2.8.27 CONSTANT SURFACE SPEED CONTROL
(G96, G 97)+
This feature may be installed when the S4 digit
specificationoption is selected.
The following G codes are used:
G 96 I Specifies the constant surface speed control.
v G97
Cancels the constant surface speed control.
~At the time of power-on, G97 (cancel) is F
vialed.
These are modal G codes which belong to 02
group.
I ro
(1) Constant surface speed control (G96)
a.
G96 S.. . (M03) ;
Using this command, specify the surface
speed of the work in a numeral of up to 4
digits after address S. The unit of the
surface speed is as follows:
Unit
i
+=+-=
When the surface speed is specified, the
equipment assumes the X-axis current value
(Note 1) to be the diameter of the work and
computes the spindle RPM every 100 msec
so that the specified surface speed is ob–
tained.
The computation result is sent as
the analog voltage output or the binary 12-
bit signal output.
In the subsequent blocks,
the surface speed may be varied by S speci–
fication.
b.
For a machine tool that allows spindle gear
change, instruct the M code for gear change
specification before the block of G96 com–
mand.
For details, refer to the instruction
manual for that machine tool.
EXAMPLE :
N8 MAA ;
M code for spindle
gear change ( gear ratio
No. 4 is specified) .
N9 G96 S1OO M03 ;
c
(2)
Before the block of G96 command, the spin-
dle maximum RPM should be specified by G !50.
This specificationprevents the spindle RPM
from getting abnormally high by the com-
putation of surface speed when the X-axis
current value is smaller.
EXAMPLE :
N1O G50 S2000 ; — Specified the upper
limit of spindle RPM.
Nll MAA ;
N12 G96 s150 M03 :
Constant surface speed control cancel (G97)
G97 S.. . (M03) ;
Using this command, directly specify the
spindle RPM in a numeral of up to 4 digits
after address S.
The constant surface
speed control is cancelled and the usual
spindle feature of S 4–digit specification is
resumed.
(3) Cautions for constant surface speed control
a.
How to set coordinate system (See Note)
When performing the constant surface speed
control, make programming by setting G50
coordinate system or G 58 work coordinate
system so that X-axis coordinate value of
the spindle rotational center become “O. “
In other words, the coordinate system should
be set such that its X-axis coordinate value
correctly represents the diameter of the
work at its machining point.
b. How to handle tool position offset amount
(i)
When per formi~g the constant surface
speed control, parameter #6020D 1 is gen-
erally set to
“O. “ This enables the con-
trol to perform the computation for con-
stant surface speed control without add-
ing the tool position offset amount to the
specified coordinate value. If a large
value is used for the offset amount, the
tool position offset is normally executed
and, at the same time, the constant sur-
face speed control is correctly performed.
(ii) When #6020Dl is set to “ 1, “ the value
(Specified coordinate value + tool position
offset amount) is assumed to be the work
diameter to compute the constant surface
speed. Hence ,
care should be taken not
to use a large value for the offset amount
by performing coordinate system setting
for each tool and using the tool position
offset for tool wear compensation.
123
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