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I am an absolute beginner looking to start 3d printing, and I have a real beginner question.

Say I have a very simple model I want to print, maybe two cubes side by side, with faces touching but not overlapping. Ie they have separate meshes.

Does one need to merge those meshes in some way before export to STL, or will the slicer automatically treat them as one component because they are touching?

I know there is a Boolean union operation, but it seems to have problems if edges colocate.

UPDATE:

I put the real model through a slicer (Cura) to see what happened - There are three screenshots at https://drive.google.com/file/d/1rQVpeUMbwKdShReWjvVIWbmQFFGO7vOV/view?usp=sharing. blender,png shows it in blender, cura.png is a preview of the first layer after slicing, cura2.png is the first layer of a test model made using extrusion.

The model is just cubes and cylinders, using boolean operations.Don't know if that is how you are supposed to do these things - I am a beginner (don't even have a printer yet). The end of each bar is cut away with one cylinder, then another cylinder with a hole is placed there. The forward bar is just made of another cube placed adjacent to the sideways bar.

The slicing (cura.png) shows the nozzle going up the bars and round the ends so it appears to treat the ends as part of the bar, but the forward bar is separate from the sideways bar - the nozzle does not go round the whole lot.

I did a quick test with a similar sideways bar, but making the forward bar by extruding the sideways bar so it really was all one mesh - the first slice is in cura2.png. In that case the base layer went right round the outside - it did not treat the forward bar as separate.

So, I am unclear, in the cases of the ends, Cura treated the rounded ends as part of the main bar, but in the case of the forward bar, it did not unless the forward bar was extruded from the sideways bar.

nmw01223
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  • you might get issues as the slicer will create a face there. However with two touching cubes merging is quit easy. Just go to edit mode and merge by distance. – Alex bries Oct 07 '20 at 17:16
  • Thanks. So I do need to. The real example was more complex. Had a cube 16x5x1, but wanted a round end on the 5x1 face. So what I first tried was create a cylinder diam 5 depth 1, placing it at the end, then using boolean union. Did not come out right, apparently because boolean doesn't like colocated edges or vertices (?). Maybe this is not the right way to do what I wanted? How should one round an end like this? – nmw01223 Oct 07 '20 at 17:35
  • could you show a screenshot or include a file pls, also look into this answer maybe it does what you wanted: https://blender.stackexchange.com/questions/7910/what-is-non-manifold-geometry/7914#7914 – Alex bries Oct 07 '20 at 22:08
  • And you might want to enable the pre installed 3d printing toolbox, that comes with usefull features for 3d printing. – Alex bries Oct 07 '20 at 22:21
  • I have added an update above, and a link to a ZIP file with three screenshots (blender and two from cura). Confusing results after slicing. I have the 3D printing addon installed - haven't worked out what it does yet! – nmw01223 Oct 08 '20 at 09:02
  • The slicer is handelig seperate meshes as seperate meshes, and single meshes as single meshes. Here is a clean exaple: https://gofile.io/d/TkqXbc. I suggest also looking up some tutorials if you are planning on using blender for future projects. – Alex bries Oct 08 '20 at 10:53
  • Thanks for your help. – nmw01223 Oct 09 '20 at 11:22

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