Multibody Part vs. Assembly in SOLIDWORKS

There are fewer differences than ever between a multibody part file and an assembly file in SOLIDWORKS.
Where commonalities exist, the user may take advantage of performance and file management benefits of a multibody part.
Where they differ, each has individual benefits that make them a clear choice in each situation

Why Assemblies

This assembly contains 19 parts, some unique, some with multiple instances.
As an assembly, this results in several files that need to be managed. 1 for the assembly and 1 each for the unique part files within this assembly.



FILE > FIND REFERENCES displays a list of each part and sub-assembly contained within the assembly above.


Reasons to remain an assembly:

• Each part has a unique name or number and is tracked individually.
• Each part has a unique name or number and is purchased individually.
• The assembly has movement where dynamic assembly motion is important
• Clearance detection and interference detection are important tests.

Turn an Assembly into a Multibody Part

Select FILE > SAVE AS and change the “Save as” type to PART .sldprt
You can choose:
Exterior Faces – SOLIDWORKS determines what faces are ‘exterior’ and which can be considered ‘interior’ and will save a multibody part full of surfaces representing those exterior faces.
Exterior Components – Using a similar algorithm, SOLIDWORKS determines what parts are ‘internal’ and which are ‘external’.
All Components – This saves a part file with bodies representing each individual instance of every part within the assembly. (This is the preferred method.)


**NOTE** The resulting multibody part is NOT ASSOCIATIVE back to the original assembly. Changes made to the original assembly will NOT show in the new part file.

Why Multibody Parts

Weldments are a classic example of a proactive reason to use multibody parts.  Weldments are much easier to create as a single part file, but you still have ‘bill of material’ like functions to get a complete part count in the form of a weldment cut list.





MOVE/COPY Bodies in a Multibody Part:


INSERT > FEATURES > Move/Copy Bodies
This is similar to inserting an additional instance of a part in an assembly.




You can choose to COPY and set the number of copies, or you can simply just MOVE the selected body.
Rotate or translate can be done using the triad or numerical input in the Property Manager.



This function adds a history based feature to the Feature Manager.
This can be edited and suppressed like any other feature in SOLIDWORKS.



Reasons to Use a Multibody Part:

• The file represents a complete ‘purchased’ item where individual components are not tracked.
• Clearance detection and interference detection between the parts is NOT important. (Note: The multibody part can still participate in an interference or clearance detection study. It is treated as a single part in the study.)
• SECURITY! Saving as a multibody part is a way to share your designs with even SolidWorks users. This process removes the Feature History.
• Performance is improved since it is now a SINGLE file, not several referenced files like assemblies.

Virtual Components in Assemblies

Virtual components are those that ‘live’ ONLY within the assembly. Similar to the individual bodies in multibody parts, virtual components do not have an ‘external’ file to track.
New parts can be created as virtual components in an assembly or existing parts can be ‘converted’ to virtual components.

Select multiple parts in the Assembly Feature Manager and choose MAKE VIRTUAL.
A “Warning” will appear!! The resulting virtual components will NOT be associative to the original parts they represent!!
Virtual components are represented in the Assembly Feature Manager with square brackets “[ ]”.
Example: [virtual component name]

Reasons to Use a Virtual Components in Assemblies:

• The file represents a complete ‘purchased’ item where individual components are not tracked.
• Easier way to share your designs with even SolidWorks users. If all the parts in the assembly are birtual, you can send a single assembly file and all the virtual components will be contained within it.
• Performance is improved since it is now a SINGLE file, not several referenced files like assemblies full of ‘traditional’ parts.