I’m trying to 3D print complicated model which consists of multiple parts.
Is there a way to export assembly STL from Rhino as Solidworks or ProE does?
You can have multiple objects in a single STL file. Some 3D printer software will automagically “fuse” multiple overlapping closed volumes into one printable part; others will not. If yours will not work with multiple parts, you won’t have much choice than to try to BooleanUnion all the parts together into one closed object and export. If that is not possible, you may need to use an external mesh fixing software such as NetFabb…
@hoon Adding Mitch’s suggestion, you can also run the MeshBooleanUnion command if what have are mesh solid objects.