Chapter 26: Modeling Multi-bodies ............................................................................................
You may find parallels between making multi-body parts and making virtual components (parts
that are saved within an assembly file). While both these techniques offer shortcuts or make some
basic tasks easier, good reasons exist for being mindful of the “one part, one file” mentality,
including:l (^) Segmenting rebuild times (the ability to rebuild one part instead of several)
l Segmenting large data sets (being able to work on one part at a time)
l (^) Switching out parts
l Reusing parts
l (^) Bills of Materials (BOMs)
Further, creating drawings of individual bodies of a multi-body part is more difficult than creating
drawings of individual parts, not that it cannot be done (remember that starting in SolidWorks
2010 you can now specify bodies from a part to be used in a drawing view), just that it is more
difficult. Also, editing the features of individual bodies is not as easy as if the individual body were
an individual part. When you create several bodies in a single part, you constantly have to carry
the feature and design intent overhead of all the features used to create all the bodies to edit any
individual body.
Using multi-body techniques appropriately
You need to have a healthy respect for the problems that you can create for yourself and others by
using multi-body modeling in inefficient or inappropriate ways. Still, appropriate uses for multi-
body modeling do exist. You may hear people recommend that at the end of the FeatureManager,
only a single solid body should remain, with the rest of the bodies either absorbed or deleted. On
the other extreme, for some people, anything they can create is allowable. I recommend that if you
decide to use multi-bodies, then you should be at least able to articulate why you have chosen to
do so in a way that does not sound like you are making excuses for careless work.
Appropriate uses for multi-body modeling include (but are not limited to):
l (^) As an intermediate step on the way to a single-body solid.
l As multiple or inserted bodies for reference (reference bodies may be deleted at the
bottom of the FeatureManager).
l As over-molded parts.
l (^) As parts that need to be assembled into a single, smooth shape, such as a computer mouse
or an automobile body where the shape is impossible (or at least far more difficult) if done
in-context.
l When the end shape of the finished product is known, but the part breaks due to
manufacturing methods, and materials have not been decided yet, multi-body techniques
can save a lot of time compared to modeling an assembly.
l (^) As captive fasteners and purchased inseparable subassemblies.
l When SolidWorks weldments result in a single multi-body part.