Siemens SINUMERIK 828D Function Manual page 168

B1: Continuous­path Mode, Exact Stop, LookAhead
3.3 Continuous-path mode
When specifying the maximum axial deviations (MD33100 $MA_COMPRESS_POS_TOL) or the maximum
rounding distance (ADIS / ADISPOS) the available rounding path is normally not used, if permitted by the
dynamics of the axes involved. Through this, the length of the rounding path depends on the active path feedrate.
In case of lower path speeds, one gets lower deviations from the programmed contours. However, it can be set
that in these cases the specified maximum axial deviation or the specified rounding distance is utilized, if
possible. In this case the deviations depend on the programmed contour independent of the programmed path
feedrate.
Note
Apart from the ones mentioned, the following limitation can also become active additionally:
The rounding distance cannot exceed half the length of the original participating blocks.
Jerk limitation
The smoothing of the velocity jump on each axis and thus the shape of the rounding path depends on whether an
interpolation is performed with or without jerk limitation.
Without jerk limitation the acceleration of each axis reaches its maximum value in the entire rounding area.
With jerk limitation, the jerk of each axis is limited to its maximum value within the rounding area. The rounding
motion thus generally consists of 3 phases:
• Phase 1
During phase 1, each axis builds up its maximum acceleration. The jerk is constant and equal to the maximum
possible jerk on the respective axis.
• Phase 2
During phase 2, the maximum permissible acceleration is applied.
• Phase 3
During phase 3, which is the last phase, the acceleration of each axis is reduced back to zero with the
maximum permissible jerk.
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Function Manual, 09/2011, 6FC5397-0BP40-2BA0
Basic Functions