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

B-63324EN/03 PROGRAMMING 5.FEED FUNCTIONS
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5.6 AUTOMATIC VELOCITY CONTROL
5.6.1 Automatic velocity control during involute interpolation
To enhance the machining precision, the function for automatic
velocity control during involute interpolation automatically overrides
the specified feedrate as follows:
- Override applied when an internal offset is applied for cutter
compensation
- Override applied near the basic circle
Explanation
- Override applied when an internal offset is applied for cutter
compensation(OVRa)
When cutter compensation is applied to involute interpolation, the
tangential velocity along the path of the tool center is continuously
limited to the specified velocity during usual involute interpolation.
In this case, the actual cutting speed at the tool periphery (the cutting
point) on the programmed path, changes because the curvature of the
involute curve sometimes changes.
In particular when the tool is offset inside the involute curve, the closer
to the basic circle the tool is, the greater than the specified feedrate the
actual cutting speed is.
To ensure smooth machining, it is desirable that the actual cutting
speed is limited to the specified feedrate. This function calculates the
override value according to the curvature of the involute curve, which
is changeable. The function continually limits the actual cutting speed,
which is the tangential velocity at the cutting point, to the specified
feedrate. This function is particularly effective during involute
interpolation with internal offset.
Programmed path
Basic circle
Cutting point
Rcp
Rofs
Fig.5.6.1 (a) Override applied when an internal offset is applied for cutter
compensation
Rcp
OVR =  × 100 (for external offset)
Rcp + Rofs

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