This document will describe the process of creating a ‘Merge Model’ in an assembly.
Merge models are useful for some simulation models. The process is performed in an assembly. An empty part is created in the assembly, and geometry from one or more components are copied, or merged into the empty part. The net result is that the merge part contains the geometry from the referenced model, but has one the merge feature in its model tree.
An assembly of a trailer is shown below. The goal here is to create a single part model of the trailer.

 

Starting from inside the assembly, create a new empty part.

Enter the part name, and create it using your preferred method. Note that it is recommended to use a start part to ensure consistency. Activate the top level assembly after the new part is created and placed into the assembly.
Select Edit > Component Operations > Merge
Creo will prompt for the new, empty part first.

Select the Merge_part model > Ok. Next, Creo will prompt for the reference parts(s). Select the desired parts from the graphics window, or the model tree. Select Ok when finished.

 

Creo will now prompt for datums, once for each part selected in the previous step.

Select Done for each part that was copied, followed by a Done/Return to complete the component operation.
Select the Merge_part from the model tree, then select RMB > open, to open the model.

 

This option determines whether to bring the datums associated with each reference part into the new merge part.

Note the merge_part now has the copied reference geometry. It is a complete part, and the analysis process can begin in Mechanica as if it was a single part, and not an assembly.