Part III: Working with Assemblies
Using Local Component Patterns
Local component patterns are limited to linear and circular patterns. The linear pattern directions
work just like the linear pattern feature in parts, and must reference a line, axis, edge, and so on to
establish the direction. In an assembly, this means that the feature uses model geometry from a
part (solid or surface edges, sketches, reference geometry), an assembly sketch entity, or an assem-
bly reference geometry entity (such as an axis). This is important to keep in mind if you are con-
cerned about circular references.Best Practice
If you have a feature pattern in a part, you should take advantage of it and use a feature-driven pattern instead
of a local pattern. The rebuild time may be longer, but associativity between the part and assembly helps main-
tain design intent. n
Local pattern references
If you still need to create a local pattern, it is best to use a reference that is not dependent on part
geometry. Remember that when part geometry is used for this purpose, the parts must be solved
first (sketches and features rebuilt), then the mates must be solved (to position the parts), then any
in-context references must be solved (which may change the part geometry), and then any assem-
bly features or component patterns must be solved. As a result, it is best practice to use as pattern
direction references assembly sketches that do not reference anything else. The assembly sketches
should sit at the top of the assembly FeatureManager to ensure that they are not picking up refer-
ences from the history-based features in the design tree (mated components, patterns, assembly
features, and so on).When a local pattern really requires a reference from a part, you have no alternative. However, if
you can avoid this by using a sketch assembly skeleton to which the parts are mated and also used
for the pattern references, then you should do so. At all costs, you should avoid using in-context
features, assembly reference geometry that is dependent on part geometry, and assembly features
(other than sketches) for the local pattern reference.Figure 15.1 shows a sample organization of one way that you can set up an assembly to properly
control local component patterns. The lines shown can be created in either two 2D sketches or a
single 3D sketch. The lines are dimensioned from planes, which enables them to be angled for pat-
terns that are not square to the coordinate system of the assembly, but still lie on its main planes.In most situations the rebuild time penalty of using model geometry to establish pattern direction
is fairly slight. The sketch method is probably most justifiable in large, complex assemblies, or in
assemblies requiring long rebuild times. Figure 15.1 also shows the PropertyManager interface for
the local pattern.