4.1.2.3 Defining a Transition Region. If a transition region is required, it shall be indicated as a separate hounded region according to paras. 4.1.2.1 and 4.1.2.2.
Refer to para. 4.22 for the method to describe transitions or gradients.
4.2 DesIgn Characteristics
Paragraph 4,2 addresses practices for communicating design-specific characteristics using the geometry characterLstics In para. 4.1. The concepts discussed in this paragraph include lattice structures, gradient control, complex geometries, and design for assembly.
4.2.1 Lattice Structures. A lattice structure can be composed of repeated patterns of unit cells that are defined as volumetric geometric elements in a defined space. The unit cell pattern can then be repeated to create complex heterogeneous or homogeneous geometric volumes. Examples of unit cells are shown in Figure 4-10.
If the lattice unit cell requires a geometric tolerance control, then an appropriate geometric control may be applied per ASME Y14.S and paras. 4.1.1 and 4.1.2.
Figure 4-11 illustrates abrupt changes in unit cells across five bounded volume regions. Each bounded volume region Indicator may have unique tolerances and materials (para. 4.2.2). A transition region (para. 4.1.2.3) may be used to Indicate how the shape, material, or other characteristic of a unit cell changes from one location in the part to another.
4.2.2 GradIent Control. If a gradient control is required, it shall be indicated with the following:
(a) hounded volume region notation (see para. 4.1.2.1). e.g.. VOL2. See Figure 4-12.
(b) equation notation for the mathematical function. e.g.. EQ 1. See Figure 4-12. See Nonmandatmy Appendix B for an example.
(c) percentage bbel indicating tolerance on the variation. e.g.. 50% MAT2. See Figure 4-12.
See Figure 4-12 for an example that combines gradient controls and transition regions.
Table 4-1 provides material gradient values for the example part shown in Figure 4-12. This example implements functions to specify a gradient. The tolerances on MAT1 and MAT2 are bilaterally identified in Table 4’l as ±12.5% and ±25%. respectively. At the material boundaries.thetolerancevaluesareunilaterallydisposcd within the hounded volume regions (e.g.. z = 10, a = 25, or when nominals are either 0% or 100%). See Nonmandatory Appendix B for a detailed explanation of the example.
NOTE: Voids in a particular unit volume may cause measured maerlal composition to no( equal 100%.
Figure 4-13 identifies a gradient control within a part that consists of S bounded volume regions. VOL2 is the transition region between material MAT1 in VOL1 and material MAT2 in VOl.3.
4.2.3 Complex Geometry. AM facilitates the production of part geometries that are complex. Complex geometry features commonly originate from topology optimization or generative design algorithms. Complex geometry may not conform to existing annotation capabilities. In such cases, complex geometries may be identified using bounded surface regions or bounded volume regions (see para. 4i.2). Figure 4-14 provides examples of complex geometries.