I am trying to convert this composite surface into a single solid body, however when I try to stich the surfaces in the construction environment it always crashes. I have also tried edditing the STEP file import options but it still always opens as a composite surface.
No file attached?
Depends on where you have it.
Drag the Red End of Part marker above the Composite body and nothing in Construction (or Repair) environment.
Save the file in a rolled up state and then zip.
If still larger than 1.5 meg the limit is 10Meg over here http://www.augi.com
The most obvious question - Why would you even need that as solids? Wouldn't you simply purchase from the company?
This seems to be a derived part from a SWX 2010 assembly, as can be seen in the translation report.
I've seen several similar parts, and most of them had lots of missing or distorted faces. SWX derived parts seem to be only minor quality.
With lots of spare time and some knowledge, you can rebuild these imports. But that's no fun.
If you need to include in assembly drawing - simply tell Inventor to include surfaces.
If you want it to "appear" solid - right click and turn off Translucent.
If you reall want to take the time to convert to solids you will need to create Groups in Repair (Construction) environment and isolate the different parts into different groups. Patch the missing surfaces, stitch and promote. (an all day job on this assembly)