ExtensionContainer::getExtension: No extension of given type available

[pjcreath]

I tried to import a CSG generated by OpenSCAD and got this error message:

ExtensionContainer::getExtension: No extension of given type available

There doesn't seem to be any other information in the report view?

[KeithSloan]

Thanks for reporting.

Please could you supply

• your FreeCAD version.

• output from running the following in the FreeCAD python console.

import Import
print(Import.listTypes())

[KeithSloan]

Are you able to post the csg file? ( Add txt to file name or zip)

[pjcreath]

OS: macOS 15.7.3
Architecture: x86_64
Version: 1.1.0rc3.20260223 (Git shallow)
Build date: 2026/02/23 23:43:19
Build type: Release
Branch: (HEAD detached at adf7760)
Hash: adf77600e2526bf02804524f0d1991ab1c534abe
Python 3.11.14, Qt 6.8.3, Coin 4.0.3, Vtk 9.3.1, boost 1_86, Eigen3 3.4.0, PySide 6.8.3
shiboken 6.8.3, xerces-c 3.3.0, IfcOpenShell 0.8.4, OCC 7.8.1
Locale: English/United States (en_US)
Navigation Style/Orbit Style/Rotation Mode: Touchpad/Turntable/Object center
Stylesheet/Theme/QtStyle: FreeCAD.qss/FreeCAD Light/
Logical DPI/Physical DPI/Pixel Ratio: 72/132.25/2
Installed mods: 
  * InventorLoader 1.5.1
  * Manipulator 1.6.3
  * Alternate_OpenSCAD 1.0.0
  * sheetmetal 0.7.58

>>> import Import
>>> print(Import.listTypes())
Traceback (most recent call last):
  File "<input>", line 1, in <module>
AttributeError: module 'Import' has no attribute 'listTypes'
>>> help(Import)
Help on module Import:

NAME
    Import - This module is the Import module.

CLASSES
    builtins.PyObjectBase(builtins.object)
        StepShape
    
    class StepShape(builtins.PyObjectBase)
     |  StepShape in Import
     |  This class gives a interface to retrieve TopoShapes out of an loaded STEP file of any kind.
     |  
     |  License: LGPL-2.1-or-later
     |  
     |  Method resolution order:
     |      StepShape
     |      builtins.PyObjectBase
     |      builtins.object
     |  
     |  Methods defined here:
     |  
     |  __delattr__(self, name, /)
     |      Implement delattr(self, name).
     |  
     |  __getattribute__(self, name, /)
     |      Return getattr(self, name).
     |  
     |  __init__(self, /, *args, **kwargs)
     |      Initialize self.  See help(type(self)) for accurate signature.
     |  
     |  __repr__(self, /)
     |      Return repr(self).
     |  
     |  __setattr__(self, name, value, /)
     |      Implement setattr(self, name, value).
     |  
     |  read(...)
     |      method read()
     |      Read a STEP file into memory and make it accessible
     |  
     |  ----------------------------------------------------------------------
     |  Static methods defined here:
     |  
     |  __new__(*args, **kwargs)
     |      Create and return a new object.  See help(type) for accurate signature.

FUNCTIONS
    export(...) method of builtins.tuple instance
        export(list,string) -- Export a list of objects into a single file.
    
    insert(...) method of builtins.tuple instance
        insert(string,string) -- Insert the file into the given document.
    
    open(...) method of builtins.tuple instance
        open(string) -- Open the file and create a new document.
    
    readDXF(...) method of builtins.tuple instance
        readDXF(filename,[document,ignore_errors,option_source]): Imports a DXF file into the given document. ignore_errors is True by default.
    
    writeDXFObject(...) method of builtins.tuple instance
        writeDXFObject([objects],filename [,version,usePolyline,optionSource]): Exports DocumentObject(s) to a DXF file.
    
    writeDXFShape(...) method of builtins.tuple instance
        writeDXFShape([shape],filename [version,usePolyline,optionSource]): Exports Shape(s) to a DXF file.

FILE
    /Applications/FreeCAD 1.1/FreeCAD.app/Contents/Resources/lib/Import.so

gridfinity_basic_cup.csg.txt

[ab-tools]

Hello @KeithSloan,

is there any news on this issue?

I get exactly the same error message.

