In-Process Measurement - Siemens SINUMERIK 840 User Manual

07.90
1.5.2

In-process measurement

IThe principle of "in-process measurement" has been implemented in the SINUMERIK control.
The advantage of this method of measurement is that the probe signal is processed directly in
the NC and not transferred to the NC via the PLC as previously done.
Position
setpoint
V
Measurement
path a
Actual pos.
Delete
distance to go
S
2
-V
Fig. 1.16 In-process measurement
Start position/position setpoint
With the method of measurement used, a position is assigned to the cycle as set value at
which the signal of the touched trigger probe is expected. Considering the fact, however, that
it is very improbable for the probe to respond at precisely this point, the start position is
displaced in front of the position setpoint by a settable distance a. This start position is
approached by the control in rapid mode (G00). This approach is followed by a feed movement
at the rate of F = 150 mm/min towards the position setpoint. The switching signal is now
expected on a distance having the maximum length of 2a from the start position.
Loading the actual value/deleting distance to go
The moment the switching signal is transmitted by the probe, the current position is loaded
into a register (R parameter) as actual value by in-process measurement. Following this, i.e.
after a distance S covered by the machine while the signal is being processed, the function
1
"Delete distance to go" is executed and the old start position is preset as the new set value.
This end position is then approached in rapid mode.
The delay for actual value measurement is of the microsecond order. In other words, it has no
influence on the attainable measuring accuracy when using comercially available probes (even
in the case of increased approach speed).
©
Siemens AG 1990 All Rights Reserved
SINUMERIK 840/850/880 (BN)
Start position
= End position
Measurement
path a
S
1
*) Probe switching
point
G00
6FC5197- AB70
1 Introduction
1.5.2 In-process measurement
G00
S = Traversing path by signal
1
processing
S = Following error
2
*) Actual value is loaded
with the probe signal.
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