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Alignment changes bring in more variation?

RobOntario

Morning all

Yesterday I got a request to add datum DEF to report one  feature along with ABC. So I added DEF measurement at the end of program, then constructed alignment DEF and reported both for the feature.  After I sent out report, ME wanted me to re-measure the parts with regular program which used ABC only. 

Last night I thought about whether there were any different between the two programs. Since I usually measure everything first and report features after that, so I always add and delete alignments in the program and have to choose accept update nominals in the following program which sometime would bring in errors and have to redo ...

My question is: Does those alignment change  bring in slight errors ( back forth )?  Is this the reason I was told to recall startup when I work on final alignment in the program ?

I am working in assembly plant, so our accuracy is not that high, we should be ok with it. 

Thank you

  • 0

    When everything has been done correctly, you can add as many different alignments as you like without causing errors.  Problems occur when...

    • The nominal (THEO) values for features are incorrect (x, y, z, AND i,j,k).
    • Alignments are not fully constrained - performing a LEVEL on it's own for example.
    • You delete a feature / alignment that is used / recalled in a subsequent alignment.
    • You have duplicate alignment / feature names or have used spaces/special characters/mathematical symbols in the names.
  • 0 in reply to Neil Challinor

    Thank you Neil  

    My question is about add and delete alignments. For example, I have A1 A2 A3 A4 A5 in the program, everything were done correctly. First, I delete A3, all nominal will be modified corresponding the change, second I add A6. Third I delete A6 and I add A3 last.  After this cycle, anything minus errors will be brought in ?

    Thank you.

  • 0 in reply to RobOntario

    If you are adding alignments that you will are deleting later put a recall in to keep data from shifting. Example if I want to make A3, I put a recall A2 first, then create the A3 above it, so anything created in A3 does not affect my program further down. Even if you delete A3 and its features.


    What you can also do before deleting your alignments, select all features in it, then CUT them, and paste them into the alignment they will be relative to.

    Example if I made A4 and put some features in it, then deleted A4, the features would fall in line with the A3 above it. Instead of that, select all features in A4, CUT with CTRL+X, then paste them above the A4 alignment before you delete it. They will paste in with the correct nominals relative to the alignment they are pasted into.

  • 0 in reply to WilliamL

    Thank you  

    We used to have a CMM guy, he liked to measure one feature and report it right away, so everything were mixed up with lots of notes from ballooned drawings, indeed make programs difficult to understand and maintain.  Now I think he might not like to delete or add alignments, so he did that.

    Delete and add would not be intentional , but with the evolvement of program, it happens. 

  • 0 in reply to RobOntario

    Old Measure and report programs are the best! We try to knock them out when we come across them! 

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