Best fit for true position

[[Su...]]

Hello guys,

I have a problem with best fit in true position.

In that the tolerance came differently for best fit true position and normal true position. The result variation almost above 0.1mm(for the same hole position). I don't know why it's came like that.
See attachment for your reference.

Thanks in advance

IMG_20190813_005319.jpg

[[Ri...]]

Look at your X Nominals between the two.

Same DRF? Is Best-Fit turned on in the Bolt Pattern?

[[De...]]

Looks like best fit shifted the pattern of holes about 0.0035 in X and 0.08 in Y (best fitted), where as regular true position did not. This seems like what should be expected if you allowed the best fit in X and Y.

[[Su...]]

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Ok where did I mistaken. I am doing settings/strategy like this(photos sequence are shuffle please understand).

Which is the best strategy for true position for hole patterns.

Can you please explain how to make best fit strategies for this measurement plan and also pcd holes(I mean circular path hole pattern)

Thanks in advance

IMG_20190813_010905.jpgIMG_20190813_010942.jpgIMG_20190813_010843.jpg

[[Ni...]]

From what I've been taught when using true position you should never use "base alignment" as your primary datum. Always pickup your Datum(s) and select each one as referenced in the tolerance frame. I'm not sure if this will make a difference in your results but just something I've been taught. Thoughts anyone??

[[Ri...]]

It all depends on how you build your Base Alignment.

Calypso follows the Can-May-Must rule, so if your Base Alignment is built following that, you shouldn't see any differences between using the Base Alignment, and picking the Datums individually.

I tend to not measure Datums in my Base Alignment, so I wouldn't ever use the Base Alignment in a Position characteristic, but that is my personal preference.