Copy of the help, possibility to import in volume:
Volumetric body. Attempts to import the data as volume bodies. In many cases (especially in complex models), the resulting volume is unusable and the data is then imported as polygon bodies by the converter. In this case, the FeatureManager authoring tree can contain a Polygon Bodies folder , a Polygon Bodies folder , imported Polygon Features, and Imported Polygon Features.
Personally I tried to open a .stl and there is no body. Neither volume nor surface. There is only one line "STL1 Graph" corresponds to the 3D "image" of the volume.
By default the import of an STL gives a graphic body, in the complements of the premium SolidWorks (and pro I think) there is a module called Scan to 3D, this adds in the file types the ability to open mesh or point files and adds mesh transformation functions... To do this, you have to right-click on the mesh to access the functions...
EDIT: I checked and you need a solidworks premium license to have scanto3d
Function recognition (creation of a function tree from an imported body) is available from the professional
@Fabrice_A is completely right, without Scan to 3D, it's impossible to do anything with STL which is a mesh file (you just have to display the shaded plus edge mode) to realize it.
So scan to 3d allows you to make real surfaces from your meshes (smoothed, swept, cone, flat sphere, ) which will allow the end of the end to have a solid.
Be careful, if the shape is relatively simple, it is still much faster to recreate it.
@+
On the other hand, for me the @opiep27 method is impossible with a triangular mesh stl, which is the majority of stls!