10. SPINDLE SPEED FUNCTION
G96 (constant surface speed control command) is a modal G code. After
a G96 command is specified, the program enters the constant surface
speed control mode (G96 mode) and specified S values are assumed as a
surface speed. A G96 command must specify the axis along which
constant surface speed control is applied. A G97 command cancels the
G96 mode.When constant surface speed control is applied, a spindle
speed higher than the value specified in G92S_; (maximum spindle
speed) is clamped at the maximum spindle speed. When the power is
turned on, the maximum spindle speed is not yet set and the speed is not
clamped.S (surface speed) commands in the G96 mode are assumed as S
= 0 (the surface speed is 0) until M03 (rotating the spindle in the positive
direction) or M04 (rotating the spindle in the negative direction) appears
in the program.
Fig. 10.3 (a)Relation between workpiece radius, spindle speed
and surface speed
The spindle speed (rpm) almost coin-
cides with the surface speed (m/min)
at approx. 160 mm (radius).
S is 600 m/min.
To execute the constant surface speed control, it is necessary to set the
work coordinate system , and so the coordinate value at the center of the
rotary axis, for example, Z axis, (axis to which the constant surface speed
control applies) becomes zero.
Fig. 10.3 (b) Example of the workpiece coordinate system for
constant surface speed control
D Constant surface speed
control command (G96)
D Setting the workpiece
coordinate system for
constant surface speed