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Scan results different from keyed-in points

I have a part with a very tight profile tolerance (form+location) of .0005. I wrote a program with a model and aligned to all 3 datums.

I keyed in gage points and read the vectors from the model. Part is out of tolerance (which I expected) by about .001, the profile being off center.

Next I added a linear TTP scan along the same section where I probed the gage points. The scan shows deviations up to .018!Confused Same program, same part, same alignment.

What could I be doing wrong with my scan to get a result that differs so much from my keyed-in points?
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  • Print is master, but angles are not defined, so I have to use the model for that. After zooming in close, it looks my keyed points are not actually on the model, as you suggest, but scanned points are. Not sure where I went wrong here. After starting a brand new program I have gotten my scans to agree with keyed in points (or at least much closer).



    I did to manual and DCC. Part was not touched during this process. I kept re-measuring and got the same divergent results.
    Probe Comp is ON. (If only it could be so simple...)


    YEA, IF ONLY. Is the part flat? Still the scanned values and TTP values should be very close to each other even if the part is bad.
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  • Print is master, but angles are not defined, so I have to use the model for that. After zooming in close, it looks my keyed points are not actually on the model, as you suggest, but scanned points are. Not sure where I went wrong here. After starting a brand new program I have gotten my scans to agree with keyed in points (or at least much closer).



    I did to manual and DCC. Part was not touched during this process. I kept re-measuring and got the same divergent results.
    Probe Comp is ON. (If only it could be so simple...)


    YEA, IF ONLY. Is the part flat? Still the scanned values and TTP values should be very close to each other even if the part is bad.
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