Siemens SINUMERIK 828D Function Manual page 181

Activation/Deactivation
The "smoothing of the path velocity" function is activated/deactivated with the machine data:
MD20460 $MC_LOOKAH_SMOOTH_FACTOR (smoothing factor for LookAhead)
Value Meaning
0.0 Smoothing of the path velocity not active (default)
> 0 Smoothing of the path velocity active
A change in the MD setting is only made effective through NEW CONF.
Parameter assignment
Smoothing factor
The smoothing factor is set via the channel-specific machine data:
MD20460 $MC_LOOKAH_SMOOTH_FACTOR (smoothing factor for LookAhead)
The percentage value defines how much longer a processing step without accelerations/decelerations may be
than the corresponding step with accelerations/decelerations.
This would be a "worst-case" value, if all accelerations within the part program, except the initial approach
motion, were smoothed. The actual extension will always be smaller, and may even be 0, if the criterion is not
met by any of the accelerations. Values between 50 and 100% may also be entered without significantly
increasing the machining time.
Consideration of the programmed feed
The path velocity can be smoothed with or without taking the programmed feedrate into consideration. The
selection is made via the machine data:
MD20462 $MC_LOOKAH_SMOOTH_WITH_FEED (path smoothing with programmed feedrate)
Value Description
0 Programmed feedrate is not taken into consideration.
1 Programmed feedrate is considered (default setting).
When considering the programmed feedrate, the specified smoothing factor (see MD20460) is maintained better
when the override is 100%.
Axis-specific limit frequencies
The axis-specific limit frequencies are defined via the machine data:
MD32440 $MA_LOOKAH_FREQUENCY (smoothing frequency for LookAhead)
Acceleration and deceleration processes, which run with a high frequency, are smoothed depending upon the
parameterization of the following machine data or else are reduced in dynamics:
MD20460 $MC_LOOKAH_SMOOTH_FACTOR (smoothing factor for LookAhead)
MD20465 $MC_ADAPT_PATH_DYNAMIC (adaptation of the dynamic path response)
Basic Functions
Function Manual, 09/2011, 6FC5397-0BP40-2BA0
B1: Continuous­path Mode, Exact Stop, LookAhead
3.4 Dynamic adaptations
181