SolidWorks 2011 Parts Bible - Matt Lombard [246]
Appropriate uses for multi-body modeling include (but are not limited to):
• As an intermediate step on the way to a single-body solid.
• As multiple or inserted bodies for reference (reference bodies may be deleted at the bottom of the FeatureManager).
• As over-molded parts.
• 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.
• When the end shape of the finished product is known, but the separation occurs between parts due to manufacturing methods, and materials have not been decided yet; in this case, multi-body techniques can save a lot of time compared to modeling an assembly.
• As captive fasteners and purchased inseparable subassemblies.
• When SolidWorks weldments result in a multi-body part.
• When features require tool bodies, such as the Indent feature.
• When the Mold Tools result in a single multi-body part representing the plastic part and the major mold components.
If you are administering a SolidWorks installation of multiple users, then you may be looking for a “bright line” test to clearly define for users which types of multi-body modeling are allowable and which are not. So many possibilities exist that it is difficult to say definitively what really should not be done, but here is a short list that you can modify for your needs:
• Do not use multi-body modeling simply to avoid making an assembly.
• Do not leave a part in a multi-body state that should be joined together into a single body.
• Hiding a body is sometimes appropriate, and deleting a body is sometimes appropriate — understand the difference.
Okay, the lecture is over. The message that you should take from all this is not to use multi-body techniques just because you can; use them only when you have a solid reason to do so. This is the criterion that I use for my own modeling, what I would like to see in models that I inherit from other SolidWorks users, and a philosophy that will serve you well if you are conscientious about it.
Multi-body modeling is powerful, and for complex parts can even increase rebuild speed compared with single body modeling or assembly modeling. You can develop and use many powerful techniques based on multi-bodies, but as I mentioned earlier, sometimes you pay a price for the shortcut.
Understanding Multi-Body Techniques
To complicate the issue somewhat, nearly all surface modeling is also multi-body modeling. In this chapter, I am referring to solids unless I specifically state otherwise. Still, most solid body techniques have some sort of equivalent in surface body techniques. Surface bodies are discussed in Chapter 20.
Multi-body techniques cover a wide range of functionality, and as soon as someone creates a list of what you can do with them, someone else will come up with a new technique. Still, here is a short list of techniques where multi-body functionality makes things either easier or simply possible:
• Complex shapes across multiple parts
• Tool bodies/Boolean operations
• Local operations
• Patterning
• Simplifying very complex parts
• As a bridge between solids
• Undetermined manufacturing methods
• Manipulating imported geometry
In the remainder of this chapter, I illustrate each technique using an example model and discuss the positives and negatives of each technique. As you get deeper into SolidWorks, you will find that the more complex functions tend to come at a price. A given feature might be the only way to accomplish a particular task, but it rebuilds slowly, might only