FreeCAD info:

OS: Windows 11 build 22631
Architecture: x86_64
Version: 1.1.0.20260325 (Git shallow)
Build date: 2026/03/25 02:17:53
Build type: Release
Branch: (HEAD detached at 34a971666)
Hash: 34a9716668b1ddeb55b914f1c5be644826bdbbbf
Python 3.11.15, Qt 6.8.3, Coin 4.0.3, Vtk 9.3.1, boost 1_86, Eigen3 3.4.0, PySide 6.8.3
shiboken 6.8.3, xerces-c 3.3.0, IfcOpenShell 0.8.4, OCC 7.8.1
Locale: German/Germany (de_DE)
Navigation Style/Orbit Style/Rotation Mode: CAD/Rounded Arcball/Window center
Stylesheet/Theme/QtStyle: FreeCAD.qss/FreeCAD Dark/
Logical DPI/Physical DPI/Pixel Ratio: 96/81.5973/1
Installed mods: 
  * Alternate_OpenSCAD 1.0.0

CSG: test-csg.zip

Any support with this would be much appreciated!

Best regards and thanks
Andreas

[KeithSloan]

The Alternate_OpenSCAD importer needs updating for FreeCAD 1.1

As a work around a

test-2.FCStd.zip

test-2.csg.zip

new OpenSCAD_Workbench is under development for FreeCAD 1.2, with it and choosing the
External_OpenSCAD_Workbench NEW CSG / AST Importer I am able to import the csg file.

New Workbench is at https://github.com/KeithSloan/OpenSCAD_Workbench
Not yet in Addon Manager so have to clone to FreeCAD Mod directory
For 1.1 this is /FreeCAD/v1-1/Mod

[ab-tools]

Hello @KeithSloan,

first really appreciate your very quick reply and effort - thanks a lot!

I've tried that and manually added your new OpenSCAD Workbrench to the Mod directory which worked first try.

And yes, when I try to import the CSG file again I at least no longer get an exception (using "External_OpenSCAD_Workbench NEW CSG / AST Importer" as you suggested), but the object that it imports to FreeCAD is unfortunately only "similar", but not exactly what I see in OpenSCAD:

You see that on the left side in FreeCAD several details are missing or are just different.

I just re-generated the CSG file (latest version attached again here: test-csg.zip) with OpenSCAD 2025.10.02 - not sure if it would make a difference if I use a newer OpenSCAD development build?

Or any other option parameter I miss which causes this import issue?

Thanks a lot
Andreas

[KeithSloan]

Hello @KeithSloan,

first really appreciate your very quick reply and effort - thanks a lot!

I've tried that and manually added your new OpenSCAD Workbrench to the Mod directory which worked first try.

And yes, when I try to import the CSG file again I at least no longer get an exception (using "External_OpenSCAD_Workbench NEW CSG / AST Importer" as you suggested), but the object that it imports to FreeCAD is unfortunately only "similar", but not exactly what I see in OpenSCAD: You see that on the left side in FreeCAD several details are missing or are just different.

I just re-generated the CSG file (latest version attached again here: test-csg.zip) with OpenSCAD 2025.10.02 - not sure if it would make a difference if I use a newer OpenSCAD development build?

Or any other option parameter I miss which causes this import issue?

Thanks a lot Andreas

The new OpenSCAD_Workbench is still under development.

I think you have now run into some things that are not yet implemented in the new AST/CSG importer.

I have looked at @pjcreath issue and it also finds a bug in the new AST/CSG importer, so I will look at that also.

As the Alternate_OpenSCAD importer needs updating for FreeCAD 1.1 just wondering if you use an old release like FreeCAD 1.0.2 and the Alternate_importer do these csg files work?

[KeithSloan]

Or any other option parameter I miss which causes this import issue?

Thanks a lot Andreas

The problems are things that are not yet implemented and bugs.

If anybody could create small examples that illustrate the issues that would be great.
At present finding the part of csg that has a problem and creating a test case takes most of the time.

Also we have just moved from a house we had lived in for 32 years, trying to downsize, so lots sorting out with the new house has to take priority at the moment

[ab-tools]

Hello @KeithSloan,

really appreciating your efforts!

But I'm afraid I know too little about the inner workings of OpenSCAD (all this CSG thing) to be able to create small examples - wouldn't even know where to start. But if it would help, happy to share with you the OpenSCAD source file directly (e. g. via e-mail).

I really enjoy creating 3D models via code using OpenSCAD, but the main limitation I ran into is a missing STEP export:
Whenever I want to get something produced via CNC machining, I need a STEP file and STL won't be accepted.

And I have a very hard time to get STL converted to STEP in a proper way. It's coming out as a complete mess if I import STL into FreeCAD and export it as STEP again - even after all the meshing and cleaning process.

