Rockwell Automation 8520 9/Series CNC Lathe - Manual (Page 345)

Chapter 13
Coordinate Control
13-3
In the above block, the control moves the cutting tool away from the
current axis position, a distance of 40 units on the X axis and 20 units on
the Z axis.
G91 is a modal G-code and remains active until cancelled by a G90.
Example 13.2
Absolute vs Incremental Commands
Absolute Command Incremental Command
G90X20.Z10.; G91X10.Z-25.;
Figure 13.1
Results of Incremental VS Absolute Example
20
10
X
Z
Start point
End point
10 35
Lathe G-code, System A
If using G-code system A, G90 and G91 are not available. To program
moves in absolute mode using G-code system A, call out axis positions
using X, Z, and C axis words.
Important: Absolute and incremental axes addresses are assigned in AMP
by your system installer, and they differ from those shown here.
Absolute command, G code system A
X40.Z20.;