Phantom unsupported "bottom" layers created mid-structure, increasing "Skin Removal Width" doesn't fix it

[ericspivey]

Cura Version

4.13.1

Operating System

Windows 10

Printer

Ultimaker S5

Reproduction steps

Set up skull to slice (it is a complicated structure, and won't slice with Cura v5.x, which is why I'm using 4.13)

Actual results

skull slices ~5 "phantom" bottom layers (not based on apparent features in the .stl) appear at various levels of the sliced structure, none are supported. Prints fail when they reach the first of these bottom layers, because filiment is air printed all over the structure.

Expected results

I would expect it to slice without introducing phantom bottom layers mid-print

Add your .zip and screenshots here ⬇️

UMS5_skull asby 240214 intact.zip Phantom bottom layer screen shots.pdf

[ericspivey]

Also, as the title suggests, when I increase the "Skin Removal WIdth" parameter up to even 5 mm, the phantom layers are not supressed.

[GregValiant]

Thanks for the report. Missing layers are often an indication that there are errors in a model. That model requires repair. Here you can see that it isn't water tight, and it has multiple errors in the structure.

You can download Microsoft 3D Builder from the Microsoft store. It has a pretty good "repair" function.

This is the repaired model in 4.13.1. This looks good to me with no phantom layers.

This is in 5.7b. (5.6 wouldn't slice it.)

I'll remove the bug label from this and close it as it appears to be a model problem. Let me know if you feel that is premature.

[ericspivey]

This is great! Microsoft actually has something that works ;-) Also great is the news that v5.7b will slice it. I would like to be on the current version of Cura, but have been hanging back because it couldn't slice the skulls, which we need for a research study.

[GregValiant]

4.13.1 works well. Of the 5.x versions 5.2.2 is the best. Starting with 5.3 there have been a lot of problems with models not slicing and Windows 11 compatibility. A lot of work has been done to 5.7 and the beta is out. So far it is slicing a lot of models that 5.3 to 5.6 would not. I use the SmartAvionics fork for spiralize and when 5.x is giving me a headache.

[ericspivey]

Thanks, good to know. I knew that my meshes were accumulating errors, because I had to do a lot of boolean union/difference to make modifications. However none of the software I tried (Blender, Meshlab, Cura) seemed to have a straightforward method for fixing the mesh. Do you know how the Microsoft 3D Builder repair tool works?

[GregValiant]

I have no idea., but it seems to work well. The program isn't very intuitive but I use it to alter model files when I don't have the CAD files. PrusaSlicer has made some sort of deal with AutoDesk for NetFabb. I don't know how that one works either, but it was the best when it was web based. In PrusaSlicer, before starting a project or importing a model, use the "File | Repair STL" tool. Then export the model from Prusa, bring it into Cura, and you can slice it.