SolidWorks 2011 Parts Bible - Matt Lombard [245]
If you are an independent contractor and do not share your models with other SolidWorks users, then you have more flexibility to model how you like. As long as you can come back to the model and change it when you need to, more power to you.
Comparing multi-body modeling with assembly modeling
I cover assembly modeling in the companion to this book, the SolidWorks 2011 Assemblies Bible (Wiley, 2011). There is some overlap of the issues between the two books. This is one topic that bridges the worlds of part and assembly modeling. If you are a new user, you may not understand what the big deal is; after all, you just make bodies within a part, right? By the end of this chapter, you should be able to recognize that the issue is more complicated than that. If you are an experienced user, you may have already run into some problems with multi-body modeling or may be having difficulty figuring out where to draw the line between parts and assemblies. This chapter will also offer you some answers.
Multi-body modeling is not assembly modeling. Many times when new users are introduced to the capabilities of multi-body modeling, the first thought that comes to mind is, “This is far easier than making assemblies.” However, multi-body modeling should not be treated as a replacement for assembly modeling. This is not just because I say so; there are practical reasons for the distinction.
Several assembly type functions are missing or more difficult to obtain from multi-bodies. They include the following:
• Interference detection
• Dynamic assembly motion
• Exploded views
• Configs for separate parts
• Drawings for individual parts
• Center-of-gravity calculations for individual parts
• Feature lists for individual parts
• Custom Property information for individual parts
• Mass property calculations for individual parts
To say that these functions are missing from or difficult in multi-bodies does not imply that they should or will be there someday. In fact, I believe that the distinction between multi-body and assembly modeling techniques should be kept as clear as possible. Simply because a technique is easier does not make it better. Above all, remember that modeling multi-body parts puts all the data for all the bodies in a single part file, in a single FeatureManager; there is no easy way to separate out the parametric features into individual parts later on, regardless of how complex the part becomes.
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:
• Segmenting rebuild times (the ability to rebuild one part instead of several)
• Segmenting large data sets (being able to work on one part at a time)
• Switching out parts
• Using multiple instances of parts
• Reusing parts
• 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