Fanuc G70 finishing cycle

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The Fanuc G70 finishing cycle is a powerful G-code used in CNC programming for lathes. It allows for the finishing of a part by repeating a sequence of operations defined in a previous block of code, typically after a roughing cycle like G71.

Usage Format

The basic syntax for G70 is as follows:

G70 P.. Q..

Where P is the start block number and Q is the end block number of the sequence to be repeated.

Explanation

G70 works in tandem with roughing cycles such as G71, G72, or G73. It uses the contours defined by these cycles and performs a finishing pass. The P and Q parameters define the range of blocks that the G70 will execute, ensuring precision in the final pass.

Example

Let’s consider a simple turning operation where we have used G71 for roughing. Here’s how we might use G70 to finish:

N10 G71 ... (Roughing cycle parameters)
N20 G0 X... Z... (Roughing pass)
N30 G1 X... Z... F... (More roughing)
...
N40 G70 P20 Q30 (Finishing cycle)

Text Diagram

[Initial Part Profile]
|----------------|
|                |
|                |
|                |
|                |
|----------------|

[After G71 Roughing]
|----------------|
|                |
|     *****      |
|     *****      |
|                |
|----------------|

[After G70 Finishing]
|----------------|
|                |
|     *****      |
|     *****      |
|     *****      |
|----------------|

In this diagram, the asterisks represent the material removed during the roughing and finishing passes.

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