
B-63943EN-1/02 7.FEEDRATE CONTROL/ACCELERATION AND DECELERATION CONTROL
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Note
NOTE
If the optional function for linear acceleration/deceleration after interpolation
for cutting feed is not provided, exponential acceleration/deceleration is
always selected, irrespective of the setting.
1 If linear acceleration/deceleration after interpolation for cutting feed is
enabled, linear acceleration/deceleration is executed during cutting feed
and during a dry run. Linear acceleration/deceleration can also be
executed during jog feed if the parameter JGL (No. 1610#4) is specified
accordingly.
2 In circular interpolation especially when circular cutting is executed at high
speed, the actual path of the accelerated or decelerated tool deviates from
the specified arc in the direction of the radius.
Specified path
ctual path
∆
r : Maximum radius error
(mm)
v : Feedrate (mm/s)
r : Radius of arc (mm)
T
1
: Exponential
acceleration/deceleration
time constant (sec) at
cutting
T
2
: Time constant of servo
motor (s)
r : Error
0
Y
X
r
The maximum error in the radial direction (∆r) can be approximated by the
following expressions:
∆rTT
V
r
=+
1
2
1
2
2
2
2
()
....... Exponential acceleration/deceleration
∆rTT
V
R
=+
1
2
1
2
2
2
2
()
....... Linear acceleration/deceleration or bell-shaped
acceleration /deceleration after interpolation
If the error caused by the time constant of the servo loop is excluded, the
error cause by linear acceleration/deceleration or bell shaped
acceleration/deceleration after interpolation is 1/12 of that caused by
exponential acceleration/deceleration.
(3) Linear acceleration/deceleration can be executed both for cutting feed and
for jog feed along a PMC axis. Acceleration/deceleration for cutting feed is
executed even if acceleration/deceleration for jog feed is selected. In jog
feed along the PMC axis, the time constant for cutting feed is used instead
of that for jog feed.