Form Checks
Geometry relationships are designed to be computed quickly and repeatedly. For this reason, form checks do not use the full GD&T mathematical evaluation methods. Instead, they use a simplified computation based on the RMS fit object. Details are as follows:
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Linearity. The linearity of a line is similar to straightness but is computed as 2*(max point deviation from the RMS fit line). In version prior to 2022.3 this was computed as the Max - Min deviation.
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Flatness, Circularity, Cylindricity, and Sphereicity. The form of all other geometry types are computed as the Max - Min de- viation with respect to the RMS fit object. This effectively adds the largest deviations on either side of the surface of the object to create a form deviation estimate.
These form results typically overestimate the form value by a small amount as compared to a full GD&T check result. A check that is true to the ASME or ISO specification can be added by linking a GD&T check to an existing GR-Feature.