Cura fails, or am I missing something?

[Umo_Alex 4]

I have a model that looks right in the preview of Cura.

When printed, it turned into a mess and here's why:

Left a screenshot of Cura, The right one a slice off of http://gcode.ws/

 

 

Am I missing something?

 

 

 

Edited July 31, 2019 by Umo_Alex

[johnse 31]

The red on the rop of the ring shows at least part of the problem. cura is thinking it needs to support the top of the arch. Normally support should only show on bottom surfaces.

 

I suspect this means the normals of the mesh are reversed.

 

look in the marketplace for Mesh Tools. 

 

Others can likely give give more explicit directions.

 

 

[ahoeben 1,763]

@johnse is correct that the normals of the model seem to be incorrect, however they don't affect slicing. Normals are only used for visualisation.

 

From the looks of it, your model is not "manifold". I think you modeled the torus and the cylinders and just moved them so they look like they make a whole. However, you did not join (or union, or boolean, or something else, depending on the modeler you use) the shapes so they don't actually form a single geometry. As is, the cylinder geometry just extends into the torus geometry, so you have what is called "internal geometry".

 

When slicing, Cura makes cross-sections of the model. Looking from the outside in, the first edge-loop it encounters will be an outer wall. Going in, if it encounters another edge-loop, that will become an inner wall of a hole. Etc. In your case, because you have (sub)objects intersecting eachother, Cura simply looses track of what should be the outside and what should be the inside.

 

Long story short: Cura fails to meet your expectation because your model is "wrong". Just because it displays well does not mean that it is suitable for printing.

[Umo_Alex 4]

22 hours ago, Umo_Alex said:

 

Thanks for your explanation. I'm using FreeCAD for moddeling. I guess I'll have to somehow clip the cylinders with the torus...But that's beyond the scope of this forum.

[johnse 31]

In Fusion 360, that would be a "Combine" operation. I expect FreeCAD has a similar operation.

 

Looks like it is the "Part Union" command: https://www.freecadweb.org/wiki/Part_Union

[Umo_Alex 4]

OK, I'll try that. Thanks for the link! 👍

[ahoeben 1,763]

In FreeCAD, the function you are looking for is making a Union of two shapes

 

[Umo_Alex 4]

Yay, that works, thanks! For some reason the fillet on the base I created in the Part Design workbench got lost, though.

Recreating it in the Part workbench fixed it.

 

[ahoeben 1,763]

6 minutes ago, Umo_Alex said:

For some reason the fillet on the base I created in the Part Design workbench got lost,

 

Are you sure you had the whole part selected when you exported the STL?

[Umo_Alex 4]

Couldn't get the fillet working in FreeCAD itself.

[johnse 31]

The slice you’ve shown is going to have problems with the bottom curve. It looks like you have generate support touching buildplate instead of everywhere. The upper arch may build ok with bridging, but the bottom of the circle will be literally printing on air generating spaghetti.

[Umo_Alex 4]

Correct. That print failed. I changed support to everywhere and it printed ok. 💩😃

[Umo_Alex 4]

7 hours ago, Umo_Alex said:

Couldn't get the fillet working in FreeCAD itself.

I've recreated the problem in an example, in case anyone is interested.

 

FusionFilletProblem.zip