Siemens SINUMERIK 840D sl Programming Manual page 32

General
1.8 Measurement principle
Measurement operation
The procedure is described using the workpiece measurement. The procedure is the same
for tool measurement. In this case, however, the tool is moved and the probe is fixed.
Depending on its design, the actual movements of a machine may be different anyway.
Workpiece measurement is described as follows:
The workpiece is stationary and the probe moves.
The starting position for the measuring procedure is a position _FA in front of the specified
set position (expected contour).
The starting position is calculated in the cycle based on parameter entries and probe data.
The starting position is approached either with rapid traverse G0 or with positioning velocity
G1; then from the starting position with measuring velocity.
The switching signal is expected along path 2 · _FA as from the starting position. Otherwise,
an alarm will be triggered or the measurement repeated.
The resulting maximum measuring position is in the measuring block of the cycle.
At the instant the switching signal is output by the probe, the current actual position is stored
internally "on-the-fly" as the actual value, the measuring axis is stopped and then the "Delete
distance-to-go" function is executed.
The distance-to-go is the path not yet covered in the measuring block. After deletion, the
next block in the cycle can be processed. The measuring axis travels back to the starting
position. Any measurement repetitions selected are restarted from this point.
Measurement path _FA
Measurement path _FA defines the distance between the starting position and the expected
switching position (setpoint) of the probe (see section 2).
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Programming Manual, 03/2009 Edition, 6FC5398-4BP10-2BA0
Measuring cycles