You can use tools from the Geometry Edit toolset to create geometry from the faces of orphan mesh elements. This technique is useful when you have a meshed part that requires modifications, but you do not have some or all of its geometry available. The decision to add geometric features to an orphan mesh, recreate the part geometry from scratch, or reverse engineer geometry from the orphan elements depends on a number of factors, including:
complexity of the existing part
complexity of the features to be added
degree of difficulty required to modify the existing orphan mesh
desire to create a new mesh for the entire part
The goal of creating a part from an orphan mesh is to create geometry that matches the original design intent while providing a platform for current and future modifications. The geometry must also be suitable for creation of a native mesh by either full association with the current mesh or creation of a new mesh.
The following guidelines will help you create geometry for an orphan mesh:
Create new geometric faces
Use the Face from element faces tool 
to create the outer surface geometry for the model. Each use of the tool creates a single shell face from selected exterior orphan element faces. The tool includes several unique methods for selection of multiple orphan element boundary faces, and it automatically stitches the newly created face to any adjacent geometry. For more information, see “Create face from element faces,” Section 69.7.10. When you are finished creating faces, all exterior orphan element faces should be covered by geometric faces.
Remove extra edges and faces
Use other tools from the Geometry Edit toolset to remove extra edges, small faces, and any other features that would restrict generation of a good quality mesh. If necessary, convert the part to precise geometry. For more information, see “A strategy for repairing geometry,” Section 69.4.
Convert to solid
If you are working with a solid part, use the Create solid from shell tool 
to fill the space inside the created shell faces.
Partition and mesh the part
Suppress or delete the orphan mesh, and create a new mesh for the part.
Create partitions after you repair
If your part contains partitions, the Geometry Edit toolset may delete them during a repair operation. To avoid this problem, you should wait to partition the part until after you have finished editing it.