[Dassoo]

Summary

Exports were assembled independently in Blade, Propeller and Shaft, each with its own sewing tolerance and its own forced cast to TopoDS_Shell. When the four blade faces do not sew into a single shell (geometry-dependent, e.g. a tip collapsing to a point), that cast raises Standard_TypeMismatch and the whole export fails. This is a failure triggering an HTTP 500 on IGES exports.

This PR moves the B-Rep assembly and the file writing into one module and makes the export path never depend on a boolean fuse or on a closed shell.

 bladex/
+├── export.py       # compounds, sewing, solid assembly, meshing, writers
 ├── blade.py        # Blade.shell() -> export_stl / export_iges
 ├── propeller.py    # blades_shape() / compound() -> export_stl / export_iges
 └── shaft/
     └── shaft.py    # generates its solid through the same helpers

Geometry and I/O are now separate:

Blade.shell()              -> shape        write_stl(shape, path, ...)
Blade.generate_solid()     -> solid|shape  write_iges(shape, path)
Propeller.blades_shape()   -> compound     mesh(shape, ...)
Propeller.compound()       -> compound
Propeller.solid            -> fused solid  (explicit, not used by exports)

Changes

New: bladex/export.py

Function	Purpose
make_compound	single implementation, previously a local helper in propeller.py
sew_shapes	sewing with explicit tolerance, clear error when a face is None
to_solid	MakeSolid only when there is exactly one shell, recursively through nested compounds; returns the sewn shape otherwise
mesh	one tessellation path with linear, angular and is_relative
write_stl	binary output only, checks the writer return value
write_iges	checks the writer return value

bladex/blade.py

• Blade.shell(sewing_tolerance=1e-2): the sewn four faces, used by STL, IGES and generate_solid.
• generate_solid(): tolerance 1e-7 -> 1e-2, no blind cast, falls back to the sewn shape.
• export_stl(): adds angular_deflection (0.3).
• export_iges(): exports the sewn shell with a tunable tolerance; leading-edge curves unchanged.

bladex/propeller.py

• blades_shape() and compound() are public: assembly is geometry, not an export detail.
• shape is now the compound; solid is the explicit boolean union, uncached.
• export_iges() / export_stl() write sewn blades plus the shaft, with include_shaft and exposed deflections; no fuse on the default path. STL is always binary.
• tmp_stl() is a deprecated alias of export_stl(include_shaft=False) and emits DeprecationWarning.
• display() shows the compound.
• generate_obj() and generate_obj_blades() are repaired: they referenced self.shaft_solid / self.blades_solid (removed in 4f2ffe4) and used fixed /tmp/temp_*.stl paths. They now use tempfile.TemporaryDirectory.
• smithers is imported inside the two OBJ methods, so import bladex no longer requires it.

bladex/shaft/shaft.py

• generate_solid() uses the same helpers, removing the same blind shell cast.

Packaging

• New optional extra: obj = ["smithers[vtk]"].

Tests

• 11 new tests in tests/test_propeller.py: to_solid nested-compound conversion, non-shell shapes left unchanged, binary STL with and without shaft (triangle counts), single-body blade shell, readable propeller IGES, blade IGES with and without leading-edge curves, export surviving unsewable faces, tmp_stl equivalence plus deprecation warning, reflect_blade contract, OBJ regions for propeller and blades.

[Dassoo]

@ndem0 : tested on marinAI, works fine

@DavideOberto you may want to see and test everything on your end before merging, I thought it would have been better to centralize export functions without rewriting the same code. Should be fine against a few errors that were previously being triggered also on the app I'm working on, which is using BladeX