Importing a DXF file in Illustrator

I frequently save files form a drawing in DXF format that gets imported in Illustrator. When they are imported the artist reports that they cannot fill or work with these files very well because they are "disconnected" entities rather than a closed chain. Most often they just need to fill closed sketch entities and print them on a printer. In SW the entities are closed and pass a "Check for feature" test for an extrude but in Illustrator they cannot be filled because they are all seperate entities. Does anybody have any experience with this and have any suggestions for solutions.SolidworksDrawings And Detailing