Siemens CNC Lathe | G79 – G94 Cycle | Facing


Straight Facing Cycle Introduction

With the commands of “G… X(U)… Z(W)… F… ;”, straight facing cycle of 1 to 4 as shown in Fig. 4-11 is executed. The code most of time is G79 but also possible sometimes as G94 or G24 depend on parameter setting or machine builder choice.

The cycle code can be change due to pre-selected G code system as below ( Selected by machine tool builder by parameter setting).

G code system A = G94
G code system B = G79
G code system C = G24
Fig. 4-11 Straight facing cycle

G94 and G79 Format

G… X… Z… F… ;

Since G79 (G94, G24) is a modal G code, thread cutting cycle is executed by simply specifying depth of cut in the Z-axis direction in the succeeding blocks. It is not necessary to specify G79 (G94, G24) repeatedly in these blocks.

Example

Fig. 4-12 Straight facing cycle (G code system B)

N60 G00 X65. Z42. ;
N61 G79 X20. Z38. F0.35 ;
N62 Z34. ;
N63 Z30. ;
N64 G00 ;
….
….