In the world of CNC machining, precision and efficiency are paramount. Fanuc’s lathe programming offers a robust solution for internal diameter (ID) machining with its G70, G71, and G74 codes. This article delves into the usage and benefits of these codes, providing a practical example for CNC engineers.

Usage Format

• G70 Finish Turning Cycle
• G71 Rough Turning Cycle
• G74 Peck Drilling Cycle

Each code serves a unique purpose in the machining process, from roughing out material to fine finishing touches.

Explanation

The G70 code is used for finishing operations to achieve a smooth surface finish. G71 is utilized for roughing material efficiently, and G74 facilitates peck drilling, which is essential for chip breaking in deep hole drilling operations.

Example

Let’s consider a scenario where we need to machine the internal diameter of a part:

1. Roughing the ID:

   G71 U2 R1
   G71 P100 Q120 U0.5 W0.2 F0.18
   

   Here, U and W denote the depth of cut in the X and Z-axis, respectively, and F is the feed rate.

2. Finishing the ID:

   G70 P100 Q120
   

   P and Q point to the start and end block numbers of the roughing cycle, ensuring a smooth finish.

3. Peck Drilling:

   G74 R1
   G74 X30 Z-50 Q2000 F0.1
   

   X and Z specify the position, Q the peck depth, and F the feed rate.

Text Diagram for ID Machining

|----------------|
|                |
|                | <- Finish Pass (G70)
|                |
|                |
|                | <- Rough Pass (G71)
|                |
|----------------|

In this simple diagram, the space between the rough and finish pass represents the material removed during the ID machining process.