176
G CODES
96-8000
June 1999
Scaling does not affect canned cycle Z axis movements such as clearance planes and incremental values. The
final results of scaling are rounded to the lowest fractional value of the variable being scaled.
G68 Rotation (This G-code is optional and requires Rotation and Scaling) Group 16
[ G17 | G18 | G19 ] G68 [a...] [b...] [R...] ;
G17,G18,G19 optional plane of rotation, default is current.
a optional center of rotation for the first axis of the selected plane.
b optional center of rotation for the second axis of the selected plane.
R optional angle of rotation specified in degrees.
Three-place decimal -360.000 to 360.000.
In the above example, îš‘aîš’ and îš‘bîš’ correspond to the axes of the current rotation plane. If G17 is the current
rotation plane, then îš‘aîš’ is X and îš‘bîš’ is Y.
When rotation is invoked, all subsequent X, Y, Z, I, J, and K values are rotated through a specified rotation
angle R using a center of rotation.
G68 is modal and modifies appropriate positional values in the blocks following the G68 command. Values in
the block containing G68 are not rotated. For subsequent blocks, only the values in the plane of rotation are
rotated. Thus, if G17 is the current plane of rotation, only X and Y values are affected.
For a positive angle, the rotation is counterclockwise. If the angle of rotation - the R code - is not specified in
the G68 command block, then the angle of rotation is taken from Setting 72. The default rotation angle in
Setting 72 is 0.0 degrees.
A center of rotation is always used by the control to determine the positional values passed to the control after
rotation. If any axisîš’ center of rotation is not specified, then the current location of the work coordinate is used
as the center of rotation.
In G90 mode (absolute), the rotation angle takes on the value specified in R. When Setting 73 (G68 INCRE-
MENTAL R) is set to ON, then the rotational value can be incremented on each call to G68. In G91 mode
(Incremental), the rotation angle is incremented by the value in R. Each G68 command block, when in G91
mode, will increment the rotation angle by the value specified in R. Angles are modulo 360, so that when an
angle is incremented past 360 degrees, the angle will become an equivalent value between 0 and 360 degrees.
The rotational angle is set to zero upon cycle start, or it can be set explicitly by using a G68 block in the G90
mode.
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