Datum Reference Frame Components & Labels The Datum Reference Frame defined by the Datum Features referenced in the encircled Feature Control Frame in Figure 1 is shown in Figure 1 superimposed on the CAD model, buried in the simulator set, and established in the actual part.ħ. What are Datum Reference Frames for? Datum reference frames serve, with the help of basic dimensions, to orient and locate tolerance zones.Īlthough the fundamental Datum Reference Frame is always a Cartesian coordinate system that consists of three mutually perpendicular axes, three mutually perpendicular base planes and a point representing the origin, a cylindrical or a spherical coordinate system may be derived from it where required. What are Datum Reference Frames? Datum reference frames are Cartesian coordinate systems that have been partially or wholly constrained by a set of Datums extracted from a set of Datum Feature Simulators, defined by a set of Datum Features referenced in a Feature Control Frame. Y14.5 2009 Definition (§4.1 p.48): “A set of three mutually perpendicular, intersecting datum planes.” What are they for? Datums serve to constrain the rotational and translational degrees of freedom of a “starter” coordinate system, thereby turning it into a Datum Reference Frame relative to which Basic dimensions serve to orient and locate tolerance zones.Īs illustrated in Figure 2, there are six datum types, each shown embedded in its defining Datum Feature Simulator: a point, a line, a plane, a point-on-a-line, a line-in-a-plane and a point-on-a-line-in-a-plane. What are Datums? The minimum, mutually embedded set of a single, perfect imaginary point, and/or axis, and/or plane, which together fully characterize the orientation and location of a Datum Feature Simulator. Y14.5 2009 Definition (§1.3.13 p.3): “A theoretically exact point, axis, plane or combination thereof derived from the theoretical datum feature simulator.” Figure 1 also shows the Datums extracted from their simulators. The simulator for planar surface A is an inverted planar surface, that the simulator for bore B is an expanding shaft, and that the simulator for the slot is a tombstone fixed in size at the virtual Maximum Material Boundary of the slot, namely of thickness 16 millimeters. With which we transfer Datum Reference Frames to actual parts.įigure 1 shows the Datum Feature Simulators which are defined by the Datum Features referenced in the encircled Feature Control Frame. In which we first establish Datum Reference Frames, and What are Datum Feature and Datum Target Simulators for? Datum Feature/Target Simulators serve as bridges between the imperfect real world of datum features and the perfect imaginary world of datums: What are Datum Target Simulators? Point Datum Target Simulators are spheres, Line Datum Target Simulators are straight or bent cylinders, and Area Datum Target Simulators are limited Datum Feature Simulators.
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