4. FEED FUNCTIONS
B–63172EN/01
NC FUNCTION
34
Speed
Time
T
C
T
C
In the linear acceleration/deceleration, the delay for the command caused
by the acceleration/ deceleration becomes 1/2 compared with that in
exponential acceleration/deceleration, substantially reducing the time
required for acceleration and deceleration.
Also, the radius direction error in the circular interpolation caused by the
acceleration/deceleration is substantially reduced.
r
Z
Z
∆r
Command
path
Actual
path
∆r : Maximum value of
radius error (mm)
v : Feedrate (mm/sec)
r : Circular radius (mm)
T
1
: Acceleration/
deceleration time
constant (sec)
T
2
: Time constant of servo
motor (sec)
The maximum value of error in this radius direction is obtained
approximately by the following equation.
Dr + (
1
2
T
1
2
)
1
2
T
2
2
)
V
2
r
Dr + (
1
24
T
1
2
)
1
2
T
2
2
)
V
2
r
For exponential acceleration/deceleration. . .
For linear acceleration/deceleration after . . .
cutting feed interpolation
Consequently, in case of the linear acceleration/deceleration after
interpolation, if an error caused by the servo loop time constant is
excluded, the radius directional error will be reduced to 1/12, compared
with the exponential acceleration/deceleration.
4.6
LINEAR
ACCELERATION/
DECELERATION
AFTER CUTTING
FEED
INTERPOLATION