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ComputerAided_Design_Engineering_amp_Manufactur.pdf

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FIGURE 9.3<br />

configuration of bodies has been determined. Five basic types of spatial relationships are listed as follows:<br />

• Against:<br />

As illustrated in Figure 9.3, this relation means that the faces touch at some point. Any<br />

two features can bear this relation to each other. For user convenience, we may also allow speaking<br />

of a plane as being against a plane.<br />

• Parallel-offset and parax-offset:<br />

Figure 9.4 illustrates the parallel_offset relation holding between<br />

planar faces and cylindrical and spherical features. In the case of two parallel planar faces, the<br />

outward normals point in the same direction, and F_2 is offset a distance from F_1 in the direction<br />

of the outward facing normal. Parax-offset (Figure 9.5(a)) differs from parallel offset in that the<br />

direction of the normal to the second body feature is reversed.<br />

• Aligned:<br />

Two features are aligned if their center lines are collinear or, when one feature is spherical,<br />

its center lies on the center line of the other. This is illustrated in Figure 9.5(b).<br />

• Incline-offset:<br />

This relation allows us to specify that the parts are related with any position and<br />

orientation. It is illustrated in the case of plane-faces in Figure 9.6.<br />

• Include-angle:<br />

As illustrated in Figure 9.7, include angle specifies the angle between the outward<br />

normals between two planar faces F_1 and F_2 pointed by z and z�.<br />

© 2001 by CRC Press LLC<br />

Against spatial relationships.

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