Siemens SINUMERIK 840D sl Programming Manual page 38

General
1.8 Measurement principle
Measuring velocity
The measuring velocity is dependent on the measurement path _FA and its default setting is
150 mm/min if _FA=1; if FA>1: 300 mm/min. Cycles parameter _VMS is then =0.
Other measuring velocities can be set by the user to a value of >0 in _VMS (see Chapter 2).
The maximum permissible measuring velocity is derived from:
• the deceleration behavior of the axis.
• the permissible deflection of the probe.
• the signal processing delay.
Deceleration distance, deflection of probe
Caution
Safe deceleration of the measuring axis to standstill within the permissible deflection path of
the probe must always be ensured.
Otherwise damage will occur!
A delay "t" typical of the control is taken into account in signal processing (IPO cycle) for the
time between detection of the switching signal and output of the deceleration command to
the measuring axis MD 10050: SYSCLOCK_CYCLE_TIME and MD 10070:
IPO_SYSCLOCK_TIME_RATIO). This results in the deceleration path component.
The following error of the measuring axis is reduced. The following error is velocity
dependent and at the same time dependent on the control factor of the measuring axis
(servo gain of the associated machine axis: servo gain factor).
The deceleration rate of the axis must also be taken into account.
Together they produce an axis-specific velocity-dependent deceleration distance.
The servo gain factor is MD 32200: POSCTRL_GAIN.
Axis acceleration / deceleration rate a is stored in MD 32300: MAX_AX_ACCEL. It may have
a lesser effect due to other influences.
Always used the lowest values of the axes involved in the measurement.
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Programming Manual, Release 04/2006, 6FC5398-4BP10-0BA0
Measuring cycles