Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 354)

Coordinate Control
Chapter 13
13-2
To rotate the current work coordinate system, program the following
command.
G68 X__ Y__ Z__ R__;
Where : Is :
X, Y, Z Specify the center of rotation using only the two axis words that are in the
current active plane (G17, G18, or G19). The value entered with these axis
words represent a position in the current work coordinate system. The values
specified with the axis words are always absolute coordinate values, the center of
rotation cannot be specified as an incremental position.
R Specify the angle of rotation that the coordinate system is to be rotated at. Enter
a value in units of degrees. R is always measured parallel to the first major axis
in the current plane. Positive R is measured counter clockwise, and a negative R
is measured clockwise. If you do not specify an angle using an R word in the
G68 block, the control uses the value of the “Programmable Part Rotation”angle
field from the rotation table shown in figure Figure 13.6.
Important: If the first motion command following the G68 command is an
incremental move, the center of rotation as described in the G68 command
is ignored and the coordinate system is rotated about its zero point (see
Example 13.1). The first motion command following a G68 block cannot
be a circular move.
Any unnecessary parameters in the G68 block are ignored. Any G codes
other then a plane selection (G17, G18, or G19) or a change from absolute
or incremental mode (G90, or G91) specified in a G68 block will result in
an error.
The G68 block will not create any axes motion. Position displays change
due to the alteration of the work coordinate system.
Any rotation of the work coordinate system by programming a G68
command will rotate only the currently active work coordinate system.
When changing to a different work coordinate system, the rotation will not
be applied to the new work coordinate system. When changing back to the
rotated coordinate system the rotation will still be in effect.
If you do not program an R word in the G68 block, the value of the angle
for programmed rotation is taken from the part rotation screen. Access this
screen as described for external part rotation on page 13-8. The last field
on this screen is the programmable part rotation angle. This angle is only
used when the R word is excluded in the G68 block.
13.1.1
Rotating the Current Work
Coordinate System (G68,
G69)