Siemens SINUMERIK 840Di Function Manual page 168

Detailed Description
2.3 Continuous-path mode
3xxx:
While, with 3xxx, the rounding distance results exclusively from the dynamic response data
of the respective axis, in the other cases the distance to the corner at which the rounding
motion begins is checked. In the first two cases, the possible rounding distance is limited to a
maximum value, which results either from the defined maximum deviation or a direct
programming command.
In contrast, in the case of 2xxx, the rounding distance is limited to a minimum value, which
results from the maximum permissible excitation frequency and the current path velocity.
Additional limitation
Any further limitations are also effective in addition to this rounding distance limitation. The
rounding distance cannot exceed half the length of the original participating blocks.
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.
Consequently, a different velocity characteristic is produced for each axis, depending on
whether BRISK or SOFT is active.
BRISK
With BRISK, no jerk limitation is active; the acceleration of each axis reaches its maximum
value in the entire rounding area.
SOFT
With SOFT, the jerk of each axis is limited to its maximum value within the rounding area.
The rounding motion thus consists of 3 general phases:
• Phase 1
• Phase 2
• Phase 3
2-20
Any axis that has a velocity jump at a corner traverses around the corner with the
maximum possible dynamic response (maximum acceleration and maximum
jerk).
SOFT: The jerk is limited.
BRISK: When BRISK is active, only the acceleration is limited to its maximum
value.
With this setting, neither the maximum deviations nor the rounding distance are
checked.
The resulting deviations or rounding distances are determined exclusively by the
dynamic limits of the respective axis and the current path velocity.
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.
During phase 2, the maximum permissible acceleration is applied.
During phase 3, which is the last phase, the acceleration of each axis is reduced back to
zero with the maximum permissible jerk (see figure below).
Continuous-Path Mode, Exact Stop, LookAhead (B1)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0