Siemens SINUMERIK 840D sl Function Manual page 226

B1: Continuous-path mode, Exact stop, Look Ahead
4.4 Dynamic adaptations
The secant error which occurs during the interpolation of curved contours is dependent on the
following factors:
● Curvature
● Interpolator clock cycle (display in the MD10071 $MN_IPO_CYCLE_TIME)
● Velocity with which the relevant contour is traversed
The maximum possible secant error is defined for each axis in the machine data:
MD33100 $MA_COMPRESS_POS_TOL (maximum tolerance with compression)
If the set interpolator clock cycle is not sufficiently small, the max. path velocity may be reduced
in the case of contours with greater curvature. This is necessary for ensuring that the surface
of the workpiece is also produced with an adequate degree of precision in this case.
By changing the contour sampling factor, the time interval with which a curved contour is
sampled in the interpolator (contour sampling time) can be set differently than the interpolator
clock cycle. A contour sampling time which is shorter than the interpolator clock cycle can
prevent a reduction in path velocity in the case of contours with greater curvature.
The contour sampling factor is set with the machine data:
MD10682 $MN_CONTOUR_SAMPLING_FACTOR
The effective contour sampling time is calculated as follows:
T = f * T
s
where: T
The default contour sampling factor is "1", i.e. the contour sampling time equals the interpolator
clock cycle.
The contour sampling factor can be both greater or less than "1".
If a value less than "1" is set, monitoring of contour sampling precision is disabled.
The set sampling time must not be below the configured minimum contour sampling time:
MD10680 $MN_MIN_CONTOUR_SAMPLING_TIME
Note
MD10680 is specifically set for every controller model and cannot be changed.
Programming
Depending on the setting in machine data MD20606 $MC_PREPDYN_SMOOTHING_ON,
"Free-form surface mode: Basic functions" can be switched on and off in the part program by
changing the active dynamic response mode.
Example:
By assigning the parameters MD20606 $MC_PREPDYN_SMOOTHING_ON[2-4] = 1 and
MD20606 $MC_PREPDYN_SMOOTHING_ON[0-1] = 0, the function can be switched on via
226
1
= Effective contour sampling time
s
T = Interpolator clock cycle
1
f = Contour sampling factor (value from MD10682)
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
Basic Functions