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

5.FEED FUNCTIONS PROGRAMMING B-63324EN/03
- 168 -
Rcp
OVR =  × 100 (for internal offset)
Rcp - Rofs
Rcp : Radius of the involute curve at the center of the tool (The involute
curve passes through the center of the tool.)
- Lower override limit (OVRlo )
When an override is applied to the specified feedrate either when an
internal offset is applied for cutter compensation or when near the basic
circle, the velocity at the center of the tool may be 0 in the proximity of
the basic circle. To prevent this, the lower override limit (OVR1o)
must be specified using its parameter (No.6630).
When the override lower than the setting of parameter (No. 6630) is
applied, the velocity is clamped at the velocity to which override
(OVR1o) is applied.
- Acceleration/deceleration clamping near a base circle
If an acceleration calculated from the curvature radius of an involute
curve exceeds the value specified in the parameter, the feedrate in the
tangent direction is controlled so that the acceleration specified in the
parameter is not exceeded. An acceleration not exceeding a limit can be
maintained, so that efficient feedrate control tailored to the machine
limits can be exercised. Moreover, smooth, continuous feedrate control
can be exercised to reduce stress and strain in machining near a base
circle. When calculating acceleration, the curvature radius of an
involute curve and a feedrate in the tangent direction are used with a
circular acceleration expression, as follows:
Acceleration = F × F/R
F : Feedrate in the tangent direction
Specify the maximum allowable acceleration in parameter No. 1663.
If a calculated acceleration/deceleration value is greater than a
maximum allowable value, the feedrate is clamped according to the
formula below:
Clamp feedrate = ationon/deceleraccelerati allowable maximum × radius curvature
CAUTION
A maximum allowable acceleration/deceleration value
is to be specified for each axis. So, use the smaller
of the maximum allowable acceleration/deceleration
values for the two involute interpolation axes. If one
of the values for the two involute interpolation axes is
0, the acceleration/deceleration clamp function is not
disabled, but the non-zero value is used as a
maximum allowable acceleration/deceleration value.
If both values are 0, the acceleration/deceleration
clamp function is disabled.