Creating Sub-Weldments
You create sub-weldments to segment complex weldment models into more
manageable entities.
Sub-weldments can include any entity listed in the Cut list folder 
, including structural members, end caps, gussets, weld fillet
beads, and structural members trimmed with the Trim/Extend
tool.
To create a sub-weldment:
In the FeatureManager design tree of the weldment
model, expand the Cut list folder
.
Select the entities to include in the sub-weldment,
using Shift or Ctrl
to group-select.
The selected entities highlight in the graphics
area.
Right-click and select Create
sub-weldment.
A sub-weldment folder 
containing
the selected entities appears under the Cut
list folder .
Right-click the sub-weldment folder and select Insert into New
Part.
The sub-weldment model opens in a new SolidWorks
window, and the Save As dialog
box appears.
Accept or edit the name for File
name, and click Save.
Changes made
in the weldment model propagate to the sub-weldment model.