Datum Features and Feature Arrays
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Datum Features and Feature Arrays. TEC 116. Datum Features. Datum features do not actually exist on a real part Datum features cannot be seen or felt Datum Features help locate and define part features There are three principle types of datum features Datum Points Datum Axes
Datum Features and Feature Arrays
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Datum Features • Datum features do not actually exist on a real part • Datum features cannot be seen or felt • Datum Features help locate and define part features • There are three principle types of datum features • Datum Points • Datum Axes • Datum Planes
Datum Points Datum points may be used to place holes and other features FIGURE 6.46. Various ways to define a datum point.
Datum Axes Datum axes are often used when creating revolved solids and circular arrays. Datum Axes are also used to indicate directions during a variety of modeling tasks. FIGURE 6.47. Various ways to define a datum axis.
Datum Planes Datum planes are often used to create sketches & holes, and also perform mirror operations. Datum Planes are very helpful and are commonly used. FIGURE 6.48. Various ways to define a datum plane. More ways to define a datum plane.
Chaining Datums Using simply-defined datums to create more complex datums FIGURE 6.49. To create a datum plane that is tangent to a cylindrical surface at a specific location, an intermediate datum plane, shown in (a), can be created through the centerline of the cylinder. The intersection of the intermediate datum with the cylinder creates a datums axis that is used to locate the final datum plane.
Feature Arrays • A Feature Array takes one feature and places copies of it on the model at specific spacing. • If the “master” feature is modified, the changes appear on the arrayed copies FIGURE 6.50. A rectangular array of protrusions created from a master feature.
Rectangular and Circular Arrays Circular Array Rectangular Array
Mirrored Features FIGURE 6.53. Creation of a mirrored feature. The master feature in (a) is mirrored by creating a datum plane as a mirror plane (b). A mirror image of the feature is produced on the opposite side of the datum plane in (c), and the final result is shown in (d).
Mirror Solid Half of a solid body is mirrored by creating a datum plane as a mirror plane. A mirror image of the solid body is produced on the opposite side of the datum plane.
Associativity in Arrays and Mirror Operations • Creating “Instances” of the master feature or solid body • An associative link is maintained between the master and the newly created features or solid (children). • Changes made to the master are reflected on the children • Associative link may be broken if desired (in some, but not all, modelers)