(This item pertains to the check boxes on the General tab of the Setup Options dialog box. You can open it through the F5 key or through the Edit | Preferences | Setup menu option.)
Each time you create an alignment (saved or otherwise), PC-DMIS creates two transformation matrices.
Machine to part transformation matrix - Computed from the input features' measured values stored internally in machine coordinates.
CAD to part transformation matrix - Computed from the input features' theoretical values stored internally in CAD coordinates.
When you don't have available CAD data, theoretical data usually comes from the measured values of the learned features. It is difficult to get consistent results using theoretical values. This can happen when some of these values are edited, while others are not.
If you have selected the Ignore CAD to Part check box when you save an alignment, PC-DMIS ignores the CAD to part matrix and instead only saves the machine to part alignment. All theoretical values will now be in the same coordinate system.
Generally, if you are not using CAD data, select this check box.
Effects on CAD Equals Part
If you want to execute an alignment from features measured without CAD data in DCC mode and you will be using the CAD Equals Part menu option (or CAD = Part button), be sure to select the Ignore CAD to Part check box prior to setting the CAD equal to the part. For information on setting the CAD equal to the part, see the "CAD Equals Part" topic in the "Creating and Using Alignments" chapter.
Theoretical Values for Copied Features
If you clear this check box and copy a feature to a new location in the Edit window, the theoretical values of the feature will be associated with the alignment at the feature's original location.
If you select this check box and copy a feature to a new location in the Edit window, the theoretical values of the feature will be associated with the alignment at the feature's new location.
See "Changing Alignment Nominal Values" in the "Creating and Using Alignments" chapter.