SOLIDWORKS Multibody Part vs Assembly

Article by Tom Ayers updated June 1, 2023

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A general rule to follow is that one part generally should represent a single part number for your bill of materials. SOLIDWORKS multibody parts are not meant to replace the use of assemblies.

For example, in part files, we lack the ability to use some tools like dynamic clearance, collision detection, etc. I don’t work in industry, but I generally see clients I work with use multibody parts for purchased parts and then insert them into assemblies. In this article I will review the key difference for a SOLIDWORKS Multibody part vs Assembly.

Below is a chart in my opinion on some of the pros and cons of multibody parts vs assemblies:

PROSCONS
Assemblies have access to dynamic motion, flexible assemblies, etc.Assemblies take longer to load in general
Multibody generally has faster file loading speed (no external references)Multibody performance is not as good as assembly graphical performance
Save time by using multi bodies instead of adding a configuration for each part and the assembly levelMultibody hide/show components are slower than assemblies
Saving multibody parts without their feature tree eliminates long rebuild timesAssemblies have more files to juggle, more potential for downstream problems

 

You also can save assemblies as a multibody part. You may want to do this because this makes file sharing easier. For example, if I design a jet engine and a client wants to see if my engine will fit in their frame. I can save the engine assembly as a part document in SOLIDWORKS and send the part file to the client without potentially risking breaking the assembly file itself. This would also cut down on overall file size as I wouldn’t have to send a large assembly file.

To save an assembly as a multi-body part document, first, open an assembly file. Go to File > Save As. Set the save as type to Part ( .PRT, .SLDPRT). There will be a few options to select from, as shown below.

  • All components to save all components as Solid Bodies
    • Components that are hidden or suppressed are not save when you select All Components
  • Exterior Faces to save the exterior faces as Surface Bodies
  • Include specified components to save the visible components as Solid Bodies

 

The last selection, “Preserve geometry references” allows you to save data for the assembly mates in the multibody part.

preserve geometry references

This is helpful for using multibody parts as simplified representations of assemblies in a higher layout assembly and then make changes later. If you change a subassembly for example and then save that subassembly again as a multibody part, you can replace the previous multibody part with the new multibody part, without having to recreate the mates.

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Tom Ayers