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Profile x y z values compared to true position values


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Hello, I have less than a year of experience creating inspection programs, and was curious as to why in the report the x y z values of a profile characteristic differ from the x y z values of the true position characteristic? I assumed they represent the location of the feature (cylinder). the true position values seem to be the correct values.

I've been looking through the zeiss knowledge base for answers with no luck.

thank you!
If you are speaking about Basics on the BP vs a True Position to (example: A_B_C).
The basics on the BP may not reflect actual values from the DRF (Datum Reference Frame).
TP_Ø.010_A_B_C
Red is the DRF.
This means the True Position can report different values than the basics.

https://www.faro.com/en/Resource-Librar ... th-figures
If your base alignment is the same as the datum reference frame, make sure to check the evaluation settings for each feature used in the alignment. If you are using least squares fit in your base alignment but outer tangential fit in the datum reference frame in the true position characteristic, you will get differing results.
Also, make sure to check your measurement method system settings. The attached screenshot is what I use for all our CMMs.

Capture.PNG

Hello all,

I hate to jump in since Jayesh's response covers it very well, but like he said, if you look at the additional report in a profile, it gives you the point driving that profile (i.e. the point furthest from the nominals in the DRF). In this case, as far as I can tell, it would be a point on the shell of the cylinder. The true position is based on the axis of the cylinder, so that point will be somewhere in the middle of that cylinder.

I've seen this question a few times on the phone support line over the years, and that option isn't super useful for a profile. It's going to move around a little based on what area is actually the worst and how it measures, and it doesn't really give you an idea of what is wrong with the profile. I would recommend looking at the CAD>CAD evaluation menu to display how the profile looks relative to the nominal instead. It is more qualitative, but it does give a good idea of what the profile actually looks like.

I hope you find this useful.
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