Siemens SINUMERIK 840D sl Function Manual page 181

MD20470 $MC_CPREC_WITH_FFW (programmable contour accuracy)
Value
0
1
2
3
For the MD20470 = 2 or 3 functional versions, the control assumes that there is a jerk filter
time constant (MD32410 $MA_AX_JERK_TIME) for which the setting of the control section
with feedforward control generates a negligible contour error. This value must be entered in
the machine data MD32415 $MA_EQUIV_CPREC_TIME (see "Parameterization").
To calculate the contour error based on the set jerk filter type (MD32402
$MA_AX_JERK_MODE), the following value is used:
● For active feedforward control, the difference:
MD32410 $MA_AX_JERK_TIME - MD32415 $MA_$MA_EQUIV_CPREC_TIME
● Without feedforward control, the complete value from MD32410 $MA_AX_JERK_TIME
This procedure allows the commissioning engineer to first change from an initially precise, but
possibly excessively hard, setting by increasing the jerk filter time constants to a softer setting
with a controlled loss of accuracy.
Supplementary conditions:
● The function does not use the "belt stop" jerk filter type (MD32412 $MA_AX_JERK_MODE
= 3).
● The MD20470 = 2 or 3 functional versions are primarily intended for use with feedforward
control. If one of the two functional versions is active for switched off feedforward control,
a contour error that results from the K
significantly faster.
Note
The MD20470 = 0 or 1 functional versions are no longer recommended. They only provide
compatibility with older software versions.
Special functions
Function Manual, 01/2015, 6FC5397-2BP40-5BA2
Meaning
The "Programmable contour accuracy" function has no effect when feedforward control is also
active.
The "Programmable contour accuracy" function also acts for feedforward control.
With active feedforward control, the reduction of the path velocity is calculated on the basis of
the effective K factor with feedforward control.
V
Like 1, the function, however, is parameterized with MD32415 $MA_EQUIV_CPREC_TIME
(time constant for the programmable contour accuracy).
The jerk filter is correctly taken into account. The SD42450 $SC_CONTPREC setting data
determines the permissible contour errors (see "Parameterization").
Like for 2, but any contour accuracy programmed with CTOL has priority over SD42450
$SC_CONTPREC.
The jerk filter is correctly taken into account. The programmed CTOL contour tolerance deter‐
mines the permissible contour errors (see "Parameterization"). $SC_CONTPREC is relevant
only if CTOL has not be programmed.
K6: Contour tunnel monitoring
4.3 Programmable contour accuracy
factor is added. This reduces the path velocity
v
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