Introduction
Feature Averaging provides the user with the tools
to evaluate a critical form dimension during the part inspection run and
determine if it exceeds the upper or lower tolerance band. Features that
are supported are: Circle, Sphere and Cylinder.
During the part inspection, Geomet will review the Diameter or Radius
and compare it against the tolerance band. If it exceeds the tolerance
band and remains within the established evaluation zone, Geomet will
automatically rerun the feature up to the cycle limit and average all
the reported form values.
Establishing the Default Settings for Feature
Averaging
You can establish basic guidelines for the two
parameters that Feature Averaging will use. To create the defaults, go
to the System Options by pressing the < F9 > key.
Locate the two setting keys:
Feature Averaging default cycles Feature Averaging default
limit
Set defaults for these two averaging
characteristics. The default cycle instructs Geomet to rerun the
same feature up to this entered cycle count. The default limit
establishes a zone outside the tolerance limits that if
the measured feature falls in this zone, then a rerun will automatically
take place. For example: if you are measuring a diameter with a nominal
value of 1.000” and a tolerance of ± .001 your limits would be 0.999 -
1.001. The evaluation zone entered as 0.0002" would be 0.9988 - 0.999
and 1.001 - 1.0012 or .0002 outside tolerance limits. The default values
entered here are only a starting point, you can change the values on a
feature by feature basis through the tagging operation listed below.
Feature Average Tagging
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figure
2, Tagging |
To start the feature tagging process, measure a
qualifying feature complete with motion. Apply tolerance to the feature
size. Highlight the feature and right-click your mouse to pop-up the
feature menu. Choose Configure Feature Averaging and the Feature
Averaging dialog will appear.
Note: If you do not see a Configure Feature
Averaging in the menu, it can be caused by two conditions. First, the
feature must have a tolerance applied to the size attribute. The second
reason is that this tool requires Direct Computer Control (DCC).
Feature Averaging Setup Dialog
This setup dialog establishes the operating
parameters for Feature Averaging on a qualifying Circle, Sphere or
Cylinder. There are three settings which you can set to control the
rerun characteristics.
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figure 3, Feature Average Setup Dialog |
Evaluation Limit
The zone outside the tolerance limits where Geomet
will determine whether to rerun a feature. As previously mentioned, this
applies only to the Diameter or Radius of the feature.
Maximum Rerun Tries
The number of ReRun cycles Geomet will try to do on the feature. When Geomet
enters a rerun cycle it retains the previous actual dimension and adds it to
the final record. Once it completes the rerun cycle, Geomet will average out
all runs to determine if it falls inside the tolerance zone.
If the average falls inside the tolerance zone, Geomet will
cease the reruns at the current cycle and report the feature. If the average
falls outside the evaluation zone, Geomet will consider the feature
out-of-tolerance and cease the rerun cycles.
Auto Reverse to SO
This check box is used to force the direction of motion back to the first
Stand Off (SO). The first SO is the starting point for the first measurement
point in the motion map for the feature. On most external features (OD / OR)
you should check this box. When Geomet completes the feature and determines
that a retry is required it will backup though the motion map through all
SOs and IPs to the start of the first measurement point and then rerun the
feature.
If the check is not in place, Geomet will drive from the
current locate directly to the first SO. On most internal features, this
will not cause a problem.
Measurement Values
All currently stored actual measurements will be displayed here for review.
Activate in Feature
When this is checked, Feature Averaging is active for this feature.
Feature Averaging during a Part Inspection
During a part inspection, Geomet constantly monitors every
feature for the Feature Averaging tag. After completing gathering the
required number of data points, Geomet will calculate the diameter or radius
and compare it to the evaluation zone. If it is found that the result falls
inside the evaluation zone, Geomet will return store the actual value and
display it on the monitor and return to the first SO and rerun the feature.
Once the rerun is completed, Geomet will then average the
first and second actual values and perform on of the following:
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Average falls inside tolerance zone: The feature
is completed and the results are added to the report.
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Average falls inside evaluation zone: Geomet adds
the new actual to the list and attempts another rerun. This cycles
continues until either a) or c) conditions exist or until maximum
allowed cycles is reached. If maximum cycles is reached, the feature is
reported as out-of-tolerance.
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Average falls outside evaluation zone: The
feature is completed and added to the report as a feature
out-of-tolerance.
The results shown in the report for the Diameter
or Radius is the average of all runs. However, the
location reported is that
of the last run. The averaging feature is designed for use on critical size
not for position.
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