Export as Step what is Bsplinesurface

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 From:  Matadem
11773.1 
Good day.

I am trying to export a step file to Freecad to do some operations but for some reason I cannot get it to work.

On Freecad forums I was told

The type of this surface is BSplineSurface
The Pocket operation can not process this type of face

Is there a way to change this when exporting to Step file?
I am trying to use Freecad for the cam portion since it has adaptive tool paths.

Tnx!
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 From:  BurrMan
11773.2 In reply to 11773.1 
In cam a “pocket” is USUALLY a 2d operation. Is you surface a simple 2d planar shape? Extract and use curves for pocket operation

If it is 3d, consider other toolpaths. A curved 3d surface cut would not normally be called a “pocket operation”

Maybe more info on your file can help?
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 From:  Michael Gibson
11773.3 In reply to 11773.1 
Hi Matadem, what types of objects are you trying to export, is it stuff like spheres and cylinders?

By default those types of surfaces will export out to a STEP file as BSplineSurfaces.

But you can set an option so spheres will be a SPHERICAL_SURFACE in the STEP file.

To do that go to Options > General > "Edit .ini file" button and inside moi,ini find the section labeled [NURBS Export] and set the option in there WriteAnalyticSurfaces=y

I'm not sure if that is what you're looking for.

- Michael
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 From:  Matadem
11773.4 
I was trying to follow this tutroial > https://www.youtube.com/watch?v=U23eLLXuX3o
attached is a pic and the file I made to test it out and the Freecad.

Id can setup this in Vcarve within a minute.
setup tool database is way confusing in Freecad lol.

but I need to learn Freecad for the adaptive toolpath and fusion360 is no option for me with online/cloud stuff.

Tnx!
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 From:  Michael Gibson
11773.5 In reply to 11773.4 
Hi Matadem, so if you set WriteAnalyticSurfaces=y inside moi.ini then MoI should write out PLANE surfaces instead of B_SPLINE_SURFACE_WITH_KNOTS.

That's what I did to make the attached version.

Does this file behave better when you load it into FreeCAD?

- Michael
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 From:  Matadem
11773.6 
Ok it is showing some toolpaths so I am going in the right direction with the file you provided.

I am running some more tests tomorrow.

Thanks!
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 From:  Matadem
11773.7 
Ok it works!
So I am going to play with it some more and do some test cuts....

I always think that Freecad could be a better program if it wasn't free lol.
I always follow its progress...

Thanks!

EDITED: 19 Jul 2025 by MATADEM

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