Cumulative runout.

[[Cl...]]

I can't share any drawings. The callout is cumulative runout relative to Datum -A- which is a very shallow (.150" depth x Ø.52535" cylinder).

The feature (a .200 Ø cylinder) is approximately 1.5" from -A-. I think it's because -A- isn't deep enough or close enough. My type-1 was 98%

for this characteristic. Any ideas as to how I can improve repeatability? 

[[Ky...]]

Not anything that conforms to the print. Unfortunately, that datum is way too shallow (for the diameter) to get a reasonable axis. Truth be told, I have a hard time believing that physically it is controlling that orientation when it spins. If I were in your place, I would probably request a change to the print so that a more reasonable datum is used. Without seeing the part, I can't say what, but like I said, it is highly unlikely that datum A by itself is controlling the orientation.

[[Cl...]]

There is a secondary (Plane) datum parallel to -A-.

[[Ky...]]

For the plane to matter (in the datum reference frame), the plane would have to be primary. You can try that (i.e. put in the plane as primary and the cylinder as secondary). If the callout is cylinder then plane, then that is probably the intended callout, even if they put it in wrong. Alternatively, you can measure the cylinder as a circle instead and then create a perpendicular from that circle to the plane.

[[Cl...]]

👍

[[To...]]

cannot delete my post.

Edited April 15

[[To...]]

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You can still use the cylinder, it will just origin the axis to the midpoint of the cylinder axis.  But, I agree that a circle would probably be just as good.

Edited April 15

[[Cl...]]

Using the plan/cylinder (A/B) the best I get on the type-1 GRR is 75%.

Edited April 16

[[Ma...]]

From the description so far, it sounds like the two cylinders should be used as a compound datum. Then cumulative runout of each cylinder could be compared to that compound datum.

[[Cl...]]

Datum -A- is a plane right next and parallel to -B-. Datum -B- is a cylinder Ø .52535 / .150 depth.

The feature being evaluated for runout is also a cylinder Ø .20025 / .200 depth and is 1.5" from Datums A&B.

[[To...]]

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How about plane/circle?

[[Ow...]]

Plane/circle is going offer the best repeatability. If you are adamant about using a cylinder, be sure to use at least 3 equally spaced circle scanning paths, 5 wouldn't hurt. Two scanning circle paths will create projection error on a cylinder feature.

Edited April 16

[[Ma...]]

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Understood, the problem is that -B- is too short to function as a planar datum. I am suggesting the planar be a 3d line constructed from -B- and the .20025 cylinder. I understand that this is not what is on the drawing, but doing it that way should greatly improve your GRR result.  I can't comment on the functional datum structure of the part from the info provided, but the datum structure on the drawing is clearly not functional.

[[Cl...]]

I agree. Thanks for the input, guys!

I think my engineer is going to talk to the customer about this as an unreliable datum. Maybe talk them into changing it.