Datum feature simulator1/8/2024 ![]() Note: When a DRM is not used, the gauge must be adjustable to achieve a regardless-of-feature-size (RFS) “best fit” to the component’s datum feature The feature on the component that is called out with the datum symbol., that does not result in datum shift.Īny features that include a DRM must be inspected with respect to the datum feature simulator, not with respect to the datum feature of the component.įor example, you may have a component drawing where a hole is identified as datum C, and other key features have position tolerances that reference datum C with a DRM. on the gauge will have a fixed size and location, allowing the component to move or shift with respect to the gauge. in the illustration below uses a DRM.Ī DRM specifies that the datum feature simulator The part of the gauge that must fit with that feature of the component. Depending on how a datum reference is called out in a FCF, the “datum” location may be either the “datum feature” of the component or the “datum feature simulator” of the gauge. For example, the B datum A location (point, axis, surface, etc.) used as a reference point for inspecting other features on the component. Likewise, a "true" True Geometric Counterpart of a cylindrical actual feature would have to be of a diameter value which is precise to infinite decimal places.A datum reference modifier (DRM) is indicated by a maximum material boundary (MMB) modifier symbol within a datum reference box of a feature control frame (FCF). To fully represent the TGC, an infinite number of points would need to be scanned with perfect precision. A plane simulator or a datum plane tangent to a portion of the scan considered as the planar datum feature may contact the 3 high points on the cloud of points, but it may not properly represent the plane which would contact the 3 highest points on the actual surface that was scanned. I would say that the simulators established by the software have perfect form and perfect relationship to each other, but an indirect and imperfect relationship to the actual surfaces of the datum features. that have perfect form and perfect relationships to each other. It's interesting because the geometric counterparts established by coordinate metrology devices are perfect - the software defines perfect planes, perfect cylinders, perfect parallel-plane widths etc. RE: Datum Feature Simulator - definition Vs. It's like someone was paid by the word and no one made a map. With the corresponding true geometric counterpart," "If irregularities on a datum feature are such that the part is unstable (i.e., it rocks) when it is brought into contact "When magnified surfaces of manufactured parts are seen to have irregularities, contact is made with a true geometric counterpart at a number of surface extremities or high points." Being theoretical there can be no contact seen by magnification. ![]() This however, is a place it runs off the rails from deep in 7.6: That clarification would not be required if "datum" was still in the term. True geometric counterpart doesn't help cement that place in the hierarchy.įrom the foreword: "The use of the “true geometric counterpart” term is limited to datums." I preferred the previous term - "theoretical datum feature simulator" as it bridged the gap from datum feature to theoretical datum. Note that step 3 can either use best-effort gauges or best-effort measurements. I'm trying to figure out what reasoning has led you to believe the train has left the tracks, seriously.Ģ) (Theoretical) True Geometric Counterpart that is aligned to the three planes.ģ) (Not theoretical) Datum feature simulator that is the imperfect not-theoretical best effort approximation as an approximation of the True Geometric CounterpartĤ) (Part) Datum feature that is aligned to the applicable Datum feature simulator Photons are physical enough I keep seeing really attractive deals on photon wood cutters.
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