Form of any circumferential arc

[[Da...]]

So, I was wondering if this were possible in Calypso. So, I have a part with a flat circular surface with 2 flatness requirements. One is that the surface must as a whole be to one requirement, but then any 15° arc along the circumference of the surface must be to another requirement. So, the whole surface must as a whole be within 0.0007 flat but any 15° arc along the surface must also be flat within 0.0003. Is this possible within Calypso?

My current solution is to scan the surface, output the total surface flatness, and then by creatively using "Recall Feature Points", try and subdivide all 360° of the surface into various segments and then outputting flatness of the individual segments as their own characteristics. For example, Flatness(Whole), Flatness(0°-15°), Flatness(15°-30°), Flatness(30°-45°), etc. However, this isn't exactly the spec. Any ideas? Also, I've included a diagram to help explain what the requirement is.

[[Br...]]

It doesn't make sense to use flatness on a nominally curved surface. Something cannot be both flat and circular simultaneously. Flatness is a tolerance for planar features. If you want to control form of a cylindrical feature, consider using Cylindricity, Circularity, or Straightness. Cylindricity will control the form of the entire feature, while Circularity will control each circular element on a cylinder. Straightness can control each longitudinal element of the surface on a cylinder, or it can control a derived median line depending on how the tolerance is applied on the drawing. Straightness though is the only one here that can be applied on a unit basis, but not by Arc or degrees.

[[Aa...]]

Maybe I'm misinterpreting, but I believe the flatness is applied to a planar face. I think what they're asking for is analogous to a surface straightness per unit length applied to a planar face, but in this case they're looking for elements in a cylindrical coordinate system.

The concept doesn't seem self-contradictory to me, but I don't know of a good way to go about it.

ASME Y14.5 doesn't spell anything like this out. It does make use of cylindrical coordinate systems for some cases with bi-directional position control. And it does have straightness per unit length and straightness applied to a planar surface. And it allows for orientation tolerance to be applied to a "each radial element" of a planar surface. Whether straightness can be applied by extension to limited extents of "each concentric element" could easily be argued back and forth.

My head starts to hurt when I think about whether this would fit in ISO GPS, and how you would go about annotating it...

[[Br...]]

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Ah ok. Well you can use Flatness on a unit basis in Y14.5 but not by angle. I would assume because you are assuming some center point that degrees start from. There would probably need to be a datum reference to determine which feature controls the center-point from which the angles come from. Plus as you approach the center, the zones would get smaller. It would be an odd way to tolerance something. The supported way to accomplish this is either by a square or circle shaped area and not a pie or fan shaped area. Calypso does support this the square shaped zone on unit basis.

[[Ri...]]

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Obviously, you have not been following the Flat Earth Society!