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Like the smaller Model 150C, range tracking is necessary for the Model 600C.
The sensor's depth of field (the distance over which the sensor is most
accurate) is about 20 mm (0.8"). Motion control assures that the proper
range is maintained as the machine scans the part.
After the setup part is fixtured in place, the part is "coarse scanned".
The sensor is moved quickly over the part measuring a coarse datacloud.
However, the coarse scan is fine enough for the operator to see the location of
details such as holes. On the datacloud image, he circles those detail
regions where small features are located. On the second (or fine) scan,
the machine scans each detail region more precisely than in the coarse scan.
To illustrate, below is the detail scan of a hole on the edge of a stamping.
The important dimension needed is the hole location. The sensor
is moved slowly over the hole to get many points from the inner surface of
the hole. It is these points which will determine the hole's location
by least squares fitting a cylinder to those data points.
If the scan were coarser, data points would be much further apart and few
would be inside the hole.
Detail Scan
During inspection, the same path is traversed. The sensor moves quickly
from one detail region to the next. But it moves slowly at each detail to get a
fine datacloud of these regions. Combining fast traversing between detail
regions with slow traversing of the details minimizes the time taken to inspect the
part. This strategy assures a fast inspection, yet accurate measurement
of details.
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