Siemens SINUMERIK 840D sl Programming Manual page 538

Glossary
Delete distance-to-go
If a measuring point is to be approached, a traverse command is transmitted to the position
control loop and the probe is moved towards the measuring point. A point behind the
expected measuring point is defined as setpoint position. As soon as the probe makes
contact, the actual axis value at the time the switching position is reached is measured and
the drive is stopped. The remaining "distance-to-go" is deleted.
Differential measurement
Differential measurement means that the 1st measuring point is measured twice, once with a
180 degree spindle reversal (rotation of the probe), i.e. opposite the cycle start position and
once with the spindle position assumed at the start of the cycle. This procedure allows
uncalibrated probes to be used without imposing less stringent precision requirements!
Dimension difference check
Is a tolerance window. On reaching a limit (_TDIF) the tool will probably be worn and have to
be replaced. The dimension difference check has no effect on generation of the
compensation value.
Empirical value
The empirical values are used to suppress constant dimensional deviations that are not
subject to a trend.
Log measurement results
Measurement results can optionally be logged in a file located in the part program memory.
The log can be output from the control either via RS-232-C or on a diskette.
Mean value
The mean value calculation takes account of the trend of the dimensional deviations of a
machining series. The -> weighting factor k from which the mean value is derived is
selectable.
Mean value calculation alone is not enough to ensure constant machining quality. The
measured dimensional deviation can be corrected for constant deviations without a trend by
an -> empirical value.
Measure workpiece
For workpiece measurement, a measuring probe is moved up to the clamped workpiece in
the same way as a tool. The flexibility of measuring cycles makes it possible to perform
nearly all measurements required on a milling or turning machine.
Measurement path
Measurement path _FA defines the distance between the starting position and the expected
switching position (setpoint) of the probe. Always specify _FA in mm.
Glossary-2
Programming Manual, Release 04/2006, 6FC5398-4BP10-0BA0
Measuring cycles