Siemens SINUMERIK 840D sl Function Manual page 56

A2: Various NC/PLC interface signals and functions
2.3 Functions
Limit angle
If AR is used to program an involute leading to the base circle with an angle of rotation that is
greater than the maximum possible value, an alarm is output and program execution aborted.
Figure 2-8
The alarm display can be suppressed using the following parameter settings:
MD21016 $MC_INVOLUTE_AUTO_ANGLE_LIMIT = TRUE (automatic angle limitation for
involute interpolation)
The programmed angle of rotation is then also limited automatically and the interpolated path
ends at the point at which the involute meets the base circle. This, for example, makes it easier
to program an involute which starts at a point outside the base circle and ends directly on it.
Tool radius compensation
2 1/2 D tool radius compensation is the only tool radius compensation function permitted for
involutes. If 3D tool radius compensation is active (both circumferential and face milling), when
an involute is programmed, machining is interrupted with alarm 10782.
With 2 1/2 D tool radius compensation, the plane of the involute must lie in the compensation
plane. or else alarm 10781 will be generated. It is however permissible to program an additional
helical component for an involute in the compensation plane.
Dynamic response
Involutes that begin or end on the base circle have an infinite curvature at this point. To ensure
that the velocity is adequately limited at this point when tool radius compensation is active,
without reducing it too far at other points, the "Velocity limitation profile" function must be
activated:
56
Limited angle of rotation towards base circle
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
Basic Functions