Machine with C-axis rotary table

This is an explanation of our 4 axis milling center with a rotary table.

The C-axis control the rotation of the table. Direction of motion is defined by the sign of the C value. Since the table rotates the workpiece, the table must rotate clockwise to achieve a counterclockwise tool motion and vice versa.


C+ = Counterclockwise workpiece rotation (viewing in the Z+ direction).
C- = Clockwise workpiece rotation.



G90 Absolute Mode

In the absolute mode (G90), the C word value defines the final position between
0 and 360. The + or - signs define the direction of rotation. The + sign causes
counterclockwise workpiece rotation, the - sign causes clockwise rotation to
the indicated degree. There are two possible ways to get to a position on the
rotary table in absolute: by rotating either from the positive or negative

G91 Incremental Mode

In the incremental mode (G91), the C axis value defines the direction and
number of degrees to rotate. A C+90, causes the workpiece to rotate
counterclockwise 90 degrees. If the next move were a C-90, the workpiece
would rotate clockwise to the original position.

For G00 and G01 only

The C-axis in this machine will work in conjunction with linear moves (G00 and G01) only.
Arcs (G02 and G03) will not work with the C-axis.

Program Example


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10 (Rotary table demo)
ET8 M6
G00 G90 X0 Y0 Z30 C0
G01 Z0 F300 S2500 M03
G01 C360
G01 X10 Y10
G01 C-360
G01 X20 Y20
G01 C360
G00 Z40
ET2 M6
G00 X0 Y0
G00 Z20
M98 P100 L12 (Cut at Z20)
G01 G90 Z10
M98 P100 L12 (Repeat at Z10)


100 (Cut slots)
G01 G91 X75 Y80 C30 F300 S2500 M3
G00 Z30
G00 X-75 Y-80
G01 Z-30