# Fanuc Series 15i/150i-MA (Programming) Operators Manual

B-63324EN/03 PROGRAMMING 18.HIGH-SPEED CUTTING FUNCTICNS
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18.2 DECELERATION BASED ON ACCELERATION DURING
CIRCULAR INTERPOLATION
When cutting is performed at high speed for circular, helical, or spiral
interpolation, the actual tool path will vary slightly from that intended..
This error in circular interpolation can be approximated by the formula
given below:
+=+= .....................(Equation 1)
When actual machining is performed, radius r of the arc to be machined
and permissible error r are given. Then, maximum allowable
acceleration a (mm/sec
2
) is determined from the above expression.
The function for clamping the feedrate by the acceleration
automatically clamps the feedrate of arc cutting to the value set in a
parameter. This function is effective when the specified feedrate may
cause the radial error for an arc with a programmed radius to exceed the
permissible degree of error.
When the permissible maximum acceleration for each axis is set for a
parameter, and the larger of the permissible maximum accelerations for
the two axes used for circular interpolation is assumed to be A, the
permissible maximum feedrate v at the radius r specified by the
program is
rAv ×= ............................................................. (Equation 2)
If the specified feedrate exceeds feedrate v, determined with equation 2,
the feedrate is automatically clamped to the determined feedrate.
The following parameters are used to specify the permissible maximum
accelerations:
In fine HPCC mode: Parameter 1663
In a mode other than fine HPCC mode (in normal mode): Parameter
1665
Programmed path
Actual path
r
: Maximum radial error (mm)
v : Feedrate (mm/sec)
r : Arc radius (mm)
a : Acceleration (mm/ sec
2
)
T
1
: Time constant (s) for
exponential acceleration /
deceleration of cutting feed
(sec)
T
2
: Time constant of the servo
motor (sec)
r : Error
0
Y
X
r