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Readpoints and Alignments..Legacy/Xact

I have a few questions and concerns I was hoping could get addressed. So thank you for your insight in advance.

A coworker and I were having a discussion about using the readpoint alignment to inspect a whole part. I said that is not good practice.

Anyway, he did so and inspected a part using just the readpoint. Numbers were coming out ok...so I was a bit confused.

Can you use the readpoint to inspect the whole part? He also said that you dont need to align to datums. That you can pick them up as normal features then when dimensioning something like true position you can just select those features.

This has really thrown me for a loop. This isn't really good practice...right? Shouldnt a basic alignment of the part be conducted after the readpoint to just solidify it a bit more? Then probe the same features again with a few more hits to refine it?

Is it necessary to do this? And one more thing, I've searched high...I've searched low, I still am not sure when folks talk about legacy or exactmeasure. How do I know what mode I'm in? How do I switch between?

Thanks for reading.
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  • 1. a readpoint alignment is only supposed to be used as a starting point on the machine. it is not used to constrain 6 dof.
    2. if the part is very basic and you're only checking some very open toleranced features, you might be able to use a readpoint as a basic x,y,z locator, but it is the incorrect use of a readpoint
    3. you absolutely need to use the datums. he's wrong.
    4. yes, a basic 3,2,1 alignment if applicable should be used after a readpoint
    5. insert>dimension>LEGACY.
    TO ME, BIGWIG, there are some slight differences between xact and Legacy. all things being equal, if you build an alignment correctly, then XACT and LEGACY should provide the same result.
    XACT is convenient if you have a part with more than 3 datums as you don't have to build a separate alignment for each DRF

    Asking these questions is healthy, but it really sounds like you're not the only ROOK handling that CMM. please dm me and I can discuss some options to help you further.
Reply
  • 1. a readpoint alignment is only supposed to be used as a starting point on the machine. it is not used to constrain 6 dof.
    2. if the part is very basic and you're only checking some very open toleranced features, you might be able to use a readpoint as a basic x,y,z locator, but it is the incorrect use of a readpoint
    3. you absolutely need to use the datums. he's wrong.
    4. yes, a basic 3,2,1 alignment if applicable should be used after a readpoint
    5. insert>dimension>LEGACY.
    TO ME, BIGWIG, there are some slight differences between xact and Legacy. all things being equal, if you build an alignment correctly, then XACT and LEGACY should provide the same result.
    XACT is convenient if you have a part with more than 3 datums as you don't have to build a separate alignment for each DRF

    Asking these questions is healthy, but it really sounds like you're not the only ROOK handling that CMM. please dm me and I can discuss some options to help you further.
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