How to prepare complex body to convert to polygon mesh, boundary fill didn't work for me

[yg_sunshine]

Hi, I got a .stp file from some 3rd party and I need to simplify and convert it into a polygon mesh for 3D rendering the outside only, not for 3D printing, so I only need the "skin". I believe the original file was created by Solid Works, it was designed for injection modeling, so the whole object has multiple parts, each are half shells with screw holes etc., the attached screenshot shows the internal structure of half of the main part. Sorry I am not allowed to show/share the whole object because of copyright. 

I believe I should clean up the internal surfaces, join all the shells, then convert the final shape into mesh. If simply convert as-is, I got too many polygon count, and more than half of those polygons are actually inside, never visible. So my question is, how to clean up the internal structures, join all the parts, so I can have the "skin" only, for converting into mesh for 3D rendering?

I tried to create 3 construction planes as shown above then use Boundary Fill, but nothing changes, maybe there are some leaks so the Boundary Fill operation could not fill it?

Any help is appreciated! Thanks!

[johnsonshiue · Accepted solution]

Hi! If you only want the skin, you could use Offset Surface command and select the outer faces to create a zero-distance offset surface. Then you may need to add a few workplanes. After that, you may use Boundary Fill command to solidify the surface body.

Many thanks!

[yg_sunshine]

Thanks! Only had a chance to try your method out today, it works! Depends on the model, sometimes it may fail, complaining there is some overlapping etc., but I managed to get the skin only and convert into mesh! Thanks!