cycles:

Text Diagram:

(O)----------------(O)
 |                |
 |     Material   |
 |                |
(O)----------------(O)

G71 Rough Turning:

G71 P100 Q150 U0.5 W0.2 F0.15;
N100 G00 X40.0 Z5.0; (Start Position)
N110 G01 Z0.0; (Start of Cutting)
N120 X50.0 Z-75.0; (End of Cutting)
N150 G00 X100.0 Z100.0; (Safety Position)

G74 Peck Drilling:

G74 R1.0;
G74 X30.0 Z-50.0 P0.5 F0.1;

In this example, the G71 cycle is programmed to rough turn the internal diameter of a workpiece, while the G74 cycle is used to drill a hole with pecking motions to break the chips.

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