### Creating an Iterative Alignment

Aside from standard alignments, capability exists to create Iterative (3-2-1)Alignments using PC-DMIS Planner.

To Create an Iterative Alignment:

1. Click Alignment from the Tools toolbar or select the Tools | Alignment menu item. This opens the Alignment dialog box.

2. If needed, type an ID for the alignment in the ID box.

3. Click Iterative to open the Iterative Alignment dialog box.

Iterative Alignment dialog box

4. Select the proper axis from the Level - 3 combo box.

5. Select the three (or more) features from the feature list on the left for the level.

Note: When selecting features use the following dialog box options:
• Typing the needed feature name in the Search ID box and the feature will be highlighted in the Feature list box when you press the TAB key.
• Selecting the last of a certain number of features by typing the needed number in the Select Last # box. For example, if you wanted to select the last four features that were created, simply type 4 and press the TAB key. PC-DMIS will highlight the features selected in the Feature list box.
• Click Clear to clear the previously selected features.

6. Click Select or the Rotate - 2 radio button.

7. Select the proper axis from the Rotate - 2 combo box.

8. Select the two (or more) features from the feature list on the left for rotation.

9. Click Select or the Origin - 1 radio button.

10. Select the proper axis from the Origin - 1 combo box.

11. Select one feature from the feature list on the left for the origin.

12. Type in the proper value for the Fixture tolerance. This value allows you to provide a fitting tolerance value against which PC-DMIS compares feature elements making up the iterative alignment to their theoretical values.

Note: If after fitting the measurement values to the theoretical values, one or more of the input features have an error along their assigned datum axis that exceeds this tolerance value, PC-DMIS displays an error message. The message shows the errors along each of the datums. You will have the choice to accept the datum as it is and continue with the rest of the part program, or to cancel the part program execution.
PC-DMIS can only use the Fixture tolerance value if you used more than the minimum number of points needed to create the feature. For example, if you are measuring a plane, the minimum number of points needed for that plane is usually three points. However, if you wanted to use the fixture tolerance value, you would need to measure at least four points. If you use only three points then only one solution exists and PC-DMIS cannot adjust or re-iterate.

13. Click OK. The iterative alignment will get added to the list of alignments in the main Alignment dialog box:

Iterative Alignment added to list of alignments

14. Click OK from the main Alignment dialog box will add this alignment to the Inspection Plan.