
B--63003EN--1/02
7. FEEDRATE CONTROL/ACCELERATION
AND DECELERATION CONTROL
595
Involute interpolation automatic speed control overrides a specified
feedrate automatically, in the following two ways, during involute
interpolation to obtain a high--quality surface with improved machining
precision.
D Override with cutter compensation inside offset
D Override near the basic circle
(1)Override with cutter compensation inside offset
In standard involute interpolation mode, when cutter compensation is
applied to involute interpolation, control is provided so that the speed
in the direction tangential to the path of the tool center (tool center
path) is always set to a specified feedrate.
In this case, the actual cutting speed, which is the speed of the tool
periphery point (cutting point) on the programmed path, varies
because the curvature of the involute curve is constantly changing.
In particular, when the tool offset is inside the involute curve, as the
tool approaches the basic circle, the actual cutting speed increases
relative to a specified feedrate.
For smooth machining, the actual cutting speed should be controlled
to match a specified feedrate. This function calculates an override
according to the curvature of the involute curve which changes from
moment to moment during involute interpolation, especially when an
inside offset is used. Then, the function controls the actual cutting
speed which is the speed in the direction tangential to the curve at the
cutting point, so that the actual cutting speed always matches a
specified feedrate.
Rofs
Rcp
Tool center path
Cutting point
Programmed path
Basic circuit
The override value is calculated as follows:
OVRa =
Rcp
Rcp + Rofs
× 100
Rcp : Radius of curvature at the tool centeron the involute curve that
passes through the tool center
Rofs : Tool radius
Automatic speed control
in in vo lute interpolatio n