Join objects doesn't completely join

Good morning everybody,

As already raised in an older thread, I have some difficulties exporting an object made up of multiple joined objects into a .stl that slices properly. Instead of bumping the older thread, here’s a new one…

It is the model of a human larynx intended for 3d-printing. The model is made up of multiple individual .obj files from a medical database. After putting them together I exported the whole thing into .stl. In the slicer (PrusaSlicer 2.3.0 and previous versions) it is obvious that it consists of individual pieces. The borders of the individual objects are clearly visible.
In the second attempt I used the join objects command to generate a single object. This got rid of some of the borders but not all of them. Especially annoying is the fact that the intersection between the larynx and the cube that I added as a base plate is partially retained, resulting in a extremely unstable print.

Here’s the blender file: (hope that works)

The second problem with the .stl is that the bottom is not really flat. The cube sits nicely flat in Blender with zero degrees rotation in any direction and the .stl has a small step halfway trough it.

This is the first layer, with only half the base.

This is the second layer with a large overhang that should be part of the first layer.

And thirdly an image of some of the “unjoined” bits.

Apologies for the convoluted question and thanks in advance for any help.


Maybe this addon will help:

Regarding the second Problem. This might be because there is a small part of your object sticking through your base plate.

Also, I checked the model with the 3D-Print addon that comes with Blender and it throws a lot of warnings. Tons of non-manifold edges, Intersecting Faces, Zero Faces and so on.

And your object imports as 100 meters long. So perhaps size is an issue because the slicer has to scale it down and then drops some accuracy due to rounding errors.

And your object is scaled non-uniformly. I don’t know if that is an issue but non-uniform scale is problematic in a lot of other areas, so perhaps this makes the export bad somehow.

I know nothing about the exportation for 3d printing, since I still don use it so I have no big hints to give on the matter but should your model have so many duplicated vertices? I’ve merged 1555 vertices.

Still have no idea if this could cause any problem but I thought I should mention it.