Ok, allow me to say you about my attempts to convert any STL (may be IPW) into true solid body.
Just few days ago my friend send me example of IPW stl-file, for experiments.
Few year ago I build UGOPEN application, read asccii STL-file and for each triangle build Bounded Plane. Very simple idea, DLL working, but appllication fast convert few 200.....1000 triangles and spend a lot of time for "Upadating objects...."
Ok. I build new version of DLL, and I dont create any bounded plane, I write each new triangle to BREP topology. AND - I switch OFF any objects update and any Display operations.
Now I can import file with 100 000 triangles in meshes, but - NX need to update all objects and spend a lot of time to do it. I found new solution - I split STL file into few files, not more 10 000 triangles for each, and import file-by-file.
For my sample (~82 000 triangles, 20 Mb ASSCII file), see some pictures.
And - IPW stl have a lot of problems - tiny triangles, or degenerated triangles, when I see triangle as object in Object tree, but - dont see on a screen, a lot of gaps, overlaps.
I think, IPW canoot be converted to true Solid Body.
IPW saved from toolpath verify was 80+MB
used "Edit" -> "Facet Body" -> "Decimate"
even using tight tolerance values
File reduced to 6MB
Maybe this would help before export STL and import to triangles etc.