## Checking and Fixing Point Nominal Deviation

Point Nominal Deviation dialog box

The Edit | Graphics Display Window | Point Nominal Deviation menu option displays the Point Nominal Deviation dialog box. This re-sizable dialog box lets you easily compare certain point measurements against a CAD model in order to check for changes or updates made to the CAD model. Essentially, you define a tolerance value, and PC-DMIS will look at the nominals for any point features in your part program and compare them against the CAD model. PC-DMIS will list all points. If any points deviate beyond the defined tolerance value, PC-DMIS will list those points in a red/orange color, allowing you to adjust them as needed.

The Point Nominal Deviation dialog box contains the following options:

Item | Description
Deviation cutoff box | This box filters which point features are displayed. The distance between a point feature's theoretical position and the CAD model nominal position is its deviation. Only points whose deviation is greater than or equal to the deviation cutoff will be listed.
Angle deviation cutoff box | This box controls the nominal CAD position. The CAD surface normal and the point vector must be within this angle. The range for this angle is 0-90 degrees.
Find Nominals Tolerance box | This defines the tolerance value that will be allowed for each point feature. Points with a deviation that exceeds this tolerance value will turn red.
Search Priority Surfaces Only check box | This check box determines whether or not PC-DMIS only uses priority surfaces when searching for a solution. You can define priority surfaces using the Set as Priority check box in the Edit CAD Elements dialog box. See the "Editing CAD" topic for more information on how to do this.

If you clear this check box, and PC-DMIS cannot find an acceptable value within the defined priority surfaces, it will then check all the other surfaces in the CAD model.

Move Checked Features | This button updates the XYZ and IJK values of those point features whose check boxes you have selected to match the CAD model's XYZ and IJK values.
Copy Checked to Clipboard | This button copies the information for all selected points to the Windows Clipboard. The information in the columns will be delimited by semi colons, as shown here: Example of Points Copied to Windows Clipboard
Override | Sometimes the best point that the algorithm finds is incorrect. If you select a single feature, the Override button becomes available for selection. Clicking this button will display an Override dialog box. This dialog box lets you override the found point with a different point.

See the "Using the Override Dialog Box" topic below.

Feature column | This column displays the name of the ID of the feature. The column header contains a check box. Selecting or clearing this check box selects or clears the check boxes for all point features in the list.
Current XYZ | This column displays the feature's current theoretical position.
Current IJK | This column displays the feature's current theoretical vectors.
CAD XYZ | This column displays the feature's nominal position if it were moved onto the CAD.
CAD IJK | This column displays the feature's nominal vector if it were moved onto the CAD.
Deviation | This column displays the distance between the feature's current theoretical position and its corresponding nominal CAD position.
Angle Dev | This column displays the angle deviation between the feature's current theoretical vector and its corresponding nominal CAD vector.

Using the Override Dialog Box

The Override dialog box appears if you select the Override button from the Point Nominals Deviation dialog box.

It shows a list of all the CAD nominal points that correspond to the selected feature from all surfaces within the Find Nominals Tolerance search zone. PC-DMIS initially sorts these points from smallest to largest deviation. Usually the first point listed is the point used in the Point Nominals Deviation dialog box. Each point is graphically represented with a cross-hair in the Graphics Display window. Selecting a point in the list highlights that point as well as any curve or surface on which the point lies in the Graphics Display window. Once you find the desired point, click the Override button. The Override dialog box closes and the Point Nominals Deviation dialog box reappears, showing the updated point value.

Use Previous Surface check box - You should use this check box when overriding several points. For example, if you know that points for several features should all lie on the same surface but the algorithm incorrectly put the points on different surfaces, you would override the first feature as usual. Then on the second and subsequent overrides, you could select the Use Previous Surface check box. This would cause PC-DMIS to only show the points found on the surface of the previous override.

Find Nominals Tolerance - This box functions the same as the field of the same name found in the Point Nominal Deviation dialog box but with different results. PC-DMIS searches the CAD for nominal points that correspond to the selected feature. It searches in a spherical zone around the current theoretical position of the selected feature. This box defines the size of that spherical search zone. The value regulates the amount of CAD that PC-DMIS evaluates while generating this point override list.

The other items used in the Override dialog box are already discussed in the Point Nominals Deviation dialog box above.