Reverse-Engineer Radial Turbine STEP

I need a precise STEP model of a radial-flow turbine housing generated from my own scan data. You will receive high-resolution 3D scans that capture both the exterior and the full internal passage geometry, so the task focuses on translating that raw mesh into a clean, parametric solid that can be edited in any mainstream CAD package.

Accuracy is not critical for flanges, we plan to modify this STEP file to suit our needs however we require the model to have minimal faces (not just an automated system for converting a mesh into a STEP.
The model will need to be built using lofts, fillets, extrusions etc, having the internal scroll as a separate STEP file is appreciated as we can use this model to simply CUT a volute scroll into any size housing as we wish.

This 3d scan has an accuracy of 0.1mm, the turbine housing has been cut in half to scan internally so this will also need to be joined together when the step file is being designed.

We are planning on initially 3d printing this exhaust housing in stainless steel for a prototype and then moving into investment casting.

Deliverables
• One watertight, feature-tree STEP file ready for downstream CAD/CAM
• A brief report noting any areas where the scan data forced design assumptions (if any)

Please let me know which CAD platform you plan to use—SolidWorks, NX, Fusion 360, or similar—so I can verify compatibility with the rest of our tool chain. If you have experience cleaning mesh artefacts and reconstructing complex internal flow paths, this job should be straightforward.