hull in freecad
I am trying to create step files and from what I have found this is really
the only way to do it from OpenSCAD. I export the design to a csg file,
import the csg file into freecad and then I get these error messages.
11:28:36 hull:
11:28:36 hull001:
11:28:36 obj [Part::PartFeature] has no Name & Shape
11:28:36 <Exception> Input shape is null
11:28:36 Recompute failed : union
11:28:36 End processing CSG file
11:28:36 pyException: Traceback (most recent call last):
File "FreeCAD\Mod\OpenSCAD\OpenSCADFeatures.py", line 554, in execute
raise ValueError
<class 'ValueError'>:
11:28:36 pyException: Traceback (most recent call last):
File "FreeCAD\Mod\OpenSCAD\OpenSCADFeatures.py", line 554, in execute
raise ValueError
<class 'ValueError'>:
11:28:36 hull:
11:28:36 hull001:
This is an image of the design
[image: spiral-bad.png]
If I don't use the hull command and just make the top knobs a cylinder, it
works fine; it just does not look as nice. This image shows the design,
which imports and exports as a STEP file in FreeCAD without issue.
[image: spiral-good.png]
Any ideas how to fix this or a different way to get this effect without
using hull?
When I needed that shape for tooling in my project I made it as a series of stacked cylinders, using trigonometry to set the radius of each end in a loop, slightly overlapping and unioning things --- see gcodepreview on Github --- while in Python, it should be pretty easy to rework to OpenSCAD. If that's a problem, let me know and I'll see if I still have the OpenSCAD version I did at first.
William
On Thursday, March 19, 2026 at 02:45:12 PM EDT, Trevor Orr via Discuss discuss@lists.openscad.org wrote:
I am trying to create step files and from what I have found this is really the only way to do it from OpenSCAD. I export the design to a csg file, import the csg file into freecad and then I get these error messages.
11:28:36 hull:
11:28:36 hull001:
11:28:36 obj [Part::PartFeature] has no Name & Shape
11:28:36 <Exception> Input shape is null
11:28:36 Recompute failed : union
11:28:36 End processing CSG file
11:28:36 pyException: Traceback (most recent call last):
File "FreeCAD\Mod\OpenSCAD\OpenSCADFeatures.py", line 554, in execute
raise ValueError
<class 'ValueError'>:
11:28:36 pyException: Traceback (most recent call last):
File "FreeCAD\Mod\OpenSCAD\OpenSCADFeatures.py", line 554, in execute
raise ValueError
<class 'ValueError'>:
11:28:36 hull:
11:28:36 hull001:
This is an image of the design
If I don't use the hull command and just make the top knobs a cylinder, it works fine; it just does not look as nice. This image shows the design, which imports and exports as a STEP file in FreeCAD without issue.
Any ideas how to fix this or a different way to get this effect without using hull?
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
Not sure this is actually the question you’re asking, but if I had to recreate that shape in OpenSCAD, the “plot-function” library would be the first tool I’d grab:
https://github.com/rcolyer/plot-function
From: Trevor Orr via Discuss discuss@lists.openscad.org
Sent: Thursday, March 19, 2026 11:45 AM
To: OpenSCAD general discussion discuss@lists.openscad.org
Cc: Trevor Orr fractorr@gmail.com
Subject: [OpenSCAD] hull in freecad
I am trying to create step files and from what I have found this is really the only way to do it from OpenSCAD. I export the design to a csg file, import the csg file into freecad and then I get these error messages.
11:28:36 hull:
11:28:36 hull001:
11:28:36 obj [Part::PartFeature] has no Name & Shape
11:28:36 <Exception> Input shape is null
11:28:36 Recompute failed : union
11:28:36 End processing CSG file
11:28:36 pyException: Traceback (most recent call last):
File "FreeCAD\Mod\OpenSCAD\OpenSCADFeatures.py", line 554, in execute
raise ValueError
<class 'ValueError'>:
11:28:36 pyException: Traceback (most recent call last):
File "FreeCAD\Mod\OpenSCAD\OpenSCADFeatures.py", line 554, in execute
raise ValueError
<class 'ValueError'>:
11:28:36 hull:
11:28:36 hull001:
This is an image of the design
If I don't use the hull command and just make the top knobs a cylinder, it works fine; it just does not look as nice. This image shows the design, which imports and exports as a STEP file in FreeCAD without issue.
Any ideas how to fix this or a different way to get this effect without using hull?
scale([2,2,1])sphere(50);
On 19/03/2026 18:44, Trevor Orr via Discuss wrote:
I am trying to create step files and from what I have found this is
really the only way to do it from OpenSCAD. I export the design to a
csg file, import the csg file into freecad and then I get these error
messages.
11:28:36 hull:
11:28:36 hull001:
11:28:36 obj [Part::PartFeature] has no Name & Shape
11:28:36 <Exception> Input shape is null
11:28:36 Recompute failed : union
11:28:36 End processing CSG file
11:28:36 pyException: Traceback (most recent call last):
File "FreeCAD\Mod\OpenSCAD\OpenSCADFeatures.py", line 554, in execute
raise ValueError
<class 'ValueError'>:
11:28:36 pyException: Traceback (most recent call last):
File "FreeCAD\Mod\OpenSCAD\OpenSCADFeatures.py", line 554, in execute
raise ValueError
<class 'ValueError'>:
11:28:36 hull:
11:28:36 hull001:
This is an image of the design
spiral-bad.png
If I don't use the hull command and just make the top knobs a
cylinder, it works fine; it just does not look as nice. This image
shows the design, which imports and exports as a STEP file in FreeCAD
without issue.
spiral-good.png
Any ideas how to fix this or a different way to get this effect
without using hull?
OpenSCAD mailing list
To unsubscribe send an email todiscuss-leave@lists.openscad.org
I ended up changing the design slightly, I this looks better anyway and no issues with FreeCAD.
On Thursday, March 19, 2026 at 11:45:04 AM PDT, Trevor Orr via Discuss <discuss@lists.openscad.org> wrote:
I am trying to create step files and from what I have found this is really the only way to do it from OpenSCAD. I export the design to a csg file, import the csg file into freecad and then I get these error messages.
11:28:36 hull:
11:28:36 hull001:
11:28:36 obj [Part::PartFeature] has no Name & Shape
11:28:36 <Exception> Input shape is null
11:28:36 Recompute failed : union
11:28:36 End processing CSG file
11:28:36 pyException: Traceback (most recent call last):
File "FreeCAD\Mod\OpenSCAD\OpenSCADFeatures.py", line 554, in execute
raise ValueError
<class 'ValueError'>:
11:28:36 pyException: Traceback (most recent call last):
File "FreeCAD\Mod\OpenSCAD\OpenSCADFeatures.py", line 554, in execute
raise ValueError
<class 'ValueError'>:
11:28:36 hull:
11:28:36 hull001:
This is an image of the design
If I don't use the hull command and just make the top knobs a cylinder, it works fine; it just does not look as nice. This image shows the design, which imports and exports as a STEP file in FreeCAD without issue.
Any ideas how to fix this or a different way to get this effect without using hull?
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
