Part III: Working with Assemblies
FIGURE 12.3An assembly layout sketch
Caution
When using layout sketches, it is assumed that the relationships are created such that the sketch drives
everything else. However, there is nothing preventing you from using other things in the assembly to drive the
sketch. You should avoid this type of conflict, called a circular reference. It can create sketches that change
with every rebuild and can seriously impact rebuild times. When using any type of in-context relations, you
need to be careful to establish one or more driving entities, which are not in turn driven by other entities.
To take this a step further, it is best to avoid daisy chaining, where A drives B, B drives C, and so on. It is
better practice to make A drive both B and C directly. This saves on rebuild times and troubleshooting. See the
sidebar on using the skeleton or wide tree approach in Chapter 11 for more details on the benefits of this type
of modeling and an example part. n
One of the drawbacks of this technique is that you give up dynamic assembly motion. To move the
parts, you have to move the sketch and rebuild. The part does not move until the sketch is
updated. If you need to combine layout functionality with dynamic assembly motion, see the
Layout feature in Chapter 16.Virtual components
Virtual components are covered in more depth in Chapter 16. Virtual components are parts that
are saved so they are internal to the assembly. You can save them out so that they are external to
the assembly and can be reused in other assemblies. You can also convert external components to
virtual components. Virtual components, as the name suggests, can be either parts or subassemblies.