I have searched this morning and read through 20 or more threads and do not see what I need to know. I am having a hard time with a customer supplied program where an iterantive alignment is used (a 3-2-1 alignment should have been used but that is another story) and I feel it is not correct. I have always been told that you have to a fixture tolerance for the interative alignment to do it's magic. They are telling me this is not what the help files say and reading what is in the help files tells me the same thing but I have told by someone (AE at Hex) that if no tolerance is entered it ignores the iterative best fit to CAD nominals.
This is from the V3.7MR3 help file and they are running V4.2MR3 and it basically says the same thing.
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 automatically goes to the error label (if one exists). See Error Label.
If you don't provide an error label, PC-DMIS displays an error message showing 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.
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