I was therefore hoping that I can use your OpenSCAD importer to get the "actual source structure" imported in FreeCAD to use this as basis for a "clean" STEP export. But apparently, that's not possible with the current state at the moment which is really a pity.

In case you know any other way to get a STEP file from OpenSCAD code import, this would be highly appreciated!

Best regards and again thanks for all your efforts
Andreas

[KeithSloan]

Best I can do at present let OpenSCAD create an STL version and export that see files in attached zip.

Ab_Tools.zip

test2.scad is a copy of test2.csg where extension is changed to scad.

Import with latest verision of Workbench should get this prompt.

Choose the External OpenSCAD Workbench import SCADFile Object.

Should get a new prompt

Take defaults which is Mesh rather than Brep .

There is a bug which causes it to create a new document test-3

And there is a also a bug to do with DXF and time stamp

You can select test_2 and export as STEP, Will be using STL rather than creating from Brep shapes

I also exported to 3mf.

Let me know if any of this helps for now.

Will let you know if I can fix the issues with the new AST importer.

[KeithSloan]

If I look more carefully at the dialog window with errors I see a number of the following.

Apart from the WARNING about time stamp, it complains it cannot find.

../PCB-DeskControl/LedLamp-DeskControl-Edge_Cuts.dxf

If I look in your csg file there are statements like

group() {
offset(delta = 0.1, chamfer = false, $fn = 0, $fa = 1, $fs = 0.25) {
import(file = "../PCB-DeskControl/LedLamp-DeskControl-Edge_Cuts.dxf", origin = [0, 0], scale = 1, center = false, convexity = 1, $fn = 0, $fa = 1, $fs = 0.25, timestamp = -4662931644);
}
}

So as well as the csg files, the importer needs any referenced dxf file.

I don't know if the new AST importer did not get as far encountering the DXF import. I don't think the import function in it is implemented yet, so if you could supply the missing DXF files, they would make good test cases.

Thanks

Geometries in cache: 76
Geometry cache size in bytes: 1028368
CGAL Polyhedrons in cache: 64
CGAL cache size in bytes: 14886960
Total rendering time: 0:00:03.338
Top level object is a 3D object (Nef polyhedron):
Simple: yes
Vertices: 2062
Halfedges: 6186
Edges: 3093
Halffacets: 2088
Facets: 1044
Volumes: 2
WARNING: variable "timestamp" not specified as parameter in file test-2.scad, line 10365 WARNING: Can't open DXF file '/Users/ksloan/Downloads/Ab_Tools/../PCB-DeskControl/LedLamp-
DeskControl-Edge_Cuts.dxf'.
Geometries in cache: 76|
Geometry cache size in bytes: 1028368
CGAL Polyhedrons in cache:

[ab-tools]

Hello Keith,

first thanks a lot again for all your efforts - really appreciating this!

Sure, no problem sharing this DXF file: dxf-file.zip

Looking at the file/screenshot you provided above though, I have to say that the resulting STEP file (independent of the missing DXF cut-out) is still far from being "clean" as needed for e. g. CNC production.

In the meantime, I actually found another surprising way to get a "proper" STEP file out of my OpenSCAD code and the solution is - as nowadays so often - AI: :-)
I just kindly asked Claude Open 4.6 for advice and 5 min. later it came back with around 300 lines of Python code completely re-implementing my OpenSCAD code to recreate the 3D object as clean B-rep (boundary-representation) geometry
using FreeCAD's Part module (OpenCASCADE kernel).

And what can I say, first try and this resulted in an absolute perfect and clean STEP file representing 100 % the OpenSCAD object (including DXF cut-out). For reference, this is the STEP output I got: generated-using-brep-by-ai.zip

You see the faces are reduced to an absolute minimum and file size got down to only around 130 KB.
This is exactly what is needed for e. g. CNC production.

If it would be possible going forward to "just" import the OpenSCAD source code file into FreeCAD and be able to get such a "clean" STEP file exported from there, this would be perfect and likely more deterministic than using AI. ;-)

Best regards
Andreas

[KeithSloan]

If it would be possible going forward to "just" import the OpenSCAD source code file into FreeCAD and be able to get such a "clean" STEP file exported from there, this would be perfect and likely more deterministic than using AI. ;-)

That would require the importer to handle all csg operations using Brep equivalent. Challenge is with hull and minkowski operations, other operations map to Brep equivalent. At present, subject to bugs it can for certain hull and minkowski requests. Polyhedron is just slow.

Don't suppose you could perform an experiment with your Claude Open 4.6 setup.

Can you take the OpenSCAD source for OpenFlexure and create in FreeCAD, ideally as an Assembly.