Blender 2.91 Mesh Object to 3D Print STL I am a Blender newbie. I started on 2.7. Recently upgraded to 2.91.
I used blender to create models for 3D printing and I use a Cura as my Slicer.
My issue is has to do with creating a “sliceable” STL file from joined mesh objects.
Here is an example.

Add ==&gt; Mesh ==&gt; Cube
a.  Set dimensions X: 8cm  Y: 8cm  Z: 1 cm
Add ==&gt; Mesh ==&gt; Cylinder =&gt; Named Cyl
a.  Set dimensions X: 12.4 cm Y: 12.4 cm Z: 4 cm
Add ==&gt; Mesh ==&gt; Cylinder =&gt; Named Cyl1
a.  Set dimensions X: 11.8 cm Y: 11.8 cm Z: 10 cm
Select Cyl ==&gt; Add Modifier ==&gt; Boolean ==&gt; Object = Cyl1 ==&gt; Difference ==&gt; Apply
Select Cyl1 ==&gt; Delete
Select Cube ==&gt; GZ move a few centimeters above top of Cyl
Select Cube and Cyl ==&gt; Ctrl-J to join objects ==&gt; Tab to enter edit mode
Click in Edge and Using MRB – Subdivide, I subdivided the equal distant edges of the Cube multiple times so that there are as many vertexes on the edge as there are on the curve it faces
Click on Vertex mode and select two facing vertexes (bottom of cube edge to inner cylinder wall top) I create and edge by clicking F. I go all the way around doing that, then go around selecting two edges and using F to create a face.
I do some clean up like the top face of the cylinder and the 1 cm edge of the cube, I remove the faces.
In object mode, it look perfect. I Merged by DIstance and Recalculated Normals.
I export to STL. Import into CURA, resize (x10), Cura can’t slice this. The error message it gives is:





Unable to Slice:
Please review settings and check if you models:

Fit within the build volume (yes I can see the gray outline of bottom and it does)
Are assigned to the enabled extruder (not sure what this is)
Are not set as modifier meshes (again not sure about this)


Bottom line, cant slice. Now If I export the cube or the cylinder as STL, then Cura can slice those, So I think I am missing a step for complex joined objects. I assume I need to fill this object but how do you do that in 2.91. Solidify modifier seems to distort the image.
Does anyone have a faster way of doing the above and any insights of export STL’s for 3D Slicing?
Just a hunch, as I don't know anything about your slicer program. But I know people often get tripped up in other cases by joining objects without realizing the limitations of doing so. So step 7 is likely your culprit, though it may not be the only issue. I'm just betting it's one of them. When joining objects in Blender, they are almost more &quot;grouped&quot; than &quot;fused&quot;; they can be separated later. My gut tells me that your slicer program is complaining about them being joined. You will likely need to separate the joined objects and combine them properly afterwards with a boolean union operation.