Rockwell Automation 8520 9/Series CNC Lathe - Manual (Page 373)

Axis Motion
Chapter 14
14-15
When a G29 is executed in a part program (or through MDI), the axis or
axes move first to the intermediate point, and then to the position indicated
in the G29 block. If a G28 was just executed, then this has the effect of
returning the axis from machine home.
For example, executing the block:
G29 X7.0 Z1.5;
in absolute mode would move the axes to (7.0, 1.5) after passing through
the intermediate point stored in control memory. In incremental mode, this
block would move the axes to a position that is X7.0 and Z1.5 units away
from the home point.
The intermediate point is stored in control memory after a G28 return to
machine home or a G30 move to alternate home is executed. A G29 block
is usually executed after a G28 or G30 block, typically to return the cutting
tool to the part after a tool change.
Although this command moves the axes at rapid feedrate as if in G00
mode, it is not modal. If G01, G02, or G03 modes are active, they are
temporarily canceled for the return from home moves.
Only the axes specified in the G29 block are moved. For example:
N1 G28 X5.0 Z1.0; (X and Z axes are moved to home after moving to X=5.0
Z=1.0)
N2 G29 X3.; (X moves to X=5.0 then to X=3.0 ------ Z does not move)
Example 14.7
Automatic Return From Machine Home
N00010 X100.Z50.;
N00020 Z150.;
N00030 G28X150.Z180.;
N00040 G29X200.Z100.;
14.2.3
Automatic Return from
Machine Home (G29)