Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 637)

Milling Fixed Cycles
Chapter 26
26-5
The plane selection codes (G17-G19) can be included in the milling fixed
cycle block, or can be programmed in a previous block.
Figure 26.2 shows typical milling fixed cycle motions in absolute (G90) or
incremental (G91) modes. Note the changes in how the R point and Z
level are referenced.
Figure 26.2
Milling Fixed Cycle Parameters in G90 and G91 Modes
Cutting feed
Rapid feed
0 0
R point level R point level
Z
Z
R
R
G90 Absolute Mode G91 Incremental Mode
Z Z