Using FreeCAD I designed a simple adapter to allow me to connect a 2.5" flexible duct to the 3" duct outlet on the Snapmaker enclosure. Here is what it looked like in FreeCAD, using three “lofts”:
About halfway through the print I took a look at how it was progressing and was surprised to see that Snapmaker had printed a thin membrane that went completely across the inside of the adapter. The membrane was added at the inflection point between the first and second lofts. Here is a photo of the finished adapter showing the membrane inside:
Since this membrane was not in my FreeCAD design, I went back to Luban, rotated the object slightly, and, sure enough, Luban was showing it as a skin (in yellow):
To see if the problem was an artifact introduced by FreeCAD or if the skin had been invented by Luban, I opened the stl file in Cura and it did not show the membrane:
So it appears to me that there is a bug in Luban causing this skin/membrane to be added.
An additional unexpected result is that Snapmaker was able to print this skin/membrane in mid-air without support!
More likely your model is not manifold.
Post the object, or run it through meshmixer to find the errors.
Brent, thank you for the response. I’m a newbie, and this is the first I’ve heard the term manifold. This prompted me to do some research and now I know a bit more! I found a post on the FreeCAD forum that matches what I did: selected all objects in the body rather than just the last one.
Thanks for helping me get educated. It is interesting, though, that Cura did not have a problem with the stl file whereas Luban did.
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And as I understand more about manifold issues, and have done some more experiments, I’ve discovered that my assertion that Cura does not have the same problem was wrong. As I’ve learned, the problem with non-manifoldness arises when you slice. I had previously not taken Cura through the slicing process. So Cura, like Luban, shows the object without the membrane before slicing is done, but then it gets added in both when the object is sliced.
So I take it back, Luban, Cura wasn’t better than you!
And, Brent, thanks again for your response and the spot-on diagnosis!
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Luban and Cura are “the same” - Luban uses an embedded instance of Cura with a specific profile. You can look up the profile in the installation directory of Luban if you’re interested.
There’s likely a Cura setting related to auto-healing non-manifold objects that’s turned on by default in Cura, that was turned off for who-knows-what reason in the Luban profile.
Glad you got it figured out! Happy printing!
Edit:
Simplify3D does have auto-healing capabilities. I did some googling and it looks like Cura, as you found, does not have that capability. Cura is still great, just requires some extra care when modelling. Meshmixer is free and great for repairing objects as well.
This is particularly important on models downloaded from thingiverse, etc - so many objects are low quality with errors just like the object you tried to print. Eventually you’ll develop a skill at repairing errors. Meshmixer has an “auto” feature that will attempt to close small holes and fix non-connected triangles that’s very useful.
