Best export file type to convert to CAD

• D

  DCLARS

  10/5/25, 5:38 PM

  Hi everyone,

  I am doing a whole lot better with this scanner after logging a whole bunch of hours with it. 

  Its actually unbelieveable how well it works when you get used to its features.

  Anyway,  I need to convert to a CAD model as an ebd result.

  I originally used an .stl file and brought it into fusion 360. After fusion choked on it for over an hour, it gave me 

  a step file to use. It didnt seem like the normal .stp files im used to working with. The whole body was black.

  I sent it to my CAD guy who said he couldnt get any dimentions off the file to work with.

  If any of this sound familiar to anyone, your experience would be greatly appriciated.

  So finally my question - Is there a better file option to export as, if I am going to try to convert to a step file??

  For that matter, is there any software out there that can do this that isnt wicked expensive??

  Thanks so much for your time!!

  Derik

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• TM

  Tom Meeks

  10/6/25, 3:16 PM

  @DCLARS I use a free application called FreeCad to convert STL files to STEP.

  https://www.freecad.org/

  It's a very simple process and there is a page that describes the steps.  

  https://grabcad.com/tutorials/how-to-convert-stl-to-step-using-freecad

  With Moment of Inspiration, I find creating a Sub-D file from a .OBJ file works if I have saved the .OBJ in QUAD format at a fairly low poly count.

   

   

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• 

  Vaclav Zdrazil

  10/21/25, 8:44 AM

  @DCLARS

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  Hey Derik,

  Your experience sounds very familiar. You've actually discovered one of the fundamental challenges in reverse engineering. Let me explain what's happening and suggest some better approaches.​

  Why the STL → STEP Conversion is Problematic

  When you convert STL to STEP (whether through Fusion or other software), the result will always be unusable for typical CAD work. The reason is simple: STL is a mesh (network of triangles), while STEP is a format based on mathematical surfaces (NURBS). During automatic mesh→STEP conversion, software essentially just takes all triangles and converts them into thousands of small surface patches - the result looks black/gray, has no editable edges, and you can't take dimensions from it.​

  Better Formats for Scan Export

  Instead of STL, try using OBJ or PLY formats:​

  • OBJ/PLY support colors, textures, and various polygon types (not just triangles)​

  • STL is the simplest but contains only monochromatic triangular meshes​

  • For mechanical parts, OBJ with quad faces is ideal instead of triangles​

  • For organic shapes STL suffices, but for mechanical parts OBJ/PLY will give you better results​

  The Real Solution: Manual Reverse Engineering

  For a usable parametric CAD model, unfortunately there's no magic button. You need to manually remodel the part:​

  1. Use the scan as a reference/template - not as the final mode​

  2. Create a new model using CAD tools (sketches, extrusions, revolves)​

  3. Align the finished model with the scan to check for deviations​

  4. Only this way you'll get a fully editable, parametric model with mathematically defined surfaces​

  Software for Reverse Engineering

  If you want to speed up the process, specialized tools exist:

  Professional (but more affordable):

  • Quick Surface - comprehensive solution for converting scans to CAD​

  • Revo Design - cheaper variant of QuickSurface Lite, works standalone​

  One-time Payment (no subscription):

  • Rhinoceros 3D with plugins Mesh2Surface or RhinoResurf​

  • Rhino isn't as user-friendly, but it gets the job done​

  • Both plugins automate the mesh → NURBS surfaces conversion​

  Working in Fusion 360

  You can work in Fusion too, but before any work:​

  1. Reduce the number of faces - especially on flat surfaces (Mesh workspace → Reduce)​

  2. Try using scan export as OBJ quads for mechanical parts​

  3. Use "Convert Mesh" with Prismatic option instead of Faceted - it will try to identify flat and cylindrical surfaces. If you're using the free Personal Use license, the advanced "Prismatic" mesh conversion isn't available - you'll only get the "Faceted" option which creates thousands of triangular faces. ​

  4. But be aware - even then it won't be a fully parametric model​

  Based on the information I've gathered, here's a note in English for Derik about FreeCAD as a free alternative:

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  Free Alternative - FreeCAD

  If budget is a concern, FreeCAD is worth considering as a free, open-source option. It has an interface that's somewhat similar to SolidWorks and other professional CAD software, which might make it easier to learn if you're familiar with traditional CAD programs.​

  However, there are important limitations to keep in mind:​

  • Manual work is still required - FreeCAD doesn't have automatic primitive recognition (cylinders, planes, etc.) like QuickSurface does​

  • It can create cross-sections from your mesh, but you'll need to manually trace them to create sketches​

  • The learning curve is steeper than commercial options​

  • The interface, while functional, isn't as polished as paid software​

  What FreeCAD CAN do:​

  • Convert STL/OBJ to solid bodies

  • Export to STEP format

  • Provide cross-sections for reference

  • Basic mesh analysis tools

  FreeCAD is a legitimate free option that can handle mesh-to-solid conversion, but you'll still be doing essentially the same manual remodeling work as in Fusion 360's free version. It's best suited if you're willing to invest time learning it and don't mind the manual workflow.​

  Bottom Line

  No software will instantly give you an editable STEP from a mesh that your CAD guy can use. That "black body" without dimensions is exactly the result of automatic conversion. The scan is useful as a reference and for checking, but the final usable model must be created by manual modeling based on the scan.​

  Good luck with your project =)

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• TM

  Tom Meeks

  10/22/25, 1:41 AM

  I have also found Instant Meshes, a free application that is very helpful.

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