About Envelopes
An envelope is a part created to represent a predetermined set of components (parts and subassemblies) in an assembly. The envelope uses simple geometry to reduce memory usage and looks similar to the components it represents.
Envelopes must have both a list of reference components, the envelope definition, and geometry, the envelope part. A default envelope definition includes all parts in the assembly, therefore it is not necessary to define the list of components. The envelope part defined for the default envelope does not have to include geometry from all parts. Envelopes can be displayed in the Model Tree along with information concerning the part geometry and the list of components. Although envelopes are stored as part files with a .prt extension, you can only use them as envelopes in the assembly in which they were created. Envelope parts do not appear in the Assembly BOM.
To use an envelope part, you must explicitly include it in a simplified representation. An envelope can be used in multiple simplified representations. To create a default envelope representation, right-click the top level assembly and choose > 
Default Envelope from the shortcut menu or use the View Manager dialog box. When you use the View Manager dialog box, components represented by the envelope can still be explicitly included, excluded, or substituted.
Default Envelope from the shortcut menu or use the View Manager dialog box. When you use the View Manager dialog box, components represented by the envelope can still be explicitly included, excluded, or substituted.If the assembly contains closed quilt zones, you can select components to be included in the envelope by selecting a zone.
 | You can create an envelope while a simplified representation is active, without the master representation being in session. Envelopes can be created using Shrinkwrap methods only when the master representation is in session. |